Hybrid sensing approaches for quantum spin sensors

Quantum sensing, for example using diamond NV spin centers, has been effectively demonstrated for magnetic and electric fields as well as to measure the local temperature. Novel methods using hybrid sensing modalities, in which auxiliary entities are exploited to interact with the quantum sensor, are now under intense investigation. These include using a nearby ferromagnetic particle with a freely orientable magnetization, which amplifies the magnetic field of a sensed object to the point where it can be detected by a quantum spin sensor. Here I will describe two recent proposals for hybrid sensing modalities. In the first proposal the magnetic field of the NV spin itself is used to generate a magnetic response from a nearby material, and the resulting magnetic field is detected by the spin center. This extends quantum sensing to diamagnetic materials, for which the magnetic susceptibility is the desired metric. In the second proposal single-photon detection by a photoreceptive molecule, which changes its conformation in response to the absorption of a photon, can be measured using quantum sensing of the resulting electric dipole change due to the new shape of the molecule. These results suggest many new hybrid modalities are possible based on current quantum spin sensors. This work done in collaboration with J. van Bree and N. J. Harmon.