Probing the Evolution of the Electron Spin Wave Function of the Nitrogen-Vacancy Center in Diamond via Pressure Tuning

Abstract

Understanding the profile of a qubit's wave function is key to its quantum applications. Unlike conducting systems, where a scanning tunneling microscope can be used to probe the electron distribution, there is no direct method for solid-state-defect-based qubits in wide-band-gap semiconductors. In this work, we use pressure as a tuning method and a nuclear spin as an atomic scale probe to monitor the hyperfine structure of negatively charged nitrogen-vacancy (N-V) centers in diamonds under pressure. We present a detailed study on the nearest-neighbor 13C hyperfine splitting in the optically detected magnetic resonance spectrum of N-V centers at different pressures. By examining the 13C hyperfine interaction upon pressurizing, we show that the N-V hyperfine parameters have prominent changes, resulting in an increase in the N-V electron spin density and rehybridization from sp3 to sp2 bonds. The ab initio calculations of strain dependence of the N-V center's hyperfine levels are done independently. The theoretical results qualitatively agree well with experimental data without introducing any fitting parameters. Furthermore, this method can be adopted to probe the evolution of wave function in other defect systems. This potential capability could play a role in developing magnetometry and quantum information processing using the defect centers.