The negatively charged nitrogen-vacancy (NV⁻) center in diamond has emerged as a versatile quantum sensor. In particular, it can be readily implemented in high-pressure experiments, relieving the prevailing lack of local sensing techniques applicable to the confined pressure chamber. In light of the potential of NV⁻ sensing in high-pressure research, this thesis is devoted to more thoroughly characterizing the NV⁻ center as a quantum sensor workable under extreme pressure as well as more fundamentally understanding the pressure effects on the NV⁻ system. In the first project, we provide a systematic comparison between two different types of NV⁻ sensors frequently used in a diamond anvil cell (DAC), which is a conventional workhorse in the high-pressure community. The two sensor types a...[ Read more ]

The negatively charged nitrogen-vacancy (NV⁻) center in diamond has emerged as a versatile quantum sensor. In particular, it can be readily implemented in high-pressure experiments, relieving the prevailing lack of local sensing techniques applicable to the confined pressure chamber. In light of the potential of NV⁻ sensing in high-pressure research, this thesis is devoted to more thoroughly characterizing the NV⁻ center as a quantum sensor workable under extreme pressure as well as more fundamentally understanding the pressure effects on the NV⁻ system. In the first project, we provide a systematic comparison between two different types of NV⁻ sensors frequently used in a diamond anvil cell (DAC), which is a conventional workhorse in the high-pressure community. The two sensor types are the implanted NV⁻ centers (INVs) in the diamond anvil culet and NV⁻-enriched nano-diamonds (NDs) immersed in the pressure medium. We incorporate them into a single DAC and compare them via various spectroscopic techniques including optically detected magnetic resonance (ODMR), photoluminescence (PL), and pulsed measurements. Their local pressurized environments, zero-phonon line (ZPL) shifts, and decoherence properties are examined under high pressure. These comparisons can serve as guidelines on choosing the accurate sensor type for one’s specific experimental purpose. We also address the role of non-hydrostaticity in restricting the maximum working pressure of the NV⁻ center, and further propose solutions to conquer the non-hydrostaticity. In the second project, we investigate the NV⁻–¹³C hyperfine system under hydrostatic pressure. We experimentally and computationally study the modifications to the hyperfine coupling strengths and the NV⁻ electronic spin wavefunction brought by hydrostatic pressure, offering an atomic-level understanding of the pressurized NV⁻ system. These two projects combined aims at bridging between the NV⁻ and high-pressure communities to realize robust NV⁻ sensing under high pressure.