Decoherence of coupled electron spins via nuclear spin dynamics in quantum dots

TL;DR

This paper investigates how nuclear spin dynamics influence electron spin decoherence in double quantum dots, revealing a transition from exponential to power-law decay due to ensemble effects and energy renormalization.

Contribution

It demonstrates the impact of exchange interaction and Overhauser field mismatch on nuclear bath dynamics and electron spin decoherence in quantum dots, highlighting differences between single and coupled spins.

Findings

Decoherence transitions from exponential to power-law under ensemble averaging.

Exchange interaction renormalizes nuclear excitation energies affecting decoherence.

Single electron spin decoherence remains consistent across nuclear configurations.

Abstract

In double quantum dots, the exchange interaction between two electron spins renormalizes the excitation energy of pair-flips in the nuclear spin bath, which in turn modifies the non-Markovian bath dynamics. As the energy renormalization varies with the Overhauser field mismatch between the quantum dots, the electron singlet-triplet decoherence resulting from the bath dynamics depends on sampling of nuclear spin states from an ensemble, leading to the transition from exponential decoherence in single-sample dynamics to power-law decay under ensemble averaging. In contrast, the decoherence of a single electron spin in one dot is essentially the same for different choices of the nuclear spin configuration.