Quantum optics and sensing with defects in diamond

Defect centres in diamond - most notably the nitrogen-vacancy (NV) centre - exhibit long-lived spin states that can be accessed by optical transitions, similar to trapped atoms or ions. These properties create an appealing solid-state platform for quantum information and precision sensing applications. Recently, the optical transitions of NV centres at low temperature have been exploited to realize optically mediated entanglement over long distances; however, due to poor photon collection efficiency, the rate is extremely low. Our group is developing an open geometry micro-cavity platform that could vastly enhance the efficiency of heralded entanglement or even enable deterministic schemes, and the first part of this talk will present recent progress on this project. Beyond applications in quantum information, the spin of the NV centre represents an exquisitely sensitive, spatially-localized probe of magnetic fields, capable of resolving static and dynamic properties of magnetic materials. The second half of this talk will discuss our NV-based measurements of a magnetic nanostructure whose dynamics are damped or anti-damped by spin currents. By probing the NV spin transitions and relaxation rates, we are able to observe spin transitions driven by anti-damped magnetization dynamics and measure spin transfer cooling to ~ 150K in a room temperature device