Quantum control-enhanced sensing and spectroscopy with NV qubits in diamond

Quantum sensors take advantage of the inherent sensitivity of quantum systems to external environment perturbations to precisely measure target signals. The same interaction with the environment, however, limits the device sensitivity by reducing the coherence of the quantum states. Quantum control can play a crucial role in improving the sensor performance. We explore quantum control tools to improve the performance of a Nitrogen-Vacancy (NV) center as a single-qubit sensor of ultra-weak magnetic fields in noisy environments. We present a method to obtain a precise spectroscopic characterization of the NV environment, instrumental to design robust sensing strategies with improved noise protection. Then, we exploit optimal quantum control - based on a set of numerical methods to optimize the temporal dependence of the sensor driving field - adapted to quantum sensing purposes, and prove its advantage to achieve best compromises between signal acquisition and noise cancellation.