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Bosco S, Loss D. Fully Tunable Hyperfine Interactions of Hole Spin Qubits in Si and Ge Quantum Dots. PHYSICAL REVIEW LETTERS 2021; 127:190501. [PMID: 34797148 DOI: 10.1103/physrevlett.127.190501] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 10/13/2021] [Indexed: 06/13/2023]
Abstract
Hole spin qubits are frontrunner platforms for scalable quantum computers, but state-of-the-art devices suffer from noise originating from the hyperfine interactions with nuclear defects. We show that these interactions have a highly tunable anisotropy that is controlled by device design and external electric fields. This tunability enables sweet spots where the hyperfine noise is suppressed by an order of magnitude and is comparable to isotopically purified materials. We identify surprisingly simple designs where the qubits are highly coherent and are largely unaffected by both charge and hyperfine noise. We find that the large spin-orbit interaction typical of elongated quantum dots not only speeds up qubit operations, but also dramatically renormalizes the hyperfine noise, altering qualitatively the dynamics of driven qubits and enhancing the fidelity of qubit gates. Our findings serve as guidelines to design high performance qubits for scaling up quantum computers.
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Affiliation(s)
- Stefano Bosco
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
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2
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Zhang T, Liu H, Gao F, Xu G, Wang K, Zhang X, Cao G, Wang T, Zhang J, Hu X, Li HO, Guo GP. Anisotropic g-Factor and Spin-Orbit Field in a Germanium Hut Wire Double Quantum Dot. NANO LETTERS 2021; 21:3835-3842. [PMID: 33914549 DOI: 10.1021/acs.nanolett.1c00263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Holes in nanowires have drawn significant attention in recent years because of the strong spin-orbit interaction, which plays an important role in constructing Majorana zero modes and manipulating spin-orbit qubits. Here, from the strongly anisotropic leakage current in the spin blockade regime for a double dot, we extract the full g-tensor and find that the spin-orbit field is in plane with an azimuthal angle of 59° to the axis of the nanowire. The direction of the spin-orbit field indicates a strong spin-orbit interaction along the nanowire, which may have originated from the interface inversion asymmetry in Ge hut wires. We also demonstrate two different spin relaxation mechanisms for the holes in the Ge hut wire double dot: spin-flip co-tunneling to the leads, and spin-orbit interaction within the double dot. These results help establish feasibility of a Ge-based quantum processor.
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Affiliation(s)
- Ting Zhang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - He Liu
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Fei Gao
- Institute of Physics and CAS Center for Excellence in Topological Quantum Computation, Chinese Academy of Sciences, Beijing 100190, China
| | - Gang Xu
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ke Wang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xin Zhang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Gang Cao
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ting Wang
- Institute of Physics and CAS Center for Excellence in Topological Quantum Computation, Chinese Academy of Sciences, Beijing 100190, China
| | - Jianjun Zhang
- Institute of Physics and CAS Center for Excellence in Topological Quantum Computation, Chinese Academy of Sciences, Beijing 100190, China
| | - Xuedong Hu
- Department of Physics, University at Buffalo, SUNY, Buffalo, New York 14260, United States
| | - Hai-Ou Li
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guo-Ping Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Origin Quantum Computing Company Limited, Hefei, Anhui 230026, China
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Gong P, Pang H, Yu H, Yao W. Nanometrology of field gradient using donor spins in silicon. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:425301. [PMID: 30198860 DOI: 10.1088/1361-648x/aae009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We proposed a novel scheme for nanometrology of magnetic field gradient based on Kane's silicon quantum computer proposal. When the system is placed in an unknown magnetic field gradient, the inhomogeneous precession of the donor nuclear spins records the field gradient information to the phase pattern of donor nuclear spins. By adding AC voltage modulations on each A-gate to induce hyperfine-mediated electron-nuclear collective flip-flop process, we demonstrate that the gradient value can be obtained by tuning the modulation phases of the A-gates. Errors of the measurements of such scheme is discussed and estimated. It is also discussed that in presence of the external field with a known gradient, the same system is possible to be used to obtain the unknown displacement of donor locations.
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Affiliation(s)
- Pu Gong
- Department of Physics, and Center for Theoretical and Computational Physics, The University of Hong Kong, Hong Kong, People's Republic of China
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Li R, Liu ZH, Wu Y, Liu CS. The impacts of the quantum-dot confining potential on the spin-orbit effect. Sci Rep 2018; 8:7400. [PMID: 29743523 PMCID: PMC5943540 DOI: 10.1038/s41598-018-25692-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 04/26/2018] [Indexed: 11/09/2022] Open
Abstract
For a nanowire quantum dot with the confining potential modeled by both the infinite and the finite square wells, we obtain exactly the energy spectrum and the wave functions in the strong spin-orbit coupling regime. We find that regardless of how small the well height is, there are at least two bound states in the finite square well: one has the σ x [Formula: see text] = -1 symmetry and the other has the σ x [Formula: see text] = 1 symmetry. When the well height is slowly tuned from large to small, the position of the maximal probability density of the first excited state moves from the center to x ≠ 0, while the position of the maximal probability density of the ground state is always at the center. A strong enhancement of the spin-orbit effect is demonstrated by tuning the well height. In particular, there exists a critical height [Formula: see text], at which the spin-orbit effect is enhanced to maximal.
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Affiliation(s)
- Rui Li
- Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao, 066004, China. .,Quantum Physics and Quantum Information Division, Beijing Computational Science Research Center, Beijing, 100193, China.
| | - Zhi-Hai Liu
- Quantum Physics and Quantum Information Division, Beijing Computational Science Research Center, Beijing, 100193, China
| | - Yidong Wu
- Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao, 066004, China
| | - C S Liu
- Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao, 066004, China
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Russ M, Burkard G. Three-electron spin qubits. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:393001. [PMID: 28562367 DOI: 10.1088/1361-648x/aa761f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the exchange-only qubit (Bacon et al 2000 Phys. Rev. Lett. 85 1758-61, DiVincenzo et al 2000 Nature 408 339) and its derived versions, e.g. the resonant exchange (RX) qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the envisioned physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby completing the list of requirements for quantum computation for a viable candidate qubit implementation. We start by describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram, restricting ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states (Russ et al 2016 Phys. Rev. B 94 165411). Introducing the various qubit implementations, we begin with the exchange-only qubit (DiVincenzo et al 2000 Nature 408 339, Laird et al 2010 Phys. Rev. B 82 075403), followed by the RX qubit (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502), the spin-charge qubit (Kyriakidis and Burkard 2007 Phys. Rev. B 75 115324), and the hybrid qubit (Shi et al 2012 Phys. Rev. Lett. 108 140503, Koh et al 2012 Phys. Rev. Lett. 109 250503, Cao et al 2016 Phys. Rev. Lett. 116 086801, Thorgrimsson et al 2016 arXiv:1611.04945). The main focus will be on the exchange-only qubit and its modification, the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange-only qubits which can be divided into short-ranged and long-ranged interactions. Both of these interaction types are expected to be necessary in a large-scale quantum computer. The short-ranged interactions use the exchange coupling by placing qubits next to each other and applying exchange-pulses (DiVincenzo et al 2000 Nature 408 339, Fong and Wandzura 2011 Quantum Inf. Comput. 11 1003, Setiawan et al 2014 Phys. Rev. B 89 085314, Zeuch et al 2014 Phys. Rev. B 90 045306, Doherty and Wardrop 2013 Phys. Rev. Lett. 111 050503, Shim and Tahan 2016 Phys. Rev. B 93 121410), while the long-ranged interactions use the photons of a superconducting microwave cavity as a mediator in order to couple two qubits over long distances (Russ and Burkard 2015 Phys. Rev. B 92 205412, Srinivasa et al 2016 Phys. Rev. B 94 205421). The nature of the three-electron qubit states each having the same total spin and total spin in z-direction (same Zeeman energy) provides a natural protection against several sources of noise (DiVincenzo et al 2000 Nature 408 339, Taylor et al 2013 Phys. Rev. Lett. 111 050502, Kempe et al 2001 Phys. Rev. A 63 042307, Russ and Burkard 2015 Phys. Rev. B 91 235411). The price to pay for this advantage is an increase in gate complexity. We also take into account the decoherence of the qubit through the influence of magnetic noise (Ladd 2012 Phys. Rev. B 86 125408, Mehl and DiVincenzo 2013 Phys. Rev. B 87 195309, Hung et al 2014 Phys. Rev. B 90 045308), in particular dephasing due to the presence of nuclear spins, as well as dephasing due to charge noise (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502, Shim and Tahan 2016 Phys. Rev. B 93 121410, Russ and Burkard 2015 Phys. Rev. B 91 235411, Fei et al 2015 Phys. Rev. B 91 205434), fluctuations of the energy levels on each dot due to noisy gate voltages or the environment. Several techniques are discussed which partly decouple the qubit from magnetic noise (Setiawan et al 2014 Phys. Rev. B 89 085314, West and Fong 2012 New J. Phys. 14 083002, Rohling and Burkard 2016 Phys. Rev. B 93 205434) while for charge noise it is shown that it is favorable to operate the qubit on the so-called '(double) sweet spots' (Taylor et al 2013 Phys. Rev. Lett. 111 050502, Shim and Tahan 2016 Phys. Rev. B 93 121410, Russ and Burkard 2015 Phys. Rev. B 91 235411, Fei et al 2015 Phys. Rev. B 91 205434, Malinowski et al 2017 arXiv: 1704.01298), which are least susceptible to noise, thus providing a longer lifetime of the qubit.
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Affiliation(s)
- Maximilian Russ
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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6
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Tosi G, Mohiyaddin FA, Schmitt V, Tenberg S, Rahman R, Klimeck G, Morello A. Silicon quantum processor with robust long-distance qubit couplings. Nat Commun 2017; 8:450. [PMID: 28878207 PMCID: PMC5587611 DOI: 10.1038/s41467-017-00378-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 06/20/2017] [Indexed: 11/11/2022] Open
Abstract
Practical quantum computers require a large network of highly coherent qubits, interconnected in a design robust against errors. Donor spins in silicon provide state-of-the-art coherence and quantum gate fidelities, in a platform adapted from industrial semiconductor processing. Here we present a scalable design for a silicon quantum processor that does not require precise donor placement and leaves ample space for the routing of interconnects and readout devices. We introduce the flip-flop qubit, a combination of the electron-nuclear spin states of a phosphorus donor that can be controlled by microwave electric fields. Two-qubit gates exploit a second-order electric dipole-dipole interaction, allowing selective coupling beyond the nearest-neighbor, at separations of hundreds of nanometers, while microwave resonators can extend the entanglement to macroscopic distances. We predict gate fidelities within fault-tolerance thresholds using realistic noise models. This design provides a realizable blueprint for scalable spin-based quantum computers in silicon.Quantum computers will require a large network of coherent qubits, connected in a noise-resilient way. Tosi et al. present a design for a quantum processor based on electron-nuclear spins in silicon, with electrical control and coupling schemes that simplify qubit fabrication and operation.
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Affiliation(s)
- Guilherme Tosi
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW, 2052, Australia.
| | - Fahd A Mohiyaddin
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW, 2052, Australia
- Quantum Computing Institute, Oak Ridge National Laboratory, Oak Ridge, 37830, TN, USA
| | - Vivien Schmitt
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW, 2052, Australia
| | - Stefanie Tenberg
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW, 2052, Australia
| | - Rajib Rahman
- Network for Computational Nanotechnology, Purdue University, West Lafayette, IN, 47907, USA
| | - Gerhard Klimeck
- Network for Computational Nanotechnology, Purdue University, West Lafayette, IN, 47907, USA
| | - Andrea Morello
- Centre for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW, 2052, Australia.
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7
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Osika EN, Chacón A, Lewenstein M, Szafran B. Spin-valley dynamics of electrically driven ambipolar carbon-nanotube quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:285301. [PMID: 28594639 DOI: 10.1088/1361-648x/aa720e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An ambipolar n-p double quantum dot defined by potential variation along a semiconducting carbon-nanotube is considered. We focus on the (1e,1h) charge configuration with a single excess electron of the conduction band confined in the n-type dot and a single missing electron in the valence band state of the p-type dot for which lifting of the Pauli blockade of the current was observed in the electric-dipole spin resonance (Laird et al 2013 Nat. Nanotechnol. 8 565). The dynamics of the system driven by periodic electric field is studied with the Floquet theory and the time-dependent configuration interaction method with the single-electron spin-valley-orbitals determined for atomistic tight-binding Hamiltonian. We find that the transitions lifting the Pauli blockade are strongly influenced by coupling to a vacuum state with an empty n dot and a fully filled p dot. The coupling shifts the transition energies and strongly modifies the effective g factors for axial magnetic field. The coupling is modulated by the bias between the dots but it appears effective for surprisingly large energy splitting between the (1e,1h) ground state and the vacuum (0e, 0h) state. Multiphoton transitions and high harmonic generation effects are also discussed.
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Affiliation(s)
- E N Osika
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków, Poland
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8
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Pei T, Pályi A, Mergenthaler M, Ares N, Mavalankar A, Warner JH, Briggs GAD, Laird EA. Hyperfine and Spin-Orbit Coupling Effects on Decay of Spin-Valley States in a Carbon Nanotube. PHYSICAL REVIEW LETTERS 2017; 118:177701. [PMID: 28498696 DOI: 10.1103/physrevlett.118.177701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Indexed: 06/07/2023]
Abstract
The decay of spin-valley states is studied in a suspended carbon nanotube double quantum dot via the leakage current in Pauli blockade and via dephasing and decoherence of a qubit. From the magnetic field dependence of the leakage current, hyperfine and spin-orbit contributions to relaxation from blocked to unblocked states are identified and explained quantitatively by means of a simple model. The observed qubit dephasing rate is consistent with the hyperfine coupling strength extracted from this model and inconsistent with dephasing from charge noise. However, the qubit coherence time, although longer than previously achieved, is probably still limited by charge noise in the device.
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Affiliation(s)
- T Pei
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - A Pályi
- Department of Physics and MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, 1111 Budapest, Hungary
| | - M Mergenthaler
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - N Ares
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - A Mavalankar
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - J H Warner
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - G A D Briggs
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - E A Laird
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
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9
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Manipulation of a Nuclear Spin by a Magnetic Domain Wall in a Quantum Hall Ferromagnet. Sci Rep 2017; 7:43553. [PMID: 28262758 PMCID: PMC5337906 DOI: 10.1038/srep43553] [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: 09/23/2016] [Accepted: 01/25/2017] [Indexed: 11/08/2022] Open
Abstract
The manipulation of a nuclear spin by an electron spin requires the energy to flip the electron spin to be vanishingly small. This can be realized in a many electron system with degenerate ground states of opposite spin polarization in different Landau levels. We present here a microscopic theory of a domain wall between spin unpolarized and spin polarized quantum Hall ferromagnet states at filling factor two with the Zeeman energy comparable to the cyclotron energy. We determine the energies and many-body wave functions of the electronic quantum Hall droplet with up to N = 80 electrons as a function of the total spin, angular momentum, cyclotron and Zeeman energies from the spin singlet ν = 2 phase, through an intermediate polarization state exhibiting a domain wall to the fully spin-polarized phase involving the lowest and the second Landau levels. We demonstrate that the energy needed to flip one electron spin in a domain wall becomes comparable to the energy needed to flip the nuclear spin. The orthogonality of orbital electronic states is overcome by the many-electron character of the domain - the movement of the domain wall relative to the position of the nuclear spin enables the manipulation of the nuclear spin by electrical means.
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10
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Chesi S, Yang LP, Loss D. Dephasing due to Nuclear Spins in Large-Amplitude Electric Dipole Spin Resonance. PHYSICAL REVIEW LETTERS 2016; 116:066806. [PMID: 26919009 DOI: 10.1103/physrevlett.116.066806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Indexed: 06/05/2023]
Abstract
We analyze effects of the hyperfine interaction on electric dipole spin resonance when the amplitude of the quantum-dot motion becomes comparable or larger than the quantum dot's size. Away from the well-known small-drive regime, the important role played by transverse nuclear fluctuations leads to a Gaussian decay with characteristic dependence on drive strength and detuning. A characterization of spin-flip gate fidelity, in the presence of such additional drive-dependent dephasing, shows that vanishingly small errors can still be achieved at sufficiently large amplitudes. Based on our theory, we analyze recent electric dipole spin resonance experiments relying on spin-orbit interactions or the slanting field of a micromagnet. We find that such experiments are already in a regime with significant effects of transverse nuclear fluctuations and the form of decay of the Rabi oscillations can be reproduced well by our theory.
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Affiliation(s)
- Stefano Chesi
- Beijing Computational Science Research Center, Beijing 100084, China
| | - Li-Ping Yang
- Beijing Computational Science Research Center, Beijing 100084, China
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
- CEMS, RIKEN, Wako, Saitama 351-0198, Japan
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11
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Osika EN, Szafran B. Spin-orbit interaction in bent carbon nanotubes: resonant spin transitions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:435301. [PMID: 26447487 DOI: 10.1088/0953-8984/27/43/435301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We develop an effective tight-binding Hamiltonian for spin-orbit (SO) interaction in bent carbon nanotubes (CNT) for the electrons forming the π bonds between the nearest neighbor atoms. We account for the bend of the CNT and the intrinsic spin-orbit interaction which introduce mixing of π and σ bonds between the p(z) orbitals along the CNT. The effect contributes to the main origin of the SO coupling-the folding of the graphene plane into the nanotube. We discuss the bend-related contribution of the SO coupling for resonant single-electron spin and charge transitions in a double quantum dot. We report that although the effect of the bend-related SO coupling is weak for the energy spectra, it produces a pronounced increase of the spin transition rates driven by an external electric field. We find that spin-flipping transitions driven by alternate electric fields have usually larger rates when accompanied by charge shift from one dot to the other. Spin-flipping transition rates are non-monotonic functions of the driving amplitude since they are masked by stronger spin-conserving charge transitions. We demonstrate that the fractional resonances-counterparts of multiphoton transitions for atoms in strong laser fields-occurring in electrically controlled nanodevices already at moderate ac amplitudes-can be used to maintain the spin-flip transitions.
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Affiliation(s)
- E N Osika
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków, Poland
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12
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Nichol JM, Harvey SP, Shulman MD, Pal A, Umansky V, Rashba EI, Halperin BI, Yacoby A. Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots. Nat Commun 2015; 6:7682. [PMID: 26184854 PMCID: PMC4518271 DOI: 10.1038/ncomms8682] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 06/01/2015] [Indexed: 11/29/2022] Open
Abstract
The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin–orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron–nuclear system, despite weak spin–orbit coupling in GaAs. Using Landau–Zener sweeps to measure static and dynamic properties of the electron spin–flip probability, we observe that the size of the spin–orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin–orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin–orbit coupling in central-spin systems. Dynamic nuclear polarization is the transfer of electronic angular momentum to nuclear spins and is a potential route for coherently manipulating spin in quantum information. Here, the authors show that spin–orbit coupling can quench dynamic nuclear polarization in a gallium arsenide quantum dot.
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Affiliation(s)
- John M Nichol
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Shannon P Harvey
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Michael D Shulman
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Arijeet Pal
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Vladimir Umansky
- Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Emmanuel I Rashba
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Bertrand I Halperin
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Amir Yacoby
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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13
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Danon J, Rudner MS. Multilevel interference resonances in strongly driven three-level systems. PHYSICAL REVIEW LETTERS 2014; 113:247002. [PMID: 25541796 DOI: 10.1103/physrevlett.113.247002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Indexed: 06/04/2023]
Abstract
We study multiphoton resonances in a strongly driven three-level quantum system, where one level is periodically swept through a pair of levels with constant energy separation E. Near the multiphoton resonance condition nℏω=E, where n is an integer, we find qualitatively different behavior for n even or odd. We explain this phenomenon in terms of families of interfering trajectories of the multilevel system. Remarkably, the behavior is insensitive to fluctuations of the energy of the driven level, and survives deep into the strong dephasing regime. The setup can be relevant for a variety of solid state and atomic or molecular systems. In particular, it provides a clear mechanism to explain recent puzzling experimental observations in strongly driven double quantum dots.
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Affiliation(s)
- Jeroen Danon
- Niels Bohr International Academy, and the Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Mark S Rudner
- Niels Bohr International Academy, and the Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
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14
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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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15
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Stehlik J, Schroer MD, Maialle MZ, Degani MH, Petta JR. Extreme harmonic generation in electrically driven spin resonance. PHYSICAL REVIEW LETTERS 2014; 112:227601. [PMID: 24949787 DOI: 10.1103/physrevlett.112.227601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Indexed: 06/03/2023]
Abstract
We report the observation of multiple harmonic generation in electric dipole spin resonance in an InAs nanowire double quantum dot. The harmonics display a remarkable detuning dependence: near the interdot charge transition as many as eight harmonics are observed, while at large detunings we only observe the fundamental spin resonance condition. The detuning dependence indicates that the observed harmonics may be due to Landau-Zener transition dynamics at anticrossings in the energy level spectrum.
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Affiliation(s)
- J Stehlik
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - M D Schroer
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - M Z Maialle
- Faculdade de Ciências Aplicadas, Universidade Estadual de Campinas, 13484-350 Limeira, São Paulo, Brazil
| | - M H Degani
- Faculdade de Ciências Aplicadas, Universidade Estadual de Campinas, 13484-350 Limeira, São Paulo, Brazil
| | - J R Petta
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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16
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Čadež T, Jefferson JH, Ramšak A. Exact nonadiabatic holonomic transformations of spin-orbit qubits. PHYSICAL REVIEW LETTERS 2014; 112:150402. [PMID: 24785014 DOI: 10.1103/physrevlett.112.150402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Indexed: 06/03/2023]
Abstract
An exact analytical solution is derived for the wave function of an electron in a one-dimensional moving quantum dot in a nanowire, in the presence of time-dependent spin-orbit coupling. For cyclic evolutions we show that the spin of the electron is rotated by an angle proportional to the area of a closed loop in the parameter space of the time-dependent quantum dot position and the amplitude of a fictitious classical oscillator driven by time-dependent spin-orbit coupling. By appropriate choice of parameters, we show that the spin may be rotated by an arbitrary angle on the Bloch sphere. Exact expressions for dynamical and geometrical phases are also derived.
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Affiliation(s)
- T Čadež
- Jožef Stefan Institute, 1000 Ljubljana, Slovenia and Institute of Mathematics, Physics and Mechanics, 1000 Ljubljana, Slovenia
| | - J H Jefferson
- Department of Physics, Lancaster University, Lancaster, LA1 4YB, United Kingdom
| | - A Ramšak
- Jožef Stefan Institute, 1000 Ljubljana, Slovenia and Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia
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17
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Medford J, Beil J, Taylor JM, Bartlett SD, Doherty AC, Rashba EI, DiVincenzo DP, Lu H, Gossard AC, Marcus CM. Self-consistent measurement and state tomography of an exchange-only spin qubit. NATURE NANOTECHNOLOGY 2013; 8:654-659. [PMID: 23995458 DOI: 10.1038/nnano.2013.168] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 07/20/2013] [Indexed: 06/02/2023]
Abstract
Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes.
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Affiliation(s)
- J Medford
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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18
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Li R, You JQ, Sun CP, Nori F. Controlling a nanowire spin-orbit qubit via electric-dipole spin resonance. PHYSICAL REVIEW LETTERS 2013; 111:086805. [PMID: 24010464 DOI: 10.1103/physrevlett.111.086805] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Indexed: 06/02/2023]
Abstract
A semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC) can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the spin-orbit qubit can respond to an external ac electric field, an effect called electric-dipole spin resonance. Here we develop a theory that can apply in the strong SOC regime. We find that there is an optimal SOC strength η(opt)=√2/2, where the Rabi frequency induced by the ac electric field becomes maximal. Also, we show that both the level spacing and the Rabi frequency of the spin-orbit qubit have periodic responses to the direction of the external static magnetic field. These responses can be used to determine the SOC in the nanowire.
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Affiliation(s)
- Rui Li
- Beijing Computational Science Research Center, Beijing 100084, China and Department of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
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19
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Chekhovich EA, Makhonin MN, Tartakovskii AI, Yacoby A, Bluhm H, Nowack KC, Vandersypen LMK. Nuclear spin effects in semiconductor quantum dots. NATURE MATERIALS 2013; 12:494-504. [PMID: 23695746 DOI: 10.1038/nmat3652] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 04/12/2013] [Indexed: 06/02/2023]
Abstract
The interaction of an electronic spin with its nuclear environment, an issue known as the central spin problem, has been the subject of considerable attention due to its relevance for spin-based quantum computation using semiconductor quantum dots. Independent control of the nuclear spin bath using nuclear magnetic resonance techniques and dynamic nuclear polarization using the central spin itself offer unique possibilities for manipulating the nuclear bath with significant consequences for the coherence and controlled manipulation of the central spin. Here we review some of the recent optical and transport experiments that have explored this central spin problem using semiconductor quantum dots. We focus on the interaction between 10(4)-10(6) nuclear spins and a spin of a single electron or valence-band hole. We also review the experimental techniques as well as the key theoretical ideas and the implications for quantum information science.
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Affiliation(s)
- E A Chekhovich
- Department of Physics and Astronomy, University of Sheffield, Sheffield, UK
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20
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Srinivasa V, Nowack KC, Shafiei M, Vandersypen LMK, Taylor JM. Simultaneous spin-charge relaxation in double quantum dots. PHYSICAL REVIEW LETTERS 2013; 110:196803. [PMID: 23705734 DOI: 10.1103/physrevlett.110.196803] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Indexed: 06/02/2023]
Abstract
We investigate phonon-induced spin and charge relaxation mediated by spin-orbit and hyperfine interactions for a single electron confined within a double quantum dot. A simple toy model incorporating both direct decay to the ground state of the double dot and indirect decay via an intermediate excited state yields an electron spin relaxation rate that varies nonmonotonically with the detuning between the dots. We confirm this model with experiments performed on a GaAs double dot, demonstrating that the relaxation rate exhibits the expected detuning dependence and can be electrically tuned over several orders of magnitude. Our analysis suggests that spin-orbit mediated relaxation via phonons serves as the dominant mechanism through which the double-dot electron spin-flip rate varies with detuning.
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Affiliation(s)
- V Srinivasa
- Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA.
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21
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Petersen G, Hoffmann EA, Schuh D, Wegscheider W, Giedke G, Ludwig S. Large nuclear spin polarization in gate-defined quantum dots using a single-domain nanomagnet. PHYSICAL REVIEW LETTERS 2013; 110:177602. [PMID: 23679779 DOI: 10.1103/physrevlett.110.177602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 03/13/2013] [Indexed: 06/02/2023]
Abstract
The electron-nuclei (hyperfine) interaction is central to spin qubits in solid state systems. It can be a severe decoherence source but also allows dynamic access to the nuclear spin states. We study a double quantum dot exposed to an on-chip single-domain nanomagnet and show that its inhomogeneous magnetic field crucially modifies the complex nuclear spin dynamics such that the Overhauser field tends to compensate external magnetic fields. This turns out to be beneficial for polarizing the nuclear spin ensemble. We reach a nuclear spin polarization of ≃50%, unrivaled in lateral dots, and explain our manipulation technique using a comprehensive rate equation model.
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Affiliation(s)
- Gunnar Petersen
- Center for Nanoscience and Fakultät für Physik, Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 München, Germany
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22
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Shafiei M, Nowack KC, Reichl C, Wegscheider W, Vandersypen LMK. Resolving spin-orbit- and hyperfine-mediated electric dipole spin resonance in a quantum dot. PHYSICAL REVIEW LETTERS 2013; 110:107601. [PMID: 23521296 DOI: 10.1103/physrevlett.110.107601] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2012] [Indexed: 06/01/2023]
Abstract
We investigate the electric manipulation of a single-electron spin in a single gate-defined quantum dot. We observe that so-far neglected differences between the hyperfine- and spin-orbit-mediated electric dipole spin resonance conditions have important consequences at high magnetic fields. In experiments using adiabatic rapid passage to invert the electron spin, we observe an unusually wide and asymmetric response as a function of the magnetic field. Simulations support the interpretation of the line shape in terms of four different resonance conditions. These findings may lead to isotope-selective control of dynamic nuclear polarization in quantum dots.
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Affiliation(s)
- M Shafiei
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
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23
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van den Berg JWG, Nadj-Perge S, Pribiag VS, Plissard SR, Bakkers EPAM, Frolov SM, Kouwenhoven LP. Fast spin-orbit qubit in an indium antimonide nanowire. PHYSICAL REVIEW LETTERS 2013; 110:066806. [PMID: 23432291 DOI: 10.1103/physrevlett.110.066806] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Indexed: 05/22/2023]
Abstract
Because of the strong spin-orbit interaction in indium antimonide, orbital motion and spin are no longer separated. This enables fast manipulation of qubit states by means of microwave electric fields. We report Rabi oscillation frequencies exceeding 100 MHz for spin-orbit qubits in InSb nanowires. Individual qubits can be selectively addressed due to intrinsic differences in their g factors. Based on Ramsey fringe measurements, we extract a coherence time T(2)(*)=8±1 ns at a driving frequency of 18.65 GHz. Applying a Hahn echo sequence extends this coherence time to 34 ns.
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Affiliation(s)
- J W G van den Berg
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
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24
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Łuczak J, Bułka BR. Entanglement in a three spin system controlled by electric and magnetic fields. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:375303. [PMID: 22913964 DOI: 10.1088/0953-8984/24/37/375303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We study the effect of electric field and magnetic flux on spin entanglement in an artificial triangular molecule built of coherently coupled quantum dots. In a subspace of doublet states an explicit relation of concurrence with spin correlation functions and chirality is presented. The electric field modifies superexchange correlations and shifts many-electron levels (the Stark effect), as well as changing spin correlations. For some specific orientation of the electric field one can observe monogamy, for which one of the spins is separated from two others. Moreover, the Stark effect manifests itself in a different spin entanglement for small and strong electric fields. The role of magnetic flux is opposite: it leads to circulation of spin supercurrents and spin delocalization.
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Affiliation(s)
- Jakub Łuczak
- Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland.
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25
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Nadj-Perge S, Pribiag VS, van den Berg JWG, Zuo K, Plissard SR, Bakkers EPAM, Frolov SM, Kouwenhoven LP. Spectroscopy of spin-orbit quantum bits in indium antimonide nanowires. PHYSICAL REVIEW LETTERS 2012; 108:166801. [PMID: 22680747 DOI: 10.1103/physrevlett.108.166801] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Indexed: 06/01/2023]
Abstract
A double quantum dot in the few-electron regime is achieved using local gating in an InSb nanowire. The spectrum of two-electron eigenstates is investigated using electric dipole spin resonance. Singlet-triplet level repulsion caused by spin-orbit interaction is observed. The size and the anisotropy of singlet-triplet repulsion are used to determine the magnitude and the orientation of the spin-orbit effective field in an InSb nanowire double dot. The obtained results are confirmed using spin blockade leakage current anisotropy and transport spectroscopy of individual quantum dots.
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Affiliation(s)
- S Nadj-Perge
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
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26
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Coupling artificial molecular spin states by photon-assisted tunnelling. Nat Commun 2011; 2:556. [PMID: 22109530 PMCID: PMC3483534 DOI: 10.1038/ncomms1561] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 10/20/2011] [Indexed: 11/17/2022] Open
Abstract
Artificial molecules containing just one or two electrons provide a powerful platform
for studies of orbital and spin quantum dynamics in nanoscale devices. A well-known
example of these dynamics is tunnelling of electrons between two coupled quantum
dots triggered by microwave irradiation. So far, these tunnelling processes have
been treated as electric-dipole-allowed spin-conserving events. Here we report that
microwaves can also excite tunnelling transitions between states with different
spin. We show that the dominant mechanism responsible for violation of spin
conservation is the spin–orbit interaction. These transitions make it
possible to perform detailed microwave spectroscopy of the molecular spin states of
an artificial hydrogen molecule and open up the possibility of realizing full
quantum control of a two-spin system through microwave excitation. Tunnelling transitions triggered by microwave irradiation between
coupled quantum dots have generally been assumed to be spin-conserving. This study shows
that this condition is violated in the presence of spin–orbit coupling, thus
opening new possibilities for manipulating a two–spin qubit system by
microwave irradiation.
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27
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Pioda A, Totoki E, Kiyama H, Fujita T, Allison G, Asayama T, Oiwa A, Tarucha S. Single-shot detection of electrons generated by individual photons in a tunable lateral quantum dot. PHYSICAL REVIEW LETTERS 2011; 106:146804. [PMID: 21561212 DOI: 10.1103/physrevlett.106.146804] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Indexed: 05/30/2023]
Abstract
We demonstrate single-shot detection of single electrons generated by single photons using an electrically tunable quantum dot and a quantum point contact charge detector. By tuning the quantum dot in a Coulomb blockade before the photoexcitation, we observe the trapping and subsequent resetting of single photogenerated electrons. The photogenerated electrons can be stored in the dot for a tunable time range from shorter to longer than the spin-flip time T1. We combine this trap-reset technique with spin-dependent tunneling under magnetic fields to observe the spin-dependent photon detection within the T1.
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Affiliation(s)
- A Pioda
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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28
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Pályi A, Burkard G. Disorder-mediated electron valley resonance in carbon nanotube quantum dots. PHYSICAL REVIEW LETTERS 2011; 106:086801. [PMID: 21405589 DOI: 10.1103/physrevlett.106.086801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Indexed: 05/30/2023]
Abstract
We propose a scheme for coherent rotation of the valley isospin of a single electron confined in a carbon nanotube quantum dot. The scheme exploits the ubiquitous atomic disorder of the nanotube crystal lattice, which induces time-dependent valley mixing as the confined electron is pushed back and forth along the nanotube axis by an applied ac electric field. Using experimentally determined values for the disorder strength we estimate that valley Rabi oscillations with a period on the nanosecond time scale are feasible. The valley resonance effect can be detected in the electric current through a double quantum dot in the single-electron transport regime.
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Affiliation(s)
- András Pályi
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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29
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Nadj-Perge S, Frolov SM, Bakkers EPAM, Kouwenhoven LP. Spin–orbit qubit in a semiconductor nanowire. Nature 2010; 468:1084-7. [DOI: 10.1038/nature09682] [Citation(s) in RCA: 532] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 11/10/2010] [Indexed: 11/09/2022]
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30
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Reilly DJ, Taylor JM, Petta JR, Marcus CM, Hanson MP, Gossard AC. Exchange control of nuclear spin diffusion in a double quantum dot. PHYSICAL REVIEW LETTERS 2010; 104:236802. [PMID: 20867261 DOI: 10.1103/physrevlett.104.236802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Indexed: 05/25/2023]
Abstract
The influence of gate-controlled two-electron exchange on the relaxation of nuclear polarization in small ensembles (N∼10(6)) of nuclear spins is examined in a GaAs double quantum dot system. Waiting in the (2,0) charge configuration, which has large exchange splitting, reduces the nuclear diffusion rate compared to that of the (1,1) configuration. Matching exchange to Zeeman splitting significantly increases the nuclear diffusion rate.
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Affiliation(s)
- D J Reilly
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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31
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Huang SM, Tokura Y, Akimoto H, Kono K, Lin JJ, Tarucha S, Ono K. Spin bottleneck in resonant tunneling through double quantum dots with different Zeeman splittings. PHYSICAL REVIEW LETTERS 2010; 104:136801. [PMID: 20481900 DOI: 10.1103/physrevlett.104.136801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Indexed: 05/29/2023]
Abstract
We investigated the electron transport property of the InGaAs/GaAs double quantum dots, the electron g factors of which are different from each other. We found that in a magnetic field, the resonant tunneling is suppressed even if one of the Zeeman sublevels is aligned. This is because the other misaligned Zeeman sublevels limit the total current. A finite broadening of the misaligned sublevel partially relieves this bottleneck effect, and the maximum current is reached when interdot detuning is half the Zeeman energy difference.
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Affiliation(s)
- S M Huang
- Low Temperature Physics Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
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32
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Shin YS, Obata T, Tokura Y, Pioro-Ladrière M, Brunner R, Kubo T, Yoshida K, Tarucha S. Single-spin readout in a double quantum dot including a micromagnet. PHYSICAL REVIEW LETTERS 2010; 104:046802. [PMID: 20366727 DOI: 10.1103/physrevlett.104.046802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Indexed: 05/29/2023]
Abstract
We use photon-assisted tunneling (PAT) and an inhomogeneous Zeeman field to demonstrate spin-selective PAT readout with a double quantum dot. The inhomogeneous Zeeman field is generated by a proximal micromagnet, which provides different stray fields between the two dots, resulting in an energy difference between the interdot PAT of the up-spin state and that of the down-spin state. We apply various external magnetic fields to modify the relative filling weight between the up-spin and down-spin states and detect it by using a charge detection technique to probe the PAT induced charge delocalization in the double dot.
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Affiliation(s)
- Yun-Sok Shin
- Quantum Spin Information Project, ICORP, JST, Atsugi-shi, Kanagawa 243-0198, Japan.
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33
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Danon J, Vink IT, Koppens FHL, Nowack KC, Vandersypen LMK, Nazarov YV. Multiple nuclear polarization States in a double quantum dot. PHYSICAL REVIEW LETTERS 2009; 103:046601. [PMID: 19659378 DOI: 10.1103/physrevlett.103.046601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Indexed: 05/28/2023]
Abstract
We observe multiple stable states of nuclear polarization and nuclear self-tuning over a large range of fields in a double quantum dot under conditions of electron spin resonance. The observations can be understood within an elaborated theoretical rate equation model for the polarization in each of the dots, in the limit of strong driving. This model also captures unusual features of the data, such as fast switching and a "wrong" sign of polarization. The results reported enable applications of this polarization effect, including accurate manipulation and control of nuclear fields.
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Affiliation(s)
- J Danon
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands
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34
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Kumada N, Kamada T, Miyashita S, Hirayama Y, Fujisawa T. Electric field induced nuclear spin resonance mediated by oscillating electron spin domains in GaAs-based semiconductors. PHYSICAL REVIEW LETTERS 2008; 101:137602. [PMID: 18851494 DOI: 10.1103/physrevlett.101.137602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Indexed: 05/26/2023]
Abstract
We demonstrate an alternative nuclear spin resonance using a radio frequency (rf) electric field [nuclear electric resonance (NER)] instead of a magnetic field. The NER is based on the electronic control of electron spins forming a domain structure. The rf electric field applied to a gate excites spatial oscillations of the domain walls and thus temporal oscillations of the hyperfine field to nuclear spins. The rf power and burst duration dependence of the NER spectrum provides insight into the interplay between nuclear spins and the oscillating domain walls.
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Affiliation(s)
- N Kumada
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi 243-0198, Japan
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35
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36
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Lambert N, Mahboob I, Pioro-Ladrière M, Tokura Y, Tarucha S, Yamaguchi H. Electron-spin manipulation and resonator readout in a double-quantum-dot nanoelectromechanical system. PHYSICAL REVIEW LETTERS 2008; 100:136802. [PMID: 18517982 DOI: 10.1103/physrevlett.100.136802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Indexed: 05/26/2023]
Abstract
We demonstrate how magnetically coupling a nanomechanical resonator to a double quantum dot confining two electrons can enable the manipulation of a single electron spin and the readout of the resonator's natural frequency. When the Larmor frequency matches the resonator frequency, the electron spin in one of the dots can be selectively and coherently flipped by the magnetized oscillator. By simultaneously measuring the charge state of the two-electron double quantum dots, this transition can be detected thus enabling the natural frequency and displacement of the mechanical oscillator to be determined.
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Affiliation(s)
- N Lambert
- Digital Materials Lab, Single Quantum Dynamics Research Group, FRS, Riken, Wako, Saitama 351-0198, Japan.
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37
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Petta JR, Taylor JM, Johnson AC, Yacoby A, Lukin MD, Marcus CM, Hanson MP, Gossard AC. Dynamic nuclear polarization with single electron spins. PHYSICAL REVIEW LETTERS 2008; 100:067601. [PMID: 18352516 DOI: 10.1103/physrevlett.100.067601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Indexed: 05/26/2023]
Abstract
We polarize nuclear spins in a GaAs double quantum dot by controlling two-electron spin states near the anticrossing of the singlet (S) and m(S)= +1 triplet (T+) using pulsed gates. An initialized S state is cyclically brought into resonance with the T+ state, where hyperfine fields drive rapid rotations between S and T+, "flipping" an electron spin and "flopping" a nuclear spin. The resulting Overhauser field approaches 80 mT, in agreement with a simple rate-equation model. A self-limiting pulse sequence is developed that allows the steady-state nuclear polarization to be set using a gate voltage.
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Affiliation(s)
- J R Petta
- Department of Physics, Harvard University, 17 Oxford St., Cambridge, Massachusetts 02138, USA
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Danon J, Nazarov YV. Nuclear tuning and detuning of the electron spin resonance in a quantum dot: theoretical consideration. PHYSICAL REVIEW LETTERS 2008; 100:056603. [PMID: 18352405 DOI: 10.1103/physrevlett.100.056603] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Indexed: 05/26/2023]
Abstract
We study nuclear spin dynamics in a quantum dot close to the conditions of electron spin resonance. We show that at a small frequency mismatch, the nuclear field detunes the resonance. Remarkably, at larger frequency mismatch, its effect is opposite: The nuclear system is bistable, and in one of the stable states, the field accurately tunes the electron spin splitting to resonance. In this state, the nuclear field fluctuations are strongly suppressed, and nuclear spin relaxation is accelerated.
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Affiliation(s)
- Jeroen Danon
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands
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Romito A, Gefen Y, Blanter YM. Weak values of electron spin in a double quantum dot. PHYSICAL REVIEW LETTERS 2008; 100:056801. [PMID: 18352406 DOI: 10.1103/physrevlett.100.056801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Indexed: 05/26/2023]
Abstract
We propose a protocol for a controlled experiment to measure a weak value of the electron's spin in a solid state device. The weak value is obtained by a two step procedure--weak measurement followed by a strong one (postselection), where the outcome of the first measurement is kept provided a second postselected outcome occurs. The setup consists of a double quantum dot and a weakly coupled quantum point contact to be used as a detector. Anomalously large values of the spin of a two electron system are predicted, as well as negative values of the total spin. We also show how to incorporate the adverse effect of decoherence into this procedure.
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Affiliation(s)
- Alessandro Romito
- Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot 76100, Israel
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Rudner MS, Levitov LS. Electrically driven reverse overhauser pumping of nuclear spins in quantum dots. PHYSICAL REVIEW LETTERS 2007; 99:246602. [PMID: 18233468 DOI: 10.1103/physrevlett.99.246602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Indexed: 05/25/2023]
Abstract
We propose a new mechanism for polarizing nuclear spins in quantum dots, based on periodic modulation of the hyperfine coupling by electric driving at the electron spin resonance frequency. Dynamical nuclear polarization results from resonant excitation rather than hyperfine relaxation mediated by a thermal bath, and thus is not subject to Overhauser-like detailed balance constraints. This allows polarization in the direction opposite to that expected from the Overhauser effect. Competition of the electrically driven and bath-assisted mechanisms can give rise to spatial modulation and sign reversal of polarization on a scale smaller than the electron confinement radius in the dot.
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Affiliation(s)
- M S Rudner
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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