Dark states of single NV centers in diamond unraveled by single shot NMR

TL;DR

This study reveals the equilibrium charge states of NV centers in diamond and demonstrates coherent nuclear spin control in both states, advancing quantum sensing and computing applications.

Contribution

It uncovers the charge state distribution of NV centers under normal conditions and shows coherent nuclear spin manipulation in the neutral state, which was previously unconfirmed.

Findings

70% NV- and 30% NV0 charge states detected

Nuclear spin coherence in NV0 with T1 ~ 90 ms and T2 ~ 6 μs

Single shot NMR enables detection of optically inactive states

Abstract

The nitrogen-vacancy (NV) center in diamond is supposed to be a building block for quantum computing and nanometer scale metrology at ambient conditions. Therefore, precise knowledge of its quantum states is crucial. Here, we experimentally show that under usual operating conditions the NV exists in an equilibrium of two charge states (70% in the expected negative (NV-) and 30% in the neutral one (NV0)). Projective quantum non-demolition measurement of the nitrogen nuclear spin enables the detection even of the additional, optically inactive state. The nuclear spin can be coherently driven also in NV0 (T1 ~ 90 ms and T2 ~ 6 micro-s).