Spin-coherence characterization of boron vacancy defects in hexagonal boron nitride with broadband microwave pulses

TL;DR

This paper characterizes the spin coherence times of boron vacancy defects in hexagonal boron nitride using broadband microwave pulses, providing insights into their quantum sensing potential.

Contribution

It demonstrates a method to measure spin coherence times of VB- defects in hBN with broadband microwave pulses, clarifying their quantum coherence properties.

Findings

T2* = 13.8 ns from Ramsey measurements

T2 = 108.7 ns from Hahn echo measurements

Method effectively evaluates coherence in broad resonance linewidths

Abstract

Negatively charged boron vacancy (VB-) defects in hexagonal boron nitride (hBN) are promising for nanoscale-proximity quantum sensing. To evaluate their performance, it is important to characterize the spin coherence times T2* and T2. In this study, we realized sub-GHz Rabi oscillations of VB- using an isotopically enriched hBN thin film directly stamped onto a narrow gold wire. Using these strong microwave pulses, we performed Ramsey interference and Hahn echo measurements. The Ramsey interference signal showed Gaussian-like decay, yielding T2* = 13.8 ns. The Hahn echo measurement gave T2 = 108.7 ns and a stretch factor of {\alpha}= 1.25. These results experimentally clarify the spin coherence properties of VB- and provide an effective method for evaluating the coherence of spin defects in van der Waals thin films with broad resonance linewidths.