This paper reviews quantum spin squeezing, which characterizes the sensitivity of a state with respect to SU(2) rotations, and is significant for both entanglement detection and high-precision metrology. We first present various definitions of spin squeezing parameters, explain their origin and properties for typical states, and then discuss spin-squeezed states produced with nonlinear twisting Hamiltonians. Afterwards, we explain pairwise correlations and entanglement in spin-squeezed states, as well as the relations between spin squeezing and quantum Fisher information, where the latter plays a central role in quantum metrology. We also review the applications of spin squeezing for detecting quantum chaos and quantum phase transitions, as well as the influence of decoherence on spin squeezing. Finally, we review several experimental realizations of spin squeezing, as well as their corresponding theoretical backgrounds, including: producing spin-squeezed states via particle collisions in Bose-Einstein condensates, transferring photon squeezing to atomic ensembles, and generating spin squeezing via quantum non-demolition measurements.This paper reviews quantum spin squeezing, which characterizes the sensitivity of a state with respect to SU(2) rotations, and is significant for both entanglement detection and high-precision metrology. We first present various definitions of spin squeezing parameters, explain their origin and properties for typical states, and then discuss spin-squeezed states produced with nonlinear twisting Hamiltonians. Afterwards, we explain pairwise correlations and entanglement in spin-squeezed states, as well as the relations between spin squeezing and quantum Fisher information, where the latter plays a central role in quantum metrology. We also review the applications of spin squeezing for detecting quantum chaos and quantum phase transitions, as well as the influence of decoherence on spin squeezing. Finally, we review several experimental realizations of spin squeezing, as well as their corresponding theoretical backgrounds, including: producing spin-squeezed states via particle collisions in Bose-Einstein condensates, transferring photon squeezing to atomic ensembles, and generating spin squeezing via quantum non-demolition measurements.

Aug 16, 20160 citations

Spin squeezing under decoherence: Role of the quantum phase transition

Zhe Sun

In order to witness multipartite correlations beyond pairwise entanglement, we study the spin-squeezing evolution of a spin-1/2 ensemble in environments with quantum phase transitions. Each spin half of the ensemble evolves under its own decoherence channel, which is modeled by a central spin 1/2 surrounded by a spin-1/2 $XY$ chain. We employ four spin-squeezing parameters to describe squeezing, and their expressions at time $t$ are analytically calculated for the spin ensemble in a collective initial state. It is found that spin squeezing of an auxiliary ensemble signals very well the critical regions of the environment. Quantum fluctuations of the environment accelerate the decay of spin squeezing and dramatically change spin squeezing.In order to witness multipartite correlations beyond pairwise entanglement, we study the spin-squeezing evolution of a spin-1/2 ensemble in environments with quantum phase transitions. Each spin half of the ensemble evolves under its own decoherence channel, which is modeled by a central spin 1/2 surrounded by a spin-1/2 $XY$ chain. We employ four spin-squeezing parameters to describe squeezing, and their expressions at time $t$ are analytically calculated for the spin ensemble in a collective initial state. It is found that spin squeezing of an auxiliary ensemble signals very well the critical regions of the environment. Quantum fluctuations of the environment accelerate the decay of spin squeezing and dramatically change spin squeezing.

Physical Review ANov 7, 201115 citations

Spin Squeezing of Superposition

Song-Song Li

International Journal of Theoretical PhysicsNov 30, 201016 citations

Entanglement and Spin Squeezing

Princeton University Press eBooksDec 13, 20100 citations

Spin squeezing, negative correlations, and concurrence in the quantum kicked top model

Xiaoqian Wang, Jian Ma, Lijun Song +2 more

We study spin squeezing, negative correlations, and concurrence in the quantum kicked top model. We prove that the spin squeezing and negative correlations are equivalent for spin systems with only symmetric Dicke states populated. We numerically analyze spin squeezing parameters and concurrence in this model and find that the maximal spin squeezing direction, which refers to the minimal pairwise correlation direction, is strongly influenced by quantum chaos. Entanglement (spin squeezing) sudden death and sudden birth occur alternatively for the periodic and quasiperiodic cases, while only entanglement (spin squeezing) sudden death is found for the chaotic case.We study spin squeezing, negative correlations, and concurrence in the quantum kicked top model. We prove that the spin squeezing and negative correlations are equivalent for spin systems with only symmetric Dicke states populated. We numerically analyze spin squeezing parameters and concurrence in this model and find that the maximal spin squeezing direction, which refers to the minimal pairwise correlation direction, is strongly influenced by quantum chaos. Entanglement (spin squeezing) sudden death and sudden birth occur alternatively for the periodic and quasiperiodic cases, while only entanglement (spin squeezing) sudden death is found for the chaotic case.

arXiv:1010.0109Physical Review ENov 12, 201015 citations

XY

chain. We employ four spin-squeezing parameters to describe squeezing, and their expressions at time

t

are analytically calculated for the spin ensemble in a collective initial state. It is found that spin squeezing of an auxiliary ensemble signals very well the critical regions of the environment. Quantum fluctuations of the environment accelerate the decay of spin squeezing and dramatically change spin squeezing.