Editor’s Pick on Applied Physics Letters (APL) “Efficient and all-carbon electrical readout of a NV-based Quantum Sensor”

The spin readout of an ensemble of nitrogen-vacancy (NV) centers in diamond can be realized by a photoconductive detection that is a complementary method to the optical detection of the NV electron spin magnetic resonance. Here, we implement the photoconductive detection through graphitic planar electrodes that collect the photocurrent. Graphitic electrodes are patterned using a xenon focused-ion beam on an optical-grade quality diamond crystal containing a nitrogen concentration of 1 ppm and a NV concentration of a few parts per billion. Resistance and current–voltage characteristics of the NV-doped diamond junction are investigated tuning the 532 nm pump beam intensity. The junction has an ohmic behavior and, under a strong bias field, we observe velocity saturation of the optically induced carriers in the diamond junction. We perform the photoconductive detection in the continuous-wave regime of the magnetic resonance of the NV centers ensemble for a magnetic field applied along the < 100 > and the < 111 > directions with a magnitude above 100 mT. This technique enables the realization of all-carbon diamond quantum sensors integrating graphitic microstructures for the electrical readout.

Magnetic sensitivity enhancement via polarimetric excitation and detection of an ensemble of NV centers

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The negatively charged nitrogen-vacancy center (NV) presents remarkable spin-dependent optical properties that make it an interesting tool for magnetic field sensing. In this paper we exploit the polarization properties of the NV center absorption and emission processes to improve the magnetic sensitivity of an ensemble of NV centers. By simply equipping the experimental set-up of a half-wave plate in the excitation path and a polarizer in the detection path we demonstrate an improvement larger than a factor of two on the NV center magnetic sensitivity.