Qubit coherence control in a nuclear spin bath

TL;DR

This paper extends semiclassical spectral diffusion theory to high nuclear spins in III-V materials and demonstrates that applying pi-rotations at a rate proportional to I^2 enhances qubit coherence without nuclear polarization.

Contribution

It introduces a method for coherence enhancement in large nuclear spin environments by applying pi-rotations at a rate scaling with I^2, expanding the applicability of spectral diffusion control.

Findings

Successive pi-rotations improve qubit coherence in high-spin environments.

Coherence enhancement does not require nuclear spin polarization.

The optimal pulse rate scales as I^{-2}.

Abstract

Coherent dynamics of localized spins in semiconductors is limited by spectral diffusion arising from dipolar fluctuation of lattice nuclear spins. Here we extend the semiclassical theory of spectral diffusion for nuclear spins I=1/2 to the high nuclear spins relevant to the III-V materials and show that applying successive qubit pi-rotations at a rate approximately proportional to the nuclear spin quantum number squared (I^2) provides an efficient method for coherence enhancement. Hence robust coherent manipulation in the large spin environments characteristic of the III-V compounds is possible without resorting to nuclear spin polarization, provided that the pi-pulses can be generated at intervals scaling as I^{-2}.