State-dependent phonon-limited spin relaxation of nitrogen-vacancy centers

TL;DR

This study investigates the spin relaxation mechanisms of nitrogen-vacancy centers in diamond, revealing phonon-limited relaxation rates and theoretical limits on coherence times at room temperature, with implications for quantum applications.

Contribution

It provides the first detailed analysis of state-dependent phonon-limited spin relaxation in NV centers, including experimental measurements and a theoretical model explaining the dominant relaxation mechanisms.

Findings

Relaxation on the |m_s=-1> ↔ |m_s=+1> transition is twice as fast as on other transitions.

Relaxation rates are independent of NV concentration, indicating phonon-limited processes.

Maximum coherence time at 295 K is limited to approximately 6.8 ms.

Abstract

Understanding the limits to the spin-coherence of the nitrogen-vacancy (NV) center in diamond is vital to realizing the full potential of this quantum system. We show that relaxation on the $|m_{s}=-1\rangle \leftrightarrow |m_{s}=+1\rangle$ transition occurs approximately twice as fast as relaxation on the $|m_{s}=0\rangle \leftrightarrow |m_{s}=\pm 1\rangle$ transitions under ambient conditions in native NVs in high-purity bulk diamond. The rates we observe are independent of NV concentration over four orders of magnitude, indicating they are limited by spin-phonon interactions. We find that the maximum theoretically achievable coherence time for an NV at 295 K is limited to 6.8(2) ms. Finally, we present a theoretical analysis of our results that suggests Orbach-like relaxation from quasilocalized phonons or contributions due to higher-order terms in the spin-phonon Hamiltonian are the dominant mechanism behind $|m_{s}=-1\rangle \leftrightarrow |m_{s}=+1\rangle$ relaxation, motivating future measurements of the temperature dependence of this relaxation rate.