Quantum Dephasing in a Gated GaAs Triple Quantum Dot due to Nonergodic Noise

We study the Zeeman splitting in lateral quantum dots that are defined in GaAs-AlGaAs heterostructures by means of split gates. We demonstrate a nonlinear dependence of the splitting on magnetic field and its substantial variations from dot to dot and from heterostructure to heterostructure. These phenomena are important in the context of information processing since the tunability and dot-dependence of the Zeeman splitting allow for a selective manipulation of spins. We show that spin-orbit effects related to the GaAs band structure quantitatively explain the observed magnitude of the nonlinear dependence of the Zeeman splitting. Furthermore, spin-orbit effects result in a dependence of the Zeeman splitting on predominantly the out-of-plane quantum dot confinement energy. We also show that the variations of the confinement energy due to charge disorder in the heterostructure may explain the dependence of Zeeman splitting on the dot position. This position may be varied by changing the gate voltages, which leads to an electrically tunable Zeeman splitting.

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“…[32]. The faster variation matches the observations of an electron spin interacting with a random distribution of nuclear spins [33,34].…”

Section: Appendix D: Edsr Data For Different Setupssupporting

confidence: 79%

Nonlinear and dot-dependent Zeeman splitting in GaAs/AlGaAs quantum dot arrays

et al. 2018

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“…Even though techniques of fabrication, tuning, and control of gated QDs are rapidly progressing [44][45][46][47][48][49][50][51][52], it is still very demanding to build long arrays. It is therefore of high practical importance to Comparison of the band gap (blue curve, defined as the largest difference of two consecutive terms in an ordered energy spectrum) and the finite-size quantization energy (purple curve, defined as the second largest difference), as functions of N for θ = 2π − δπ/λ, which is a phase differing by π from the phase at which the in-gap states cross in the lowest gap.…”

Section: Minimal Array Sizementioning

confidence: 99%

Fractional boundary charges in quantum dot arrays with density modulation

et al. 2016

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We show that fractional charges can be realized at the boundaries of a linear array of tunnel-coupled quantum dots in the presence of a periodically modulated onsite potential. While the charge fractionalization mechanism is similar to the one in polyacetylene, here the values of fractional charges can be tuned to arbitrary values by varying the phase of the onsite potential or the total number of dots in the array. We also find that the fractional boundary charges, unlike the in-gap bound states, are stable against static random disorder. We discuss the minimum array size where fractional boundary charges can be observed.

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“…However, the same coupling makes the spin vulnerable to the electric noise of the environment, in addition to the magnetic noise [25][26][27]. The latter is predominantly a low-frequency noise from nuclear spins, and can be efficiently suppressed by spin echo [28,29], feedback control [30,31], and a Hamiltonian estimation by fast measurements [32,33]. No such remedies are known for the high-frequency electrical noise, which then fundamentally limits the spin lifetime as predicted by theory [34][35][36][37] and confirmed in experiments [38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Optimal geometry of lateral GaAs and Si/SiGe quantum dots for electrical control of spin qubits

Malkoc¹,

Stano²,

Loss³

2016

Phys. Rev. B

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We investigate the effects of the orientation of the magnetic field and the orientation of a quantum dot, with respect to crystallographic coordinates, on the quality of an electrically controlled qubit realized in a gated semiconductor quantum dot. We find that, due to the anisotropy of the spin-orbit interactions, by varying the two orientations it is possible to tune the qubit in the sense of optimizing the ratio of its couplings to phonons and to a control electric field. We find conditions under which such optimal setup can be reached by solely reorienting the magnetic field, and when a specific positioning of the dot is required. We also find that the knowledge of the relative sign of the spin-orbit interaction strengths allows to choose a robust optimal dot geometry, with the dot main axis along [110], or [110], where the qubit can be always optimized by reorienting the magnetic field.

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Quantum Dephasing in a Gated GaAs Triple Quantum Dot due to Nonergodic Noise

Cited by 57 publications

References 36 publications

Nonlinear and dot-dependent Zeeman splitting in GaAs/AlGaAs quantum dot arrays

Nonlinear and dot-dependent Zeeman splitting in GaAs/AlGaAs quantum dot arrays

Fractional boundary charges in quantum dot arrays with density modulation

Optimal geometry of lateral GaAs and Si/SiGe quantum dots for electrical control of spin qubits

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