Spin squeezing in itinerant atomic and molecular systems

We focus on the problem of developing practical, scalable and robust protocols that produce quantum entangled states useful for sensing beyond the standard quantum limit. Spin squeezing is an example of such a quench protocol for generating such many body entangled spin states.



We study quench protocols for producing “spin-squeezed” states, applicable to cold atomic and cold molecular systems. We develop a hydrodynamic theory of spin squeezing and subsequently apply it to address a simple question motivated by these experiments: Is spin squeezing most favourable when the spins are itinerant (mobile) or trapped (immobile)? We find that despite the additional noise introduced by having mobile spins, a “motional narrowing” effect dominates, leading to optimal squeezing (and hence optimal measurement sensitivity) occurring in highly itinerant systems.