Germanium Vacancy in Diamond Quantum Memory Exceeding 20 ms

TL;DR

This paper demonstrates that germanium vacancy centers in diamond can achieve coherence times exceeding 20 milliseconds at millikelvin temperatures, significantly advancing their potential as quantum network nodes.

Contribution

It reports the first long coherence time of over 20 ms for GeV centers and models noise effects to optimize quantum memory performance.

Findings

Coherence time of GeV centers extended to over 20 ms

Magnetic and amplitude noise modeled as Ornstein-Uhlenbeck process

Method enables optimized coherence times for group-IV defects

Abstract

Negatively charged group-IV defects in diamond show great potential as quantum network nodes due to their efficient spin-photon interface. However, reaching sufficiently long coherence times remains a challenge. In this work, we demonstrate coherent control of germanium vacancy center (GeV) at millikelvin temperatures and extend its coherence time by several orders of magnitude to more than 20 ms. We model the magnetic and amplitude noise as an Ornstein-Uhlenbeck process, reproducing the experimental results well. The utilized method paves the way to optimized coherence times of group-IV defects in various experimental conditions and their successful applications in quantum technologies