Exciton-spin memory with a semiconductor quantum dot molecule

TL;DR

This paper demonstrates a semiconductor quantum dot molecule device capable of storing single photons and transferring their polarization to electron-hole spin states with high fidelity, enabling microsecond-scale quantum memory.

Contribution

It introduces a novel quantum dot molecule system for high-fidelity photon-to-spin conversion and long-duration single-photon storage.

Findings

Single photons stored up to 1 microsecond.

Polarization transfer fidelity above 80%.

Storage fidelity maintained for 12.5 ns repetition period.

Abstract

We report on a single photon and spin storage device based on a semiconductor quantum dot molecule. Optically excited single electron-hole pairs are trapped within the molecule and their recombination rate is electrically controlled over three orders of magnitude. Single photons are stored up to 1 microsecond and read out on a sub-nanosecond timescale. Using resonant excitation, the circular polarisation of individual photons is transferred into the spin state of electron-hole pairs with a fidelity above 80%, which does not degrade for storage times up to the 12.5ns repetition period of the experiment.