A fast optimal control algorithm for quantum sensing

NV centers in diamond have been established in the last decade as a prime platform for quantum sensing, with applications ranging from nanomaterial characterization to biosensing, and magnetic resonance imaging. With the burgeoning of these applications, more relevant becomes the demand for improving the sensor performance.

We introduce an innovative method to optimize the sensitivity of the NV center to time-varying magnetic fields, based on simulated quantum annealing. The method aims at finding optimal spin control protocols in the form of pulsed dynamical decoupling, to protect the sensor from noise while ensuring optimal coupling to the target signal. We show that the problem of extremizing the Fisher information of the sensing task can be mapped into a problem of energy minimization in a spin glass model, for which we implement a fast and robust quantum annealing algorithm.

We demonstrate that quantum annealing outperforms other optimal control algorithms in terms of noise protection and sensitivity achieved, as well as in terms of computational time.

We envisage that embedding this algorithm in a closed loop can further push the capabilities of the sensor to frequency identification on top of amplitude measurements.