Characterization of S-T$_+$ Transition Dynamics via Correlation Measurements

TL;DR

This paper introduces a method to probe the transverse hyperfine field dynamics in GaAs quantum dots by correlating Landau-Zener sweeps, revealing nuclear spin dephasing and spin-orbit coupling effects through oscillation patterns.

Contribution

It demonstrates experimentally and theoretically that correlation measurements can reveal transverse nuclear spin dynamics and spin-orbit coupling effects in two-electron spin qubits.

Findings

Oscillations in correlations reflect nuclear Larmor precession.

Decay of oscillations indicates nuclear dephasing.

Spin orbit coupling influences oscillation amplitude.

Abstract

Nuclear spins are an important source of dephasing for electron spin qubits in GaAs quantum dots. Most studies of their dynamics have focused on the relatively slow longitudinal polarization. We show, based on a semiclassical model and experimentally, that the dynamics of the transverse hyperfine field can be probed by correlating individual Landau-Zener sweeps across the S-T$_+$ transition of a two-electron spin qubit. The relative Larmor precession of different nuclear spin species leads to oscillations in these correlations, whose decay arises from dephasing of the nuclei. In the presence of spin orbit coupling, oscillations with the absolute Larmor frequencies whose amplitude reflects the spin orbit coupling strength are expected.