Spin-Orbit Coupling Induced Spin Squeezing in Three-Component Bose Gases

TL;DR

This paper demonstrates that synthetic spin-orbit coupling in three-component Bose gases induces and enhances spin-nematic squeezing, a form of quantum entanglement, with potential for experimental realization in ^87Rb gases.

Contribution

It provides an analytical and numerical study of spin-nematic squeezing induced by spin-orbit coupling in three-component Bose gases, highlighting its dependence on system parameters and experimental feasibility.

Findings

Spin-nematic squeezing is enhanced by increasing spin-orbit coupling strength.

Harmonic traps support stronger spin-nematic squeezing.

Spin-nematic squeezing can be viewed as two-mode entanglement or two-spin squeezing.

Abstract

We observe spin squeezing in three-component Bose gases where all three hyperfine states are coupled by synthetic spin-orbit coupling. This phenomenon is a direct consequence of spin-orbit coupling, as can be seen clearly from an effective spin Hamiltonian. By solving this effective model analytically with the aid of a Holstein-Primakoff transformation for spin-1 system in the low excitation limit, we conclude that the spin-nematic squeezing, a novel category of spin squeezing existing exclusively in large spin systems, is enhanced with increasing spin-orbit intensity and effective Zeeman field, which correspond to Rabi frequency and two-photon detuning within the Raman scheme for synthetic spin-orbit coupling, respectively. These trends of dependence are in clear contrast to spin-orbit coupling induced spin squeezing in spin-1/2 systems. We also analyze the effects of harmonic trap and interaction with realistic experimental parameters numerically, and find that a strong harmonic trap favors spin-nematic squeezing. We further show spin-nematic squeezing can be interpreted as two-mode entanglement or two-spin squeezing at low excitation. Our findings can be observed in ^{87}Rb gases with existing techniques of synthetic spin-orbit coupling and spin-selectively imaging.