npj Quantum Information, Published online: 07 November 2024; doi:10.1038/s41534-024-00905-x
Finding the optimal probe state for multiparameter quantum metrology using conic programming
The ultimate precision in quantum sensing could be achieved using optimal quantum probe states.
However, current quantum sensing protocols do not use probe states optimally. Indeed, the calculation of optimal probe states remains an outstanding challenge.
In this paper, the team of researchers present an algorithm that efficiently calculates a probe state for correlated and uncorrelated measurement strategies.
The algorithm involves a conic program, which minimizes a linear objective function subject to conic constraints on an operator-valued variable. Their algorithm outputs a probe state that is a simple function of the optimal variable.
They have proved that their algorithm finds the optimal probe state for channel estimation problems, even in the multiparameter setting. For many noiseless quantum sensing problems, they have proved the optimality of maximally entangled probe states. We have also analyzed the performance of 3D-field sensing using various probe states.
Tis work opens the door for a plethora of applications in quantum metrology.