Coherence of Nitrogen-Vacancy Electronic Spin Ensembles in Diamond

TL;DR

This study demonstrates that nitrogen-vacancy (NV) spin ensembles in high-purity diamond can achieve coherence times comparable to single NVs at room temperature, enhancing their potential for quantum sensing and information applications.

Contribution

It provides both experimental measurements and theoretical modeling of NV ensemble coherence times, highlighting the effects of magnetic field alignment and impurity environment.

Findings

NV ensemble T2 > 600 microseconds in high-purity diamond

Coherence time sharply decreases with magnetic field misalignment

Long coherence times improve NV-based quantum sensing capabilities

Abstract

We present an experimental and theoretical study of electronic spin decoherence in ensembles of nitrogen-vacancy (NV) color centers in bulk high-purity diamond at room temperature. Under appropriate conditions, we find ensemble NV spin coherence times (T_2) comparable to that of single NVs, with T_2 > 600 microseconds for a sample with natural abundance of 13C and paramagnetic impurity density ~10^15 cm^(-3). We also observe a sharp decrease of the coherence time with misalignment of the static magnetic field relative to the NV electronic spin axis, consistent with theoretical modeling of NV coupling to a 13C nuclear spin bath. The long coherence times and increased signal-to-noise provided by room-temperature NV ensembles will aid many applications of NV centers in precision magnetometry and quantum information.