Charge noise suppression in capacitively coupled singlet-triplet spin qubits under magnetic field

Xuan, Chan, Guo; Kestner, J. P.; Wang, Xin

doi:10.1103/physrevb.103.l161409

Cited by 5 publications

(3 citation statements)

References 82 publications

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“…) 1 2 2ee 14 (q x qy ξz + qy qz ξx + qz qx ξy ) (19) and one should note that M DP GaAs (q) only couples electrons to longitudinal acoustic phonons and M PE GaAs (q) can couple electrons to both LA and transverse acoustic phonons. Here, D = 8.6 eV is the deformation constant, 𝜌 = 5.3 × 10 3 kg m −3 the mass density, e is elementary electric charge, e 14 = 1.38 × 10 9 V m −1 is elasticity tensor component, ξ is the polarization vector, and 𝜔 q the angular frequency of the phonon mode q.…”

Section: Multi-electron Dephasing Of Electron-phonon Interactionmentioning

confidence: 99%

“…Semiconductor quantum‐dot spin qubits as platforms for the physical realization of quantum computation, have attracted extensive research interests due to their promises of tunability, scalability and high‐fidelity gate operations. [ 1–26 ] While each quantum dot typically hosts no more than two electrons in traditional spin qubits, recent researches reveal that the multi‐electron qubits, in which certain dot is allowed to host more than two electrons, may be advantageous in some aspects. [ 27–44 ] For example, a multi‐electron quantum dot may serve as a mediator for fast spin exchange [ 27 ] or a tunable coupling between nearby dots.…”

Section: Introductionmentioning

confidence: 99%

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Theory on Electron–Phonon Spin Dephasing in GaAs Multi‐Electron Double Quantum Dots

Xuan

Wang

2023

Adv Quantum Tech

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Recent studies reveal that a double‐quantum‐dot system hosting more than two electrons may be superior in certain aspects as compared to the traditional case in which only two electrons are confined (a singlet–triplet qubit). The electron–phonon dephasing occurring in a GaAs multi‐electron double‐quantum‐dot system is studied, in a biased case in which the singlet state is hybridized, as well as in an unbiased case in which the hybridization is absent. It is found that while the electron–phonon dephasing rate increases with the number of electrons confined in the unbiased case, this does not hold in the biased case. A merit figure is defined as a ratio between the exchange energy and the dephasing rate, and have shown that in experimentally relevant range of the exchange energy, the merit figure actually increases with the number of electrons in the biased case. The results show that the multi‐electron quantum‐dot system has another advantage in mitigating the effect of electron–phonon dephasing, which is previously under‐appreciated in the literature.

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Section: Multi-electron Dephasing Of Electron-phonon Interactionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theory on Electron–Phonon Spin Dephasing in GaAs Multi‐Electron Double Quantum Dots

Xuan

Wang

2023

Adv Quantum Tech

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“…32, by balancing the local exchange energies and capacitive shift by inter-DQD Coulomb interaction, has shown that the effective exchange energies of two qubits can be made simultaneously insensitive to both DQD detunings. However, a more rigorous calculation based on full Configuration Interaction (full CI) shows the sweet spots are absent under the same dot parameters [48].…”

Section: Introductionmentioning

confidence: 99%

Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits

Chan,

Wang

2022

Preprint

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The search of a sweet spot, locus in qubit parameters where quantum control is first-order insensitive to noises, is key to achieve high-fidelity quantum gates. Efforts to search for such a sweet spot in conventional double-quantum-dot singlet-triplet qubits where each dot hosts one electron ("two-electron singlet-triplet qubit"), especially for two-qubit operations, have been unsuccessful. Here we consider singlet-triplet qubits allowing each dot to host more than one electron, with a total of four electrons in the double quantum dots ("four-electron singlet-triplet qubit"). We theoretically demonstrate, using configuration-interaction calculations, that sweet spots appear in this coupled qubit system. We further demonstrate that, under realistic charge noise and hyperfine noise, two-qubit operation at the proposed sweet spot could offer gate fidelities (∼ 99%) that are higher than conventional two-electron singlet-triplet qubit system (∼ 90%). Our results should facilitate realization of high-fidelity two-qubit gates in singlet-triplet qubit systems.

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Limitations on the maximal level of entanglement of two singlet–triplet qubits in GaAs quantum dots

Bragar,

Cywiński

2024

Quantum Inf Process

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We analyze in detail a procedure of entangling of two singlet–triplet (S–$$T_{0}$$ T 0 ) qubits operated in a regime when energy associated with the magnetic field gradient, $$\Delta B_{z}$$ Δ B z , is an order of magnitude smaller than the exchange energy, J, between singlet and triplet states (Shulman et al. in Science 336:202, 2012). We have studied theoretically a single S–$$T_{0}$$ T 0 qubit in free induction decay and spin echo experiments. We have obtained analytical expressions for the time dependence of components of its Bloch vector for quasistatic fluctuations of $$\Delta B_{z}$$ Δ B z and quasistatic or dynamical $$1/f^{\beta }$$ 1 / f β -type fluctuations of J. We have then considered the impact of fluctuations of these parameters on the efficiency of the entangling procedure which uses an Ising-type coupling between two S–$$T_{0}$$ T 0 qubits. In particular, we have obtained an analytical expression for evolution of two qubits affected by $$1/f^{\beta }$$ 1 / f β -type fluctuations of J. This expression indicates the maximal level of entanglement that can be generated by performing the entangling procedure. Our results deliver also an evidence that in the above-mentioned experiment S–$$T_{0}$$ T 0 qubits were affected by uncorrelated $$1/f^{\beta }$$ 1 / f β charge noises.

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Charge noise suppression in capacitively coupled singlet-triplet spin qubits under magnetic field

Cited by 5 publications

References 82 publications

Theory on Electron–Phonon Spin Dephasing in GaAs Multi‐Electron Double Quantum Dots

Theory on Electron–Phonon Spin Dephasing in GaAs Multi‐Electron Double Quantum Dots

Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits

Limitations on the maximal level of entanglement of two singlet–triplet qubits in GaAs quantum dots

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