Two-Qubit Gate of Combined Single-Spin Rotation and Interdot Spin Exchange in a Double Quantum Dot

Brunner, Roland; Shin, Yoojin; Obata, T.; Pioro‐Ladrière, Michel; Kubo, T.; Yoshida, Kazushi; Taniyama, Tomoyasu; Tokura, Y.; Tarucha, Seigo

doi:10.1103/physrevlett.107.146801

Cited by 213 publications

(240 citation statements)

References 23 publications

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“…The revival of interest in Rabi oscillations during the past decade has been fueled by the fact that they can now be measured in a single two-level system (qubit). In fact, the observation 2-15 of high-quality Rabi oscillations in certain isolated two-level systems such as an exciton in quantum dot 2-4 , a Josephson junction [5][6][7] , a single spin in a dot [8][9][10][11][12] , or a vacancy spin [13][14][15] is viewed as evidence that the corresponding qubit can be coherently manipulated.…”

Section: Introductionmentioning

confidence: 99%

Magnetic resonance in slowly modulated longitudinal field: Modified shape of the Rabi oscillations

et al. 2013

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The sensitivity of the Rabi oscillations of a resonantly driven spin-1 2 system to a weak and slow modulation of the static longitudinal magnetic field, B0, is studied theoretically. We establish the mapping of a weakly driven two-level system with modulation onto a strongly driven system without modulation. The mapping suggests that different regimes of spin dynamics, known for a strongly driven system, can be realized under common experimental conditions of weak driving (driving field B1 B0) upon proper choice of the domains of modulation frequency, ωm, and amplitude, B2. Fast modulation ωm ΩR, where ΩR is the Rabi frequency, emulates the regime of driving frequency much bigger than the resonant frequency. Strong modulation, B2 B1, emulates the regime B1 B0. Resonant modulation, ωm ≈ ΩR, gives rise to an envelope of the Rabi oscillations. The shape of this envelope is highly sensitive to the detuning of the driving frequency from the resonance. Theoretical predictions for different domains of B2 and ωm were tested experimentally using NMR of protons in water, where, without modulation, the pattern of Rabi oscillations could be observed over many periods. We present experimental results which reproduce the three predicted modulation regimes, and agree with theory quantitatively.

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Section: Introductionmentioning

confidence: 99%

Magnetic resonance in slowly modulated longitudinal field: Modified shape of the Rabi oscillations

et al. 2013

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“…[2][3][4] In GaAs-based qubits, which are the state of the art, the essential gate operations 1, 5,6 for quantum computation 7,8 have been demonstrated. [9][10][11][12][13][14][15][16][17][18] But GaAs possesses a serious handicap for coherent spin manipulations-the nuclear spins. 19,20 Controlling this source of decoherence is of major interest and an active field of research.…”

Section: Introductionmentioning

confidence: 99%

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

2012

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Highly accurate numerical results of phonon-induced two-electron spin relaxation in silicon double quantum dots are presented. The relaxation, enabled by spin-orbit coupling and the nuclei of 29 Si (natural or purified abundance), is investigated for experimentally relevant parameters, the interdot coupling, the magnetic field magnitude and orientation, and the detuning. We calculate relaxation rates for zero and finite temperatures (100 mK), concluding that our findings for zero temperature remain qualitatively valid also for 100 mK. We confirm the same anisotropic switch of the axis of prolonged spin lifetime with varying detuning as recently predicted in GaAs. Conditions for possibly hyperfine-dominated relaxation are much more stringent in Si than in GaAs. For experimentally relevant regimes, the spin-orbit coupling, although weak, is the dominant contribution, yielding anisotropic relaxation rates of at least two orders of magnitude lower than in GaAs.

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“…[49][50][51] Such electrical control has recently been demonstrated for hole spins in III-V nanowire quantum dots, 52 and coherence times have now been measured for hole spins in Ge-Si core-shell nanowire quantum dots. 53 The very recent achievement of the few-hole regime in lateral gated double-dot devices, 54 suggests that previous highly successful measurements performed for electron spins [55][56][57][58][59][60] can now be performed for hole spins, which show promise for much longer coherence times. 33,35 In the rest of this paper, we introduce a general method that can be used to calculate and enhance the purity of a qubit interacting with an anisotropic environment.…”

Section: Introductionmentioning

confidence: 99%

Maximizing the purity of a qubit evolving in an anisotropic environment

2015

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We provide a general method to calculate and maximize the purity of a qubit interacting with an anisotropic non-Markovian environment. Counter to intuition, we find that the purity is often maximized by preparing and storing the qubit in a superposition of non-interacting eigenstates. For a model relevant to decoherence of a heavy-hole spin qubit in a quantum dot or for a singlettriplet qubit for two electrons in a double quantum dot, we show that preparation of the qubit in its non-interacting ground state can actually be the worst choice to maximize purity. We further give analytical results for spin-echo envelope modulations of arbitrary spin components of a hole spin in a quantum dot, going beyond a standard secular approximation. We account for general dynamics in the presence of a pure-dephasing process and identify a crossover timescale at which it is again advantageous to initialize the qubit in the non-interacting ground state. Finally, we consider a general two-axis dynamical decoupling sequence and determine initial conditions that maximize purity, minimizing leakage to the environment.

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Two-Qubit Gate of Combined Single-Spin Rotation and Interdot Spin Exchange in a Double Quantum Dot

Cited by 213 publications

References 23 publications

Magnetic resonance in slowly modulated longitudinal field: Modified shape of the Rabi oscillations

Magnetic resonance in slowly modulated longitudinal field: Modified shape of the Rabi oscillations

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

Maximizing the purity of a qubit evolving in an anisotropic environment

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