Precision measurements with strongly correlated atoms: beating the decoherence limit

It is well-known that~entangled~atomic states (e.g. so-called spin squeezed states) potentially allow to significantly improve~resolution in Ramsey spectroscopy. However,~entangled states are more~fragile to phase decoherence than uncorrelated states and when decoherence~~ is taken into account~~ both~of them yield the similar limit to~resolution. We propose a method to improve the limit associated with decoherence~~ by using strongly correlated atoms with~dynamics~governed by~ a spherically symmetric and gapped Hamiltonian. We show that under certain conditions the gapped~evolution of the atoms,~can~provide an~~ increase in~the signal-to-noise ratio even in decoherence-limited measurements. Finally, we discuss possible physical systems that can be used to implement this technique in real experiments.