Multiparameter quantum metrology and mode entanglement with spatially split nonclassical spin states

TL;DR

This paper explores how spatially split nonclassical spin states can enhance multiparameter quantum sensing, revealing the role of mode entanglement and providing optimal strategies for distributed quantum metrology.

Contribution

It introduces analytical tools to quantify quantum gain and mode entanglement in spatially distributed spin states, advancing multiparameter quantum metrology techniques.

Findings

Quantum gain in sensitivity for split spin states

Mode entanglement as a resource for distributed sensing

Optimal protocols for multiparameter estimation

Abstract

We identify the multiparameter sensitivity of split nonclassical spin states, such as spin-squeezed and Dicke states spatially distributed into several addressable modes. Analytical expressions for the spin-squeezing matrix of a family of states that are accessible by current atomic experiments reveal the quantum gain in multiparameter metrology, as well as the optimal strategies to maximize the sensitivity. We further study the mode entanglement of these states by deriving a witness for genuine $k$-partite mode entanglement from the spin-squeezing matrix. Our results highlight the advantage of mode entanglement for distributed sensing, and outline optimal protocols for multiparameter estimation with nonclassical spatially-distributed spin ensembles.