We show storage of the circular polarisation of an optical field, transferring it to the spin-state of an individual electron confined in a single semiconductor quantum dot. The state is subsequently readout through the electronically-triggered emission of a single photon. The emitted photon shares the same polarisation as the initial pulse but has a different energy, making the transfer of quantum information between different physical systems possible. With an applied magnetic field of 2 Tesla, spin memory is preserved for at least 1000 times more than the exciton's radiative lifetime.
@article{arxiv.0706.2143,
title = {Single electron-spin memory with a semiconductor quantum dot},
author = {Robert J. Young and Samuel J. Dewhurst and R. Mark Stevenson and Paola Atkinson and Anthony J. Bennett and Martin B. Ward and Ken Cooper and David A. Ritchie and Andrew J. Shields},
journal= {arXiv preprint arXiv:0706.2143},
year = {2009}
}