Narrowing of the Overhauser field distribution by feedback-enhanced dynamic nuclear polarization

TL;DR

This paper models and proposes a feedback scheme using electron dipole spin resonance to significantly narrow the Overhauser field distribution, thereby extending the electron spin coherence time in quantum dot systems.

Contribution

It introduces a new feedback method with electron dipole spin resonance and models its effectiveness in enhancing nuclear spin bath control.

Findings

Model predicts achievable Overhauser field narrowing

Proposed scheme can extend $T_2^*$ to microseconds

Limitations of previous experiments identified

Abstract

In many electron spin qubit systems coherent control is impaired by the fluctuating nuclear spin bath of the host material. Previous experiments have shown dynamic nuclear polarization with feedback to significantly prolong the inhomogeneous dephasing time $T_2^*$ by narrowing the distribution of nuclear Overhauser field fluctuations. We present a model relating the achievable narrowing of the Overhauser field to both the pump rate and the noise magnitude and find reasonable agreement with experimental data. It shows that former experiments on gated GaAs quantum dots were limited by the pump rate of the pumping mechanism used. Here we propose an alternative feedback scheme using electron dipole spin resonance. Sequentially applying two ac electric fields with frequencies slightly detuned from the desired Larmor frequency results in a pump curve with a stable fixed point. Our model predicts that $T_2^*$ values on the order of microseconds can be achieved.