Hyperfine induced electron spin and entanglement dynamics in double quantum dots: The case of separate baths

TL;DR

This paper investigates the dynamics of electron spins and their entanglement in double quantum dots with separate nuclear spin baths, revealing how decoherence scales with bath size and polarization, and demonstrating full entanglement under certain conditions.

Contribution

It introduces a numerical study using the long spin approximation to analyze hyperfine-induced spin and entanglement dynamics in double quantum dots with separate baths, highlighting new effects of geometry and polarization.

Findings

Decoherence time scales with bath size according to a power law.

Increasing bath polarization reduces the decay of spin dynamics.

Electron spins can become fully entangled even with weak exchange coupling.

Abstract

We consider a system of two strongly coupled electron spins in zero magnetic field, each of which is interacting with an individual bath of nuclear spins via the hyperfine interaction. Applying the long spin approximation (LSA) introduced in Europhys. Lett. 95, 47009 (here each bath is replaced by a single long spin), we numerically study the electron spin and entanglement dynamics. We demonstrate that the decoherence time is scaling with the bath size according to a power law. As expected, the decaying part of the dynamics decreases with increasing bath polarization. However, surprisingly it turns out that, under certain circumstances, combining quantum dots of different geometry to the double dot setup has a very similar effect on the magnitude of the spin decay. Finally, we show that even for a comparatively weak exchange coupling the electron spins can be fully entangled.