Single Photon Detection using Chromophores and Nitrogen Vacancies in Diamond

Summary form only given. Long spin coherence times of nitrogen vacancy (NV) center spins in diamond under ambient conditions have made these systems attractive candidates for quantum information processing and magnetometry [1]. Recently, progress has been made using the ground state energy splitting of an NV center spin as a nanoscale magnetometer with extremely high sensitivity [2]. The spin-orbit interaction in conjunction with an electric field also induces spin splitting of the ms = ±1 states [3] which suggests the dependence of the NV ground state on electric field might be useful as an electric field sensor. We develop a theory in which the optical output of an NV center is used to determine the presence of an electric field. The NV spin is initiated in a specified state and evolved according to the Liouville equation. The theory of quantum state discrimination [5] allows us to choose a particular basis of measurement to optimally determine whether at some instant there is an electric fi eld present or absent. We predict the existence of the photo -excited electric dipole fi eld and, by extension, the incident photon given a measured readout state (photoemission) from the NV center. By the quantum nature of our proposed sensor, there is inherent uncertainty when reading out the NV spin state. This uncertainty is quantified by the minimum error probability which is plotted in Figure 2 as a function of time for different magnetic fi elds. The larger the electric fi eld the smaller the error rate. We find that an applied magnetic field plays a non -trivial role that can reduce the error rate. We describe a scheme by which the time of the incident photon can be resolved. Finally we investigate the role of multiple, independent NV centers interfaced with a single chromophores. Such a set up allows for an exponential decrease in error probability.