Nitrogen-vacancy center

The nitrogen-vacancy center (N-V center or NV center) is one of numerous point defects in diamond. Its most explored and useful property is its photoluminescence, which allows observers to read out its spin-state. The NV center's electron spin, localized at atomic scales, can be manipulated at room temperature by external factors such as magnetic, or electric fields, microwave radiation, or optical light, resulting in sharp resonances in the intensity of the photoluminescence. These resonances can be explained in terms of electron spin related phenomena such as quantum entanglement, spin–orbit interaction and Rabi oscillations, and analysed using advanced quantum optics theory. An individual NV center can be used as a basic unit for a quantum computer, a qubit, and used for quantum cryptography. Further potential applications in novel fields of electronics and sensing include spintronics, masers, and quantum sensors. If the charge is not specified the term "NV center" refers to the negatively charged NV− center. The nitrogen-vacancy center is a point defect in the diamond lattice. It consists of a nearest-neighbor pair of a nitrogen atom, which substitutes for a carbon atom, and a lattice vacancy. Two charge states of this defect, neutral NV0 and negative NV−, are known from spectroscopic studies using optical absorption, photoluminescence (PL), electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR), which can be viewed as a hybrid of PL and EPR; most details of the structure originate from EPR. The nitrogen atom on one hand has five valence electrons. Three of them are covalently bonded to the carbon atoms, while the other two remain non-bonded and are called a lone pair. The vacancy on the other hand has three unpaired electrons. Two of them form a quasi covalent bond and one remains unpaired. The overall symmetry, however, is axial (trigonal C3V); one can visualize this by imagining the three unpaired vacancy electrons continuously exchanging their roles.