1
|
Jang W, Kim J, Park J, Kim G, Cho MK, Jang H, Sim S, Kang B, Jung H, Umansky V, Kim D. Wigner-molecularization-enabled dynamic nuclear polarization. Nat Commun 2023; 14:2948. [PMID: 37221217 DOI: 10.1038/s41467-023-38649-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 05/10/2023] [Indexed: 05/25/2023] Open
Abstract
Multielectron semiconductor quantum dots (QDs) provide a novel platform to study the Coulomb interaction-driven, spatially localized electron states of Wigner molecules (WMs). Although Wigner-molecularization has been confirmed by real-space imaging and coherent spectroscopy, the open system dynamics of the strongly correlated states with the environment are not yet well understood. Here, we demonstrate efficient control of spin transfer between an artificial three-electron WM and the nuclear environment in a GaAs double QD. A Landau-Zener sweep-based polarization sequence and low-lying anticrossings of spin multiplet states enabled by Wigner-molecularization are utilized. Combined with coherent control of spin states, we achieve control of magnitude, polarity, and site dependence of the nuclear field. We demonstrate that the same level of control cannot be achieved in the non-interacting regime. Thus, we confirm the spin structure of a WM, paving the way for active control of correlated electron states for application in mesoscopic environment engineering.
Collapse
Affiliation(s)
- Wonjin Jang
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Jehyun Kim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Jaemin Park
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Gyeonghun Kim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Min-Kyun Cho
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Hyeongyu Jang
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Sangwoo Sim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Byoungwoo Kang
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Hwanchul Jung
- Department of Physics, Pusan National University, Busan, 46241, Korea
| | - Vladimir Umansky
- Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Dohun Kim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.
| |
Collapse
|
2
|
Child T, Sheekey O, Lüscher S, Fallahi S, Gardner GC, Manfra M, Mitchell A, Sela E, Kleeorin Y, Meir Y, Folk J. Entropy Measurement of a Strongly Coupled Quantum Dot. PHYSICAL REVIEW LETTERS 2022; 129:227702. [PMID: 36493429 DOI: 10.1103/physrevlett.129.227702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 10/28/2022] [Indexed: 06/17/2023]
Abstract
The spin 1/2 entropy of electrons trapped in a quantum dot has previously been measured with great accuracy, but the protocol used for that measurement is valid only within a restrictive set of conditions. Here, we demonstrate a novel entropy measurement protocol that is universal for arbitrary mesoscopic circuits and apply this new approach to measure the entropy of a quantum dot hybridized with a reservoir. The experimental results match closely to numerical renormalization group (NRG) calculations for small and intermediate coupling. For the largest couplings investigated in this Letter, NRG calculations predict a suppression of spin entropy at the charge transition due to the formation of a Kondo singlet, but that suppression is not observed in the experiment.
Collapse
Affiliation(s)
- Timothy Child
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T1Z1, Canada
| | - Owen Sheekey
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T1Z1, Canada
| | - Silvia Lüscher
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T1Z1, Canada
| | - 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 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
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Andrew Mitchell
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
- Centre for Quantum Engineering, Science, and Technology, University College Dublin, Dublin 4, Ireland
| | - Eran Sela
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, IL-69978 Tel Aviv, Israel
| | - Yaakov Kleeorin
- Center for the Physics of Evolving Systems, University of Chicago, Chicago, Illinois 60637, USA
| | - Yigal Meir
- Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
- The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Joshua Folk
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T1Z1, Canada
| |
Collapse
|
3
|
Jang W, Cho MK, Jang H, Kim J, Park J, Kim G, Kang B, Jung H, Umansky V, Kim D. Single-Shot Readout of a Driven Hybrid Qubit in a GaAs Double Quantum Dot. NANO LETTERS 2021; 21:4999-5005. [PMID: 34109799 DOI: 10.1021/acs.nanolett.1c00783] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We report a single-shot-based projective readout of a semiconductor hybrid qubit formed by three electrons in a GaAs double quantum dot. Voltage-controlled adiabatic transitions between the qubit operations and readout conditions allow high-fidelity mapping of quantum states. We show that a large ratio both in relaxation time vs tunneling time (≈50) and singlet-triplet splitting vs thermal energy (≈20) allows energy-selective tunneling-based spin-to-charge conversion with a readout visibility of ≈92.6%. Combined with ac driving, we demonstrate high visibility coherent Rabi and Ramsey oscillations of a hybrid qubit in GaAs. Further, we discuss the generality of the method for use in other materials, including silicon.
Collapse
Affiliation(s)
- Wonjin Jang
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Min-Kyun Cho
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Hyeongyu Jang
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Jehyun Kim
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Jaemin Park
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Gyeonghun Kim
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Byoungwoo Kang
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Hwanchul Jung
- Department of Physics, Pusan National University, Busan 46241, Korea
| | - Vladimir Umansky
- Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Dohun Kim
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| |
Collapse
|
4
|
Cerfontaine P, Botzem T, Ritzmann J, Humpohl SS, Ludwig A, Schuh D, Bougeard D, Wieck AD, Bluhm H. Closed-loop control of a GaAs-based singlet-triplet spin qubit with 99.5% gate fidelity and low leakage. Nat Commun 2020; 11:4144. [PMID: 32811818 PMCID: PMC7434764 DOI: 10.1038/s41467-020-17865-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 07/16/2020] [Indexed: 11/17/2022] Open
Abstract
Semiconductor spin qubits have recently seen major advances in coherence time and control fidelities, leading to a single-qubit performance that is on par with other leading qubit platforms. Most of this progress is based on microwave control of single spins in devices made of isotopically purified silicon. For controlling spins, the exchange interaction is an additional key ingredient which poses new challenges for high-fidelity control. Here, we demonstrate exchange-based single-qubit gates of two-electron spin qubits in GaAs double quantum dots. Using careful pulse optimization and closed-loop tuning, we achieve a randomized benchmarking fidelity of (99.50±0.04)% and a leakage rate of 0.13% out of the computational subspace. These results open new perspectives for microwave-free control of singlet-triplet qubits in GaAs and other materials. The exchange interaction between spins poses considerable challenges for high-fidelity control of semiconductor spin qubits. Here, the authors use pulse optimization and closed-loop control to achieve a gate fidelity of 99.5% for exchange-based single-qubit gates of two-electron spin qubits in GaAs.
Collapse
Affiliation(s)
- Pascal Cerfontaine
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany.
| | - Tim Botzem
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Julian Ritzmann
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780, Bochum, Germany
| | - Simon Sebastian Humpohl
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany
| | - Arne Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780, Bochum, Germany
| | - Dieter Schuh
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040, Regensburg, Germany
| | - Dominique Bougeard
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040, Regensburg, Germany
| | - Andreas D Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780, Bochum, Germany
| | - Hendrik Bluhm
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074, Aachen, Germany.
| |
Collapse
|
5
|
Deng GW, Xu N, Li WJ. Gate-Defined Quantum Dots: Fundamentals and Applications. QUANTUM DOT OPTOELECTRONIC DEVICES 2020. [DOI: 10.1007/978-3-030-35813-6_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
6
|
Coherent spin-state transfer via Heisenberg exchange. Nature 2019; 573:553-557. [PMID: 31554982 DOI: 10.1038/s41586-019-1566-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 07/11/2019] [Indexed: 11/09/2022]
Abstract
Quantum information science has the potential to revolutionize modern technology by providing resource-efficient approaches to computing1, communication2 and sensing3. Although the physical qubits in a realistic quantum device will inevitably suffer errors, quantum error correction creates a path to fault-tolerant quantum information processing4. Quantum error correction, however, requires that individual qubits can interact with many other qubits in the processor. Engineering such high connectivity can pose a challenge for platforms such as electron spin qubits5, which naturally favour linear arrays. Here we present an experimental demonstration of the transmission of electron spin states via the Heisenberg exchange interaction in an array of spin qubits. Heisenberg exchange coupling-a direct manifestation of the Pauli exclusion principle, which prevents any two electrons with the same spin state from occupying the same orbital-tends to swap the spin states of neighbouring electrons. By precisely controlling the wavefunction overlap between electrons in a semiconductor quadruple quantum dot array, we generate a series of coherent SWAP operations to transfer both single-spin and entangled states back and forth in the array without moving any electrons. Because the process is scalable to large numbers of qubits, state transfer through Heisenberg exchange will be useful for multi-qubit gates and error correction in spin-based quantum computers.
Collapse
|
7
|
Gimeno-Segovia M, Rudolph T, Economou SE. Deterministic Generation of Large-Scale Entangled Photonic Cluster State from Interacting Solid State Emitters. PHYSICAL REVIEW LETTERS 2019; 123:070501. [PMID: 31491104 DOI: 10.1103/physrevlett.123.070501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Indexed: 06/10/2023]
Abstract
The ability to create large highly entangled "cluster" states is crucial for measurement-based quantum computing. We show that deterministic multiphoton entanglement can be created from coupled solid state quantum emitters without the need for any two-qubit gates and regardless of whether the emitters are identical. In particular, we present a general method for controlled entanglement creation by making direct use of the always-on exchange interaction, in combination with single-qubit operations. This is used to provide a recipe for the generation of two-dimensional, cluster-state entangled photons that can be carried out with existing experimental capabilities in quantum dots.
Collapse
Affiliation(s)
- Mercedes Gimeno-Segovia
- Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering, University of Bristol, BS8 1FD, United Kingdom
- Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom
| | - Terry Rudolph
- Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom
| | - Sophia E Economou
- Department of Physics, Virginia Tech, Blacksburg Virginia 24061, USA
| |
Collapse
|
8
|
Harvey-Collard P, Jacobson NT, Bureau-Oxton C, Jock RM, Srinivasa V, Mounce AM, Ward DR, Anderson JM, Manginell RP, Wendt JR, Pluym T, Lilly MP, Luhman DR, Pioro-Ladrière M, Carroll MS. Spin-orbit Interactions for Singlet-Triplet Qubits in Silicon. PHYSICAL REVIEW LETTERS 2019; 122:217702. [PMID: 31283344 DOI: 10.1103/physrevlett.122.217702] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 02/25/2019] [Indexed: 06/09/2023]
Abstract
Spin-orbit coupling is relatively weak for electrons in bulk silicon, but enhanced interactions are reported in nanostructures such as the quantum dots used for spin qubits. These interactions have been attributed to various dissimilar interface effects, including disorder or broken crystal symmetries. In this Letter, we use a double-quantum-dot qubit to probe these interactions by comparing the spins of separated singlet-triplet electron pairs. We observe both intravalley and intervalley mechanisms, each dominant for [110] and [100] magnetic field orientations, respectively, that are consistent with a broken crystal symmetry model. We also observe a third spin-flip mechanism caused by tunneling between the quantum dots. This improved understanding is important for qubit uniformity, spin control and decoherence, and two-qubit gates.
Collapse
Affiliation(s)
- Patrick Harvey-Collard
- Département de physique et Institut quantique, Université de Sherbrooke, Sherbrooke (Québec) J1K 2R1, Canada
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - N Tobias Jacobson
- Center for Computing Research, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Chloé Bureau-Oxton
- Département de physique et Institut quantique, Université de Sherbrooke, Sherbrooke (Québec) J1K 2R1, Canada
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Ryan M Jock
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Vanita Srinivasa
- Center for Computing Research, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Andrew M Mounce
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Daniel R Ward
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - John M Anderson
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | | | - Joel R Wendt
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Tammy Pluym
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Michael P Lilly
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Dwight R Luhman
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Michel Pioro-Ladrière
- Département de physique et Institut quantique, Université de Sherbrooke, Sherbrooke (Québec) J1K 2R1, Canada
- Quantum Information Science Program, Canadian Institute for Advanced Research, Toronto (Ontario) M5G 1Z8, Canada
| | | |
Collapse
|
9
|
Abstract
For spin-based quantum computation in semiconductors, dephasing of electron spins by a fluctuating background of nuclear spins is a main obstacle. Here we show that this nuclear background can be precisely controlled in generic quantum dots by periodically exciting electron spins. We demonstrate this universal phenomenon in many-electron GaAs/AlGaAs quantum dot ensembles using optical pump-probe spectroscopy. A feedback mechanism between the electron spin polarization and the nuclear system focuses the electron spin precession frequency into discrete spin modes. Employing such control of nuclear spin polarization, the electron spin lifetime within individual dots can surpass the limit of nuclear background fluctuations, thus substantially enhancing the spin coherence time. This opens the door to achieve long electron spin coherence times also in lithographically defined many-electron systems that can be controlled in shape, size and position.
Collapse
|
10
|
Gangloff DA, Éthier-Majcher G, Lang C, Denning EV, Bodey JH, Jackson DM, Clarke E, Hugues M, Le Gall C, Atatüre M. Quantum interface of an electron and a nuclear ensemble. Science 2019; 364:62-66. [DOI: 10.1126/science.aaw2906] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 02/08/2019] [Indexed: 11/02/2022]
Abstract
Coherent excitation of an ensemble of quantum objects underpins quantum many-body phenomena and offers the opportunity to realize a memory that stores quantum information. Thus far, a deterministic and coherent interface between a spin qubit and such an ensemble has remained elusive. In this study, we first used an electron to cool the mesoscopic nuclear spin ensemble of a semiconductor quantum dot to the nuclear sideband–resolved regime. We then implemented an all-optical approach to access individual quantized electronic-nuclear spin transitions. Lastly, we performed coherent optical rotations of a single collective nuclear spin excitation—a spin wave. These results constitute the building blocks of a dedicated local memory per quantum-dot spin qubit and promise a solid-state platform for quantum-state engineering of isolated many-body systems.
Collapse
|
11
|
Zhang X, Li HO, Cao G, Xiao M, Guo GC, Guo GP. Semiconductor quantum computation. Natl Sci Rev 2019; 6:32-54. [PMID: 34691830 PMCID: PMC8291422 DOI: 10.1093/nsr/nwy153] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 11/05/2018] [Accepted: 12/18/2018] [Indexed: 11/12/2022] Open
Abstract
Semiconductors, a significant type of material in the information era, are becoming more and more powerful in the field of quantum information. In recent decades, semiconductor quantum computation was investigated thoroughly across the world and developed with a dramatically fast speed. The research varied from initialization, control and readout of qubits, to the architecture of fault-tolerant quantum computing. Here, we first introduce the basic ideas for quantum computing, and then discuss the developments of single- and two-qubit gate control in semiconductors. Up to now, the qubit initialization, control and readout can be realized with relatively high fidelity and a programmable two-qubit quantum processor has even been demonstrated. However, to further improve the qubit quality and scale it up, there are still some challenges to resolve such as the improvement of the readout method, material development and scalable designs. We discuss these issues and introduce the forefronts of progress. Finally, considering the positive trend of the research on semiconductor quantum devices and recent theoretical work on the applications of quantum computation, we anticipate that semiconductor quantum computation may develop fast and will have a huge impact on our lives in the near future.
Collapse
Affiliation(s)
- Xin Zhang
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China
- Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Hai-Ou Li
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China
- Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Gang Cao
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China
- Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ming Xiao
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China
- Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Guang-Can Guo
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China
- Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Guo-Ping Guo
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China
- Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| |
Collapse
|
12
|
Zhao X, Hu X. Toward high-fidelity coherent electron spin transport in a GaAs double quantum dot. Sci Rep 2018; 8:13968. [PMID: 30228299 PMCID: PMC6143546 DOI: 10.1038/s41598-018-31879-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 08/14/2018] [Indexed: 11/18/2022] Open
Abstract
In this paper, we investigate how to achieve high-fidelity electron spin transport in a GaAs double quantum dot. Our study examines fidelity loss in spin transport from multiple perspectives. We first study incoherent fidelity loss due to hyperfine and spin-orbit interaction. We calculate fidelity loss due to the random Overhauser field from hyperfine interaction, and spin relaxation rate due to spin-orbit interaction in a wide range of experimental parameters with a focus on the occurrence of spin hot spots. A safe parameter regime is identified in order to avoid these spin hot spots. We then analyze systematic errors due to non-adiabatic transitions in the Landau-Zener process of sweeping the interdot detuning, and propose a scheme to take advantage of possible Landau-Zener-Stückelberg interference to achieve high-fidelity spin transport at a higher speed. At last, we study another systematic error caused by the correction to the electron g-factor from the double dot potential, which can lead to a notable phase error. In all, our results should provide a useful guidance for future experiments on coherent electron spin transport.
Collapse
Affiliation(s)
- Xinyu Zhao
- Department of Physics, University at Buffalo, SUNY, Buffalo, New York, 14260-1500, USA
| | - Xuedong Hu
- Department of Physics, University at Buffalo, SUNY, Buffalo, New York, 14260-1500, USA.
| |
Collapse
|
13
|
Coherent transfer of electron spin correlations assisted by dephasing noise. Nat Commun 2018; 9:2133. [PMID: 29849025 PMCID: PMC5976655 DOI: 10.1038/s41467-018-04544-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 05/03/2018] [Indexed: 12/05/2022] Open
Abstract
Quantum coherence of superposed states, especially of entangled states, is indispensable for many quantum technologies. However, it is vulnerable to environmental noises, posing a fundamental challenge in solid-state systems including spin qubits. Here we show a scheme of entanglement engineering where pure dephasing assists the generation of quantum entanglement at distant sites in a chain of electron spins confined in semiconductor quantum dots. One party of an entangled spin pair, prepared at a single site, is transferred to the next site and then adiabatically swapped with a third spin using a transition across a multi-level avoided crossing. This process is accelerated by the noise-induced dephasing through a variant of the quantum Zeno effect, without sacrificing the coherence of the entangled state. Our finding brings insight into the spin dynamics in open quantum systems coupled to noisy environments, opening an avenue to quantum state manipulation utilizing decoherence effects. Methods for coherently transferring quantum states are needed in order to develop larger scale quantum devices. Here the authors implement an adiabatic transfer protocol in a triple quantum dot and show that dephasing noise can accelerate the process while maintaining the coherence of the transferred state.
Collapse
|
14
|
Zhukov EA, Kirstein E, Kopteva NE, Heisterkamp F, Yugova IA, Korenev VL, Yakovlev DR, Pawlis A, Bayer M, Greilich A. Discretization of the total magnetic field by the nuclear spin bath in fluorine-doped ZnSe. Nat Commun 2018; 9:1941. [PMID: 29769536 PMCID: PMC5955946 DOI: 10.1038/s41467-018-04359-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 04/19/2018] [Indexed: 11/17/2022] Open
Abstract
The coherent spin dynamics of fluorine donor-bound electrons in ZnSe induced by pulsed optical excitation is studied in a perpendicular applied magnetic field. The Larmor precession frequency serves as a measure for the total magnetic field exerted onto the electron spins and, surprisingly, does not increase linearly with the applied field, but shows a step-like behavior with pronounced plateaus, given by multiples of the laser repetition rate. This discretization occurs by a feedback mechanism in which the electron spins polarize the nuclear spins, which in turn generate a local Overhauser field adjusting the total magnetic field accordingly. Varying the optical excitation power, we can control the plateaus, in agreement with our theoretical model. From this model, we trace the observed discretization to the optically induced Stark field, which causes the dynamic nuclear polarization. Understanding the electron and nuclear spin interactions is essential to the application of quantum information devices. Here the authors report a step-like electron Larmor frequency versus external magnetic field due to the discretization of the total magnetic field by the nuclear spin bath in ZnSe:F.
Collapse
Affiliation(s)
- E A Zhukov
- Experimentelle Physik 2, Technische Universität Dortmund, 44221, Dortmund, Germany
| | - E Kirstein
- Experimentelle Physik 2, Technische Universität Dortmund, 44221, Dortmund, Germany
| | - N E Kopteva
- Physical Faculty of St. Petersburg State University, 198504, St. Petersburg, Russia.,Spin Optics Laboratory, St. Petersburg State University, 198504, St. Petersburg, Russia
| | - F Heisterkamp
- Experimentelle Physik 2, Technische Universität Dortmund, 44221, Dortmund, Germany.,Federal Institute for Occupational Safety and Health (BAuA), 44149, Dortmund, Germany
| | - I A Yugova
- Physical Faculty of St. Petersburg State University, 198504, St. Petersburg, Russia
| | - V L Korenev
- Ioffe Institute, Russian Academy of Sciences, 194021, St. Petersburg, Russia
| | - D R Yakovlev
- Experimentelle Physik 2, Technische Universität Dortmund, 44221, Dortmund, Germany.,Ioffe Institute, Russian Academy of Sciences, 194021, St. Petersburg, Russia
| | - A Pawlis
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - M Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44221, Dortmund, Germany.,Ioffe Institute, Russian Academy of Sciences, 194021, St. Petersburg, Russia
| | - A Greilich
- Experimentelle Physik 2, Technische Universität Dortmund, 44221, Dortmund, Germany.
| |
Collapse
|
15
|
Éthier-Majcher G, Gangloff D, Stockill R, Clarke E, Hugues M, Le Gall C, Atatüre M. Improving a Solid-State Qubit through an Engineered Mesoscopic Environment. PHYSICAL REVIEW LETTERS 2017; 119:130503. [PMID: 29341723 DOI: 10.1103/physrevlett.119.130503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Indexed: 06/07/2023]
Abstract
A controlled quantum system can alter its environment by feedback, leading to reduced-entropy states of the environment and to improved system coherence. Here, using a quantum-dot electron spin as a control and probe, we prepare the quantum-dot nuclei under the feedback of coherent population trapping and observe their evolution from a thermal to a reduced-entropy state, with the immediate consequence of extended qubit coherence. Via Ramsey interferometry on the electron spin, we directly access the nuclear distribution following its preparation and measure the emergence and decay of correlations within the nuclear ensemble. Under optimal feedback, the inhomogeneous dephasing time of the electron, T_{2}^{*}, is extended by an order of magnitude to 39 ns. Our results can be readily exploited in quantum information protocols utilizing spin-photon entanglement and represent a step towards creating quantum many-body states in a mesoscopic nuclear-spin ensemble.
Collapse
Affiliation(s)
- G Éthier-Majcher
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - D Gangloff
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - R Stockill
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - E Clarke
- EPSRC National Centre for III-V Technologies, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - M Hugues
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Gregory, 06560 Valbonne, France
| | - C Le Gall
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - M Atatüre
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| |
Collapse
|
16
|
Szańkowski P, Ramon G, Krzywda J, Kwiatkowski D, Cywiński Ł. Environmental noise spectroscopy with qubits subjected to dynamical decoupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:333001. [PMID: 28569239 DOI: 10.1088/1361-648x/aa7648] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A qubit subjected to pure dephasing due to classical Gaussian noise can be turned into a spectrometer of this noise by utilizing its readout under properly chosen dynamical decoupling (DD) sequences to reconstruct the power spectral density of the noise. We review the theory behind this DD-based noise spectroscopy technique, paying special attention to issues that arise when the environmental noise is non-Gaussian and/or it has truly quantum properties. While we focus on the theoretical basis of the method, we connect the discussed concepts with specific experiments, and provide an overview of environmental noise models relevant for solid-state based qubits, including quantum-dot based spin qubits, superconducting qubits, and NV centers in diamond.
Collapse
Affiliation(s)
- P Szańkowski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
| | | | | | | | | |
Collapse
|
17
|
Zhang C, Throckmorton RE, Yang XC, Wang X, Barnes E, Das Sarma S. Randomized Benchmarking of Barrier versus Tilt Control of a Singlet-Triplet Qubit. PHYSICAL REVIEW LETTERS 2017; 118:216802. [PMID: 28598661 DOI: 10.1103/physrevlett.118.216802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Indexed: 06/07/2023]
Abstract
Decoherence due to charge noise is one of the central challenges in using spin qubits in semiconductor quantum dots as a platform for quantum information processing. Recently, it has been experimentally demonstrated in both Si and GaAs singlet-triplet qubits that the effects of charge noise can be suppressed if qubit operations are implemented using symmetric barrier control instead of the standard tilt control. Here, we investigate the key issue of whether the benefits of barrier control persist over the entire set of single-qubit gates by performing randomized benchmarking simulations. We find the surprising result that the improvement afforded by barrier control depends sensitively on the amount of spin noise: for the minimal nuclear spin noise levels present in Si, the coherence time improves by more than 2 orders of magnitude whereas in GaAs, by contrast the coherence time is essentially the same for barrier and tilt control. However, we establish that barrier control becomes beneficial if qubit operations are performed using a new family of composite pulses that reduce gate times by up to 90%. With these optimized pulses, barrier control is the best way to achieve high-fidelity quantum gates in singlet-triplet qubits.
Collapse
Affiliation(s)
- Chengxian Zhang
- Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen, Guangdong 518057, China
| | - Robert E Throckmorton
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Xu-Chen Yang
- Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen, Guangdong 518057, China
| | - Xin Wang
- Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen, Guangdong 518057, China
| | - Edwin Barnes
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - S Das Sarma
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| |
Collapse
|
18
|
Malinowski FK, Martins F, Cywiński Ł, Rudner MS, Nissen PD, Fallahi S, Gardner GC, Manfra MJ, Marcus CM, Kuemmeth F. Spectrum of the Nuclear Environment for GaAs Spin Qubits. PHYSICAL REVIEW LETTERS 2017; 118:177702. [PMID: 28498694 DOI: 10.1103/physrevlett.118.177702] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Indexed: 05/25/2023]
Abstract
Using a singlet-triplet spin qubit as a sensitive spectrometer of the GaAs nuclear spin bath, we demonstrate that the spectrum of Overhauser noise agrees with a classical spin diffusion model over 6 orders of magnitude in frequency, from 1 mHz to 1 kHz, is flat below 10 mHz, and falls as 1/f^{2} for frequency f≳1 Hz. Increasing the applied magnetic field from 0.1 to 0.75 T suppresses electron-mediated spin diffusion, which decreases the spectral content in the 1/f^{2} region and lowers the saturation frequency, each by an order of magnitude, consistent with a numerical model. Spectral content at megahertz frequencies is accessed using dynamical decoupling, which shows a crossover from the few-pulse regime (≲16π pulses), where transverse Overhauser fluctuations dominate dephasing, to the many-pulse regime (≳32 π pulses), where longitudinal Overhauser fluctuations with a 1/f spectrum dominate.
Collapse
Affiliation(s)
- Filip K Malinowski
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Frederico Martins
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Łukasz Cywiński
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
| | - Mark S Rudner
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Niels Bohr International Academy, Niels Bohr Institute, 2100 Copenhagen, Denmark
| | - Peter D Nissen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Saeed Fallahi
- Department of Physics and Astronomy, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Geoffrey C Gardner
- Department of Physics and Astronomy, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Michael J Manfra
- Department of Physics and Astronomy, Birck Nanotechnology Center, and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Charles M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Ferdinand Kuemmeth
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| |
Collapse
|
19
|
Wagner T, Strasberg P, Bayer JC, Rugeramigabo EP, Brandes T, Haug RJ. Strong suppression of shot noise in a feedback-controlled single-electron transistor. NATURE NANOTECHNOLOGY 2017; 12:218-222. [PMID: 27819692 DOI: 10.1038/nnano.2016.225] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 09/19/2016] [Indexed: 06/06/2023]
Abstract
Feedback control of quantum mechanical systems is rapidly attracting attention not only due to fundamental questions about quantum measurements, but also because of its novel applications in many fields in physics. Quantum control has been studied intensively in quantum optics but progress has recently been made in the control of solid-state qubits as well. In quantum transport only a few active and passive feedback experiments have been realized on the level of single electrons, although theoretical proposals exist. Here we demonstrate the suppression of shot noise in a single-electron transistor using an exclusively electronic closed-loop feedback to monitor and adjust the counting statistics. With increasing feedback response we observe a stronger suppression and faster freezing of charge current fluctuations. Our technique is analogous to the generation of squeezed light with in-loop photodetection as used in quantum optics. Sub-Poisson single-electron sources will pave the way for high-precision measurements in quantum transport similar to optical or optomechanical equivalents.
Collapse
Affiliation(s)
- Timo Wagner
- Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany
| | - Philipp Strasberg
- Institut für Theoretische Physik, Hardenbergstr. 36, TU Berlin, D-10623 Berlin, Germany
| | - Johannes C Bayer
- Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany
| | - Eddy P Rugeramigabo
- Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany
| | - Tobias Brandes
- Institut für Theoretische Physik, Hardenbergstr. 36, TU Berlin, D-10623 Berlin, Germany
| | - Rolf J Haug
- Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany
| |
Collapse
|
20
|
Mavadia S, Frey V, Sastrawan J, Dona S, Biercuk MJ. Prediction and real-time compensation of qubit decoherence via machine learning. Nat Commun 2017; 8:14106. [PMID: 28090085 PMCID: PMC5241809 DOI: 10.1038/ncomms14106] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Accepted: 11/29/2016] [Indexed: 11/18/2022] Open
Abstract
The wide-ranging adoption of quantum technologies requires practical, high-performance advances in our ability to maintain quantum coherence while facing the challenge of state collapse under measurement. Here we use techniques from control theory and machine learning to predict the future evolution of a qubit's state; we deploy this information to suppress stochastic, semiclassical decoherence, even when access to measurements is limited. First, we implement a time-division multiplexed approach, interleaving measurement periods with periods of unsupervised but stabilised operation during which qubits are available, for example, in quantum information experiments. Second, we employ predictive feedback during sequential but time delayed measurements to reduce the Dick effect as encountered in passive frequency standards. Both experiments demonstrate significant improvements in qubit-phase stability over ‘traditional' measurement-based feedback approaches by exploiting time domain correlations in the noise processes. This technique requires no additional hardware and is applicable to all two-level quantum systems where projective measurements are possible. Control engineering techniques are promising for realizing stable quantum systems to counter their extreme fragility. Here the authors use techniques from machine learning to enable real-time feedback suppression of decoherence in a trapped ion qubit by predicting its future stochastic evolution.
Collapse
Affiliation(s)
- Sandeep Mavadia
- ARC Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia.,National Measurement Institute, West Lindfield, New South Wales 2070, Australia
| | - Virginia Frey
- ARC Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia.,National Measurement Institute, West Lindfield, New South Wales 2070, Australia
| | - Jarrah Sastrawan
- ARC Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia.,National Measurement Institute, West Lindfield, New South Wales 2070, Australia
| | - Stephen Dona
- ARC Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia.,National Measurement Institute, West Lindfield, New South Wales 2070, Australia
| | - Michael J Biercuk
- ARC Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia.,National Measurement Institute, West Lindfield, New South Wales 2070, Australia
| |
Collapse
|
21
|
Yang W, Ma WL, Liu RB. Quantum many-body theory for electron spin decoherence in nanoscale nuclear spin baths. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:016001. [PMID: 27811398 DOI: 10.1088/0034-4885/80/1/016001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Decoherence of electron spins in nanoscale systems is important to quantum technologies such as quantum information processing and magnetometry. It is also an ideal model problem for studying the crossover between quantum and classical phenomena. At low temperatures or in light-element materials where the spin-orbit coupling is weak, the phonon scattering in nanostructures is less important and the fluctuations of nuclear spins become the dominant decoherence mechanism for electron spins. Since the 1950s, semi-classical noise theories have been developed for understanding electron spin decoherence. In spin-based solid-state quantum technologies, the relevant systems are in the nanometer scale and nuclear spin baths are quantum objects which require a quantum description. Recently, quantum pictures have been established to understand the decoherence and quantum many-body theories have been developed to quantitatively describe this phenomenon. Anomalous quantum effects have been predicted and some have been experimentally confirmed. A systematically truncated cluster-correlation expansion theory has been developed to account for the many-body correlations in nanoscale nuclear spin baths that are built up during electron spin decoherence. The theory has successfully predicted and explained a number of experimental results in a wide range of physical systems. In this review, we will cover this recent progress. The limitations of the present quantum many-body theories and possible directions for future development will also be discussed.
Collapse
Affiliation(s)
- Wen Yang
- Beijing Computational Science Research Center, Beijing 100193, People's Republic of China
| | | | | |
Collapse
|
22
|
Noise filtering of composite pulses for singlet-triplet qubits. Sci Rep 2016; 6:28996. [PMID: 27383129 PMCID: PMC4935950 DOI: 10.1038/srep28996] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/13/2016] [Indexed: 11/18/2022] Open
Abstract
Semiconductor quantum dot spin qubits are promising candidates for quantum computing. In these systems, the dynamically corrected gates offer considerable reduction of gate errors and are therefore of great interest both theoretically and experimentally. They are, however, designed under the static-noise model and may be considered as low-frequency filters. In this work, we perform a comprehensive theoretical study of the response of a type of dynamically corrected gates, namely the supcode for singlet-triplet qubits, to realistic 1/f noises with frequency spectra 1/ωα. Through randomized benchmarking, we have found that supcode offers improvement of the gate fidelity for α 1 and the improvement becomes exponentially more pronounced with the increase of the noise exponent in the range 1 α ≤ 3 studied. On the other hand, for small α, supcode will not offer any improvement. The δJ-supcode, specifically designed for systems where the nuclear noise is absent, is found to offer additional error reduction than the full supcode for charge noises. The computed filter transfer functions of the supcode gates are also presented.
Collapse
|
23
|
Salfi J, Tong M, Rogge S, Culcer D. Quantum computing with acceptor spins in silicon. NANOTECHNOLOGY 2016; 27:244001. [PMID: 27171901 DOI: 10.1088/0957-4484/27/24/244001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time [Formula: see text] as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.
Collapse
Affiliation(s)
- Joe Salfi
- School of Physics, The University of New South Wales, Sydney 2052, Australia
| | | | | | | |
Collapse
|
24
|
Abstract
Feedback loops are known as a versatile tool for controlling transport in small systems, which usually have large intrinsic fluctuations. Here we investigate the control of a temporal correlation function, the waiting-time distribution, under active and passive feedback conditions. We develop a general formalism and then specify to the simple unidirectional transport model, where we compare costs of open-loop and feedback control and use methods from optimal control theory to optimize waiting-time distributions.
Collapse
Affiliation(s)
- Tobias Brandes
- Institut für Theoretische Physik, Hardenbergstr. 36, TU Berlin, D-10623 Berlin, Germany
| | - Clive Emary
- Joint Quantum Centre Durham-Newcastle, School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
| |
Collapse
|
25
|
Martins F, Malinowski FK, Nissen PD, Barnes E, Fallahi S, Gardner GC, Manfra MJ, Marcus CM, Kuemmeth F. Noise Suppression Using Symmetric Exchange Gates in Spin Qubits. PHYSICAL REVIEW LETTERS 2016; 116:116801. [PMID: 27035316 DOI: 10.1103/physrevlett.116.116801] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Indexed: 06/05/2023]
Abstract
We demonstrate a substantial improvement in the spin-exchange gate using symmetric control instead of conventional detuning in GaAs spin qubits, up to a factor of six increase in the quality factor of the gate. For symmetric operation, nanosecond voltage pulses are applied to the barrier that controls the interdot potential between quantum dots, modulating the exchange interaction while maintaining symmetry between the dots. Excellent agreement is found with a model that separately includes electrical and nuclear noise sources for both detuning and symmetric gating schemes. Unlike exchange control via detuning, the decoherence of symmetric exchange rotations is dominated by rotation-axis fluctuations due to nuclear field noise rather than direct exchange noise.
Collapse
Affiliation(s)
- Frederico Martins
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Filip K Malinowski
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Peter D Nissen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Edwin Barnes
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - Saeed Fallahi
- Department of Physics and Astronomy and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Geoffrey C Gardner
- School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Michael J Manfra
- Department of Physics and Astronomy and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Charles M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Ferdinand Kuemmeth
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| |
Collapse
|
26
|
Kondo Y, Amaha S, Ono K, Kono K, Tarucha S. Critical Behavior of Alternately Pumped Nuclear Spins in Quantum Dots. PHYSICAL REVIEW LETTERS 2015; 115:186803. [PMID: 26565487 DOI: 10.1103/physrevlett.115.186803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Indexed: 06/05/2023]
Abstract
Nuclear spins in a spin-blocked quantum dot can be pumped and eventually polarized in either of two opposite directions that are selected by applying two different source-drain voltages. Applying a square pulse train as the source-drain voltage can continuously switch the pumping direction alternately. We propose and demonstrate a critical behavior in the polarization after alternate pumping, where the final polarization is sensitive to the initial polarization and pulse conditions. This sensitivity leads to stochastic behavior in the final polarization under nominally the same pumping conditions.
Collapse
Affiliation(s)
- Y Kondo
- Center of Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - S Amaha
- Center of Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - K Ono
- Center of Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Low Temperature Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - K Kono
- Center of Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Low Temperature Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - S Tarucha
- Center of Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| |
Collapse
|
27
|
Imanaka D, Sharmin S, Hashisaka M, Muraki K, Fujisawa T. Exchange-Induced Spin Blockade in a Two-Electron Double Quantum Dot. PHYSICAL REVIEW LETTERS 2015; 115:176802. [PMID: 26551135 DOI: 10.1103/physrevlett.115.176802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Indexed: 06/05/2023]
Abstract
We have experimentally identified the exchange-induced spin blockade in a GaAs double quantum dot. The transport is suppressed only when the eigenstates are well-defined singlet and triplet states, and thus sensitive to dynamic nuclear-spin polarization that causes singlet-triplet mixing. This gives rise to unusual current spectra, such as a sharp current dip and an asymmetric current profile near the triplet resonance of a double quantum dot. Numerical simulations suggest that the current dip is a signature of identical nuclear-spin polarization in the two dots, which is attractive for coherent spin manipulations in a material with nuclear spins.
Collapse
Affiliation(s)
- D Imanaka
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro 152-8551, Japan
| | - S Sharmin
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro 152-8551, Japan
| | - M Hashisaka
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro 152-8551, Japan
| | - K Muraki
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi 243-0198, Japan
| | - T Fujisawa
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro 152-8551, Japan
| |
Collapse
|
28
|
Nichol JM, Harvey SP, Shulman MD, Pal A, Umansky V, Rashba EI, Halperin BI, Yacoby A. Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots. Nat Commun 2015; 6:7682. [PMID: 26184854 PMCID: PMC4518271 DOI: 10.1038/ncomms8682] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 06/01/2015] [Indexed: 11/29/2022] Open
Abstract
The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin–orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron–nuclear system, despite weak spin–orbit coupling in GaAs. Using Landau–Zener sweeps to measure static and dynamic properties of the electron spin–flip probability, we observe that the size of the spin–orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin–orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin–orbit coupling in central-spin systems. Dynamic nuclear polarization is the transfer of electronic angular momentum to nuclear spins and is a potential route for coherently manipulating spin in quantum information. Here, the authors show that spin–orbit coupling can quench dynamic nuclear polarization in a gallium arsenide quantum dot.
Collapse
Affiliation(s)
- John M Nichol
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Shannon P Harvey
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Michael D Shulman
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Arijeet Pal
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Vladimir Umansky
- Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Emmanuel I Rashba
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Bertrand I Halperin
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Amir Yacoby
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| |
Collapse
|
29
|
Buddhiraju S, Muralidharan B. Role of dual nuclear baths on spin blockade leakage current bistabilities. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:485302. [PMID: 25374371 DOI: 10.1088/0953-8984/26/48/485302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Spin-blockaded electronic transport across a double quantum dot (DQD) system represents an important advancement in the area of spin-based quantum information. The basic mechanism underlying the blockade is the formation of a blocking triplet state. The bistability of the leakage current as a function of the applied magnetic field in this regime is believed to arise from the effect of nuclear Overhauser fields on spin-flip transitions between the blocking triplet and the conducting singlet states. The objective of this paper is to present the nuances of considering a two bath model on the experimentally observed current bistability by employing a self consistent simulation of the nuclear spin dynamics coupled with the electronic transport of the DQD set up. In doing so, we first discuss the important subtleties involved in the microscopic derivation of the hyperfine mediated spin flip rates. We then give insights as to how the differences between the two nuclear baths and the resulting difference Overhauser field affect the two-electron states of the DQD and their connection with the experimentally observed current hysteresis curve.
Collapse
Affiliation(s)
- Siddharth Buddhiraju
- Department of Electrical Engineering, Center of Excellence in Nanoelectronics, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India
| | | |
Collapse
|
30
|
Veldhorst M, Hwang JCC, Yang CH, Leenstra AW, de Ronde B, Dehollain JP, Muhonen JT, Hudson FE, Itoh KM, Morello A, Dzurak AS. An addressable quantum dot qubit with fault-tolerant control-fidelity. NATURE NANOTECHNOLOGY 2014; 9:981-985. [PMID: 25305743 DOI: 10.1038/nnano.2014.216] [Citation(s) in RCA: 202] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 08/28/2014] [Indexed: 06/04/2023]
Abstract
Exciting progress towards spin-based quantum computing has recently been made with qubits realized using nitrogen-vacancy centres in diamond and phosphorus atoms in silicon. For example, long coherence times were made possible by the presence of spin-free isotopes of carbon and silicon. However, despite promising single-atom nanotechnologies, there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered, but strong coupling to noise has severely limited their dephasing times and control fidelities. Here, we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford-based randomized benchmarking and consistent with that required for fault-tolerant quantum computing. This qubit has dephasing time T2* = 120 μs and coherence time T2 = 28 ms, both orders of magnitude larger than in other types of semiconductor qubit. By gate-voltage-tuning the electron g*-factor we can Stark shift the electron spin resonance frequency by more than 3,000 times the 2.4 kHz electron spin resonance linewidth, providing a direct route to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies.
Collapse
Affiliation(s)
- M Veldhorst
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - J C C Hwang
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - C H Yang
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - A W Leenstra
- University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - B de Ronde
- University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - J P Dehollain
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - J T Muhonen
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - F E Hudson
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - K M Itoh
- School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - A Morello
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - A S Dzurak
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| |
Collapse
|
31
|
Cerfontaine P, Botzem T, DiVincenzo DP, Bluhm H. High-fidelity single-qubit gates for two-electron spin qubits in GaAs. PHYSICAL REVIEW LETTERS 2014; 113:150501. [PMID: 25375696 DOI: 10.1103/physrevlett.113.150501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Indexed: 06/04/2023]
Abstract
Single-qubit operations on singlet-triplet qubits in GaAs double quantum dots have not yet reached the fidelities required for fault-tolerant quantum information processing. Considering experimentally important constraints and using measured noise spectra, we numerically minimize the effect of decoherence (including high-frequency 1/f-like noise) and show, theoretically, that quantum gates with fidelities higher than 99.9% are achievable. We also present a self-consistent tuning protocol which should allow the elimination of individual systematic gate errors directly in an experiment.
Collapse
Affiliation(s)
- Pascal Cerfontaine
- JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany
| | - Tim Botzem
- JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany
| | - David P DiVincenzo
- JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany and Peter Grünberg Institute: Theoretical Nanoelectronics, Research Center Jülich, D-52425 Jülich, Germany
| | - Hendrik Bluhm
- JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany
| |
Collapse
|
32
|
Suppressing qubit dephasing using real-time Hamiltonian estimation. Nat Commun 2014; 5:5156. [PMID: 25295674 PMCID: PMC4214408 DOI: 10.1038/ncomms6156] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 09/04/2014] [Indexed: 12/17/2022] Open
Abstract
Unwanted interaction between a quantum system and its fluctuating environment leads to decoherence and is the primary obstacle to establishing a scalable quantum information processing architecture. Strategies such as environmental and materials engineering, quantum error correction and dynamical decoupling can mitigate decoherence, but generally increase experimental complexity. Here we improve coherence in a qubit using real-time Hamiltonian parameter estimation. Using a rapidly converging Bayesian approach, we precisely measure the splitting in a singlet-triplet spin qubit faster than the surrounding nuclear bath fluctuates. We continuously adjust qubit control parameters based on this information, thereby improving the inhomogenously broadened coherence time (T2*) from tens of nanoseconds to >2 μs. Because the technique demonstrated here is compatible with arbitrary qubit operations, it is a natural complement to quantum error correction and can be used to improve the performance of a wide variety of qubits in both meteorological and quantum information processing applications.
Collapse
|
33
|
Dréau A, Jamonneau P, Gazzano O, Kosen S, Roch JF, Maze JR, Jacques V. Probing the dynamics of a nuclear spin bath in diamond through time-resolved central spin magnetometry. PHYSICAL REVIEW LETTERS 2014; 113:137601. [PMID: 25302916 DOI: 10.1103/physrevlett.113.137601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Indexed: 06/04/2023]
Abstract
Using fast electron spin resonance spectroscopy of a single nitrogen-vacancy defect in diamond, we demonstrate real-time readout of the Overhauser field produced by its nuclear spin environment under ambient conditions. These measurements enable narrowing the Overhauser field distribution by postselection, corresponding to a conditional preparation of the nuclear spin bath. Correlations of the Overhauser field fluctuations are quantitatively inferred by analyzing the Allan deviation over consecutive measurements. This method allows us to extract the dynamics of weakly coupled nuclear spins of the reservoir.
Collapse
Affiliation(s)
- A Dréau
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and Ecole Normale Supérieure de Cachan, 91405 Orsay, France
| | - P Jamonneau
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and Ecole Normale Supérieure de Cachan, 91405 Orsay, France
| | - O Gazzano
- Universität des Saarlandes, Fachrichtung 7.2 (Experimentalphysik), Campus E2.6, 66123 Saarbrücken, Germany
| | - S Kosen
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and Ecole Normale Supérieure de Cachan, 91405 Orsay, France
| | - J-F Roch
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and Ecole Normale Supérieure de Cachan, 91405 Orsay, France
| | - J R Maze
- Facultad de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| | - V Jacques
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud and Ecole Normale Supérieure de Cachan, 91405 Orsay, France
| |
Collapse
|
34
|
Kawakami E, Scarlino P, Ward DR, Braakman FR, Savage DE, Lagally MG, Friesen M, Coppersmith SN, Eriksson MA, Vandersypen LMK. Electrical control of a long-lived spin qubit in a Si/SiGe quantum dot. NATURE NANOTECHNOLOGY 2014; 9:666-670. [PMID: 25108810 DOI: 10.1038/nnano.2014.153] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 06/27/2014] [Indexed: 06/03/2023]
Abstract
Nanofabricated quantum bits permit large-scale integration but usually suffer from short coherence times due to interactions with their solid-state environment. The outstanding challenge is to engineer the environment so that it minimally affects the qubit, but still allows qubit control and scalability. Here, we demonstrate a long-lived single-electron spin qubit in a Si/SiGe quantum dot with all-electrical two-axis control. The spin is driven by resonant microwave electric fields in a transverse magnetic field gradient from a local micromagnet, and the spin state is read out in the single-shot mode. Electron spin resonance occurs at two closely spaced frequencies, which we attribute to two valley states. Thanks to the weak hyperfine coupling in silicon, a Ramsey decay timescale of 1 μs is observed, almost two orders of magnitude longer than the intrinsic timescales in GaAs quantum dots, whereas gate operation times are comparable to those reported in GaAs. The spin echo decay time is ~40 μs, both with one and four echo pulses, possibly limited by intervalley scattering. These advances strongly improve the prospects for quantum information processing based on quantum dots.
Collapse
Affiliation(s)
- E Kawakami
- 1] Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, The Netherlands [2]
| | - P Scarlino
- 1] Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, The Netherlands [2]
| | - D R Ward
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - F R Braakman
- 1] Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, The Netherlands [2]
| | - D E Savage
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M G Lagally
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Mark Friesen
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S N Coppersmith
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M A Eriksson
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L M K Vandersypen
- Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| |
Collapse
|
35
|
Higginbotham AP, Larsen TW, Yao J, Yan H, Lieber CM, Marcus CM, Kuemmeth F. Hole spin coherence in a Ge/Si heterostructure nanowire. NANO LETTERS 2014; 14:3582-6. [PMID: 24797219 DOI: 10.1021/nl501242b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Relaxation and dephasing of hole spins are measured in a gate-defined Ge/Si nanowire double quantum dot using a fast pulsed-gate method and dispersive readout. An inhomogeneous dephasing time T2* 0.18 μs exceeds corresponding measurements in III–V semiconductors by more than an order of magnitude, as expected for predominately nuclear-spin-free materials. Dephasing is observed to be exponential in time, indicating the presence of a broadband noise source, rather than Gaussian, previously seen in systems with nuclear-spin-dominated dephasing.
Collapse
Affiliation(s)
- A P Higginbotham
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen , 2100 Copenhagen, Denmark
| | | | | | | | | | | | | |
Collapse
|
36
|
Schuetz MJA, Kessler EM, Vandersypen LMK, Cirac JI, Giedke G. Steady-state entanglement in the nuclear spin dynamics of a double quantum dot. PHYSICAL REVIEW LETTERS 2013; 111:246802. [PMID: 24483686 DOI: 10.1103/physrevlett.111.246802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Indexed: 06/03/2023]
Abstract
We propose a scheme for the deterministic generation of steady-state entanglement between the two nuclear spin ensembles in an electrically defined double quantum dot. Because of quantum interference in the collective coupling to the electronic degrees of freedom, the nuclear system is actively driven into a two-mode squeezedlike target state. The entanglement buildup is accompanied by a self-polarization of the nuclear spins towards large Overhauser field gradients. Moreover, the feedback between the electronic and nuclear dynamics leads to multistability and criticality in the steady-state solutions.
Collapse
Affiliation(s)
- M J A Schuetz
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
| | - E M Kessler
- Physics Department, Harvard University, Cambridge, Massachusetts 02318, USA and ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
| | - L M K Vandersypen
- Kavli Institute of NanoScience, TU Delft, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - J I Cirac
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
| | - G Giedke
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
| |
Collapse
|
37
|
Abstract
Several logical qubits and quantum gates have been proposed for semiconductor quantum dots controlled by voltages applied to top gates. The different schemes can be difficult to compare meaningfully. Here we develop a theoretical framework to evaluate disparate qubit-gating schemes on an equal footing. We apply the procedure to two types of double-dot qubits: the singlet-triplet and the semiconducting quantum dot hybrid qubit. We investigate three quantum gates that flip the qubit state: a DC pulsed gate, an AC gate based on logical qubit resonance, and a gate-like process known as stimulated Raman adiabatic passage. These gates are all mediated by an exchange interaction that is controlled experimentally using the interdot tunnel coupling g and the detuning [Symbol: see text], which sets the energy difference between the dots. Our procedure has two steps. First, we optimize the gate fidelity (f) for fixed g as a function of the other control parameters; this yields an f(opt)(g) that is universal for different types of gates. Next, we identify physical constraints on the control parameters; this yields an upper bound f(max) that is specific to the qubit-gate combination. We show that similar gate fidelities (~99:5%) should be attainable for singlet-triplet qubits in isotopically purified Si, and for hybrid qubits in natural Si. Considerably lower fidelities are obtained for GaAs devices, due to the fluctuating magnetic fields ΔB produced by nuclear spins.
Collapse
|
38
|
Ribeiro H, Burkard G. Nuclear spins keep coming back. NATURE MATERIALS 2013; 12:469-471. [PMID: 23695732 DOI: 10.1038/nmat3671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Affiliation(s)
- Hugo Ribeiro
- Department of Physics, University of Basel, Basel, Switzerland.
| | | |
Collapse
|
39
|
Warburton RJ. Single spins in self-assembled quantum dots. NATURE MATERIALS 2013; 12:483-93. [PMID: 23695745 DOI: 10.1038/nmat3585] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 01/29/2013] [Indexed: 05/22/2023]
Abstract
Self-assembled quantum dots have excellent photonic properties. For instance, a single quantum dot is a high-brightness, narrow-linewidth source of single photons. Furthermore, the environment of a single quantum dot can be tailored relatively easily using semiconductor heterostructure and post-growth processing techniques, enabling electrical control of the quantum dot charge and control over the photonic modes with which the quantum dot interacts. A single electron or hole trapped inside a quantum dot has spintronics applications. Although the spin dephasing is rather rapid, a single spin can be manipulated using optical techniques on subnanosecond timescales. Optical experiments are also providing new insights into old issues, such as the central spin problem. This Review provides a snapshot of this active field, with some indications for the future. It covers the basic materials and optical properties of single quantum dots, techniques for initializing, manipulating and reading out single spin qubits, and the mechanisms that limit the electron-spin and hole-spin coherence.
Collapse
|
40
|
Chekhovich EA, Makhonin MN, Tartakovskii AI, Yacoby A, Bluhm H, Nowack KC, Vandersypen LMK. Nuclear spin effects in semiconductor quantum dots. NATURE MATERIALS 2013; 12:494-504. [PMID: 23695746 DOI: 10.1038/nmat3652] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 04/12/2013] [Indexed: 06/02/2023]
Abstract
The interaction of an electronic spin with its nuclear environment, an issue known as the central spin problem, has been the subject of considerable attention due to its relevance for spin-based quantum computation using semiconductor quantum dots. Independent control of the nuclear spin bath using nuclear magnetic resonance techniques and dynamic nuclear polarization using the central spin itself offer unique possibilities for manipulating the nuclear bath with significant consequences for the coherence and controlled manipulation of the central spin. Here we review some of the recent optical and transport experiments that have explored this central spin problem using semiconductor quantum dots. We focus on the interaction between 10(4)-10(6) nuclear spins and a spin of a single electron or valence-band hole. We also review the experimental techniques as well as the key theoretical ideas and the implications for quantum information science.
Collapse
Affiliation(s)
- E A Chekhovich
- Department of Physics and Astronomy, University of Sheffield, Sheffield, UK
| | | | | | | | | | | | | |
Collapse
|
41
|
Petersen G, Hoffmann EA, Schuh D, Wegscheider W, Giedke G, Ludwig S. Large nuclear spin polarization in gate-defined quantum dots using a single-domain nanomagnet. PHYSICAL REVIEW LETTERS 2013; 110:177602. [PMID: 23679779 DOI: 10.1103/physrevlett.110.177602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 03/13/2013] [Indexed: 06/02/2023]
Abstract
The electron-nuclei (hyperfine) interaction is central to spin qubits in solid state systems. It can be a severe decoherence source but also allows dynamic access to the nuclear spin states. We study a double quantum dot exposed to an on-chip single-domain nanomagnet and show that its inhomogeneous magnetic field crucially modifies the complex nuclear spin dynamics such that the Overhauser field tends to compensate external magnetic fields. This turns out to be beneficial for polarizing the nuclear spin ensemble. We reach a nuclear spin polarization of ≃50%, unrivaled in lateral dots, and explain our manipulation technique using a comprehensive rate equation model.
Collapse
Affiliation(s)
- Gunnar Petersen
- Center for Nanoscience and Fakultät für Physik, Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 München, Germany
| | | | | | | | | | | |
Collapse
|
42
|
Dial OE, Shulman MD, Harvey SP, Bluhm H, Umansky V, Yacoby A. Charge noise spectroscopy using coherent exchange oscillations in a singlet-triplet qubit. PHYSICAL REVIEW LETTERS 2013; 110:146804. [PMID: 25167023 DOI: 10.1103/physrevlett.110.146804] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Indexed: 06/03/2023]
Abstract
Two level systems that can be reliably controlled and measured hold promise as qubits both for metrology and for quantum information science. Since a fluctuating environment limits the performance of qubits in both capacities, understanding environmental coupling and dynamics is key to improving qubit performance. We show measurements of the level splitting and dephasing due to the voltage noise of a GaAs singlet-triplet qubit during exchange oscillations. Unexpectedly, the voltage fluctuations are non-Markovian even at high frequencies and exhibit a strong temperature dependence. This finding has impacts beyond singlet-triplet qubits since nearly all solid state qubits suffer from some kind of charge noise. The magnitude of the fluctuations allows the qubit to be used as a charge sensor with a sensitivity of 2 × 10(-8)e/sqrt[Hz], 2 orders of magnitude better than a quantum-limited rf single electron transistor. Based on these measurements, we provide recommendations for improving qubit coherence, allowing for higher fidelity operations and improved charge sensitivity.
Collapse
Affiliation(s)
- O E Dial
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - M D Shulman
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - S P Harvey
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - H Bluhm
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - V Umansky
- Department of Condensed Matter Physics, Braun Center for Submicron Research, Weizmann Institute of Science, Rehovot 76100, Israel
| | - A Yacoby
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| |
Collapse
|
43
|
Kestner JP, Wang X, Bishop LS, Barnes E, Das Sarma S. Noise-resistant control for a spin qubit array. PHYSICAL REVIEW LETTERS 2013; 110:140502. [PMID: 25166970 DOI: 10.1103/physrevlett.110.140502] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Indexed: 06/03/2023]
Abstract
We develop a systematic method of performing corrected gate operations on an array of exchange-coupled singlet-triplet qubits in the presence of both fluctuating nuclear Overhauser field gradients and charge noise. The single-qubit control sequences we present have a simple form, are relatively short, and form the building blocks of a corrected cnot gate when also implemented on the interqubit exchange link. This is a key step towards enabling large-scale quantum computation in a semiconductor-based architecture by facilitating error reduction below the quantum error correction threshold for both single-qubit and multiqubit gate operations.
Collapse
Affiliation(s)
- J P Kestner
- Department of Physics, University of Maryland Baltimore County, Baltimore, Maryland 21250, USA and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Xin Wang
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Lev S Bishop
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
| | - Edwin Barnes
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - S Das Sarma
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
| |
Collapse
|
44
|
van Heck B, Burrello M, Yacoby A, Akhmerov AR. Topological blockade and measurement of topological charge. PHYSICAL REVIEW LETTERS 2013; 110:086803. [PMID: 23473185 DOI: 10.1103/physrevlett.110.086803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Indexed: 06/01/2023]
Abstract
The fractionally charged quasiparticles appearing in the 5/2 fractional quantum Hall plateau are predicted to have an extra nonlocal degree of freedom, known as topological charge. We show how this topological charge can block the tunneling of these particles, and how such topological blockade can be used to read out their topological charge. We argue that the short time scale required for this measurement is favorable for the detection of the non-Abelian anyonic statistics of the quasiparticles. We also show how topological blockade can be used to measure braiding statistics, and to couple a topological qubit with a conventional one.
Collapse
Affiliation(s)
- B van Heck
- Instituut-Lorentz, Universiteit Leiden, PO Box 9506, 2300 RA Leiden, The Netherlands
| | | | | | | |
Collapse
|
45
|
Fink T, Bluhm H. Noise spectroscopy using correlations of single-shot qubit readout. PHYSICAL REVIEW LETTERS 2013; 110:010403. [PMID: 23383763 DOI: 10.1103/physrevlett.110.010403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Indexed: 06/01/2023]
Abstract
A better understanding of the noise causing qubit decoherence is crucial for improving qubit performance. The noise spectrum affecting the qubit may be extracted by measuring dephasing under the application of pulse sequences but requires accurate qubit control and sufficiently long relaxation times, which are not always available. Here, we describe an alternative method to extract the spectrum from correlations of single-shot measurement outcomes of successive free induction decays. This method only requires qubit initialization and readout with a moderate fidelity and also allows independent tuning of both the overall sensitivity and the frequency region over which it is sensitive. Thus, it is possible to maintain a good detection contrast over a very wide frequency range. We discuss using our method for measuring both 1/f noise and the fluctuation spectrum of the nuclear bath of GaAs spin qubits.
Collapse
Affiliation(s)
- T Fink
- 2nd Institute of Physics C, RWTH Aachen University, D-52074 Aachen, Germany and JARA-Fundamentals of Future Information Technology, D-52425 Jülich, Germany
| | | |
Collapse
|
46
|
Brataas A, Rashba EI. Dynamical self-quenching of spin pumping into double quantum dots. PHYSICAL REVIEW LETTERS 2012; 109:236803. [PMID: 23368239 DOI: 10.1103/physrevlett.109.236803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Indexed: 06/01/2023]
Abstract
Nuclear spin polarization can be pumped into spin-blockaded quantum dots by multiple Landau-Zener passages through singlet-triplet anticrossings. By numerical simulations of realistic systems with 10(7) nuclear spins during 10(5) sweeps, we uncover a mechanism of dynamical self-quenching which results in a fast saturation of the nuclear polarization under stationary pumping. This is caused by screening the random field of the nuclear spins. For moderate spin-orbit coupling, self-quenching persists but its patterns are modified. Our finding explains low polarization levels achieved experimentally and calls for developing new protocols that break the self-quenching limitations.
Collapse
Affiliation(s)
- Arne Brataas
- Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | | |
Collapse
|
47
|
Frolov SM, Danon J, Nadj-Perge S, Zuo K, van Tilburg JWW, Pribiag VS, van den Berg JWG, Bakkers EPAM, Kouwenhoven LP. Suppression of Zeeman gradients by nuclear polarization in double quantum dots. PHYSICAL REVIEW LETTERS 2012; 109:236805. [PMID: 23368241 DOI: 10.1103/physrevlett.109.236805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Indexed: 06/01/2023]
Abstract
We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the high current states correspond to different total Zeeman energy gradients between the two quantum dots. In the low current state, dynamic nuclear polarization efficiently compensates the Zeeman gradient due to the g-factor mismatch, resulting in a suppressed total Zeeman gradient. We present a theoretical model of electron-nuclear feedback that demonstrates a fixed point in nuclear polarization for nearly equal Zeeman splittings in the two dots and predicts a narrowed hyperfine gradient distribution.
Collapse
Affiliation(s)
- S M Frolov
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Barnes E, Cywiński Ł, Das Sarma S. Nonperturbative master equation solution of central spin dephasing dynamics. PHYSICAL REVIEW LETTERS 2012; 109:140403. [PMID: 23083231 DOI: 10.1103/physrevlett.109.140403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Indexed: 06/01/2023]
Abstract
We solve the long-standing central spin problem for a general set of inhomogeneous bath couplings and a large class of initial bath states. We compute the time evolution of the coherence of a central spin coupled to a spin bath by resumming all orders of the time-convolutionless master equation, thus avoiding the need to assume weak coupling to the bath. The fully quantum, non-markovian solution is obtained in the large-bath limit and is valid up to a time scale set by the largest coupling constant. Our result captures the full decoherence of an electron spin qubit coupled to a nuclear spin bath in a GaAs quantum dot for experimentally relevant parameters. In addition, our solution is quite compact and can readily be used to make quantitative predictions for the decoherence process and to guide the design of nuclear state preparation protocols.
Collapse
Affiliation(s)
- Edwin Barnes
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
| | | | | |
Collapse
|
49
|
Shulman MD, Dial OE, Harvey SP, Bluhm H, Umansky V, Yacoby A. Demonstration of entanglement of electrostatically coupled singlet-triplet qubits. Science 2012; 336:202-5. [PMID: 22499942 DOI: 10.1126/science.1217692] [Citation(s) in RCA: 441] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Quantum computers have the potential to solve certain problems faster than classical computers. To exploit their power, it is necessary to perform interqubit operations and generate entangled states. Spin qubits are a promising candidate for implementing a quantum processor because of their potential for scalability and miniaturization. However, their weak interactions with the environment, which lead to their long coherence times, make interqubit operations challenging. We performed a controlled two-qubit operation between singlet-triplet qubits using a dynamically decoupled sequence that maintains the two-qubit coupling while decoupling each qubit from its fluctuating environment. Using state tomography, we measured the full density matrix of the system and determined the concurrence and the fidelity of the generated state, providing proof of entanglement.
Collapse
Affiliation(s)
- M D Shulman
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | | | | | | | | | | |
Collapse
|
50
|
Weiss KM, Elzerman JM, Delley YL, Miguel-Sanchez J, Imamoğlu A. Coherent two-electron spin qubits in an optically active pair of coupled InGaAs quantum dots. PHYSICAL REVIEW LETTERS 2012; 109:107401. [PMID: 23005324 DOI: 10.1103/physrevlett.109.107401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Indexed: 06/01/2023]
Abstract
In semiconductors, the T2* coherence time of a single confined spin is limited either by the fluctuating magnetic environment (via the hyperfine interaction), or by charge fluctuations (via the spin-orbit interaction). We demonstrate that both limitations can be overcome simultaneously by using two exchange-coupled electron spins that realize a single decoherence-avoiding qubit. Using coherent population trapping, we generate a coherent superposition of the singlet and triplet states of an optically active quantum dot molecule, and show that the corresponding T2* may exceed 200 ns.
Collapse
Affiliation(s)
- K M Weiss
- Institute of Quantum Electronics, ETH Zurich, Zurich, Switzerland
| | | | | | | | | |
Collapse
|