Limits of atomic entanglement by cavity feedback: From weak to strong coupling
1 Center for Theoretical Physics PAN - Al. Lotników 32/46, 02-668 Warsaw, Poland
2 Laboratoire Kastler Brossel, ENS, UPMC, Collège de France and CNRS - 24 rue Lhomond, 75231 Paris, France
Received: 30 November 2015
Accepted: 16 February 2016
We theoretically investigate the entangled states of an atomic ensemble that can be obtained via cavity feedback, varying the atom-light coupling from weak to strong, and including a systematic treatment of decoherence. In the strong-coupling regime for small atomic ensembles, the system is driven by cavity losses into a long-lived, highly entangled many-body state that we characterize analytically. In the weak-coupling regime for large ensembles, we find analytically the maximum spin-squeezing that can be achieved by optimizing both the coupling and the atom number. This squeezing is fundamentally limited by spontaneous emission to a constant value, which is independent of the atom number.
PACS: 42.50.Pq – Cavity quantum electrodynamics; micromasers / 42.50.Dv – Quantum state engineering and measurements / 03.67.Bg – Entanglement production and manipulation
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