1
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Zhu J, Li Y, Lin X, Han Y, Wu K. Coherent phenomena and dynamics of lead halide perovskite nanocrystals for quantum information technologies. NATURE MATERIALS 2024; 23:1027-1040. [PMID: 38951651 DOI: 10.1038/s41563-024-01922-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 05/15/2024] [Indexed: 07/03/2024]
Abstract
Solution-processed colloidal nanocrystals of lead halide perovskites have been intensively investigated in recent years in the context of optoelectronic devices, during which time their quantum properties have also begun to attract attention. Their unmatched ease of synthetic tunability and unique structural, optical and electronic properties, in conjunction with the confinement of carriers in three dimensions, have motivated studies on observing and controlling coherent light-matter interaction in these materials for quantum information technologies. This Review outlines the recent efforts and achievements in this direction. Particularly notable examples are the observation of coherent single-photon emission, evidence for superfluorescence and the realization of room-temperature coherent spin manipulation for ensemble samples, which have not been achieved for prototypical colloidal CdSe nanocrystals that have been under investigation for decades. This Review aims to highlight these results, point out the challenges ahead towards realistic applications and bring together the efforts of multidisciplinary communities in this nascent field.
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Affiliation(s)
- Jingyi Zhu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Yuxuan Li
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xuyang Lin
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yaoyao Han
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
- University of Chinese Academy of Sciences, Beijing, China.
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2
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Na HG, Kim S, Jin C. Physical interpretation of entropy, Boltzmann constant, and temperature. Sci Rep 2024; 14:17705. [PMID: 39085416 PMCID: PMC11291489 DOI: 10.1038/s41598-024-68673-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 07/26/2024] [Indexed: 08/02/2024] Open
Abstract
Through the previously reported the quantum-identity, the light-model, and the T(temperature) · S(entropy) energy, the implied meaning of temperature and entropy, respectively, which it was difficult to intuitively recognize, was clearly defined. In order to minimize possible errors at this time, the interrelationship of the SI base unit, which is the smallest unit, and the T(temperature) · S(entropy) unit integration was used. In the process of converting to Planck units, each unit (criterion) for entropy and temperature was calculated, and their physical and chemical meanings were compared and reinterpreted. Thus, the unit of entropy is related to the Boltzmann constant, and the temperature is the oscillation of pure mass units. Therefore, the intuitive recognition of physical and chemical factors based on the unit of meter(m)-time(s) is considered sufficient as an initiator to move closer to new science beyond the current limited application.
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Affiliation(s)
- Han Gil Na
- UDerive, GJ Gajwa Tower Knowledge Industry Center, 16, Baekbeom-ro 630 beon-gil, Seo-gu, Incheon, 22824, Republic of Korea
| | - Sangwoo Kim
- Materials Supply Chain R&D Department, Korea Institute of Industrial Technology, Incheon, 21999, Republic of Korea
| | - Changhyun Jin
- Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Republic of Korea.
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3
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Künne M, Willmes A, Oberländer M, Gorjaew C, Teske JD, Bhardwaj H, Beer M, Kammerloher E, Otten R, Seidler I, Xue R, Schreiber LR, Bluhm H. The SpinBus architecture for scaling spin qubits with electron shuttling. Nat Commun 2024; 15:4977. [PMID: 38862531 PMCID: PMC11166970 DOI: 10.1038/s41467-024-49182-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 05/24/2024] [Indexed: 06/13/2024] Open
Abstract
Quantum processor architectures must enable scaling to large qubit numbers while providing two-dimensional qubit connectivity and exquisite operation fidelities. For microwave-controlled semiconductor spin qubits, dense arrays have made considerable progress, but are still limited in size by wiring fan-out and exhibit significant crosstalk between qubits. To overcome these limitations, we introduce the SpinBus architecture, which uses electron shuttling to connect qubits and features low operating frequencies and enhanced qubit coherence. Device simulations for all relevant operations in the Si/SiGe platform validate the feasibility with established semiconductor patterning technology and operation fidelities exceeding 99.9%. Control using room temperature instruments can plausibly support at least 144 qubits, but much larger numbers are conceivable with cryogenic control circuits. Building on the theoretical feasibility of high-fidelity spin-coherent electron shuttling as key enabling factor, the SpinBus architecture may be the basis for a spin-based quantum processor that meets the scalability requirements for practical quantum computing.
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Affiliation(s)
- Matthias Künne
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Alexander Willmes
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Max Oberländer
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Christian Gorjaew
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Julian D Teske
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Harsh Bhardwaj
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Max Beer
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Eugen Kammerloher
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - René Otten
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
- ARQUE Systems GmbH, 52074, Aachen, Germany
| | - Inga Seidler
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Ran Xue
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Lars R Schreiber
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany.
- ARQUE Systems GmbH, 52074, Aachen, Germany.
| | - Hendrik Bluhm
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany.
- ARQUE Systems GmbH, 52074, Aachen, Germany.
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4
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Ruckriegel MJ, Gächter LM, Kealhofer D, Bahrami Panah M, Tong C, Adam C, Masseroni M, Duprez H, Garreis R, Watanabe K, Taniguchi T, Wallraff A, Ihn T, Ensslin K, Huang WW. Electric Dipole Coupling of a Bilayer Graphene Quantum Dot to a High-Impedance Microwave Resonator. NANO LETTERS 2024; 24:7508-7514. [PMID: 38833415 PMCID: PMC11194813 DOI: 10.1021/acs.nanolett.4c01791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/31/2024] [Accepted: 05/31/2024] [Indexed: 06/06/2024]
Abstract
We implement circuit quantum electrodynamics (cQED) with quantum dots in bilayer graphene, a maturing material platform that can host long-lived spin and valley states. Our device combines a high-impedance (Zr ≈ 1 kΩ) superconducting microwave resonator with a double quantum dot electrostatically defined in a graphene-based van der Waals heterostructure. Electric dipole coupling between the subsystems allows the resonator to sense the electric susceptibility of the double quantum dot from which we reconstruct its charge stability diagram. We achieve sensitive and fast detection of the interdot transition with a signal-to-noise ratio of 3.5 within 1 μs integration time. The charge-photon interaction is quantified in the dispersive and resonant regimes by comparing the resonator response to input-output theory, yielding a coupling strength of g/2π = 49.7 MHz. Our results introduce cQED as a probe for quantum dots in van der Waals materials and indicate a path toward coherent charge-photon coupling with bilayer graphene quantum dots.
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Affiliation(s)
- Max J. Ruckriegel
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Lisa M. Gächter
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - David Kealhofer
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Mohsen Bahrami Panah
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum
Center, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Chuyao Tong
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Christoph Adam
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Michele Masseroni
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Hadrien Duprez
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Rebekka Garreis
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Kenji Watanabe
- Research
Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Andreas Wallraff
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum
Center, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum
Center, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Klaus Ensslin
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum
Center, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Wei Wister Huang
- Laboratory
for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
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5
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Wu HB, Liu YJ, Liu YD, Liu JJ. Resonant exchange of chiral Majorana Fermions modulated by two parallel quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:345301. [PMID: 38729174 DOI: 10.1088/1361-648x/ad49fc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 05/10/2024] [Indexed: 05/12/2024]
Abstract
Resonant exchange of the chiral Majorana fermions (MFs) that is coupled to two parallel Majorana zero modes (MZMs) or two parallel quantum dots (QDs) is investigated. We find that, in the two QDs coupling case, the resonant exchange for the chiral MFs is analogous to that in the MZM coupling case. We further propose a circuit based on topological superconductor, which is formed by the proximity coupling of a quantum anomalous Hall insulator and a s-wave superconductor, to observe the resonant exchange of chiral MFs pairs. The numerical calculations show that the resonant transmission of the chiral MFs can be adjusted by varying the coupling parameters at superconductor phase differenceΔφ=π. It is particularly noteworthy that, by only modulating the coupling strength between the two QDs, the resonant exchange may be switched on or off. By adding another MZM, the non-Abelian braiding like operation can be realized. Therefore, our design scheme may provide another way for non-Abelian braiding operation of MFs and the findings may have potential application value in the realization of topological quantum computers.
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Affiliation(s)
- Hai-Bin Wu
- College of Science, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China
| | - Yan-Jun Liu
- College of Science, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China
| | - Ying-Di Liu
- College of Science, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China
| | - Jian-Jun Liu
- College of Science, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China
- College of Physics, Hebei Normal University, Shijiazhuang 050024, People's Republic of China
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6
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Kang JH, Yoon T, Lee C, Lim S, Ryu H. Design of high-performance entangling logic in silicon quantum dot systems with Bayesian optimization. Sci Rep 2024; 14:10080. [PMID: 38698015 PMCID: PMC11066012 DOI: 10.1038/s41598-024-60478-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 04/23/2024] [Indexed: 05/05/2024] Open
Abstract
Device engineering based on computer-aided simulations is essential to make silicon (Si) quantum bits (qubits) be competitive to commercial platforms based on superconductors and trapped ions. Combining device simulations with the Bayesian optimization (BO), here we propose a systematic design approach that is quite useful to procure fast and precise entangling operations of qubits encoded to electron spins in electrode-driven Si quantum dot (QD) systems. For a target problem of the controlled-X (CNOT) logic operation, we employ BO with the Gaussian process regression to evolve design factors of a Si double QD system to the ones that are optimal in terms of speed and fidelity of a CNOT logic driven by a single microwave pulse. The design framework not only clearly contributes to cost-efficient securing of solutions that enhance performance of the target quantum operation, but can be extended to implement more complicated logics with Si QD structures in experimentally unprecedented ways.
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Affiliation(s)
- Ji-Hoon Kang
- Division of National Supercomputing, Korea Institute of Science and Technology Information, Daejeon, 34141, Republic of Korea
| | - Taehyun Yoon
- Artificial Intelligence Graduate School, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Chanhui Lee
- Department of Artificial Intelligence, Korea University, Seoul, 02841, Republic of Korea
| | - Sungbin Lim
- Department of Statistics, Korea University, Seoul, 02841, Republic of Korea.
| | - Hoon Ryu
- Division of National Supercomputing, Korea Institute of Science and Technology Information, Daejeon, 34141, Republic of Korea.
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7
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Struck T, Volmer M, Visser L, Offermann T, Xue R, Tu JS, Trellenkamp S, Cywiński Ł, Bluhm H, Schreiber LR. Spin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe. Nat Commun 2024; 15:1325. [PMID: 38351007 PMCID: PMC10864332 DOI: 10.1038/s41467-024-45583-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 01/29/2024] [Indexed: 02/16/2024] Open
Abstract
Long-ranged coherent qubit coupling is a missing function block for scaling up spin qubit based quantum computing solutions. Spin-coherent conveyor-mode electron-shuttling could enable spin quantum-chips with scalable and sparse qubit-architecture. Its key feature is the operation by only few easily tuneable input terminals and compatibility with industrial gate-fabrication. Single electron shuttling in conveyor-mode in a 420 nm long quantum bus has been demonstrated previously. Here we investigate the spin coherence during conveyor-mode shuttling by separation and rejoining an Einstein-Podolsky-Rosen (EPR) spin-pair. Compared to previous work we boost the shuttle velocity by a factor of 10000. We observe a rising spin-qubit dephasing time with the longer shuttle distances due to motional narrowing and estimate the spin-shuttle infidelity due to dephasing to be 0.7% for a total shuttle distance of nominal 560 nm. Shuttling several loops up to an accumulated distance of 3.36 μm, spin-entanglement of the EPR pair is still detectable, giving good perspective for our approach of a shuttle-based scalable quantum computing architecture in silicon.
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Affiliation(s)
- Tom Struck
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
- ARQUE Systems GmbH, Aachen, Germany
| | - Mats Volmer
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Lino Visser
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Tobias Offermann
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Ran Xue
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Jhih-Sian Tu
- Helmholtz Nano Facility (HNF), Forschungszentrum Jülich, Jülich, Germany
| | - Stefan Trellenkamp
- Helmholtz Nano Facility (HNF), Forschungszentrum Jülich, Jülich, Germany
| | - Łukasz Cywiński
- Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Hendrik Bluhm
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
- ARQUE Systems GmbH, Aachen, Germany
| | - Lars R Schreiber
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany.
- ARQUE Systems GmbH, Aachen, Germany.
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8
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Gao K, Li Y, Yang Y, Liu Y, Liu M, Liang W, Zhang B, Wang L, Zhu J, Wu K. Manipulating Coherent Exciton Dynamics in CsPbI 3 Perovskite Quantum Dots Using Magnetic Field. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2309420. [PMID: 38009823 DOI: 10.1002/adma.202309420] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 11/02/2023] [Indexed: 11/29/2023]
Abstract
Lead halide perovskite quantum dots (QDs) have recently emerged as a promising material platform for quantum information processing owing to their strong light-matter interaction and relatively long-lived optical and spin coherences. In particular, the coherence of the fine-structure bright excitons is sustainable up to room temperature and can be observed even at an ensemble level. Here modulation of the polarization of these excitons in CsPbI3 QDs and manipulation of their time-domain coherent dynamics using a longitudinal magnetic field are demonstrated. The manipulation is realized using femtosecond quantum beat spectroscopy performed with both circularly- and linearly-polarized pulses. The results are well captured by the density of matrix simulation and are picturized using a Bloch sphere. This study forms the basis for preparing arbitrary coherent superpositions of excitons in perovskite QDs for an array of quantum technologies under near-ambient conditions.
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Affiliation(s)
- Kaimin Gao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuxuan Li
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yupeng Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuan Liu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Meng Liu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wenfei Liang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Boyu Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Lifeng Wang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jingyi Zhu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
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9
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Hecker K, Banszerus L, Schäpers A, Möller S, Peters A, Icking E, Watanabe K, Taniguchi T, Volk C, Stampfer C. Coherent charge oscillations in a bilayer graphene double quantum dot. Nat Commun 2023; 14:7911. [PMID: 38036517 PMCID: PMC10689829 DOI: 10.1038/s41467-023-43541-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 11/13/2023] [Indexed: 12/02/2023] Open
Abstract
The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-Stückelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and [Formula: see text] charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield [Formula: see text] average values in the range of 400-500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.
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Affiliation(s)
- K Hecker
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany.
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany.
| | - L Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Schäpers
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - S Möller
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Peters
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - E Icking
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - C Volk
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
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10
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Fletcher JD, Park W, Ryu S, See P, Griffiths JP, Jones GAC, Farrer I, Ritchie DA, Sim HS, Kataoka M. Time-resolved Coulomb collision of single electrons. NATURE NANOTECHNOLOGY 2023:10.1038/s41565-023-01369-4. [PMID: 37169897 DOI: 10.1038/s41565-023-01369-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 03/10/2023] [Indexed: 05/13/2023]
Abstract
A series of recent experiments have shown that collision of ballistic electrons in semiconductors can be used to probe the indistinguishability of single-electron wavepackets. Perhaps surprisingly, their Coulomb interaction has not been seen due to screening. Here we show Coulomb-dominated collision of high-energy single electrons in counter-propagating ballistic edge states, probed by measuring partition statistics while adjusting the collision timing. Although some experimental data suggest antibunching behaviour, we show that this is not due to quantum statistics but to strong repulsive Coulomb interactions. This prevents the wavepacket overlap needed for fermionic exchange statistics but suggests new ways to utilize Coulomb interactions: microscopically isolated and time-resolved interactions between ballistic electrons can enable the use of the Coulomb interaction for high-speed sensing or gate operations on flying electron qubits.
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Affiliation(s)
| | - W Park
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
| | - S Ryu
- Instituto de Física Interdisciplinary Sistemas Complejos IFISC (CSIC-UIB), Palma de Mallorca, Spain
| | - P See
- National Physical Laboratory, Teddington, UK
| | - J P Griffiths
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - G A C Jones
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - I Farrer
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield, UK
| | - D A Ritchie
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - H-S Sim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
| | - M Kataoka
- National Physical Laboratory, Teddington, UK.
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11
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Liu H, Wang K, Gao F, Leng J, Liu Y, Zhou YC, Cao G, Wang T, Zhang J, Huang P, Li HO, Guo GP. Ultrafast and Electrically Tunable Rabi Frequency in a Germanium Hut Wire Hole Spin Qubit. NANO LETTERS 2023; 23:3810-3817. [PMID: 37098786 DOI: 10.1021/acs.nanolett.3c00213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Hole spin qubits based on germanium (Ge) have strong tunable spin-orbit interaction (SOI) and ultrafast qubit operation speed. Here we report that the Rabi frequency (fRabi) of a hole spin qubit in a Ge hut wire (HW) double quantum dot (DQD) is electrically tuned through the detuning energy (ϵ) and middle gate voltage (VM). fRabi gradually decreases with increasing ϵ; on the contrary, fRabi is positively correlated with VM. We attribute our results to the change of electric field on SOI and the contribution of the excited state in quantum dots to fRabi. We further demonstrate an ultrafast fRabi exceeding 1.2 GHz, which indicates the strong SOI in our device. The discovery of an ultrafast and electrically tunable fRabi in a hole spin qubit has potential applications in semiconductor quantum computing.
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Affiliation(s)
- He Liu
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ke Wang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Fei Gao
- Institute of Physics and CAS Center for Excellence in Topological Quantum Computation, Chinese Academy of Sciences, Beijing 100190, China
- Qilu Institute of Technology, Jinan 250200, China
| | - Jin Leng
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yang Liu
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yu-Chen Zhou
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Gang Cao
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Ting Wang
- Institute of Physics and CAS Center for Excellence in Topological Quantum Computation, Chinese Academy of Sciences, Beijing 100190, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Jianjun Zhang
- Institute of Physics and CAS Center for Excellence in Topological Quantum Computation, Chinese Academy of Sciences, Beijing 100190, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Peihao Huang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- International Quantum Academy, Shenzhen 518048, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Hai-Ou Li
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Guo-Ping Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
- Origin Quantum Computing Company Limited, Hefei, Anhui 230026, China
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12
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Lin T, Gu SS, Xu YQ, Jiang SL, Ye SK, Wang BC, Li HO, Guo GC, Zou CL, Hu X, Cao G, Guo GP. Collective Microwave Response for Multiple Gate-Defined Double Quantum Dots. NANO LETTERS 2023; 23:4176-4182. [PMID: 37133858 DOI: 10.1021/acs.nanolett.3c00036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We fabricate and characterize a hybrid quantum device that consists of five gate-defined double quantum dots (DQDs) and a high-impedance NbTiN transmission resonator. The controllable interactions between DQDs and the resonator are spectroscopically explored by measuring the microwave transmission through the resonator in the detuning parameter space. Utilizing the high tunability of the system parameters and the high cooperativity (Ctotal > 17.6) interaction between the qubit ensemble and the resonator, we tune the charge-photon coupling and observe the collective microwave response changing from linear to nonlinear. Our results present the maximum number of DQDs coupled to a resonator and manifest a potential platform for scaling up qubits and studying collective quantum effects in semiconductor-superconductor hybrid cavity quantum electrodynamics systems.
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Affiliation(s)
- Ting Lin
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Si-Si Gu
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yong-Qiang Xu
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shun-Li Jiang
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shu-Kun Ye
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bao-Chuan Wang
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hai-Ou Li
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Guang-Can Guo
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Chang-Ling Zou
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Xuedong Hu
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260-1500, United States of America
| | - Gang Cao
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Guo-Ping Guo
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
- Origin Quantum Computing Company Limited, Hefei, Anhui 230088, China
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13
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Reducing charge noise in quantum dots by using thin silicon quantum wells. Nat Commun 2023; 14:1385. [PMID: 36914637 PMCID: PMC10011559 DOI: 10.1038/s41467-023-36951-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 02/25/2023] [Indexed: 03/16/2023] Open
Abstract
Charge noise in the host semiconductor degrades the performance of spin-qubits and poses an obstacle to control large quantum processors. However, it is challenging to engineer the heterogeneous material stack of gate-defined quantum dots to improve charge noise systematically. Here, we address the semiconductor-dielectric interface and the buried quantum well of a 28Si/SiGe heterostructure and show the connection between charge noise, measured locally in quantum dots, and global disorder in the host semiconductor, measured with macroscopic Hall bars. In 5 nm thick 28Si quantum wells, we find that improvements in the scattering properties and uniformity of the two-dimensional electron gas over a 100 mm wafer correspond to a significant reduction in charge noise, with a minimum value of 0.29 ± 0.02 μeV/Hz½ at 1 Hz averaged over several quantum dots. We extrapolate the measured charge noise to simulated dephasing times to CZ-gate fidelities that improve nearly one order of magnitude. These results point to a clean and quiet crystalline environment for integrating long-lived and high-fidelity spin qubits into a larger system.
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14
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Kranz L, Gorman SK, Thorgrimsson B, Monir S, He Y, Keith D, Charde K, Keizer JG, Rahman R, Simmons MY. The Use of Exchange Coupled Atom Qubits as Atomic-Scale Magnetic Field Sensors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2201625. [PMID: 36208088 DOI: 10.1002/adma.202201625] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 09/09/2022] [Indexed: 06/16/2023]
Abstract
Phosphorus atoms in silicon offer a rich quantum computing platform where both nuclear and electron spins can be used to store and process quantum information. While individual control of electron and nuclear spins has been demonstrated, the interplay between them during qubit operations has been largely unexplored. This study investigates the use of exchange-based operation between donor bound electron spins to probe the local magnetic fields experienced by the qubits with exquisite precision at the atomic scale. To achieve this, coherent exchange oscillations are performed between two electron spin qubits, where the left and right qubits are hosted by three and two phosphorus donors, respectively. The frequency spectrum of exchange oscillations shows quantized changes in the local magnetic fields at the qubit sites, corresponding to the different hyperfine coupling between the electron and each of the qubit-hosting nuclear spins. This ability to sense the hyperfine fields of individual nuclear spins using the exchange interaction constitutes a unique metrology technique, which reveals the exact crystallographic arrangements of the phosphorus atoms in the silicon crystal for each qubit. The detailed knowledge obtained of the local magnetic environment can then be used to engineer hyperfine fields in multi-donor qubits for high-fidelity two-qubit gates.
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Affiliation(s)
- Ludwik Kranz
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Samuel K Gorman
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Brandur Thorgrimsson
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Serajum Monir
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Yu He
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Daniel Keith
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Keshavi Charde
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Joris G Keizer
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Rajib Rahman
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
| | - Michelle Y Simmons
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales, 2052, Australia
- Silicon Quantum Computing Pty Ltd., UNSW, Sydney, 2052, Australia
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15
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SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits. Nat Commun 2022; 13:7777. [PMID: 36522370 PMCID: PMC9755230 DOI: 10.1038/s41467-022-35510-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 12/07/2022] [Indexed: 12/23/2022] Open
Abstract
Large-scale arrays of quantum-dot spin qubits in Si/SiGe quantum wells require large or tunable energy splittings of the valley states associated with degenerate conduction band minima. Existing proposals to deterministically enhance the valley splitting rely on sharp interfaces or modifications in the quantum well barriers that can be difficult to grow. Here, we propose and demonstrate a new heterostructure, the "Wiggle Well", whose key feature is Ge concentration oscillations inside the quantum well. Experimentally, we show that placing Ge in the quantum well does not significantly impact our ability to form and manipulate single-electron quantum dots. We further observe large and widely tunable valley splittings, from 54 to 239 μeV. Tight-binding calculations, and the tunability of the valley splitting, indicate that these results can mainly be attributed to random concentration fluctuations that are amplified by the presence of Ge alloy in the heterostructure, as opposed to a deterministic enhancement due to the concentration oscillations. Quantitative predictions for several other heterostructures point to the Wiggle Well as a robust method for reliably enhancing the valley splitting in future qubit devices.
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16
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Li W, Mu J, Liu ZH, Huang S, Pan D, Chen Y, Wang JY, Zhao J, Xu HQ. Charge detection of a quantum dot under different tunneling barrier symmetries and bias voltages. NANOSCALE 2022; 14:14029-14037. [PMID: 36048093 DOI: 10.1039/d2nr03459j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We report the realization of a coupled quantum dot (QD) system containing two single QDs made in two adjacent InAs nanowires. One QD (sensor QD) was used as a charge sensor to detect the charge state transitions in the other QD (target QD). We investigated the effect of the tunneling barrier asymmetry of the target QD on the detection visibility of the charge state transitions in the target QD. The charge stability diagrams of the target QD under different configurations of barrier-gate voltages were simultaneously measured via the direct signals of electron transport through the target QD and via the detection signals of the charge state transitions in the target QD revealed by the sensor QD. We find that the complete Coulomb diamond boundaries of the target QD and the transport processes involving the excited states in the target QD can be observed in the transconductance signals of the sensor QD only when the tunneling barriers of the target QD are nearly symmetric. These observations were explained by analyzing the effect of the ratio of the two tunneling rates on the electron transport processes through the target QD. Our results imply that it is important to consider the symmetry of the tunnel couplings when constructing a charge sensor integrated QD device.
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Affiliation(s)
- Weijie Li
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Jingwei Mu
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Zhi-Hai Liu
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Dong Pan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
| | - Yuanjie Chen
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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17
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Noiri A, Takeda K, Nakajima T, Kobayashi T, Sammak A, Scappucci G, Tarucha S. A shuttling-based two-qubit logic gate for linking distant silicon quantum processors. Nat Commun 2022; 13:5740. [PMID: 36180449 PMCID: PMC9525571 DOI: 10.1038/s41467-022-33453-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 09/16/2022] [Indexed: 12/04/2022] Open
Abstract
Control of entanglement between qubits at distant quantum processors using a two-qubit gate is an essential function of a scalable, modular implementation of quantum computation. Among the many qubit platforms, spin qubits in silicon quantum dots are promising for large-scale integration along with their nanofabrication capability. However, linking distant silicon quantum processors is challenging as two-qubit gates in spin qubits typically utilize short-range exchange coupling, which is only effective between nearest-neighbor quantum dots. Here we demonstrate a two-qubit gate between spin qubits via coherent spin shuttling, a key technology for linking distant silicon quantum processors. Coherent shuttling of a spin qubit enables efficient switching of the exchange coupling with an on/off ratio exceeding 1000, while preserving the spin coherence by 99.6% for the single shuttling between neighboring dots. With this shuttling-mode exchange control, we demonstrate a two-qubit controlled-phase gate with a fidelity of 93%, assessed via randomized benchmarking. Combination of our technique and a phase coherent shuttling of a qubit across a large quantum dot array will provide feasible path toward a quantum link between distant silicon quantum processors, a key requirement for large-scale quantum computation. A coherent quantum link between distant quantum processors is desirable for scaling up of quantum computation. Noiri et al. demonstrate a strategy to link distant quantum processors in silicon, by implementing a shuttling-based two-qubit gate between spin qubits in a Si/SiGe triple quantum dot.
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Affiliation(s)
- Akito Noiri
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan.
| | - Kenta Takeda
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
| | | | | | - Amir Sammak
- QuTech, Delft University of Technology, Delft, The Netherlands.,Netherlands Organization for Applied Scientific Research (TNO), Delft, The Netherlands
| | - Giordano Scappucci
- QuTech, Delft University of Technology, Delft, The Netherlands.,Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Seigo Tarucha
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan. .,RIKEN Center for Quantum Computing (RQC), Wako, Japan.
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18
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Keith D, Chung Y, Kranz L, Thorgrimsson B, Gorman SK, Simmons MY. Ramped measurement technique for robust high-fidelity spin qubit readout. SCIENCE ADVANCES 2022; 8:eabq0455. [PMID: 36070386 PMCID: PMC9451149 DOI: 10.1126/sciadv.abq0455] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 07/21/2022] [Indexed: 06/15/2023]
Abstract
State preparation and measurement of single-electron spin qubits typically rely on spin-to-charge conversion where a spin-dependent charge transition of the electron is detected by a coupled charge sensor. For high-fidelity, fast readout, this process requires that the qubit energy is much larger than the temperature of the system limiting the temperature range for measurements. Here, we demonstrate an initialization and measurement technique that involves voltage ramps rather than static voltages allowing us to achieve state-to-charge readout fidelities above 99% for qubit energies almost half that required by traditional methods. This previously unidentified measurement technique is highly relevant for achieving high-fidelity electron spin readout at higher temperature operation and offers a number of pragmatic benefits compared to traditional energy-selective readout such as real-time dynamic feedback and minimal alignment procedures.
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19
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Ryu H, Kang JH. Devitalizing noise-driven instability of entangling logic in silicon devices with bias controls. Sci Rep 2022; 12:15200. [PMID: 36071130 PMCID: PMC9452571 DOI: 10.1038/s41598-022-19404-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 08/29/2022] [Indexed: 11/20/2022] Open
Abstract
The quality of quantum bits (qubits) in silicon is highly vulnerable to charge noise that is omnipresent in semiconductor devices and is in principle hard to be suppressed. For a realistically sized quantum dot system based on a silicon-germanium heterostructure whose confinement is manipulated with electrical biases imposed on top electrodes, we computationally explore the noise-robustness of 2-qubit entangling operations with a focus on the controlled-X (CNOT) logic that is essential for designs of gate-based universal quantum logic circuits. With device simulations based on the physics of bulk semiconductors augmented with electronic structure calculations, we not only quantify the degradation in fidelity of single-step CNOT operations with respect to the strength of charge noise, but also discuss a strategy of device engineering that can significantly enhance noise-robustness of CNOT operations with almost no sacrifice of speed compared to the single-step case. Details of device designs and controls that this work presents can establish practical guideline for potential efforts to secure silicon-based quantum processors using an electrode-driven quantum dot platform.
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Affiliation(s)
- Hoon Ryu
- Korea Institute of Science and Technology Information, Daejeon, 34141, Republic of Korea.
| | - Ji-Hoon Kang
- Korea Institute of Science and Technology Information, Daejeon, 34141, Republic of Korea
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20
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Philips SGJ, Mądzik MT, Amitonov SV, de Snoo SL, Russ M, Kalhor N, Volk C, Lawrie WIL, Brousse D, Tryputen L, Wuetz BP, Sammak A, Veldhorst M, Scappucci G, Vandersypen LMK. Universal control of a six-qubit quantum processor in silicon. Nature 2022; 609:919-924. [PMID: 36171383 PMCID: PMC9519456 DOI: 10.1038/s41586-022-05117-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 07/15/2022] [Indexed: 11/25/2022]
Abstract
Future quantum computers capable of solving relevant problems will require a large number of qubits that can be operated reliably1. However, the requirements of having a large qubit count and operating with high fidelity are typically conflicting. Spins in semiconductor quantum dots show long-term promise2,3 but demonstrations so far use between one and four qubits and typically optimize the fidelity of either single- or two-qubit operations, or initialization and readout4-11. Here, we increase the number of qubits and simultaneously achieve respectable fidelities for universal operation, state preparation and measurement. We design, fabricate and operate a six-qubit processor with a focus on careful Hamiltonian engineering, on a high level of abstraction to program the quantum circuits, and on efficient background calibration, all of which are essential to achieve high fidelities on this extended system. State preparation combines initialization by measurement and real-time feedback with quantum-non-demolition measurements. These advances will enable testing of increasingly meaningful quantum protocols and constitute a major stepping stone towards large-scale quantum computers.
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Affiliation(s)
- Stephan G J Philips
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Mateusz T Mądzik
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Sergey V Amitonov
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Sander L de Snoo
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Maximilian Russ
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Nima Kalhor
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Christian Volk
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - William I L Lawrie
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Delphine Brousse
- QuTech and Netherlands Organization for Applied Scientific Research (TNO), Delft, the Netherlands
| | - Larysa Tryputen
- QuTech and Netherlands Organization for Applied Scientific Research (TNO), Delft, the Netherlands
| | - Brian Paquelet Wuetz
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Amir Sammak
- QuTech and Netherlands Organization for Applied Scientific Research (TNO), Delft, the Netherlands
| | - Menno Veldhorst
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Giordano Scappucci
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Lieven M K Vandersypen
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands.
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21
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Demonstration of a two-bit controlled-NOT quantum-like gate using classical acoustic qubit-analogues. Sci Rep 2022; 12:14066. [PMID: 35982078 PMCID: PMC9388580 DOI: 10.1038/s41598-022-18314-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 08/09/2022] [Indexed: 11/17/2022] Open
Abstract
The Controlled-NOT (CNOT) gate is the key to unlock the power of quantum computing as it is a fundamental component of a universal set of gates. We demonstrate the operation of a two-bit C-NOT quantum-like gate using classical qubit acoustic analogues, called herein logical phi-bits. The logical phi-bits are supported by an externally driven nonlinear acoustic metamaterial composed of a parallel array of three elastically coupled waveguides. A logical phi-bit has a two-state degree of freedom associated with the two independent relative phases of the acoustic wave in the three waveguides. A simple physical manipulation involving the detuning of the frequency of one of the external drivers is shown to operate on the complex vectors in the Hilbert space of pairs of logical phi-bits. This operation achieves a systematic and predictable C-NOT gate with unambiguously measurable input and output. The possibility of scaling the approach to more phi-bits is promising.
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22
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Mantsevich VN, Smirnov DS. Current-induced hole spin polarization in a quantum dot via a chiral quasi bound state. NANOSCALE HORIZONS 2022; 7:752-758. [PMID: 35593642 DOI: 10.1039/d1nh00685a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We put forward a mechanism for the current-induced spin polarization in semiconductor heterostructures, which is based on the complex structure of the valence band. It takes place for a light hole in a quantum dot side-coupled to a quantum wire with heavy holes. In stark contrast with the traditional mechanisms based on the linear in momentum spin-orbit coupling, an exponentially small bias applied to this structure is enough to create the 100% spin polarization in the quantum dot. Microscopically, this effect is related to the formation of the chiral quasi bound states and the spin-dependent tunneling of holes from the quantum wire to the quantum dot. This new concept is equally valid for the GaAs-, Si- and Ge-based nanostructures.
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Affiliation(s)
- V N Mantsevich
- Chair of Semiconductors and Cryoelectronics & Quantum Technology Center, Physics department, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - D S Smirnov
- Ioffe Institute, 194021 St. Petersburg, Russia.
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23
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Spin relaxation in a single-electron graphene quantum dot. Nat Commun 2022; 13:3637. [PMID: 35752620 PMCID: PMC9233672 DOI: 10.1038/s41467-022-31231-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 06/08/2022] [Indexed: 12/02/2022] Open
Abstract
The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T1) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 μs at a magnetic field of 1.9 T. The T1 values show a strong dependence on the spin splitting, promising even longer T1 at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits. Graphene has long been considered to be a promising host for spin qubits, however a demonstration of long spin relaxation times for a potential qubit has been lacking. Here, the authors report the electrical measurement of the single-electron spin relaxation time exceeding 200 μs in a bilayer graphene quantum dot.
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24
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Sarkar S, Dubi Y. Emergence and Dynamical Stability of a Charge Time-Crystal in a Current-Carrying Quantum Dot Simulator. NANO LETTERS 2022; 22:4445-4451. [PMID: 35580301 DOI: 10.1021/acs.nanolett.2c00976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Periodically driven open quantum systems that never thermalize exhibit a discrete time-crystal behavior, a nonequilibrium quantum phenomenon that has shown promise in quantum information processing applications. Measurements of time-crystallinity are currently limited to (magneto-) optical experiments in atom-cavity systems and spin-systems making it an indirect measurement. We theoretically show that time-crystallinity can be measured directly in the charge-current from a spin-less Hubbard ladder, which can be simulated on a quantum-dot array. We demonstrate that one can dynamically tune the system out and then back on a time-crystal phase, proving its robustness against external forcings. These findings motivate further theoretical and experimental efforts to simulate the time-crystal phenomena in current-carrying nanoscale systems.
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Affiliation(s)
- Subhajit Sarkar
- Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
- School of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Yonatan Dubi
- Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
- Ilse Katz Center for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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25
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Dodson JP, Ercan HE, Corrigan J, Losert MP, Holman N, McJunkin T, Edge LF, Friesen M, Coppersmith SN, Eriksson MA. How Valley-Orbit States in Silicon Quantum Dots Probe Quantum Well Interfaces. PHYSICAL REVIEW LETTERS 2022; 128:146802. [PMID: 35476478 DOI: 10.1103/physrevlett.128.146802] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 12/24/2021] [Accepted: 02/24/2022] [Indexed: 06/14/2023]
Abstract
The energies of valley-orbit states in silicon quantum dots are determined by an as yet poorly understood interplay between interface roughness, orbital confinement, and electron interactions. Here, we report measurements of one- and two-electron valley-orbit state energies as the dot potential is modified by changing gate voltages, and we calculate these same energies using full configuration interaction calculations. The results enable an understanding of the interplay between the physical contributions and enable a new probe of the quantum well interface.
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Affiliation(s)
- J P Dodson
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - H Ekmel Ercan
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Corrigan
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Merritt P Losert
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Nathan Holman
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Thomas McJunkin
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L F Edge
- HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, California 90265, USA
| | - Mark Friesen
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S N Coppersmith
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- University of New South Wales, Sydney, New South Wales 2052, Australia
| | - M A Eriksson
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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26
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Mills AR, Guinn CR, Gullans MJ, Sigillito AJ, Feldman MM, Nielsen E, Petta JR. Two-qubit silicon quantum processor with operation fidelity exceeding 99. SCIENCE ADVANCES 2022; 8:eabn5130. [PMID: 35385308 PMCID: PMC8986105 DOI: 10.1126/sciadv.abn5130] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/23/2022] [Indexed: 05/20/2023]
Abstract
Silicon spin qubits satisfy the necessary criteria for quantum information processing. However, a demonstration of high-fidelity state preparation and readout combined with high-fidelity single- and two-qubit gates, all of which must be present for quantum error correction, has been lacking. We use a two-qubit Si/SiGe quantum processor to demonstrate state preparation and readout with fidelity greater than 97%, combined with both single- and two-qubit control fidelities exceeding 99%. The operation of the quantum processor is quantitatively characterized using gate set tomography and randomized benchmarking. Our results highlight the potential of silicon spin qubits to become a dominant technology in the development of intermediate-scale quantum processors.
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Affiliation(s)
- Adam R. Mills
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Charles R. Guinn
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Michael J. Gullans
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
- Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, MD 20742, USA
| | | | - Mayer M. Feldman
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Erik Nielsen
- Sandia National Laboratories, Albuquerque, NM 87185, USA
| | - Jason R. Petta
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
- Corresponding author.
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27
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Connors EJ, Nelson J, Edge LF, Nichol JM. Charge-noise spectroscopy of Si/SiGe quantum dots via dynamically-decoupled exchange oscillations. Nat Commun 2022; 13:940. [PMID: 35177606 PMCID: PMC8854405 DOI: 10.1038/s41467-022-28519-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 01/26/2022] [Indexed: 11/23/2022] Open
Abstract
Electron spins in silicon quantum dots are promising qubits due to their long coherence times, scalable fabrication, and potential for all-electrical control. However, charge noise in the host semiconductor presents a major obstacle to achieving high-fidelity single- and two-qubit gates in these devices. In this work, we measure the charge-noise spectrum of a Si/SiGe singlet-triplet qubit over nearly 12 decades in frequency using a combination of methods, including dynamically-decoupled exchange oscillations with up to 512 π pulses during the qubit evolution. The charge noise is colored across the entire frequency range of our measurements, although the spectral exponent changes with frequency. Moreover, the charge-noise spectrum inferred from conductance measurements of a proximal sensor quantum dot agrees with that inferred from coherent oscillations of the singlet-triplet qubit, suggesting that simple transport measurements can accurately characterize the charge noise over a wide frequency range in Si/SiGe quantum dots.
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Affiliation(s)
- Elliot J Connors
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA
| | - J Nelson
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA
| | - Lisa F Edge
- HRL Laboratories LLC, 3011 Malibu Canyon Road, Malibu, CA, 90265, USA
| | - John M Nichol
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA.
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28
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Noiri A, Takeda K, Nakajima T, Kobayashi T, Sammak A, Scappucci G, Tarucha S. Fast universal quantum gate above the fault-tolerance threshold in silicon. Nature 2022; 601:338-342. [PMID: 35046603 DOI: 10.1038/s41586-021-04182-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 10/26/2021] [Indexed: 11/09/2022]
Abstract
Fault-tolerant quantum computers that can solve hard problems rely on quantum error correction1. One of the most promising error correction codes is the surface code2, which requires universal gate fidelities exceeding an error correction threshold of 99 per cent3. Among the many qubit platforms, only superconducting circuits4, trapped ions5 and nitrogen-vacancy centres in diamond6 have delivered this requirement. Electron spin qubits in silicon7-15 are particularly promising for a large-scale quantum computer owing to their nanofabrication capability, but the two-qubit gate fidelity has been limited to 98 per cent owing to the slow operation16. Here we demonstrate a two-qubit gate fidelity of 99.5 per cent, along with single-qubit gate fidelities of 99.8 per cent, in silicon spin qubits by fast electrical control using a micromagnet-induced gradient field and a tunable two-qubit coupling. We identify the qubit rotation speed and coupling strength where we robustly achieve high-fidelity gates. We realize Deutsch-Jozsa and Grover search algorithms with high success rates using our universal gate set. Our results demonstrate universal gate fidelity beyond the fault-tolerance threshold and may enable scalable silicon quantum computers.
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Affiliation(s)
- Akito Noiri
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan.
| | - Kenta Takeda
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
| | | | | | - Amir Sammak
- QuTech, Delft University of Technology, Delft, The Netherlands.,Netherlands Organisation for Applied Scientific Research (TNO), Delft, The Netherlands
| | - Giordano Scappucci
- QuTech, Delft University of Technology, Delft, The Netherlands.,Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Seigo Tarucha
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan. .,RIKEN Center for Quantum Computing (RQC), Wako, Japan.
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29
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Ultrafast coherent control of a hole spin qubit in a germanium quantum dot. Nat Commun 2022; 13:206. [PMID: 35017522 PMCID: PMC8752786 DOI: 10.1038/s41467-021-27880-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/16/2021] [Indexed: 11/23/2022] Open
Abstract
Operation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo’s criteria for a scalable quantum information processor. Hole-spin qubits in germanium are promising candidates for rapid, all-electrical qubit control. Here the authors report Rabi oscillations with the record frequency of 540 MHz in a hole-based double quantum dot in a germanium hut wire, which is attributed to strong spin-orbit interaction of heavy holes.
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30
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Xue X, Russ M, Samkharadze N, Undseth B, Sammak A, Scappucci G, Vandersypen LMK. Quantum logic with spin qubits crossing the surface code threshold. Nature 2022; 601:343-347. [PMID: 35046604 PMCID: PMC8770146 DOI: 10.1038/s41586-021-04273-w] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 11/22/2021] [Indexed: 11/12/2022]
Abstract
High-fidelity control of quantum bits is paramount for the reliable execution of quantum algorithms and for achieving fault tolerance-the ability to correct errors faster than they occur1. The central requirement for fault tolerance is expressed in terms of an error threshold. Whereas the actual threshold depends on many details, a common target is the approximately 1% error threshold of the well-known surface code2,3. Reaching two-qubit gate fidelities above 99% has been a long-standing major goal for semiconductor spin qubits. These qubits are promising for scaling, as they can leverage advanced semiconductor technology4. Here we report a spin-based quantum processor in silicon with single-qubit and two-qubit gate fidelities, all of which are above 99.5%, extracted from gate-set tomography. The average single-qubit gate fidelities remain above 99% when including crosstalk and idling errors on the neighbouring qubit. Using this high-fidelity gate set, we execute the demanding task of calculating molecular ground-state energies using a variational quantum eigensolver algorithm5. Having surpassed the 99% barrier for the two-qubit gate fidelity, semiconductor qubits are well positioned on the path to fault tolerance and to possible applications in the era of noisy intermediate-scale quantum devices.
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Affiliation(s)
- Xiao Xue
- QuTech, Delft University of Technology, Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Maximilian Russ
- QuTech, Delft University of Technology, Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Nodar Samkharadze
- QuTech, Delft University of Technology, Delft, The Netherlands
- Netherlands Organisation for Applied Scientific Research (TNO), Delft, The Netherlands
| | - Brennan Undseth
- QuTech, Delft University of Technology, Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Amir Sammak
- QuTech, Delft University of Technology, Delft, The Netherlands
- Netherlands Organisation for Applied Scientific Research (TNO), Delft, The Netherlands
| | - Giordano Scappucci
- QuTech, Delft University of Technology, Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Lieven M K Vandersypen
- QuTech, Delft University of Technology, Delft, The Netherlands.
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
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31
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Turner EM, Campbell Q, Pizarro J, Yang H, Sapkota KR, Lu P, Baczewski AD, Wang GT, Jones KS. Controlled Formation of Stacked Si Quantum Dots in Vertical SiGe Nanowires. NANO LETTERS 2021; 21:7905-7912. [PMID: 34582219 DOI: 10.1021/acs.nanolett.1c01670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We demonstrate the ability to fabricate vertically stacked Si quantum dots (QDs) within SiGe nanowires with QD diameters down to 2 nm. These QDs are formed during high-temperature dry oxidation of Si/SiGe heterostructure pillars, during which Ge diffuses along the pillars' sidewalls and encapsulates the Si layers. Continued oxidation results in QDs with sizes dependent on oxidation time. The formation of a Ge-rich shell that encapsulates the Si QDs is observed, a configuration which is confirmed to be thermodynamically favorable with molecular dynamics and density functional theory. The type-II band alignment of the Si dot/SiGe pillar suggests that charge trapping on the Si QDs is possible, and electron energy loss spectra show that a conduction band offset of at least 200 meV is maintained for even the smallest Si QDs. Our approach is compatible with current Si-based manufacturing processes, offering a new avenue for realizing Si QD devices.
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Affiliation(s)
- Emily M Turner
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Quinn Campbell
- Quantum Computer Science Department, Sandia National Laboratories, Albuquerque, New Mexico 87158, United States
| | - Joaquín Pizarro
- Department of Computer Engineering, University of Cádiz, Puerto Real 11519, Spain
| | - Hongbin Yang
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Keshab R Sapkota
- Advanced Materials Sciences Department, Sandia National Laboratories, Albuquerque, New Mexico 87158, United States
| | - Ping Lu
- Department of Materials Characterization and Performance, Sandia National Laboratories, Albuquerque, New Mexico 87158, United States
| | - Andrew D Baczewski
- Quantum Computer Science Department, Sandia National Laboratories, Albuquerque, New Mexico 87158, United States
| | - George T Wang
- Advanced Materials Sciences Department, Sandia National Laboratories, Albuquerque, New Mexico 87158, United States
| | - Kevin S Jones
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, United States
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32
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Tadokoro M, Nakajima T, Kobayashi T, Takeda K, Noiri A, Tomari K, Yoneda J, Tarucha S, Kodera T. Designs for a two-dimensional Si quantum dot array with spin qubit addressability. Sci Rep 2021; 11:19406. [PMID: 34593827 PMCID: PMC8484262 DOI: 10.1038/s41598-021-98212-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 09/03/2021] [Indexed: 11/16/2022] Open
Abstract
Electron spins in Si are an attractive platform for quantum computation, backed with their scalability and fast, high-fidelity quantum logic gates. Despite the importance of two-dimensional integration with efficient connectivity between qubits for medium- to large-scale quantum computation, however, a practical device design that guarantees qubit addressability is yet to be seen. Here, we propose a practical 3 × 3 quantum dot device design and a larger-scale design as a longer-term target. The design goal is to realize qubit connectivity to the four nearest neighbors while ensuring addressability. We show that a 3 × 3 quantum dot array can execute four-qubit Grover’s algorithm more efficiently than the one-dimensional counterpart. To scale up the two-dimensional array beyond 3 × 3, we propose a novel structure with ferromagnetic gate electrodes. Our results showcase the possibility of medium-sized quantum processors in Si with fast quantum logic gates and long coherence times.
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Affiliation(s)
- Masahiro Tadokoro
- Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8552, Japan.,Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama, 351-0198, Japan
| | - Takashi Nakajima
- Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama, 351-0198, Japan
| | - Takashi Kobayashi
- RIKEN Center for Quantum Computing, RIKEN, Wako-shi, Saitama, 351-0198, Japan
| | - Kenta Takeda
- Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama, 351-0198, Japan
| | - Akito Noiri
- Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama, 351-0198, Japan
| | - Kaito Tomari
- Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8552, Japan
| | - Jun Yoneda
- Tokyo Tech Academy for Super Smart Society, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8552, Japan
| | - Seigo Tarucha
- Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama, 351-0198, Japan.,RIKEN Center for Quantum Computing, RIKEN, Wako-shi, Saitama, 351-0198, Japan
| | - Tetsuo Kodera
- Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8552, Japan.
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33
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Hu RZ, Ma RL, Ni M, Zhang X, Zhou Y, Wang K, Luo G, Cao G, Kong ZZ, Wang GL, Li HO, Guo GP. An Operation Guide of Si-MOS Quantum Dots for Spin Qubits. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2486. [PMID: 34684927 PMCID: PMC8540968 DOI: 10.3390/nano11102486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/13/2021] [Accepted: 09/18/2021] [Indexed: 11/23/2022]
Abstract
In the last 20 years, silicon quantum dots have received considerable attention from academic and industrial communities for research on readout, manipulation, storage, near-neighbor and long-range coupling of spin qubits. In this paper, we introduce how to realize a single spin qubit from Si-MOS quantum dots. First, we introduce the structure of a typical Si-MOS quantum dot and the experimental setup. Then, we show the basic properties of the quantum dot, including charge stability diagram, orbital state, valley state, lever arm, electron temperature, tunneling rate and spin lifetime. After that, we introduce the two most commonly used methods for spin-to-charge conversion, i.e., Elzerman readout and Pauli spin blockade readout. Finally, we discuss the details of how to find the resonance frequency of spin qubits and show the result of coherent manipulation, i.e., Rabi oscillation. The above processes constitute an operation guide for helping the followers enter the field of spin qubits in Si-MOS quantum dots.
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Affiliation(s)
- Rui-Zi Hu
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Rong-Long Ma
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ming Ni
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xin Zhang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yuan Zhou
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ke Wang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Gang Luo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Gang Cao
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Zhen-Zhen Kong
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China;
| | - Gui-Lei Wang
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China;
| | - Hai-Ou Li
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Guo-Ping Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; (R.-Z.H.); (R.-L.M.); (M.N.); (X.Z.); (Y.Z.); (K.W.); (G.L.); (G.C.); (G.-P.G.)
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
- Origin Quantum Computing Company Limited, Hefei 230026, China
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34
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Takeda K, Noiri A, Nakajima T, Yoneda J, Kobayashi T, Tarucha S. Quantum tomography of an entangled three-qubit state in silicon. NATURE NANOTECHNOLOGY 2021; 16:965-969. [PMID: 34099899 DOI: 10.1038/s41565-021-00925-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 04/30/2021] [Indexed: 06/12/2023]
Abstract
Quantum entanglement is a fundamental property of coherent quantum states and an essential resource for quantum computing1. In large-scale quantum systems, the error accumulation requires concepts for quantum error correction. A first step toward error correction is the creation of genuinely multipartite entanglement, which has served as a performance benchmark for quantum computing platforms such as superconducting circuits2,3, trapped ions4 and nitrogen-vacancy centres in diamond5. Among the candidates for large-scale quantum computing devices, silicon-based spin qubits offer an outstanding nanofabrication capability for scaling-up. Recent studies demonstrated improved coherence times6-8, high-fidelity all-electrical control9-13, high-temperature operation14,15 and quantum entanglement of two spin qubits9,11,12. Here we generated a three-qubit Greenberger-Horne-Zeilinger state using a low-disorder, fully controllable array of three spin qubits in silicon. We performed quantum state tomography16 and obtained a state fidelity of 88.0%. The measurements witness a genuine Greenberger-Horne-Zeilinger class quantum entanglement that cannot be separated into any biseparable state. Our results showcase the potential of silicon-based spin qubit platforms for multiqubit quantum algorithms.
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Affiliation(s)
- Kenta Takeda
- Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama, Japan.
| | - Akito Noiri
- Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama, Japan
| | - Takashi Nakajima
- Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama, Japan
| | - Jun Yoneda
- Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama, Japan
- Tokyo Tech Academy for Super Smart Society, Tokyo Institute of Technology, Tokyo, Japan
| | - Takashi Kobayashi
- Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama, Japan
| | - Seigo Tarucha
- Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama, Japan.
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35
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Yoneda J, Huang W, Feng M, Yang CH, Chan KW, Tanttu T, Gilbert W, Leon RCC, Hudson FE, Itoh KM, Morello A, Bartlett SD, Laucht A, Saraiva A, Dzurak AS. Coherent spin qubit transport in silicon. Nat Commun 2021; 12:4114. [PMID: 34226564 PMCID: PMC8257656 DOI: 10.1038/s41467-021-24371-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 05/23/2021] [Indexed: 11/09/2022] Open
Abstract
A fault-tolerant quantum processor may be configured using stationary qubits interacting only with their nearest neighbours, but at the cost of significant overheads in physical qubits per logical qubit. Such overheads could be reduced by coherently transporting qubits across the chip, allowing connectivity beyond immediate neighbours. Here we demonstrate high-fidelity coherent transport of an electron spin qubit between quantum dots in isotopically-enriched silicon. We observe qubit precession in the inter-site tunnelling regime and assess the impact of qubit transport using Ramsey interferometry and quantum state tomography techniques. We report a polarization transfer fidelity of 99.97% and an average coherent transfer fidelity of 99.4%. Our results provide key elements for high-fidelity, on-chip quantum information distribution, as long envisaged, reinforcing the scaling prospects of silicon-based spin qubits.
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Affiliation(s)
- J Yoneda
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia. .,Tokyo Tech Academy for Super Smart Society, Tokyo Institute of Technology, Tokyo, Japan.
| | - W Huang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia.,Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - M Feng
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - C H Yang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - K W Chan
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - T Tanttu
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - W Gilbert
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - R C C Leon
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - F E Hudson
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - K M Itoh
- School of Fundamental Science and Technology, Keio University, Yokohama, Japan
| | - A Morello
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - S D Bartlett
- Centre for Engineered Quantum Systems, School of Physics, University of Sydney, Sydney, NSW, Australia
| | - A Laucht
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - A Saraiva
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia
| | - A S Dzurak
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW, Australia.
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36
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Zwolak JP, McJunkin T, Kalantre SS, Neyens SF, MacQuarrie ER, Eriksson MA, Taylor JM. Ray-based framework for state identification in quantum dot devices. PRX QUANTUM : A PHYSICAL REVIEW JOURNAL 2021; 2:10.1103/PRXQuantum.2.020335. [PMID: 36733712 PMCID: PMC9890618 DOI: 10.1103/prxquantum.2.020335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Quantum dots (QDs) defined with electrostatic gates are a leading platform for a scalable quantum computing implementation. However, with increasing numbers of qubits, the complexity of the control parameter space also grows. Traditional measurement techniques, relying on complete or near-complete exploration via two-parameter scans (images) of the device response, quickly become impractical with increasing numbers of gates. Here we propose to circumvent this challenge by introducing a measurement technique relying on one-dimensional projections of the device response in the multidimensional parameter space. Dubbed the "ray-based classification (RBC) framework," we use this machine learning approach to implement a classifier for QD states, enabling automated recognition of qubit-relevant parameter regimes. We show that RBC surpasses the 82% accuracy benchmark from the experimental implementation of image-based classification techniques from prior work, while reducing the number of measurement points needed by up to 70%. The reduction in measurement cost is a significant gain for time-intensive QD measurements and is a step forward toward the scalability of these devices. We also discuss how the RBC-based optimizer, which tunes the device to a multiqubit regime, performs when tuning in the two-dimensional and three-dimensional parameter spaces defined by plunger and barrier gates that control the QDs. This work provides experimental validation of both efficient state identification and optimization with machine learning techniques for non-traditional measurements in quantum systems with high-dimensional parameter spaces and time-intensive measurements.
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Affiliation(s)
- Justyna P. Zwolak
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Thomas McJunkin
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Sandesh S. Kalantre
- Joint Quantum Institute, University of Maryland, College Park, MD 20742, USA
- Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, MD 20742, USA
| | - Samuel F. Neyens
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - E. R. MacQuarrie
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Mark A. Eriksson
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jacob M. Taylor
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, MD 20742, USA
- Joint Quantum Institute, University of Maryland, College Park, MD, 20742 USA
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37
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Bell-state tomography in a silicon many-electron artificial molecule. Nat Commun 2021; 12:3228. [PMID: 34050152 PMCID: PMC8163798 DOI: 10.1038/s41467-021-23437-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 04/13/2021] [Indexed: 12/04/2022] Open
Abstract
An error-corrected quantum processor will require millions of qubits, accentuating the advantage of nanoscale devices with small footprints, such as silicon quantum dots. However, as for every device with nanoscale dimensions, disorder at the atomic level is detrimental to quantum dot uniformity. Here we investigate two spin qubits confined in a silicon double quantum dot artificial molecule. Each quantum dot has a robust shell structure and, when operated at an occupancy of 5 or 13 electrons, has single spin-\documentclass[12pt]{minimal}
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\begin{document}$$\frac{1}{2}$$\end{document}12 valence electron in its p- or d-orbital, respectively. These higher electron occupancies screen static electric fields arising from atomic-level disorder. The larger multielectron wavefunctions also enable significant overlap between neighbouring qubit electrons, while making space for an interstitial exchange-gate electrode. We implement a universal gate set using the magnetic field gradient of a micromagnet for electrically driven single qubit gates, and a gate-voltage-controlled inter-dot barrier to perform two-qubit gates by pulsed exchange coupling. We use this gate set to demonstrate a Bell state preparation between multielectron qubits with fidelity 90.3%, confirmed by two-qubit state tomography using spin parity measurements. Multielectron quantum dots offer a promising platform for high-performance spin qubits; however, previous demonstrations have been limited to single-qubit operation. Here, the authors report a universal gate set and two-qubit Bell state tomography in a high-occupancy double quantum dot in silicon.
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38
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CMOS-based cryogenic control of silicon quantum circuits. Nature 2021; 593:205-210. [PMID: 33981049 DOI: 10.1038/s41586-021-03469-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 03/18/2021] [Indexed: 11/08/2022]
Abstract
The most promising quantum algorithms require quantum processors that host millions of quantum bits when targeting practical applications1. A key challenge towards large-scale quantum computation is the interconnect complexity. In current solid-state qubit implementations, an important interconnect bottleneck appears between the quantum chip in a dilution refrigerator and the room-temperature electronics. Advanced lithography supports the fabrication of both control electronics and qubits in silicon using technology compatible with complementary metal oxide semiconductors (CMOS)2. When the electronics are designed to operate at cryogenic temperatures, they can ultimately be integrated with the qubits on the same die or package, overcoming the 'wiring bottleneck'3-6. Here we report a cryogenic CMOS control chip operating at 3 kelvin, which outputs tailored microwave bursts to drive silicon quantum bits cooled to 20 millikelvin. We first benchmark the control chip and find an electrical performance consistent with qubit operations of 99.99 per cent fidelity, assuming ideal qubits. Next, we use it to coherently control actual qubits encoded in the spin of single electrons confined in silicon quantum dots7-9 and find that the cryogenic control chip achieves the same fidelity as commercial instruments at room temperature. Furthermore, we demonstrate the capabilities of the control chip by programming a number of benchmarking protocols, as well as the Deutsch-Josza algorithm10, on a two-qubit quantum processor. These results open up the way towards a fully integrated, scalable silicon-based quantum computer.
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39
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de Leon NP, Itoh KM, Kim D, Mehta KK, Northup TE, Paik H, Palmer BS, Samarth N, Sangtawesin S, Steuerman DW. Materials challenges and opportunities for quantum computing hardware. Science 2021; 372:372/6539/eabb2823. [PMID: 33859004 DOI: 10.1126/science.abb2823] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Quantum computing hardware technologies have advanced during the past two decades, with the goal of building systems that can solve problems that are intractable on classical computers. The ability to realize large-scale systems depends on major advances in materials science, materials engineering, and new fabrication techniques. We identify key materials challenges that currently limit progress in five quantum computing hardware platforms, propose how to tackle these problems, and discuss some new areas for exploration. Addressing these materials challenges will require scientists and engineers to work together to create new, interdisciplinary approaches beyond the current boundaries of the quantum computing field.
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Affiliation(s)
- Nathalie P de Leon
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Kohei M Itoh
- School of Fundamental Science and Technology, Keio University, Yokohama 223-8522, Japan
| | - Dohun Kim
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Karan K Mehta
- Department of Physics, Institute for Quantum Electronics, ETH Zürich, 8092 Zürich, Switzerland
| | - Tracy E Northup
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - Hanhee Paik
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA.
| | - B S Palmer
- Laboratory for Physical Sciences, University of Maryland, College Park, MD 20740, USA.,Quantum Materials Center, University of Maryland, College Park, MD 20742, USA
| | - N Samarth
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Sorawis Sangtawesin
- School of Physics and Center of Excellence in Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - D W Steuerman
- Kavli Foundation, 5715 Mesmer Avenue, Los Angeles, CA 90230, USA
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40
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Radio-frequency single electron transistors in physically defined silicon quantum dots with a sensitive phase response. Sci Rep 2021; 11:5863. [PMID: 33712690 PMCID: PMC7955042 DOI: 10.1038/s41598-021-85231-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 02/26/2021] [Indexed: 12/04/2022] Open
Abstract
Radio-frequency reflectometry techniques are instrumental for spin qubit readout in semiconductor quantum dots. However, a large phase response is difficult to achieve in practice. In this work, we report radio-frequency single electron transistors using physically defined quantum dots in silicon-on-insulator. We study quantum dots which do not have the top gate structure considered to hinder radio frequency reflectometry measurements using physically defined quantum dots. Based on the model which properly takes into account the parasitic components, we precisely determine the gate-dependent device admittance. Clear Coulomb peaks are observed in the amplitude and the phase of the reflection coefficient, with a remarkably large phase signal of ∼45°. Electrical circuit analysis indicates that it can be attributed to a good impedance matching and a detuning from the resonance frequency. We anticipate that our results will be useful in designing and simulating reflectometry circuits to optimize qubit readout sensitivity and speed.
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41
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Mortemousque PA, Chanrion E, Jadot B, Flentje H, Ludwig A, Wieck AD, Urdampilleta M, Bäuerle C, Meunier T. Coherent control of individual electron spins in a two-dimensional quantum dot array. NATURE NANOTECHNOLOGY 2021; 16:296-301. [PMID: 33349684 DOI: 10.1038/s41565-020-00816-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/03/2020] [Indexed: 06/12/2023]
Abstract
The coherent manipulation of individual quantum objects organized in arrays is a prerequisite to any scalable quantum information platform. The cumulated efforts to control electron spins in quantum dot arrays have permitted the recent realization of quantum simulators and multielectron spin-coherent manipulations. Although a natural path to resolve complex quantum-matter problems and to process quantum information, two-dimensional (2D) scaling with a high connectivity of such implementations remains undemonstrated. Here we demonstrate the 2D coherent control of individual electron spins in a 3 × 3 array of tunnel-coupled quantum dots. We focus on several key quantum functionalities: charge-deterministic loading and displacement, local spin readout and local coherent exchange manipulation between two electron spins trapped in adjacent dots. This work lays some of the foundations to exploit a 2D array of electron spins for quantum simulation and information processing.
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Affiliation(s)
- Pierre-André Mortemousque
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France.
- Université Grenoble Alpes, CEA, Leti, Grenoble, France.
| | - Emmanuel Chanrion
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Baptiste Jadot
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Hanno Flentje
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Arne Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Bochum, Germany
| | - Andreas D Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Bochum, Germany
| | - Matias Urdampilleta
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Christopher Bäuerle
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Tristan Meunier
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France.
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42
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Abstract
The prospect of building quantum circuits1,2 using advanced semiconductor manufacturing makes quantum dots an attractive platform for quantum information processing3,4. Extensive studies of various materials have led to demonstrations of two-qubit logic in gallium arsenide5, silicon6-12 and germanium13. However, interconnecting larger numbers of qubits in semiconductor devices has remained a challenge. Here we demonstrate a four-qubit quantum processor based on hole spins in germanium quantum dots. Furthermore, we define the quantum dots in a two-by-two array and obtain controllable coupling along both directions. Qubit logic is implemented all-electrically and the exchange interaction can be pulsed to freely program one-qubit, two-qubit, three-qubit and four-qubit operations, resulting in a compact and highly connected circuit. We execute a quantum logic circuit that generates a four-qubit Greenberger-Horne-Zeilinger state and we obtain coherent evolution by incorporating dynamical decoupling. These results are a step towards quantum error correction and quantum simulation using quantum dots.
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43
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Froning FNM, Camenzind LC, van der Molen OAH, Li A, Bakkers EPAM, Zumbühl DM, Braakman FR. Ultrafast hole spin qubit with gate-tunable spin-orbit switch functionality. NATURE NANOTECHNOLOGY 2021; 16:308-312. [PMID: 33432204 DOI: 10.1038/s41565-020-00828-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 11/30/2020] [Indexed: 06/12/2023]
Abstract
Quantum computers promise to execute complex tasks exponentially faster than any possible classical computer, and thus spur breakthroughs in quantum chemistry, material science and machine learning. However, quantum computers require fast and selective control of large numbers of individual qubits while maintaining coherence. Qubits based on hole spins in one-dimensional germanium/silicon nanostructures are predicted to experience an exceptionally strong yet electrically tunable spin-orbit interaction, which allows us to optimize qubit performance by switching between distinct modes of ultrafast manipulation, long coherence and individual addressability. Here we used millivolt gate voltage changes to tune the Rabi frequency of a hole spin qubit in a germanium/silicon nanowire from 31 to 219 MHz, its driven coherence time between 7 and 59 ns, and its Landé g-factor from 0.83 to 1.27. We thus demonstrated spin-orbit switch functionality, with on/off ratios of roughly seven, which could be further increased through improved gate design. Finally, we used this control to optimize our qubit further and approach the strong driving regime, with spin-flipping times as short as ~1 ns.
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Affiliation(s)
| | | | - Orson A H van der Molen
- University of Basel, Basel, Switzerland
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Ang Li
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Erik P A M Bakkers
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands
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44
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Wang B, Lin T, Li H, Gu S, Chen M, Guo G, Jiang H, Hu X, Cao G, Guo G. Correlated spectrum of distant semiconductor qubits coupled by microwave photons. Sci Bull (Beijing) 2021; 66:332-338. [PMID: 36654412 DOI: 10.1016/j.scib.2020.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 09/10/2020] [Accepted: 09/30/2020] [Indexed: 01/20/2023]
Abstract
We develop a new spectroscopic method to quickly and intuitively characterize the coupling of two microwave-photon-coupled semiconductor qubits via a high-impedance resonator. Highly distinctive and unique geometric patterns are revealed as we tune the qubit tunnel couplings relative to the frequency of the mediating photons. These patterns are in excellent agreement with a simulation using the Tavis-Cummings model, and allow us to readily identify different parameter regimes for both qubits in the detuning space. This method could potentially be an important component in the overall spectroscopic toolbox for quickly characterizing certain collective properties of multiple cavity quantum electrodynamics (QED) coupled qubits.
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Affiliation(s)
- Baochuan Wang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ting Lin
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Haiou Li
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Sisi Gu
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Mingbo Chen
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Guangcan Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Hongwen Jiang
- Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Xuedong Hu
- Department of Physics, University at Buffalo, SUNY, Buffalo, NY 14260-1500, USA
| | - Gang Cao
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China.
| | - Guoping Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China; Origin Quantum Computing Company Limited, Hefei 230026, China.
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45
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Chan KW, Sahasrabudhe H, Huang W, Wang Y, Yang HC, Veldhorst M, Hwang JCC, Mohiyaddin FA, Hudson FE, Itoh KM, Saraiva A, Morello A, Laucht A, Rahman R, Dzurak AS. Exchange Coupling in a Linear Chain of Three Quantum-Dot Spin Qubits in Silicon. NANO LETTERS 2021; 21:1517-1522. [PMID: 33481612 DOI: 10.1021/acs.nanolett.0c04771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum gates between spin qubits can be implemented leveraging the natural Heisenberg exchange interaction between two electrons in contact with each other. This interaction is controllable by electrically tailoring the overlap between electronic wave functions in quantum dot systems, as long as they occupy neighboring dots. An alternative route is the exploration of superexchange-the coupling between remote spins mediated by a third idle electron that bridges the distance between quantum dots. We experimentally demonstrate direct exchange coupling and provide evidence for second neighbor mediated superexchange in a linear array of three single-electron spin qubits in silicon, inferred from the electron spin resonance frequency spectra. We confirm theoretically, through atomistic modeling, that the device geometry only allows for sizable direct exchange coupling for neighboring dots, while next-nearest neighbor coupling cannot stem from the vanishingly small tail of the electronic wave function of the remote dots, and is only possible if mediated.
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Affiliation(s)
- Kok Wai Chan
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Harshad Sahasrabudhe
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Wister Huang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Yu Wang
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Henry C Yang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Menno Veldhorst
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Jason C C Hwang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Fahd A Mohiyaddin
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Fay E Hudson
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Kohei M Itoh
- School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
| | - Andre Saraiva
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrea Morello
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Arne Laucht
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Rajib Rahman
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrew S Dzurak
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
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46
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Ma Dzik MT, Laucht A, Hudson FE, Jakob AM, Johnson BC, Jamieson DN, Itoh KM, Dzurak AS, Morello A. Conditional quantum operation of two exchange-coupled single-donor spin qubits in a MOS-compatible silicon device. Nat Commun 2021; 12:181. [PMID: 33420013 PMCID: PMC7794236 DOI: 10.1038/s41467-020-20424-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 12/02/2020] [Indexed: 11/09/2022] Open
Abstract
Silicon nanoelectronic devices can host single-qubit quantum logic operations with fidelity better than 99.9%. For the spins of an electron bound to a single-donor atom, introduced in the silicon by ion implantation, the quantum information can be stored for nearly 1 second. However, manufacturing a scalable quantum processor with this method is considered challenging, because of the exponential sensitivity of the exchange interaction that mediates the coupling between the qubits. Here we demonstrate the conditional, coherent control of an electron spin qubit in an exchange-coupled pair of 31P donors implanted in silicon. The coupling strength, J = 32.06 ± 0.06 MHz, is measured spectroscopically with high precision. Since the coupling is weaker than the electron-nuclear hyperfine coupling A ≈ 90 MHz which detunes the two electrons, a native two-qubit controlled-rotation gate can be obtained via a simple electron spin resonance pulse. This scheme is insensitive to the precise value of J, which makes it suitable for the scale-up of donor-based quantum computers in silicon that exploit the metal-oxide-semiconductor fabrication protocols commonly used in the classical electronics industry.
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Affiliation(s)
- Mateusz T Ma Dzik
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Arne Laucht
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Fay E Hudson
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Alexander M Jakob
- Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Brett C Johnson
- Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - David N Jamieson
- Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Kohei M Itoh
- School of Fundamental Science and Technology, Keio University, 3-14-1, Hiyoshi, 223-8522, Japan
| | - Andrew S Dzurak
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Andrea Morello
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW, 2052, Australia.
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47
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Qiao H, Kandel YP, Fallahi S, Gardner GC, Manfra MJ, Hu X, Nichol JM. Long-Distance Superexchange between Semiconductor Quantum-Dot Electron Spins. PHYSICAL REVIEW LETTERS 2021; 126:017701. [PMID: 33480772 DOI: 10.1103/physrevlett.126.017701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
Because of their long coherence times and potential for scalability, semiconductor quantum-dot spin qubits hold great promise for quantum information processing. However, maintaining high connectivity between quantum-dot spin qubits, which favor linear arrays with nearest neighbor coupling, presents a challenge for large-scale quantum computing. In this work, we present evidence for long-distance spin-chain-mediated superexchange coupling between electron spin qubits in semiconductor quantum dots. We weakly couple two electron spins to the ends of a two-site spin chain. Depending on the spin state of the chain, we observe oscillations between the distant end spins. We resolve the dynamics of both the end spins and the chain itself, and our measurements agree with simulations. Superexchange is a promising technique to create long-distance coupling between quantum-dot spin qubits.
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Affiliation(s)
- Haifeng Qiao
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Yadav P Kandel
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Saeed Fallahi
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Geoffrey C Gardner
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Michael J Manfra
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Xuedong Hu
- Department of Physics, University at Buffalo, Buffalo, New York 14260, USA
| | - John M Nichol
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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48
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Kang JH, Ryu J, Ryu H. Exploring the behaviors of electrode-driven Si quantum dot systems: from charge control to qubit operations. NANOSCALE 2021; 13:332-339. [PMID: 33346301 DOI: 10.1039/d0nr05070a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Charge stabilities and spin-based quantum bit (qubit) operations in Si double quantum dot (DQD) systems, whose confinement potentials are controlled with multiple gate electrodes, are theoretically studied with a multi-scale modeling approach that combines electronic structure simulations and the Thomas-Fermi method. Taking Si/SiGe heterostructures as the target of modeling, this work presents an in-depth discussion on the designs of electron reservoirs, electrostatic controls of quantum dot (QD) shapes and their corresponding charge confinements, and spin qubit manipulations. The effects of unintentional inaccuracies in DC control biases and geometric symmetries on the Rabi cycle of spin qubits are investigated to examine the robustness of logic operations. Solid connections to the latest experimental results are also established to validate the simulation method. As a rare modeling study that explores the full-stack functionality of Si DQD structures as quantum logic gate devices, this work delivers the knowledge of engineering details that are not uncovered by the latest experimental work and can serve as a basic but practical guideline for potential device designs.
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Affiliation(s)
- Ji-Hoon Kang
- Division of National Supercomputing, Korea Institute of Science and Technology Information, Daejeon 34141, Republic of Korea.
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49
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Kobayashi T, Salfi J, Chua C, van der Heijden J, House MG, Culcer D, Hutchison WD, Johnson BC, McCallum JC, Riemann H, Abrosimov NV, Becker P, Pohl HJ, Simmons MY, Rogge S. Engineering long spin coherence times of spin-orbit qubits in silicon. NATURE MATERIALS 2021; 20:38-42. [PMID: 32690913 DOI: 10.1038/s41563-020-0743-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 06/18/2020] [Indexed: 06/11/2023]
Abstract
Electron-spin qubits have long coherence times suitable for quantum technologies. Spin-orbit coupling promises to greatly improve spin qubit scalability and functionality, allowing qubit coupling via photons, phonons or mutual capacitances, and enabling the realization of engineered hybrid and topological quantum systems. However, despite much recent interest, results to date have yielded short coherence times (from 0.1 to 1 μs). Here we demonstrate ultra-long coherence times of 10 ms for holes where spin-orbit coupling yields quantized total angular momentum. We focus on holes bound to boron acceptors in bulk silicon 28, whose wavefunction symmetry can be controlled through crystal strain, allowing direct control over the longitudinal electric dipole that causes decoherence. The results rival the best electron-spin qubits and are 104 to 105 longer than previous spin-orbit qubits. These results open a pathway to develop new artificial quantum systems and to improve the functionality and scalability of spin-based quantum technologies.
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Affiliation(s)
- Takashi Kobayashi
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia.
- Department of Physics, Tohoku University, Sendai, Japan.
- CEMS, RIKEN, Wako, Japan.
| | - Joseph Salfi
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Cassandra Chua
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Joost van der Heijden
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Matthew G House
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Dimitrie Culcer
- School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia
- Australian Research Council Centre of Excellence in Low-Energy Electronics Technologies, The University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Wayne D Hutchison
- School of Science, The University of New South Wales Canberra, Canberra, Australian Capital Territory, Australia
| | - Brett C Johnson
- Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, Victoria, Australia
| | - Jeff C McCallum
- Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, Victoria, Australia
| | - Helge Riemann
- Leibniz-Institut für Kristallzüchtung, Berlin, Germany
| | | | | | | | - Michelle Y Simmons
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Sven Rogge
- Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales Sydney, Sydney, New South Wales, Australia.
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50
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Stein RM, Barcikowski ZS, Pookpanratana SJ, Pomeroy JM, Stewart MD. Alternatives to aluminum gates for silicon quantum devices: defects and strain. JOURNAL OF APPLIED PHYSICS 2021; 130:10.1063/5.0036520. [PMID: 36733463 PMCID: PMC9890375 DOI: 10.1063/5.0036520] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 02/16/2021] [Indexed: 06/13/2023]
Abstract
Gate-defined quantum dots (QD) benefit from the use of small grain size metals for gate materials because it aids in shrinking the device dimensions. However, it is not clear what differences arise with respect to process-induced defect densities and inhomogeneous strain. Here, we present measurements of fixed charge, Q f , interface trap density, D it , the intrinsic film stress, σ, and the coefficient of thermal expansion, α as a function of forming gas anneal temperature for Al, Ti/Pd, and Ti/Pt gates. We show D it is minimal at an anneal temperature of 350 °C for all materials but Ti/Pd and Ti/Pt have higher Q f and D it compared to Al. In addition, σ and α increase with anneal temperature for all three metals with α larger than the bulk value. These results indicate that there is a tradeoff between minimizing defects and minimizing the impact of strain in quantum device fabrication.
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Affiliation(s)
- Ryan M. Stein
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Z. S. Barcikowski
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - S. J. Pookpanratana
- National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - J. M. Pomeroy
- National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - M. D. Stewart
- National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
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