Quantum metrology at high pressures using the nitrogen vacancy center

The nitrogen vacancy (NV) center in diamond is a robust and versatile quantum sensor that can be reliably operated over a wide range of temperature (up to 1000 K) and pressure (up to 60 GPa) conditions. Incorporating NV centers into diamond anvils cells provides a powerful technique of in situ sensing with high spatial resolution for exploring the rich landscape of high-pressure phenomena. However, previous work has brought into question the feasibility of NV measurements in the megabar pressure regimes owing to loss of contrast and blue shifting of the NV zero phonon line (ZPL). We show that controlling the application of stress by playing with the crystal orientation can overcome these road blocks and demonstrate continuous wave ODMR measurements at 120 GPa with sensitivity of 0.6 G/√Hz. This work provides a crucial tool for the investigation of high temperature superconductivity in high pressure super hydrides.