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 high fidelity qubit initialization, manipulation, and readout. 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 $\sim 10$ s Hahn echo coherence times, even for applied static magnetic fields below Earth's field.

• Received 31 January 2018

DOI:https://doi.org/10.1103/PhysRevB.97.115205