Identifying optimal magnetic field configurations for decoherence mitigation of boron vacancies in hexagonal boron nitride

TL;DR

This paper identifies specific static magnetic field configurations that can significantly enhance the coherence times of boron vacancy centers in hexagonal boron nitride by minimizing energy gradients and suppressing decoherence caused by nuclear spin fluctuations.

Contribution

The study introduces a detailed numerical and analytical approach to find optimal magnetic field orientations for decoherence mitigation in spin-1 systems with nuclear spin coupling.

Findings

Certain magnetic field configurations reduce decoherence significantly.

Analytical model accurately predicts low-gradient subspaces.

Coherence lifetimes can be extended in specific bias field regions.

Abstract

The negatively charged boron vacancy center in 2D hexagonal boron nitride has emerged as a promising quantum sensor. However, its sensitivity is constrained due to ubiquitous nuclear spins in the environment. The nuclear spins, hyperfine coupled with the central electron spin, effectively behave as magnetic field fluctuators, leading to rapid decoherence. Here, we explore the effectiveness of static magnetic field strength and orientation in realizing peculiar subspaces that can lead to enhanced spin coherence. Specifically, using detailed numerical simulations of the spin Hamiltonian, we identify specific field configurations that minimize energy gradients and, consequently, are expected to facilitate decoherence suppression. We also develop an approximate analytical model based on the perturbation theory that accurately predicts these low-gradient subspaces for magnetic fields aligned with the electron spin quantization axis, applicable not only to boron vacancies but to any spin-1 electronic system coupled to nearby nuclear spins. Furthermore, to stimulate experimental validation, we estimate coherence lifetimes as a function of various bias field configurations and demonstrate that significant decoherence suppression can indeed be achieved in certain regions. These findings and the developed methodology offer valuable insights for mitigating decoherence in a low-field regime.