Enhanced hyperfine-induced spin dephasing in a magnetic-field gradient

Abstract

Magnetic-field gradients are important for single-site addressability and electric-dipole spin resonance of spin qubits in semiconductor devices. We show that these advantages are offset by a potential reduction in coherence time due to the non-uniformity of the magnetic field experienced by a nuclear-spin bath interacting with the spin qubit. We theoretically study spins confined to quantum dots or at single donor impurities, considering both free-induction and spin-echo decay. For quantum dots in GaAs, we find that, in a realistic setting, a magnetic-field gradient can reduce the Hahn-echo coherence time by almost an order of magnitude. This problem can, however, be resolved by applying a moderate external magnetic field to enter a motional averaging regime. For quantum dots in silicon, we predict a cross-over from non-Markovian to Markovian behavior that is unique to these devices. Finally, for very small systems such as single phosphorus donors in silicon, we predict a breakdown of the common Gaussian approximation due to finite-size effects.

16 pages, 5 figures

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Cited by in corpus (9)

• Two-axis control of a singlet-triplet qubit with an integrated micromagnet
• Electrical control of g-factors in a few-hole silicon nanowire MOSFET
• Hole Spin Coherence in a Ge/Si Heterostructure Nanowire
• Robust two-qubit gates for donors in silicon controlled by hyperfine interactions
• Single-spin manipulation in a double quantum dot in the field of a micromagnet
• Dynamics of entanglement of two electron spins interacting with nuclear spin baths in quantum dots
• Non-Markovian transient spectroscopy in cavity QED
• Anisotropy with respect to the applied magnetic field of spin qubit decoherence times
• Maximizing the purity of a qubit evolving in an anisotropic environment