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arXiv:1812.11548

Entangling and squeezing atoms by weak measurement

Mingfeng Wang, Weizhi Qu, Han Bao, Pengxiong Li, Yanhong Xiao

Published Dec 30, 2018• 0 citations
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Abstract

A weak measurement approach is proposed to entangle and squeeze atoms. We show that even for very small coupling strength between light and atoms, one can achieve large squeezing unattainable with normal measurement-based squeezing. Post-selecting the photons interacting with spins via a weak off-resonant quantum nondemolition interaction (QND) in a state nearly orthogonal to its initial state can strengthen the entanglement among elementary spins and thus enhance spin squeezing. The squeezing process is probabilistic but the created state is unconditionally determined. Further control of the post-selection parameter and the detection process can transform the QND-like spin squeezing into the one-axis-twisting or even two-axis-twisting type.

DOI
10.48550/arxiv.1812.11548

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A weak measurement approach is proposed to entangle and squeeze atoms. We show that even for very small coupling strength between light and atoms, one can achieve large squeezing unattainable with normal measurement-based squeezing. Post-selecting the photons interacting with spins via a weak off-resonant quantum nondemolition interaction (QND) in a state nearly orthogonal to its initial state can strengthen the entanglement among elementary spins and thus enhance spin squeezing. The squeezing process is probabilistic but the created state is unconditionally determined. Further control of the post-selection parameter and the detection process can transform the QND-like spin squeezing into the one-axis-twisting or even two-axis-twisting type.
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We theoretically investigate the use of quantum nondemolition measurement to enhance the sensitivity of atom interferometry with Bose-condensed atoms. In particular, we are concerned with enhancing existing high-precision atom interferometry apparatuses, and so restrict ourselves to dilute atomic samples and the use of free-propagating light or optical cavities in the weak-coupling regime. We find the optimum parameter regime that balances between spin squeezing and atomic loss and find that significant improvements in sensitivity are possible. Finally, we consider the use of squeezed light and show that this can provide further boosts to sensitivity.