1
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Hecker K, Banszerus L, Schäpers A, Möller S, Peters A, Icking E, Watanabe K, Taniguchi T, Volk C, Stampfer C. Coherent charge oscillations in a bilayer graphene double quantum dot. Nat Commun 2023; 14:7911. [PMID: 38036517 PMCID: PMC10689829 DOI: 10.1038/s41467-023-43541-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 11/13/2023] [Indexed: 12/02/2023] Open
Abstract
The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-Stückelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and [Formula: see text] charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield [Formula: see text] average values in the range of 400-500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.
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Affiliation(s)
- K Hecker
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany.
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany.
| | - L Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Schäpers
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - S Möller
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Peters
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - E Icking
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - C Volk
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
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2
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Lin T, Gu SS, Xu YQ, Jiang SL, Ye SK, Wang BC, Li HO, Guo GC, Zou CL, Hu X, Cao G, Guo GP. Collective Microwave Response for Multiple Gate-Defined Double Quantum Dots. NANO LETTERS 2023; 23:4176-4182. [PMID: 37133858 DOI: 10.1021/acs.nanolett.3c00036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We fabricate and characterize a hybrid quantum device that consists of five gate-defined double quantum dots (DQDs) and a high-impedance NbTiN transmission resonator. The controllable interactions between DQDs and the resonator are spectroscopically explored by measuring the microwave transmission through the resonator in the detuning parameter space. Utilizing the high tunability of the system parameters and the high cooperativity (Ctotal > 17.6) interaction between the qubit ensemble and the resonator, we tune the charge-photon coupling and observe the collective microwave response changing from linear to nonlinear. Our results present the maximum number of DQDs coupled to a resonator and manifest a potential platform for scaling up qubits and studying collective quantum effects in semiconductor-superconductor hybrid cavity quantum electrodynamics systems.
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Affiliation(s)
- Ting Lin
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Si-Si Gu
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yong-Qiang Xu
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shun-Li Jiang
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shu-Kun Ye
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bao-Chuan Wang
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hai-Ou Li
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Guang-Can Guo
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Chang-Ling Zou
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Xuedong Hu
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260-1500, United States of America
| | - Gang Cao
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Guo-Ping Guo
- Chinese Academy of Science Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Chinese Academy of Science Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
- Origin Quantum Computing Company Limited, Hefei, Anhui 230088, China
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3
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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.
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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
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4
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Keith D, Chung Y, Kranz L, Thorgrimsson B, Gorman SK, Simmons MY. Ramped measurement technique for robust high-fidelity spin qubit readout. SCIENCE ADVANCES 2022; 8:eabq0455. [PMID: 36070386 PMCID: PMC9451149 DOI: 10.1126/sciadv.abq0455] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 07/21/2022] [Indexed: 06/15/2023]
Abstract
State preparation and measurement of single-electron spin qubits typically rely on spin-to-charge conversion where a spin-dependent charge transition of the electron is detected by a coupled charge sensor. For high-fidelity, fast readout, this process requires that the qubit energy is much larger than the temperature of the system limiting the temperature range for measurements. Here, we demonstrate an initialization and measurement technique that involves voltage ramps rather than static voltages allowing us to achieve state-to-charge readout fidelities above 99% for qubit energies almost half that required by traditional methods. This previously unidentified measurement technique is highly relevant for achieving high-fidelity electron spin readout at higher temperature operation and offers a number of pragmatic benefits compared to traditional energy-selective readout such as real-time dynamic feedback and minimal alignment procedures.
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5
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Spin relaxation in a single-electron graphene quantum dot. Nat Commun 2022; 13:3637. [PMID: 35752620 PMCID: PMC9233672 DOI: 10.1038/s41467-022-31231-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 06/08/2022] [Indexed: 12/02/2022] Open
Abstract
The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T1) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 μs at a magnetic field of 1.9 T. The T1 values show a strong dependence on the spin splitting, promising even longer T1 at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits. Graphene has long been considered to be a promising host for spin qubits, however a demonstration of long spin relaxation times for a potential qubit has been lacking. Here, the authors report the electrical measurement of the single-electron spin relaxation time exceeding 200 μs in a bilayer graphene quantum dot.
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6
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Hai K, Wang Y, Chen Q, Hai W. Transparent qubit manipulations with spin-orbit coupled two-electron nanowire quantum dot. Sci Rep 2021; 11:18839. [PMID: 34552131 PMCID: PMC8458319 DOI: 10.1038/s41598-021-98152-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 09/01/2021] [Indexed: 11/12/2022] Open
Abstract
We report on the first set of exact orthonormalized states to an ac driven one-dimensional (1D) two-electron nanowire quantum dot with the Rashba-Dresselhaus coexisted spin-orbit coupling (SOC) and the controlled magnetic field orientation and trapping frequency. In the ground state case, it is shown that the spatiotemporal evolutions of probability densities occupying internal spin states and the transfer rates between different spin states can be adjusted by the ac electric field and the intensities of SOC and magnetic field. Effects of the system parameters and initial-state-dependent constants on the mean entanglement are revealed, where the approximately maximal entanglement associated with the stronger SOC and its insensitivity to the initial and parametric perturbations are demonstrated numerically. A novel resonance transition mechanism is found, in which the ladder-like time-evolution process of expected energy and the transition time between two arbitrary exact states are controlled by the ac field strength. Using such maximally entangled exact states to encode qubits can render the qubit control more transparent and robust. The results could be extended to 2D case and to an array of two-electron quantum dots with weak neighboring coupling for quantum information processing.
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Affiliation(s)
- Kuo Hai
- Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, 410081, China.
| | - Yifan Wang
- Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, 410081, China
| | - Qiong Chen
- Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, 410081, China
| | - Wenhua Hai
- Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, 410081, China.
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7
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Robust and fast post-processing of single-shot spin qubit detection events with a neural network. Sci Rep 2021; 11:16203. [PMID: 34376730 PMCID: PMC8355192 DOI: 10.1038/s41598-021-95562-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/23/2021] [Indexed: 11/15/2022] Open
Abstract
Establishing low-error and fast detection methods for qubit readout is crucial for efficient quantum error correction. Here, we test neural networks to classify a collection of single-shot spin detection events, which are the readout signal of our qubit measurements. This readout signal contains a stochastic peak, for which a Bayesian inference filter including Gaussian noise is theoretically optimal. Hence, we benchmark our neural networks trained by various strategies versus this latter algorithm. Training of the network with 106 experimentally recorded single-shot readout traces does not improve the post-processing performance. A network trained by synthetically generated measurement traces performs similar in terms of the detection error and the post-processing speed compared to the Bayesian inference filter. This neural network turns out to be more robust to fluctuations in the signal offset, length and delay as well as in the signal-to-noise ratio. Notably, we find an increase of 7% in the visibility of the Rabi oscillation when we employ a network trained by synthetic readout traces combined with measured signal noise of our setup. Our contribution thus represents an example of the beneficial role which software and hardware implementation of neural networks may play in scalable spin qubit processor architectures.
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8
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Zwolak JP, McJunkin T, Kalantre SS, Neyens SF, MacQuarrie ER, Eriksson MA, Taylor JM. Ray-based framework for state identification in quantum dot devices. PRX QUANTUM : A PHYSICAL REVIEW JOURNAL 2021; 2:10.1103/PRXQuantum.2.020335. [PMID: 36733712 PMCID: PMC9890618 DOI: 10.1103/prxquantum.2.020335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Quantum dots (QDs) defined with electrostatic gates are a leading platform for a scalable quantum computing implementation. However, with increasing numbers of qubits, the complexity of the control parameter space also grows. Traditional measurement techniques, relying on complete or near-complete exploration via two-parameter scans (images) of the device response, quickly become impractical with increasing numbers of gates. Here we propose to circumvent this challenge by introducing a measurement technique relying on one-dimensional projections of the device response in the multidimensional parameter space. Dubbed the "ray-based classification (RBC) framework," we use this machine learning approach to implement a classifier for QD states, enabling automated recognition of qubit-relevant parameter regimes. We show that RBC surpasses the 82% accuracy benchmark from the experimental implementation of image-based classification techniques from prior work, while reducing the number of measurement points needed by up to 70%. The reduction in measurement cost is a significant gain for time-intensive QD measurements and is a step forward toward the scalability of these devices. We also discuss how the RBC-based optimizer, which tunes the device to a multiqubit regime, performs when tuning in the two-dimensional and three-dimensional parameter spaces defined by plunger and barrier gates that control the QDs. This work provides experimental validation of both efficient state identification and optimization with machine learning techniques for non-traditional measurements in quantum systems with high-dimensional parameter spaces and time-intensive measurements.
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Affiliation(s)
- Justyna P. Zwolak
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Thomas McJunkin
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Sandesh S. Kalantre
- Joint Quantum Institute, University of Maryland, College Park, MD 20742, USA
- Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, MD 20742, USA
| | - Samuel F. Neyens
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - E. R. MacQuarrie
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Mark A. Eriksson
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jacob M. Taylor
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, MD 20742, USA
- Joint Quantum Institute, University of Maryland, College Park, MD, 20742 USA
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9
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Mu J, Huang S, Liu ZH, Li W, Wang JY, Pan D, Huang GY, Chen Y, Zhao J, Xu HQ. A highly tunable quadruple quantum dot in a narrow bandgap semiconductor InAs nanowire. NANOSCALE 2021; 13:3983-3990. [PMID: 33595588 DOI: 10.1039/d0nr08655j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum dots (QDs) made from semiconductors are among the most promising platforms for the development of quantum computing and simulation chips, and they have the advantages of high density integration and compatibility with the standard semiconductor chip fabrication technology compared to other platforms. However, the development of a highly tunable semiconductor multiple QD system still remains a major challenge. Here, we demonstrate the realization of a highly tunable linear quadruple QD (QQD) in a narrow bandgap semiconductor InAs nanowire via a fine finger gate technique. The QQD is studied by electron transport measurements in the linear response regime. Characteristic two-dimensional charge stability diagrams containing four groups of resonant current lines of different slopes are obtained for the QQD. It is shown that these current lines arise from and can be individually assigned to resonant electron transport through the energy levels of different QDs. Benefitting from the excellent gate tunability, we also demonstrate the tuning of the QQD to regimes where the energy levels of two QDs, three QDs and all four QDs are energetically in resonance, respectively, with the Fermi level of the source and drain contacts. A capacitance network model is developed for the linear QQD and the simulated charge stability diagrams based on this model show good agreement with the experiments. Our work provides solid experimental evidence that narrow bandgap semiconductor nanowire multiple QDs could be used as a versatile platform to achieve integrated qubits for quantum computing and to perform quantum simulations of complex many-body systems.
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Affiliation(s)
- Jingwei Mu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China and Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Zhi-Hai Liu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Weijie Li
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China and Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
| | - Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Dong Pan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China. and Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Guang-Yao Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Yuanjie Chen
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China. and Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China and Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China. and Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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10
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Qiao H, Kandel YP, Fallahi S, Gardner GC, Manfra MJ, Hu X, Nichol JM. Long-Distance Superexchange between Semiconductor Quantum-Dot Electron Spins. PHYSICAL REVIEW LETTERS 2021; 126:017701. [PMID: 33480772 DOI: 10.1103/physrevlett.126.017701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
Because of their long coherence times and potential for scalability, semiconductor quantum-dot spin qubits hold great promise for quantum information processing. However, maintaining high connectivity between quantum-dot spin qubits, which favor linear arrays with nearest neighbor coupling, presents a challenge for large-scale quantum computing. In this work, we present evidence for long-distance spin-chain-mediated superexchange coupling between electron spin qubits in semiconductor quantum dots. We weakly couple two electron spins to the ends of a two-site spin chain. Depending on the spin state of the chain, we observe oscillations between the distant end spins. We resolve the dynamics of both the end spins and the chain itself, and our measurements agree with simulations. Superexchange is a promising technique to create long-distance coupling between quantum-dot spin qubits.
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Affiliation(s)
- Haifeng Qiao
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Yadav P Kandel
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Saeed Fallahi
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Geoffrey C Gardner
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Michael J Manfra
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Xuedong Hu
- Department of Physics, University at Buffalo, Buffalo, New York 14260, USA
| | - John M Nichol
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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11
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Gnidenko AA, Chibisov AN, Chibisova MA, Prokhorenko AV. Quantum mechanical modelling of phosphorus qubits in silicene under constrained magnetization. RSC Adv 2021; 11:33890-33894. [PMID: 35497321 PMCID: PMC9042333 DOI: 10.1039/d1ra05422h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 10/11/2021] [Indexed: 12/04/2022] Open
Abstract
A non-collinear density functional theory calculation of the electronic and magnetic structure of phosphorus-doped silicene was performed using atomic constrained magnetization. The antiferromagnetic state for the local magnetic moments of a pair of phosphorus atoms was found to be preferable both without and with constrained magnetization. A spatial change in the charge densities in the regions of substituting phosphorus atoms was shown. It was found that upon rotation from the |0〉 state to the |1〉 state, the charge density in the intermediate state changes asymmetrically relative to the bonds of the P atom with the neighbouring Si atoms. The dependent behaviour of a pair of phosphorus atoms in silicene was shown by a DFT calculation with constrained magnetization. The total energy and charge distribution change with the rotation of the local magnetic moment of the P atoms.![]()
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Affiliation(s)
- Anton A. Gnidenko
- Pacific National University, 136 Tihookeanskaya Street, Khabarovsk 680042, Russia
- Institute of Material Science of Khabarovsk Scientific Centre, Far Eastern Branch, Russian Academy of Sciences, 153 Tihookeanskaya Street, Khabarovsk 680042, Russia
| | - Andrey N. Chibisov
- Pacific National University, 136 Tihookeanskaya Street, Khabarovsk 680042, Russia
| | - Mary A. Chibisova
- Computing Center, Far Eastern Branch, Russian Academy of Sciences, 65 Kim Yu Chen Street, Khabarovsk, 680000, Russia
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12
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Banszerus L, Rothstein A, Fabian T, Möller S, Icking E, Trellenkamp S, Lentz F, Neumaier D, Watanabe K, Taniguchi T, Libisch F, Volk C, Stampfer C. Electron-Hole Crossover in Gate-Controlled Bilayer Graphene Quantum Dots. NANO LETTERS 2020; 20:7709-7715. [PMID: 32986437 PMCID: PMC7564435 DOI: 10.1021/acs.nanolett.0c03227] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/28/2020] [Indexed: 05/21/2023]
Abstract
Electron and hole Bloch states in bilayer graphene exhibit topological orbital magnetic moments with opposite signs, which allows for tunable valley-polarization in an out-of-plane magnetic field. This property makes electron and hole quantum dots (QDs) in bilayer graphene interesting for valley and spin-valley qubits. Here, we show measurements of the electron-hole crossover in a bilayer graphene QD, demonstrating opposite signs of the magnetic moments associated with the Berry curvature. Using three layers of top gates, we independently control the tunneling barriers while tuning the occupation from the few-hole regime to the few-electron regime, crossing the displacement-field-controlled band gap. The band gap is around 25 meV, while the charging energies of the electron and hole dots are between 3 and 5 meV. The extracted valley g-factor is around 17 and leads to opposite valley polarization for electrons and holes at moderate B-fields. Our measurements agree well with tight-binding calculations for our device.
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Affiliation(s)
- L. Banszerus
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - A. Rothstein
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
| | - T. Fabian
- Institute
for Theoretical Physics, TU Wien, 1040 Vienna, Austria, E.U
| | - S. Möller
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - E. Icking
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - S. Trellenkamp
- Helmholtz
Nano Facility, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - F. Lentz
- Helmholtz
Nano Facility, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - D. Neumaier
- AMO
GmbH, Gesellschaft für
Angewandte Mikro- und Optoelektronik, 52074 Aachen, Germany, E.U
- University
of Wuppertal, 42285 Wuppertal, Germany, E.U
| | - K. Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T. Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - F. Libisch
- Institute
for Theoretical Physics, TU Wien, 1040 Vienna, Austria, E.U
| | - C. Volk
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - C. Stampfer
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
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13
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Kranz L, Gorman SK, Thorgrimsson B, He Y, Keith D, Keizer JG, Simmons MY. Exploiting a Single-Crystal Environment to Minimize the Charge Noise on Qubits in Silicon. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2003361. [PMID: 32830388 DOI: 10.1002/adma.202003361] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 06/11/2023]
Abstract
Electron spins in silicon offer a competitive, scalable quantum-computing platform with excellent single-qubit properties. However, the two-qubit gate fidelities achieved so far have fallen short of the 99% threshold required for large-scale error-corrected quantum computing architectures. In the past few years, there has been a growing realization that the critical obstacle in meeting this threshold in semiconductor qubits is charge noise arising from the qubit environment. In this work, a notably low level of charge noise of S0 = 0.0088 ± 0.0004 μeV2 Hz-1 is demonstrated using atom qubits in crystalline silicon, achieved by separating the qubits from surfaces and interface states. The charge noise is measured using both a single electron transistor and an exchange-coupled qubit pair that collectively provide a consistent charge noise spectrum over four frequency decades, with the noise level S0 being an order of magnitude lower than previously reported. Low-frequency detuning noise, set by the total measurement time, is shown to be the dominant dephasing source of two-qubit exchange oscillations. With recent advances in fast (≈μs) single-shot readout, it is shown that by reducing the total measurement time to ≈1 s, 99.99% two-qubit S W A P gate fidelities can be achieved in single-crystal atom qubits in silicon.
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Affiliation(s)
- Ludwik Kranz
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Samuel Keith Gorman
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Brandur Thorgrimsson
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Yu He
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Daniel Keith
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Joris Gerhard Keizer
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Michelle Yvonne Simmons
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
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14
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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.
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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.
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15
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Banszerus L, Möller S, Icking E, Watanabe K, Taniguchi T, Volk C, Stampfer C. Single-Electron Double Quantum Dots in Bilayer Graphene. NANO LETTERS 2020; 20:2005-2011. [PMID: 32083885 DOI: 10.1021/acs.nanolett.9b05295] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We present transport measurements through an electrostatically defined bilayer graphene double quantum dot in the single-electron regime. With the help of a back gate, two split gates, and two finger gates, we are able to control the number of charge carriers on two gate-defined quantum dots independently between zero and five. The high tunability of the device meets requirements to make such a device a suitable building block for spin-qubits. In the single-electron regime, we determine interdot tunnel rates on the order of 2 GHz. Both, the interdot tunnel coupling as well as the capacitive interdot coupling increase with dot occupation, leading to the transition to a single quantum dot. Finite bias magneto-spectroscopy measurements allow to resolve the excited-state spectra of the first electrons in the double quantum dot and are in agreement with spin and valley conserving interdot tunneling processes.
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Affiliation(s)
- Luca Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Samuel Möller
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Eike Icking
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Christian Volk
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
| | - Christoph Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
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16
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Hensen B, Wei Huang W, Yang CH, Wai Chan K, Yoneda J, Tanttu T, Hudson FE, Laucht A, Itoh KM, Ladd TD, Morello A, Dzurak AS. A silicon quantum-dot-coupled nuclear spin qubit. NATURE NANOTECHNOLOGY 2020; 15:13-17. [PMID: 31819245 DOI: 10.1038/s41565-019-0587-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 11/05/2019] [Indexed: 06/10/2023]
Abstract
Single nuclear spins in the solid state are a potential future platform for quantum computing1-3, because they possess long coherence times4-6 and offer excellent controllability7. Measurements can be performed via localized electrons, such as those in single atom dopants8,9 or crystal defects10-12. However, establishing long-range interactions between multiple dopants or defects is challenging13,14. Conversely, in lithographically defined quantum dots, tunable interdot electron tunnelling allows direct coupling of electron spin-based qubits in neighbouring dots15-20. Moreover, the compatibility with semiconductor fabrication techniques21 may allow for scaling to large numbers of qubits in the future. Unfortunately, hyperfine interactions are typically too weak to address single nuclei. Here we show that for electrons in silicon metal-oxide-semiconductor quantum dots the hyperfine interaction is sufficient to initialize, read out and control single 29Si nuclear spins. This approach combines the long coherence times of nuclear spins with the flexibility and scalability of quantum dot systems. We demonstrate high-fidelity projective readout and control of the nuclear spin qubit, as well as entanglement between the nuclear and electron spins. Crucially, we find that both the nuclear spin and electron spin retain their coherence while moving the electron between quantum dots. Hence we envision long-range nuclear-nuclear entanglement via electron shuttling3. Our results establish nuclear spins in quantum dots as a powerful new resource for quantum processing.
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Affiliation(s)
- Bas Hensen
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
- Delft University of Technology, Delft, The Netherlands
| | - Wister Wei Huang
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Chih-Hwan Yang
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Kok Wai Chan
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Jun Yoneda
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Tuomo Tanttu
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Fay E Hudson
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Arne Laucht
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Kohei M Itoh
- School of Fundamental Science and Technology, Keio University, Yokohama, Japan
| | | | - Andrea Morello
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia
| | - Andrew S Dzurak
- Center for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales, Australia.
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17
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A two-qubit gate between phosphorus donor electrons in silicon. Nature 2019; 571:371-375. [DOI: 10.1038/s41586-019-1381-2] [Citation(s) in RCA: 151] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 05/28/2019] [Indexed: 11/08/2022]
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18
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Coherent microwave-photon-mediated coupling between a semiconductor and a superconducting qubit. Nat Commun 2019; 10:3011. [PMID: 31285437 PMCID: PMC6614454 DOI: 10.1038/s41467-019-10798-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 05/28/2019] [Indexed: 12/04/2022] Open
Abstract
Semiconductor qubits rely on the control of charge and spin degrees of freedom of electrons or holes confined in quantum dots. They constitute a promising approach to quantum information processing, complementary to superconducting qubits. Here, we demonstrate coherent coupling between a superconducting transmon qubit and a semiconductor double quantum dot (DQD) charge qubit mediated by virtual microwave photon excitations in a tunable high-impedance SQUID array resonator acting as a quantum bus. The transmon-charge qubit coherent coupling rate (~21 MHz) exceeds the linewidth of both the transmon (~0.8 MHz) and the DQD charge qubit (~2.7 MHz). By tuning the qubits into resonance for a controlled amount of time, we observe coherent oscillations between the constituents of this hybrid quantum system. These results enable a new class of experiments exploring the use of two-qubit interactions mediated by microwave photons to create entangled states between semiconductor and superconducting qubits. Hybrid quantum devices combine different platforms with the prospect of exploiting the advantages of each. Scarlino et al. demonstrate strong, coherent coupling between a semiconductor qubit and a superconducting qubit by using a high-impedance superconducting resonator as a quantum bus.
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19
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Fidelity benchmarks for two-qubit gates in silicon. Nature 2019; 569:532-536. [PMID: 31086337 DOI: 10.1038/s41586-019-1197-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 02/28/2019] [Indexed: 11/08/2022]
Abstract
Universal quantum computation will require qubit technology based on a scalable platform1, together with quantum error correction protocols that place strict limits on the maximum infidelities for one- and two-qubit gate operations2,3. Although various qubit systems have shown high fidelities at the one-qubit level4-10, the only solid-state qubits manufactured using standard lithographic techniques that have demonstrated two-qubit fidelities near the fault-tolerance threshold6 have been in superconductor systems. Silicon-based quantum dot qubits are also amenable to large-scale fabrication and can achieve high single-qubit gate fidelities (exceeding 99.9 per cent) using isotopically enriched silicon11,12. Two-qubit gates have now been demonstrated in a number of systems13-15, but as yet an accurate assessment of their fidelities using Clifford-based randomized benchmarking, which uses sequences of randomly chosen gates to measure the error, has not been achieved. Here, for qubits encoded on the electron spin states of gate-defined quantum dots, we demonstrate Bell state tomography with fidelities ranging from 80 to 89 per cent, and two-qubit randomized benchmarking with an average Clifford gate fidelity of 94.7 per cent and an average controlled-rotation fidelity of 98 per cent. These fidelities are found to be limited by the relatively long gate times used here compared with the decoherence times of the qubits. Silicon qubit designs employing fast gate operations with high Rabi frequencies16,17, together with advanced pulsing techniques18, should therefore enable much higher fidelities in the near future.
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20
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Mills AR, Zajac DM, Gullans MJ, Schupp FJ, Hazard TM, Petta JR. Shuttling a single charge across a one-dimensional array of silicon quantum dots. Nat Commun 2019; 10:1063. [PMID: 30837460 PMCID: PMC6401174 DOI: 10.1038/s41467-019-08970-z] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 02/08/2019] [Indexed: 11/09/2022] Open
Abstract
Significant advances have been made towards fault-tolerant operation of silicon spin qubits, with single qubit fidelities exceeding 99.9%, several demonstrations of two-qubit gates based on exchange coupling, and the achievement of coherent single spin-photon coupling. Coupling arbitrary pairs of spatially separated qubits in a quantum register poses a significant challenge as most qubit systems are constrained to two dimensions with nearest neighbor connectivity. For spins in silicon, new methods for quantum state transfer should be developed to achieve connectivity beyond nearest-neighbor exchange. Here we demonstrate shuttling of a single electron across a linear array of nine series-coupled silicon quantum dots in ~50 ns via a series of pairwise interdot charge transfers. By constructing more complex pulse sequences we perform parallel shuttling of two and three electrons at a time through the array. These experiments demonstrate a scalable approach to physically transporting single electrons across large silicon quantum dot arrays.
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Affiliation(s)
- A R Mills
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - D M Zajac
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - M J Gullans
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - F J Schupp
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - T M Hazard
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - J R Petta
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
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21
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Probing and driving of spin and charge states in double quantum dot under the quench. Sci Rep 2019; 9:3130. [PMID: 30816339 PMCID: PMC6395824 DOI: 10.1038/s41598-019-40038-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 02/07/2019] [Indexed: 11/14/2022] Open
Abstract
We have analyzed theoretically quenched dynamics of correlated double quantum dot (DQD) due to the switching “on” and “off” coupling to reservoirs. The possibility for controllable manipulation of charge and spin states in the double quantum dot was revealed and discussed. The proposed experimental scheme allows to prepare in DQD maximally entangled pure triplet state and to drive it to another entangled singlet state by tuning both applied bias and gate voltage. It was also demonstrated that the symmetry properties of the total system (double quantum dot coupled to electron reservoirs) allow to resolve the initially prepared two-electron states by detecting non-stationary spin-polarized currents flowing in both reservoirs and controlling the residual charge.
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22
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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.
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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
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23
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Paquette MM, Plaul D, Kurimoto A, Patrick BO, Frank NL. Opto-Spintronics: Photoisomerization-Induced Spin State Switching at 300 K in Photochrome Cobalt-Dioxolene Thin Films. J Am Chem Soc 2018; 140:14990-15000. [PMID: 30351017 DOI: 10.1021/jacs.8b09190] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Controllable quantum systems are under active investigation for quantum computing, secure information processing, and nonvolatile memory. The optical manipulation of spin quantum states provides an important strategy for quantum control with both temporal and spatial resolution. Challenges in increasing the lifetime of photoinduced magnetic states at T > 200 K have hindered progress toward utilizing photomagnetic materials in quantum device architectures. Here we demonstrate reversible light-induced magnetization switching in an organic thin film at device operating temperatures of 300-330 K. By utilizing photochromic ligands that undergo structural changes in the solid state, the changes in ligand field associated with photoisomerization modulate the ligand field and in turn the oxidation and spin state of a bound metal center. Green light irradiation (λexc = 550 nm) of a spirooxazine cobalt-dioxolene complex induces photoisomerization of the ligand that in turn triggers a reversible intramolecular charge-transfer coupled spin-transition process at the cobalt center. The generation of photomagnetic states through conversion between a low-spin Co(III)-semiquinone doublet and a high-spin Co(II)-bis-semiquinone sextet state has been demonstrated in both solution and the solid state and is described as a photoisomerization-induced spin-charge excited state (PISCES) process. The high transition temperature (325 K) and long-lived photoinduced state (τ = 10 s at 300 K) are dictated by the photochromic ligand. Theory provides effective modeling of the phenomenon and long-term strategies to further modulate the lifetimes of photomagnetic states for quantum information technologies at the single molecule level.
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Affiliation(s)
- Michelle M Paquette
- Department of Chemistry , University of Victoria , PO Box 1700 STN CSC , Victoria , British Columbia V8W 2Y2 , Canada
| | - Daniel Plaul
- Department of Chemistry , University of Victoria , PO Box 1700 STN CSC , Victoria , British Columbia V8W 2Y2 , Canada
| | - Aiko Kurimoto
- Department of Chemistry , University of Victoria , PO Box 1700 STN CSC , Victoria , British Columbia V8W 2Y2 , Canada
| | - Brian O Patrick
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z1 , Canada
| | - Natia L Frank
- Department of Chemistry , University of Victoria , PO Box 1700 STN CSC , Victoria , British Columbia V8W 2Y2 , Canada
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24
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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.
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25
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Broome MA, Gorman SK, House MG, Hile SJ, Keizer JG, Keith D, Hill CD, Watson TF, Baker WJ, Hollenberg LCL, Simmons MY. Two-electron spin correlations in precision placed donors in silicon. Nat Commun 2018. [PMID: 29515115 PMCID: PMC5841377 DOI: 10.1038/s41467-018-02982-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Substitutional donor atoms in silicon are promising qubits for quantum computation with extremely long relaxation and dephasing times demonstrated. One of the critical challenges of scaling these systems is determining inter-donor distances to achieve controllable wavefunction overlap while at the same time performing high fidelity spin readout on each qubit. Here we achieve such a device by means of scanning tunnelling microscopy lithography. We measure anti-correlated spin states between two donor-based spin qubits in silicon separated by 16 ± 1 nm. By utilising an asymmetric system with two phosphorus donors at one qubit site and one on the other (2P−1P), we demonstrate that the exchange interaction can be turned on and off via electrical control of two in-plane phosphorus doped detuning gates. We determine the tunnel coupling between the 2P−1P system to be 200 MHz and provide a roadmap for the observation of two-electron coherent exchange oscillations. Donor impurities in silicon are promising candidates as qubits but in order to create a large-scale quantum computer inter-qubit coupling must be introduced by precise positioning of the donors. Here the authors demonstrate the fabrication, manipulation and readout of a two qubit phosphorous donor device.
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Affiliation(s)
- M A Broome
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - S K Gorman
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - M G House
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - S J Hile
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - J G Keizer
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - D Keith
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - C D Hill
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - T F Watson
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - W J Baker
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - L C L Hollenberg
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - M Y Simmons
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia.
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26
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Maslova NS, Arseyev PI, Mantsevich VN. Collective spin correlations and entangled state dynamics in coupled quantum dots. Phys Rev E 2018; 97:022135. [PMID: 29548085 DOI: 10.1103/physreve.97.022135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Indexed: 06/08/2023]
Abstract
Here we demonstrate that the dynamics of few-electron states in a correlated quantum-dot system coupled to an electronic reservoir is governed by the symmetry properties of the total system leading to the collective behavior of all the electrons. Time evolution of two-electron states in a correlated double quantum dot after coupling to the reservoir has been analyzed by means of kinetic equations for pseudoparticle occupation numbers with constraint on possible physical states. It was revealed that the absolute value of the spin correlation function and the degree of entanglement for two-electron states could considerably increase after coupling to the reservoir. The obtained results demonstrate the possibility of a controllable tuning of both the spin correlation function and the concurrence value in a coupled quantum-dot system by changing of the gate voltage applied to the barrier separating the dots.
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Affiliation(s)
- N S Maslova
- Department of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - P I Arseyev
- P.N. Lebedev Physical Institute RAS, 119991 Moscow, Russia
| | - V N Mantsevich
- Department of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
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27
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Zajac DM, Sigillito AJ, Russ M, Borjans F, Taylor JM, Burkard G, Petta JR. Resonantly driven CNOT gate for electron spins. Science 2018; 359:439-442. [DOI: 10.1126/science.aao5965] [Citation(s) in RCA: 327] [Impact Index Per Article: 54.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 11/28/2017] [Indexed: 01/25/2023]
Affiliation(s)
- D. M. Zajac
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - A. J. Sigillito
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - M. Russ
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - F. Borjans
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - J. M. Taylor
- Joint Quantum Institute and Joint Center for Quantum Information and Computer Science, NIST and University of Maryland, College Park, MD 20742, USA
- Research Center for Advanced Science and Technology, University of Tokyo, Tokyo, Japan
| | - G. Burkard
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - J. R. Petta
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
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28
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Harvey-Collard P, Jacobson NT, Rudolph M, Dominguez J, Ten Eyck GA, Wendt JR, Pluym T, Gamble JK, Lilly MP, Pioro-Ladrière M, Carroll MS. Coherent coupling between a quantum dot and a donor in silicon. Nat Commun 2017; 8:1029. [PMID: 29044099 PMCID: PMC5715091 DOI: 10.1038/s41467-017-01113-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 08/18/2017] [Indexed: 11/30/2022] Open
Abstract
Individual donors in silicon chips are used as quantum bits with extremely low error rates. However, physical realizations have been limited to one donor because their atomic size causes fabrication challenges. Quantum dot qubits, in contrast, are highly adjustable using electrical gate voltages. This adjustability could be leveraged to deterministically couple donors to quantum dots in arrays of qubits. In this work, we demonstrate the coherent interaction of a 31P donor electron with the electron of a metal-oxide-semiconductor quantum dot. We form a logical qubit encoded in the spin singlet and triplet states of the two-electron system. We show that the donor nuclear spin drives coherent rotations between the electronic qubit states through the contact hyperfine interaction. This provides every key element for compact two-electron spin qubits requiring only a single dot and no additional magnetic field gradients, as well as a means to interact with the nuclear spin qubit. In silicon, quantum information can be stored in donors or quantum dots, each with its advantages and limitations—particularly in terms of fabrication. Here the authors coherently couple a phosphorous donor’s electron spin to a quantum dot, encoding information in the hybrid two-electron system’s state.
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Affiliation(s)
- Patrick Harvey-Collard
- Département de Physique et Institut Quantique, Université de Sherbrooke, Sherbrooke, QC, Canada, J1K 2R1. .,Sandia National Laboratories, Albuquerque, NM, 87185, USA.
| | - N Tobias Jacobson
- Center for Computing Research, Sandia National Laboratories, Albuquerque, NM, 87185, USA
| | - Martin Rudolph
- Sandia National Laboratories, Albuquerque, NM, 87185, USA
| | | | | | - Joel R Wendt
- Sandia National Laboratories, Albuquerque, NM, 87185, USA
| | - Tammy Pluym
- Sandia National Laboratories, Albuquerque, NM, 87185, USA
| | - John King Gamble
- Center for Computing Research, Sandia National Laboratories, Albuquerque, NM, 87185, USA
| | - Michael P Lilly
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NM, 87185, USA
| | - Michel Pioro-Ladrière
- Département de Physique et Institut Quantique, Université de Sherbrooke, Sherbrooke, QC, Canada, J1K 2R1.,Quantum Information Science Program, Canadian Institute for Advanced Research, Toronto, ON, Canada, M5G 1Z8
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29
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Nguyen T, Hill CD, Hollenberg LCL, James MR. Fan-out Estimation in Spin-based Quantum Computer Scale-up. Sci Rep 2017; 7:13386. [PMID: 29042570 PMCID: PMC5645404 DOI: 10.1038/s41598-017-13308-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 09/21/2017] [Indexed: 11/26/2022] Open
Abstract
Solid-state spin-based qubits offer good prospects for scaling based on their long coherence times and nexus to large-scale electronic scale-up technologies. However, high-threshold quantum error correction requires a two-dimensional qubit array operating in parallel, posing significant challenges in fabrication and control. While architectures incorporating distributed quantum control meet this challenge head-on, most designs rely on individual control and readout of all qubits with high gate densities. We analysed the fan-out routing overhead of a dedicated control line architecture, basing the analysis on a generalised solid-state spin qubit platform parameterised to encompass Coulomb confined (e.g. donor based spin qubits) or electrostatically confined (e.g. quantum dot based spin qubits) implementations. The spatial scalability under this model is estimated using standard electronic routing methods and present-day fabrication constraints. Based on reasonable assumptions for qubit control and readout we estimate 102–105 physical qubits, depending on the quantum interconnect implementation, can be integrated and fanned-out independently. Assuming relatively long control-free interconnects the scalability can be extended. Ultimately, the universal quantum computation may necessitate a much higher number of integrated qubits, indicating that higher dimensional electronics fabrication and/or multiplexed distributed control and readout schemes may be the preferredstrategy for large-scale implementation.
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Affiliation(s)
- Thien Nguyen
- Research School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia.
| | - Charles D Hill
- ARC Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Victoria, 3010, Australia
| | - Lloyd C L Hollenberg
- ARC Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Victoria, 3010, Australia
| | - Matthew R James
- ARC Centre for Quantum Computation and Communication Technology, Research School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
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30
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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.
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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
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31
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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.
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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
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32
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Watson TF, Weber B, Hsueh YL, Hollenberg LLC, Rahman R, Simmons MY. Atomically engineered electron spin lifetimes of 30 s in silicon. SCIENCE ADVANCES 2017; 3:e1602811. [PMID: 29159289 PMCID: PMC5477090 DOI: 10.1126/sciadv.1602811] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Accepted: 02/09/2017] [Indexed: 05/02/2023]
Abstract
Scaling up to large arrays of donor-based spin qubits for quantum computation will require the ability to perform high-fidelity readout of multiple individual spin qubits. Recent experiments have shown that the limiting factor for high-fidelity readout of many qubits is the lifetime of the electron spin. We demonstrate the longest reported lifetimes (up to 30 s) of any electron spin qubit in a nanoelectronic device. By atomic-level engineering of the electron wave function within phosphorus atom quantum dots, we can minimize spin relaxation in agreement with recent theoretical predictions. These lifetimes allow us to demonstrate the sequential readout of two electron spin qubits with fidelities as high as 99.8%, which is above the surface code fault-tolerant threshold. This work paves the way for future experiments on multiqubit systems using donors in silicon.
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Affiliation(s)
- Thomas F. Watson
- Centre for Quantum Computation and Communication
Technology, University of New South Wales, Sydney, New South Wales 2052,
Australia
- Corresponding author. (T.F.W.);
(M.Y.S.)
| | - Bent Weber
- Centre for Quantum Computation and Communication
Technology, University of New South Wales, Sydney, New South Wales 2052,
Australia
| | - Yu-Ling Hsueh
- School of Electrical and Computer Engineering, Purdue
University, West Lafayette, IN 47907, USA
| | - Lloyd L. C. Hollenberg
- Centre for Quantum Computation and Communication
Technology, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Rajib Rahman
- School of Electrical and Computer Engineering, Purdue
University, West Lafayette, IN 47907, USA
| | - Michelle Y. Simmons
- Centre for Quantum Computation and Communication
Technology, University of New South Wales, Sydney, New South Wales 2052,
Australia
- Corresponding author. (T.F.W.);
(M.Y.S.)
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33
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Malinowski FK, Martins F, Nissen PD, Barnes E, Cywiński Ł, Rudner MS, Fallahi S, Gardner GC, Manfra MJ, Marcus CM, Kuemmeth F. Notch filtering the nuclear environment of a spin qubit. NATURE NANOTECHNOLOGY 2017; 12:16-20. [PMID: 27694847 DOI: 10.1038/nnano.2016.170] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 08/12/2016] [Indexed: 06/06/2023]
Abstract
Electron spins in gate-defined quantum dots provide a promising platform for quantum computation. In particular, spin-based quantum computing in gallium arsenide takes advantage of the high quality of semiconducting materials, reliability in fabricating arrays of quantum dots and accurate qubit operations. However, the effective magnetic noise arising from the hyperfine interaction with uncontrolled nuclear spins in the host lattice constitutes a major source of decoherence. Low-frequency nuclear noise, responsible for fast (10 ns) inhomogeneous dephasing, can be removed by echo techniques. High-frequency nuclear noise, recently studied via echo revivals, occurs in narrow-frequency bands related to differences in Larmor precession of the three isotopes 69Ga, 71Ga and 75As (refs 15,16,17). Here, we show that both low- and high-frequency nuclear noise can be filtered by appropriate dynamical decoupling sequences, resulting in a substantial enhancement of spin qubit coherence times. Using nuclear notch filtering, we demonstrate a spin coherence time (T2) of 0.87 ms, five orders of magnitude longer than typical exchange gate times, and exceeding the longest coherence times reported to date in Si/SiGe gate-defined quantum dots.
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Affiliation(s)
- Filip K Malinowski
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - Frederico Martins
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - Peter D Nissen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, 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
| | - Łukasz Cywiński
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
| | - Mark S Rudner
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
- Niels Bohr International Academy, Niels Bohr Institute, Copenhagen 2100, Denmark
| | - Saeed Fallahi
- Department of Physics and Astronomy, Birck Nanotechnology Center, and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
| | - Geoffrey C Gardner
- 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
| | - 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, Copenhagen 2100, Denmark
| | - Ferdinand Kuemmeth
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
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34
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Fujita T, Stano P, Allison G, Morimoto K, Sato Y, Larsson M, Park JH, Ludwig A, Wieck AD, Oiwa A, Tarucha S. Signatures of Hyperfine, Spin-Orbit, and Decoherence Effects in a Pauli Spin Blockade. PHYSICAL REVIEW LETTERS 2016; 117:206802. [PMID: 27886503 DOI: 10.1103/physrevlett.117.206802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Indexed: 06/06/2023]
Abstract
We detect in real time interdot tunneling events in a weakly coupled two-electron double quantum dot in GaAs. At finite magnetic fields, we observe two characteristic tunneling times T_{d} and T_{b}, belonging to, respectively, a direct and a blocked (spin-flip-assisted) tunneling. The latter corresponds to the lifting of a Pauli spin blockade, and the tunneling times ratio η=T_{b}/T_{d} characterizes the blockade efficiency. We find pronounced changes in the behavior of η upon increasing the magnetic field, with η increasing, saturating, and increasing again. We explain this behavior as due to the crossover of the dominant blockade-lifting mechanism from the hyperfine to spin-orbit interactions and due to a change in the contribution of the charge decoherence.
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Affiliation(s)
- T Fujita
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - P Stano
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Institute of Physics, Slovak Academy of Sciences, 845 11 Bratislava, Slovakia
| | - G Allison
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - K Morimoto
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Y Sato
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - M Larsson
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - J-H Park
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - A Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780 Bochum, Germany
| | - A D Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780 Bochum, Germany
| | - A Oiwa
- The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - S Tarucha
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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35
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Hofmann A, Maisi VF, Gold C, Krähenmann T, Rössler C, Basset J, Märki P, Reichl C, Wegscheider W, Ensslin K, Ihn T. Measuring the Degeneracy of Discrete Energy Levels Using a GaAs/AlGaAs Quantum Dot. PHYSICAL REVIEW LETTERS 2016; 117:206803. [PMID: 27886466 DOI: 10.1103/physrevlett.117.206803] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Indexed: 06/06/2023]
Abstract
We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance and the ability to perform precise and efficient measurements of energy-dependent tunneling-in and -out rates from a reservoir. The method is realized using a GaAs/AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunneling with a precision enhanced by a feedback control. It is thoroughly tested by tuning orbital and spin degeneracies with electric and magnetic fields. The technique also lends itself to studying the connection between the ground-state degeneracy and the lifetime of the excited states.
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Affiliation(s)
- A Hofmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - V F Maisi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Gold
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Krähenmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Rössler
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - J Basset
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - P Märki
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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36
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Otsuka T, Nakajima T, Delbecq MR, Amaha S, Yoneda J, Takeda K, Allison G, Ito T, Sugawara R, Noiri A, Ludwig A, Wieck AD, Tarucha S. Single-electron Spin Resonance in a Quadruple Quantum Dot. Sci Rep 2016; 6:31820. [PMID: 27550534 PMCID: PMC4994114 DOI: 10.1038/srep31820] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/21/2016] [Indexed: 11/09/2022] Open
Abstract
Electron spins in semiconductor quantum dots are good candidates of quantum bits for quantum information processing. Basic operations of the qubit have been realized in recent years: initialization, manipulation of single spins, two qubit entanglement operations, and readout. Now it becomes crucial to demonstrate scalability of this architecture by conducting spin operations on a scaled up system. Here, we demonstrate single-electron spin resonance in a quadruple quantum dot. A few-electron quadruple quantum dot is formed within a magnetic field gradient created by a micro-magnet. We oscillate the wave functions of the electrons in the quantum dots by applying microwave voltages and this induces electron spin resonance. The resonance energies of the four quantum dots are slightly different because of the stray field created by the micro-magnet and therefore frequency-resolved addressable control of each electron spin resonance is possible.
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Affiliation(s)
- Tomohiro Otsuka
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Takashi Nakajima
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Matthieu R Delbecq
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Shinichi Amaha
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Jun Yoneda
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Kenta Takeda
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Giles Allison
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Takumi Ito
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Retsu Sugawara
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Akito Noiri
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Arne Ludwig
- Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Andreas D Wieck
- Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Seigo Tarucha
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.,Quantum-Phase Electronics Center, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.,Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan
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37
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Yu GD, Li HO, Cao G, Xiao M, Jiang HW, Guo GP. Tunable capacitive coupling between two semiconductor charge qubits. NANOTECHNOLOGY 2016; 27:324003. [PMID: 27354414 DOI: 10.1088/0957-4484/27/32/324003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Strong coupling between two qubits is one of the main requirements for high fidelity two-qubit logic operations. Here we experimentally investigate the capacitive coupling between two double quantum dots. A pair of open slot confinement gates is used to enhance the coupling. We find that the coupling energy J can be conveniently tuned in a broad range. Through numerical simulations, we study the effect of J on two-qubit operations. The analysis shows that our experimentally obtained J is adequate to achieve high fidelity two-qubit entanglement and logic gates.
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Affiliation(s)
- Guo-Dong Yu
- Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China. Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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38
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Abstract
Quantum computation requires qubits that can be coupled in a scalable manner, together with universal and high-fidelity one- and two-qubit logic gates. Many physical realizations of qubits exist, including single photons, trapped ions, superconducting circuits, single defects or atoms in diamond and silicon, and semiconductor quantum dots, with single-qubit fidelities that exceed the stringent thresholds required for fault-tolerant quantum computing. Despite this, high-fidelity two-qubit gates in the solid state that can be manufactured using standard lithographic techniques have so far been limited to superconducting qubits, owing to the difficulties of coupling qubits and dephasing in semiconductor systems. Here we present a two-qubit logic gate, which uses single spins in isotopically enriched silicon and is realized by performing single- and two-qubit operations in a quantum dot system using the exchange interaction, as envisaged in the Loss-DiVincenzo proposal. We realize CNOT gates via controlled-phase operations combined with single-qubit operations. Direct gate-voltage control provides single-qubit addressability, together with a switchable exchange interaction that is used in the two-qubit controlled-phase gate. By independently reading out both qubits, we measure clear anticorrelations in the two-spin probabilities of the CNOT gate.
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39
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Otsuka T, Amaha S, Nakajima T, Delbecq MR, Yoneda J, Takeda K, Sugawara R, Allison G, Ludwig A, Wieck AD, Tarucha S. Fast probe of local electronic states in nanostructures utilizing a single-lead quantum dot. Sci Rep 2015; 5:14616. [PMID: 26416582 PMCID: PMC4586608 DOI: 10.1038/srep14616] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 09/02/2015] [Indexed: 11/30/2022] Open
Abstract
Transport measurements are powerful tools to probe electronic properties of solid-state materials. To access properties of local electronic states in nanostructures, such as local density of states, electronic distribution and so on, micro-probes utilizing artificial nanostructures have been invented to perform measurements in addition to those with conventional macroscopic electronic reservoirs. Here we demonstrate a new kind of micro-probe: a fast single-lead quantum dot probe, which utilizes a quantum dot coupled only to the target structure through a tunneling barrier and fast charge readout by RF reflectometry. The probe can directly access the local electronic states with wide bandwidth. The probe can also access more electronic states, not just those around the Fermi level, and the operations are robust against bias voltages and temperatures.
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Affiliation(s)
- Tomohiro Otsuka
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Shinichi Amaha
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Takashi Nakajima
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Matthieu R Delbecq
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Jun Yoneda
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Kenta Takeda
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Retsu Sugawara
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Giles Allison
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Arne Ludwig
- Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Andreas D Wieck
- Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Seigo Tarucha
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.,Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.,Quantum-Phase Electronics Center, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.,Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan
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40
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Mueller F, Konstantaras G, Spruijtenburg PC, van der Wiel WG, Zwanenburg FA. Electron-Hole Confinement Symmetry in Silicon Quantum Dots. NANO LETTERS 2015; 15:5336-5341. [PMID: 26134900 DOI: 10.1021/acs.nanolett.5b01706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report electrical transport measurements on a gate-defined ambipolar quantum dot in intrinsic silicon. The ambipolarity allows its operation as either an electron or a hole quantum dot of which we change the dot occupancy by 20 charge carriers in each regime. Electron-hole confinement symmetry is evidenced by the extracted gate capacitances and charging energies. The results demonstrate that ambipolar quantum dots offer great potential for spin-based quantum information processing, since confined electrons and holes can be compared and manipulated in the same crystalline environment.
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Affiliation(s)
- Filipp Mueller
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Georgios Konstantaras
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Paul C Spruijtenburg
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Wilfred G van der Wiel
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Floris A Zwanenburg
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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41
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Conditional rotation of two strongly coupled semiconductor charge qubits. Nat Commun 2015; 6:7681. [PMID: 26184756 PMCID: PMC4518268 DOI: 10.1038/ncomms8681] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 06/01/2015] [Indexed: 11/08/2022] Open
Abstract
Universal multiple-qubit gates can be implemented by a set of universal single-qubit gates and any one kind of entangling two-qubit gate, such as a controlled-NOT gate. For semiconductor quantum dot qubits, two-qubit gate operations have so far only been demonstrated in individual electron spin-based quantum dot systems. Here we demonstrate the conditional rotation of two capacitively coupled charge qubits, each consisting of an electron confined in a GaAs/AlGaAs double quantum dot. Owing to the strong inter-qubit coupling strength, gate operations with a clock speed up to 6 GHz have been realized. A truth table measurement for controlled-NOT operation shows comparable fidelities to that of spin-based two-qubit gates, although phase coherence is not explicitly measured. Our results suggest that semiconductor charge qubits have a considerable potential for scalable quantum computing and may stimulate the use of long-range Coulomb interaction for coherent quantum control in other devices.
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42
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Prance JR, Van Bael BJ, Simmons CB, Savage DE, Lagally MG, Friesen M, Coppersmith SN, Eriksson MA. Identifying single electron charge sensor events using wavelet edge detection. NANOTECHNOLOGY 2015; 26:215201. [PMID: 25930073 DOI: 10.1088/0957-4484/26/21/215201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The operation of solid-state qubits often relies on single-shot readout using a nanoelectronic charge sensor, and the detection of events in a noisy sensor signal is crucial for high fidelity readout of such qubits. The most common detection scheme, comparing the signal to a threshold value, is accurate at low noise levels but is not robust to low-frequency noise and signal drift. We describe an alternative method for identifying charge sensor events using wavelet edge detection. The technique is convenient to use and we show that, with realistic signals and a single tunable parameter, wavelet detection can outperform thresholding and is significantly more tolerant to 1/f and low-frequency noise.
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Affiliation(s)
- J R Prance
- University of Wisconsin-Madison, Wisconsin 53706, USA. Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK
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43
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Yamamoto S, Nakazawa S, Sugisaki K, Sato K, Toyota K, Shiomi D, Takui T. Adiabatic quantum computing with spin qubits hosted by molecules. Phys Chem Chem Phys 2015; 17:2742-9. [DOI: 10.1039/c4cp04744c] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Molecular spin QCs for adiabatic quantum computing: a phthalocyanine derivative with three electron qubits and a glutaconic acid radical with one electron bus qubit and two nuclear client qubits.
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Affiliation(s)
- Satoru Yamamoto
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
| | - Shigeaki Nakazawa
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
| | - Kenji Sugisaki
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
| | - Kazunobu Sato
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
| | - Kazuo Toyota
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
| | - Daisuke Shiomi
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
| | - Takeji Takui
- Department of Chemistry and Molecular Materials Science
- Graduate School of Science
- Osaka City University
- Sumiyoshi
- Japan
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44
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Scarlino P, Kawakami E, Stano P, Shafiei M, Reichl C, Wegscheider W, Vandersypen LMK. Spin-relaxation anisotropy in a GaAs quantum dot. PHYSICAL REVIEW LETTERS 2014; 113:256802. [PMID: 25554903 DOI: 10.1103/physrevlett.113.256802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Indexed: 06/04/2023]
Abstract
We report that the electron spin-relaxation time T_{1} in a GaAs quantum dot with a spin-1/2 ground state has a 180° periodicity in the orientation of the in-plane magnetic field. This periodicity has been predicted for circular dots as being due to the interplay of Rashba and Dresselhaus spin orbit contributions. Different from this prediction, we find that the extrema in the T_{1} do not occur when the magnetic field is along the [110] and [11[over ¯]0] crystallographic directions. This deviation is attributed to an elliptical dot confining potential. The T_{1} varies by more than 1 order of magnitude when rotating a 3 T field, reaching about 80 ms for the optimal angle. We infer from the data that in our device the signs of the Rashba and Dresselhaus constants are opposite.
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Affiliation(s)
- P Scarlino
- Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - E Kawakami
- Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - P Stano
- RIKEN Center for Emergent Matter Science, Wako-shi, Saitama 351-0198, Japan and Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 84511 Bratislava, Slovakia
| | - M Shafiei
- Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, Schafmattstrasse 16, 8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, Schafmattstrasse 16, 8093 Zurich, Switzerland
| | - L M K Vandersypen
- Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, Netherlands
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45
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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.
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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
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46
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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.
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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
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47
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Pawłowski J, Szumniak P, Skubis A, Bednarek S. Electron spin separation without magnetic field. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:345302. [PMID: 25106038 DOI: 10.1088/0953-8984/26/34/345302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A nanodevice capable of separating spins of two electrons confined in a quantum dot formed in a gated semiconductor nanowire is proposed. Two electrons confined initially in a single quantum dot in the singlet state are transformed into the system of two electrons confined in two spatially separated quantum dots with opposite spins. In order to separate the electrons' spins we exploit transitions between the singlet and the triplet state, which are induced by resonantly oscillating Rashba spin-orbit coupling strength. The proposed device is all electrically controlled and the electron spin separation can be realized within tens of picoseconds. The results are supported by solving numerically the quasi-one-dimensional time-dependent Schroedinger equation for two electrons, where the electron-electron correlations are taken into account in the exact manner.
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Affiliation(s)
- J Pawłowski
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Kraków, Poland
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48
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Two-axis control of a singlet-triplet qubit with an integrated micromagnet. Proc Natl Acad Sci U S A 2014; 111:11938-42. [PMID: 25092298 DOI: 10.1073/pnas.1412230111] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The qubit is the fundamental building block of a quantum computer. We fabricate a qubit in a silicon double-quantum dot with an integrated micromagnet in which the qubit basis states are the singlet state and the spin-zero triplet state of two electrons. Because of the micromagnet, the magnetic field difference ΔB between the two sides of the double dot is large enough to enable the achievement of coherent rotation of the qubit's Bloch vector around two different axes of the Bloch sphere. By measuring the decay of the quantum oscillations, the inhomogeneous spin coherence time T2* is determined. By measuring T2* at many different values of the exchange coupling J and at two different values of ΔB, we provide evidence that the micromagnet does not limit decoherence, with the dominant limits on T2* arising from charge noise and from coupling to nuclear spins.
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Dehollain JP, Muhonen JT, Tan KY, Saraiva A, Jamieson DN, Dzurak AS, Morello A. Single-shot readout and relaxation of singlet and triplet states in exchange-coupled 31P electron spins in silicon. PHYSICAL REVIEW LETTERS 2014; 112:236801. [PMID: 24972221 DOI: 10.1103/physrevlett.112.236801] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Indexed: 06/03/2023]
Abstract
We present the experimental observation of a large exchange coupling J ≈ 300 μeV between two (31)P electron spin qubits in silicon. The singlet and triplet states of the coupled spins are monitored in real time by a single-electron transistor, which detects ionization from tunnel-rate-dependent processes in the coupled spin system, yielding single-shot readout fidelities above 95%. The triplet to singlet relaxation time T(1) ≈ 4 ms at zero magnetic field agrees with the theoretical prediction for J-coupled 31P dimers in silicon. The time evolution of the two-electron state populations gives further insight into the valley-orbit eigenstates of the donor dimer, valley selection rules and relaxation rates, and the role of hyperfine interactions. These results pave the way to the realization of two-qubit quantum logic gates with spins in silicon and highlight the necessity to adopt gating schemes compatible with weak J-coupling strengths.
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Affiliation(s)
- Juan P Dehollain
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia
| | - Juha T Muhonen
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia
| | - Kuan Y Tan
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia
| | - Andre Saraiva
- Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, Brazil and University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - David N Jamieson
- Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Andrew S Dzurak
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia
| | - Andrea Morello
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia
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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.
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Affiliation(s)
- A P Higginbotham
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen , 2100 Copenhagen, Denmark
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