Unconditional Spin Squeezing via Quantum Measurement and Control

Leigh Norris, Collin M. Trail, Ivan Deutsch +1 more

L K Thomsen, Stefano Mancini, Howard M. Wiseman

We discuss the theory and experimental considerations of a quantum feedback scheme for producing deterministically reproducible spin squeezing. Continuous nondemolition atom number measurement from monitoring a probe field conditionally squeezes the sample. Simultaneous feedback of the measurement results controls the quantum state such that the squeezing becomes unconditional. We find that for very strong cavity coupling and a limited number of atoms, the theoretical squeezing approaches the Heisenberg limit. Strong squeezing will still be produced at weaker coupling and even in free space (thus presenting a simple experimental test for quantum feedback). The measurement and feedback can be stopped at any time, thereby freezing the sample with a desired amount of squeezing.

Jian Ma, Xiaoguang Wang, C. P. Sun +1 more

L. K. Thomsen, Howard M. Wiseman

Conditional spin squeezing can be achieved by continuous quantum-nondemolition measurement of an atomic sample. We show that simultaneous feedback of the measurement results can control the quantum state such that the squeezing becomes unconditional. For very strong cavity coupling, the squeezing approaches the Heisenberg limit. Squeezing is also produced at weaker couplings and even in free space, thus presenting a simple experimental test for quantum feedback.

Mingfeng Wang, Weizhi Qu, Pengxiong Li +2 more

Zilong Chen, Jiayan Dai, Justin Bohnet +1 more