  We put forth the concept of quantum noise sensors based on nonlinear two-mode
interferometers coupled to mechanical oscillators. These simple, autonomous
machines are capable of a hitherto unexplored quantum thermodynamic
functionality: the ability to sense quantum nonlinear correlations of noisy
fields via the thermodynamic variable of extractable work. The machines filter
thermal noise input and turn it into quantum correlated output. Such nonlinear
correlations arise in feasible experimental setups involving Rydberg polaritons
coupled via dipole-dipole interactions or cavity modes that exchange quanta via
their coupling to multi-level atoms. By monitoring a mechanical oscillator
coupled to the interferometer, one can sense the work capacity of one of the
interferometer output modes and thereby reveal its quantum nonlinear
correlations. The proposed quantum sensing method can provide a much simpler
alternative to quantum multiport interferometry supplemented by process
tomography.

Quantum Physics