Spin Squeezing with a BEC: the effect of decoherence
Spin-squeezed states [1] could be used to further improve the accuracy of atomic clocks, and beat the
fundamental limits imposed by the quantum noise of the atoms
used in the measurement. For this reason, the achievement of large squeezing in
atomic ensembles is a major challenge in our field.
As it is the case for all non trivial quantum states, the
major enemy of squeezing is decoherence.
The main source of decoherence in cold atoms systems are particle losses, and
recently, we analyzed a particular proposal to create highly entangled states in a bimodal atomic Bose-Einstein condensate [2] and identify the limits imposed by the de-coherence due to particle losses. In particular we could
calculate analytically the maximum spin squeezing obtainable
in the presence of losses [3], when the bimodal condensate is
initially prepared in a state with a well defined relative phase for the two components (phase state).
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(This result here is for two spatially separated BECs. M is the mass, a is the scattering length and K1, K2, K3 are the loss rate
constants for one-body, two-body and three-body losses respectively.)
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References