A variational toolbox for quantum multi-parameter estimation

With an ever-expanding ecosystem of noisy and intermediate-scale quantum devices, exploring their possible applications is a rapidly growing field information science. In this work, we demonstrate that variational algorithms feasible on such devices address challenge central to the metrology: The identification near-optimal probes measurement operators for multi-parameter estimation problems. We first introduce general framework which allows sequential updates parameters improve probe states measurements widely applicable both discrete continuous-variable settings. then practical functioning approach through numerical simulations, showcasing how tailored over standard methods in regime. Along way, prove validity parameter-shift rule evolutions, expected be interest algorithms. our approach, advocate mindset quantum-aided design, exploiting technology learn close optimal, experimentally metrology protocols.