# The neutral silicon-vacancy center in diamond: spin polarization and lifetimes

## TL;DR

This paper reports on the optical spin polarization, long coherence times, and telecom-band emission of the neutral silicon-vacancy center in diamond, highlighting its potential for quantum communication.

## Contribution

It demonstrates efficient optical spin polarization and long coherence times of the SiV^0 center, and explores its suitability for telecom-band quantum communication.

## Key findings

- Spin polarization is most efficient under resonant excitation.
- Ensemble spin coherence time exceeds 100 microseconds.
- Spin relaxation time is greater than 25 seconds.

## Abstract

We demonstrate optical spin polarization of the neutrally-charged silicon-vacancy defect in diamond ($\mathrm{SiV^{0}}$), an $S=1$ defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but non-zero at below-resonant energies. We measure an ensemble spin coherence time $T_2>100~\mathrm{\mu s}$ at low-temperature, and a spin relaxation limit of $T_1>25~\mathrm{s}$. Optical spin state initialization around 946 nm allows independent initialization of $\mathrm{SiV^{0}}$ and $\mathrm{NV^{-}}$ within the same optically-addressed volume, and $\mathrm{SiV^{0}}$ emits within the telecoms downconversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that $\mathrm{SiV^{0}}$ is a promising candidate for a long-range quantum communication technology.