Silicon-Vacancy Spin Qubit in Diamond: A Quantum Memory Exceeding 10 ms with Single-Shot State Readout

TL;DR

This paper demonstrates that silicon-vacancy centers in diamond can achieve spin coherence times exceeding 10 milliseconds at very low temperatures, with high-fidelity single-shot readout, making them promising for scalable quantum networks.

Contribution

The study achieves a five-order-of-magnitude increase in SiV$^-$ spin coherence time and demonstrates single-shot readout with high fidelity at millikelvin temperatures.

Findings

Spin coherence time $T_2$ of 13 ms at 100 mK.

Single-shot readout fidelity of 89%.

Spin relaxation time $T_1$ exceeds 1 second.

Abstract

The negatively-charged silicon-vacancy (SiV$^-$) color center in diamond has recently emerged as a promising system for quantum photonics. Its symmetry-protected optical transitions enable creation of indistinguishable emitter arrays and deterministic coupling to nanophotonic devices. Despite this, the longest coherence time associated with its electronic spin achieved to date ($\sim 250$ ns) has been limited by coupling to acoustic phonons. We demonstrate coherent control and suppression of phonon-induced dephasing of the SiV$^-$ electronic spin coherence by five orders of magnitude by operating at temperatures below 500 mK. By aligning the magnetic field along the SiV$^-$ symmetry axis, we demonstrate spin-conserving optical transitions and single-shot readout of the SiV$^-$ spin with 89% fidelity. Coherent control of the SiV$^-$ spin with microwave fields is used to demonstrate a spin coherence time $T_2$ of 13 ms and a spin relaxation time $T_1$ exceeding 1 s at 100 mK. These results establish the SiV$^-$ as a promising solid-state candidate for the realization of scalable quantum networks.