Many-Body Nonlocality as a Resource for Quantum-Enhanced Metrology

We demonstrate that the many-body nonlocality witnessed by a broad family of Bell inequalities is a resource for ultraprecise metrology. We formulate a general scheme which allows one to track how the sensitivity grows with the nonlocality extending over an increasing number of particles. We illustrate our findings with some prominent examples-a collection of spins forming an Ising chain and a gas of ultracold atoms in any two-mode configuration. We show that in the vicinity of a quantum critical point the rapid increase of the sensitivity is accompanied by the emergence of the many-body Bell nonlocality. The method described in this work allows for a systematic study of highly quantum phenomena in complex systems, and also extends the understanding of the beneficial role played by fundamental nonclassical effects in implementations of quantum-enhanced protocols.

Automated summary

The study demonstrates that many-body nonlocality witnessed by a broad family of Bell inequalities is a resource for ultraprecise metrology, allowing for tracking sensitivity growth with extending nonlocality. Near a quantum critical point, rapid sensitivity increase is accompanied by the emergence of many-body Bell nonlocality, providing a systematic study of highly quantum phenomena in complex systems. This work extends the understanding of the beneficial role played by fundamental nonclassical effects in implementations of quantum-enhanced protocols.