Examining how fluid motion affects the quantum spin relaxation of nitrogen-vacancy (NV) centers in diamond

Nitrogen-vacancy (NV) centers have gained significant interest over the past decade as a versatile nanoscale, quantum-based sensing platform. These vacancies are point defects within a diamond lattice, with electron spin states that are highly sensitive to external influences, including temperature, strain, and magnetic and electric fields. NV center-based sensors operate by monitoring changes in the spin states -- either in individual or ensembles of NV centers -- to gather information about a parameter of interest. Because the spin state can be optically manipulated and read at room temperature, NV center-based diagnostics are becoming increasingly accessible for nanoscale sensing across various applications and conditions. Despite the rapid development and spread of NV center-based sensing protocols, many open questions remain about how to leverage these capabilities to uncover new insights into fluid mechanics. Here, we investigate whether proximal fluid flow can influence the stability of the NV center spin states. Our approach utilizes spin relaxometry to monitor the spin states of NV centers within diamond nanoparticles as they are exposed to effects from an overlying aqueous fluid flow inside a millimeter-scale laminar channel.