Probing the electronic ground state of the nitrogen-vacancy center in nanodiamonds at room temperature

Abstract

The color centers in diamonds are promising candidates in the context of quantum information science, quantum computation, and spin-based quantum sensors due to their spin-dependent optical transitions. The manipulation and optical readout of electronic spin state is measured using a technique known as optically detected magnetic resonance (ODMR). Here, we discuss the indigenous development of ODMR setup to coherently manipulate and precise readout of spin state of nitrogen-vacancy centers (NV) in nanodiamond at room-temperature. The study involves the confocal mapping of an ensemble of NV centers to measure spin state-dependent optical transition by applying an optical excitation and microwave field simultaneously. The spin state control appears as a dip at 2.87 GHz in the measured emission intensity spectra as a function of microwave frequency. An ODMR contrast of 3.4 % is achieved at the NV center emission maximum of 660 nm and an inhomogeneous dephasing time of 0.03 microseconds. We find an inherent small split in the ODMR dip which is induced by local strain in nanodiamonds. The split becomes stronger while applying an external magnetic field, which forms the basis of NV center-based magnetometry. The results are useful for spin-based microwave-optical quantum transducers, quantum sensing, and quantum memory devices.