Spin-based quantum computing and magnetic resonance techniques rely on the ability to measure the coherence time, T2, of a spin system. We report on the experimental implementation of all-optical spin echo to determine the T2 time of a semiconductor electron-spin system. We use three ultrafast optical pulses to rotate spins an arbitrary angle and measure an echo signal as the time between pulses is lengthened. Unlike previous spin-echo techniques using microwaves, ultrafast optical pulses allow clean T2 measurements of systems with dephasing times T2* fast in comparison to the timescale for microwave control. This demonstration provides a step toward ultrafast optical dynamic decoupling of spin-based qubits.
@article{arxiv.0904.0632,
title = {Ultrafast optical spin echo for electron spins in semiconductors},
author = {Susan M. Clark and Kai-Mei C. Fu and Qiang Zhang and Thaddeus D. Ladd and Colin Stanley and Yoshihisa Yamamoto},
journal= {arXiv preprint arXiv:0904.0632},
year = {2015}
}