Generation of a macroscopic singlet state in an atomic ensemble

We report on an experiment underway for generating a singlet state in a cold atomic ensemble. The experiment is based on a recent proposal to generate these states by applying a quantum non-demolition (QND) measurement and feedback to an unpolarized ensemble [1]. Our criteria for generating the singlet state is the spin squeezing parameter equation where Fi are the components of the collective angular momentum, N is the number of atoms and f is the spin of a single particle. Any state with ξs < 1 is an entangled state [2]. Our procedure, described bellow, will lead to a highly entangled state with ξs ≪ 1 starting from a non-entangled state with ξ ∼ 1.