Measurement-induced spin squeezing in a cavity

Kevin C. Cox, Joshua M. Weiner, Matthew A. Norcia +3 more

Matthew A. Norcia, Justin Bohnet, Kevin C. Cox +3 more

Hiroki Saito, Masahito Ueda

Spin squeezing of an ensemble of N atoms in a high-Q cavity is enhanced by continuous measurement of photons in the cavity. A degree of spin squeezing proportional to ${N}^{\ensuremath{-}1/3}$ is achieved as a quasi-steady-state over a broad set of initial states of atoms and photons. Our method of spin squeezing is robust against the imperfect photodetection efficiency in current experiments.

Jing Zhang, Kunchi Peng, Samuel L. Braunstein

We propose a scheme for producing entangled spin-squeezed states of an atomic ensemble inside an optical cavity by backaction of a detuned quantum-nondemolition (QND) measurement. By illuminating the atoms with bichromatic light, an interaction Hamiltonian of the cross-Kerr effect between the cavity and atoms is generated to implement QND measurements. The feedback effect is obtained through mixing the phase and amplitude quadratures of the cavity field, due to the detuning of the optical cavity. Therefore the continuous nondemolition measurements are fed back to correct the quantum state of the atomic sample such that unconditional spin squeezing is produced without requiring the use of any external electronics.

Mingfeng Wang, Weizhi Qu, Pengxiong Li +2 more

Peter Groszkowski, Catherine Leroux, Luke C. G. Govia +1 more