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Electrical control of a spin qubit in InSb nanowire quantum dots: Strongly suppressed spin relaxation in high magnetic field
摘要： In this paper we investigate the impact of gating potential and magnetic ?eld on phonon induced spin relaxation rate and the speed of the electrically driven single-qubit operations inside the InSb nanowire spin qubit. We show that a strong g factor and high magnetic ?eld strength lead to the prevailing in?uence of electron-phonon scattering due to deformation potential, considered irrelevant for materials with a weak g factor, like GaAs or Si/SiGe. In this regime we ?nd that spin relaxation between qubit states is signi?cantly suppressed due to the con?nement perpendicular to the nanowire axis. We also ?nd that maximization of the number of single-qubit operations that can be performed during the lifetime of the spin qubit requres single quantum dot gating potential.
关键词： spin qubit,spin relaxation,Rabi frequency,InSb nanowire,quantum dots
更新于2025-09-23 15:19:57
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Coherence of a Driven Electron Spin Qubit Actively Decoupled from Quasistatic Noise
摘要： The coherence of electron spin qubits in semiconductor quantum dots suffers mostly from low-frequency noise. During the past decade, efforts have been devoted to mitigate such noise by material engineering, leading to substantial enhancement of the spin dephasing time for an idling qubit. However, the role of the environmental noise during spin manipulation, which determines the control fidelity, is less understood. We demonstrate an electron spin qubit whose coherence in the driven evolution is limited by high-frequency charge noise rather than the quasistatic noise inherent to any semiconductor device. We employ a feedback-control technique to actively suppress the latter, demonstrating a π-flip gate fidelity as high as 99.04 (cid:1) 0.23% in a gallium arsenide quantum dot. We show that the driven-evolution coherence is limited by the longitudinal noise at the Rabi frequency, whose spectrum resembles the 1=f noise observed in isotopically purified silicon qubits.
关键词： gallium arsenide quantum dot,low-frequency noise,Rabi frequency,1=f noise,semiconductor quantum dots,π-flip gate fidelity,isotopically purified silicon qubits,feedback-control technique,high-frequency charge noise,electron spin qubits
更新于2025-09-19 17:13:59
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Control of a spin qubit in a lateral GaAs quantum dot based on symmetry of gating potential
摘要： We study the influence of quantum dot symmetry on the Rabi frequency and phonon-induced spin relaxation rate in a single-electron GaAs spin qubit. We find that anisotropic dependence on the magnetic field direction is independent of the choice of the gating potential. Also, we discover that relative orientation of the quantum dot, with respect to the crystallographic frame, is relevant in systems with C1v, C2v, or Cn (n ≠ 4r) symmetry. To demonstrate the important impact of the gating potential shape on the spin qubit lifetime, we compare the effects of an infinite-wall equilateral triangle, square, and rectangular confinement with the known results for the harmonic potential. In the studied cases, enhanced spin qubit lifetime is revealed, reaching almost six orders of magnitude increase for the equilateral triangle gating.
关键词： spin qubit,GaAs,spin relaxation rate,Rabi frequency,quantum dot,gating potential
更新于2025-09-19 17:13:59
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Cavity-QED interactions of several atoms
摘要： We study many-atom van der Waals forces arising from reversible atom–field interactions in cavity quantum electrodynamics by using a dressed-state approximation. In the most general case, a single-mode Dicke model for atoms, sharing an arbitrary number of excitations, placed in an imperfect cavity has been developed that leads to the vdW potential of such system. As special cases, we consider the single-excitation Dicke model and also the case of one atom in the presence of multi-photon excitation inside the cavity. In most of the paper, it is assumed that the atoms are distributed symmetrically with respect to the mode structure. This will decouple all asymmetric states, allowing us to ignore them throughout our calculations. The impact of asymmetric states is taken into account for a system wherein one atom, freely placed in a cavity, together with n ? 1 equally-coupled atoms is interacting with the cavity field. By assuming broadened Lorentzian modes instead of sharp ones, the cavity imperfections have been added to the calculations. The position dependence of the effective Rabi frequency is studied for the example of a planar cavity.
关键词： cavity quantum electrodynamics,van der Waals forces,planar cavity,dressed-state approximation,Dicke model,Rabi frequency
更新于2025-09-04 15:30:14