Unitary cavity spin squeezing by quantum erasure

Abstract

Deterministic light-induced spin squeezing in an atomic gas is limited by photon shot noise or, equivalently, by atomic state information escaping with the light field mediating the effective atom-atom interaction. We show theoretically that the performance of cavity spin squeezing [M. H. Schleier-Smith, I. D. Leroux, and V. Vuleti\ifmmode \acute{c}\else \'{c}\fi{}, Phys. Rev. A 81, 021804(R) (2010)] can be substantially improved by erasing the light-atom entanglement, and propose several methods for doing so. Accounting for light scattering into free space, quantum erasure improves the scaling of cavity squeezing from ${S}^{\ensuremath{-}1/2}$ to ${S}^{\ensuremath{-}2/3}$, where $S$ is the total atomic spin.