Orbit-induced spin squeezing in a spin-orbit coupled Bose-Einstein condensate

Abstract

In recent pioneer experiment, a strong spin-orbit coupling, with equal Rashba and Dresselhaus strengths, has been created in a trapped Bose-Einstein condensate. Moreover, many exotic superfluid phenomena induced by this strong spin-orbit coupling have been predicted. In this report, we show that this novel spin-orbit coupling has important applications in quantum metrology, such as spin squeezing. We first demonstrate that an effective spin-spin interaction, which is the heart for producing spin squeezing, can be generated by controlling the orbital degree of freedom (i.e., the momentum) of the ultracold atoms. Compared with previous schemes, this realized spin-spin interaction has advantages of no dissipation, high tunability, and strong coupling. More importantly, a giant squeezing factor (lower than −30 dB) can be achieved by tuning a pair of Raman lasers in current experimental setup. Finally, we find numerically that the phase factor of the prepared initial state affects dramatically on spin squeezing.

Spin-orbit-coupling-induced spin squeezing in three-component Bose gases

“…As the commutators relation between spin and nematic operators are not present in the spin-1/2 case, next we focus on spin squeezing of this type. The method can be straightforwardly applied to the spin-spin and nematicnematic commutators, and the results are qualitatively consistent with the findings for the spin-spin case in spin-1/2 system with SOC [19,20].…”

“…2(a), spin-nematic squeezing can be enhanced with increasing Ω R . This behavior is in stark contrast to the case of spin-1/2 systems, where the spin-spin squeezing is favored by decreasing Ω R [19,20].…”

“…Recently, theoretical studies have proposed to realize spin squeezing in two-component BEC by synthetic spinorbit coupling (SOC) [19,20]. It has been shown that the presence of SOC will induce an effective spin-spin interaction which can lead to spin squeezing.…”

Creating a tunable spin squeezing via a time-dependent collective atom-photon coupling

“…However, the generated spin-spin interactions are weak, and thus the corresponding maximal squeezing factors (MSFs) acquired are lower than 10 dB [2,3]. Recently, many proposals [21][22][23][24][25][26][27][28][29][30] have been suggested to enhance the upper limits of the MSFs in laboratory conditions, but the experimental challenges are difficult.Here we present an experimentally-feasible method to achieve a giant and tunable spin squeezing, when an ensemble of many four-level atoms interacts simultaneously with a single-mode photon and classical driving lasers. Recently, a similar setup has been considered experimentally in a BEC-cavity system, and a remarkable quantum phase transition, from a normal phase to a superradiant phase of the Dicke model, was observed [31,32].…”

“…However, the generated spin-spin interactions are weak, and thus the corresponding maximal squeezing factors (MSFs) acquired are lower than 10 dB [2,3]. Recently, many proposals [21][22][23][24][25][26][27][28][29][30] have been suggested to enhance the upper limits of the MSFs in laboratory conditions, but the experimental challenges are difficult.…”