Donor spins in silicon are some of the most promising qubits for upcoming solid-state quantum technologies. The nuclear spins of phosphorus donors in enriched silicon have among the longest coherence times of any solid-state system as well as simultaneous qubit initialization, manipulation and readout fidelities near ~99.9%. Here we characterize the phosphorus in silicon system in the regime of "zero" magnetic field, where a singlet-triplet spin clock transition can be accessed, using laser spectroscopy and magnetic resonance methods. We show the system can be optically hyperpolarized and has ~10 s Hahn echo coherence times, even at Earth's magnetic field and below.
@article{arxiv.1801.10265,
title = {Zero field optical magnetic resonance study of phosphorus donors in 28-silicon},
author = {Kevin J. Morse and Phillip Dluhy and Julian Huber and Jeff Z. Salvail and Kamyar Saeedi and Helge Riemann and Nikolay V. Abrosimov and Peter Becker and Hans-Joachim Pohl and S. Simmons and M. L. W. Thewalt},
journal= {arXiv preprint arXiv:1801.10265},
year = {2018}
}