Self-induced spatial dynamics to enhance spin squeezing via one-axis twisting in a two-component Bose-Einstein condensate

Abstract

We theoretically investigate a scheme to enhance relative number squeezing and spin squeezing in a twocomponent Bose-Einstein condensate (BEC) by utilizing the inherent mean-field dynamics of the condensate. Due to the asymmetry in the scattering lengths, the two components exhibit large density oscillations where they spatially separate and recombine. The effective nonlinearity responsible for the squeezing is increased by up to 3 orders of magnitude when the two components spatially separate. We perform a multimode simulation of the system using the truncated Wigner method and show that this method can be used to create significant squeezing in systems where the effective nonlinearity would ordinarily be too small to produce any significant squeezing in sensible time frames, and we show that strong spatial dynamics resulting from large particle numbers aren't necessarily detrimental to generating squeezing. We develop a simplified semianalytic model that gives good agreement with our multimode simulation and will be useful for predicting squeezing in a range of different systems.

Quantum noise in bright soliton matterwave interferometry

“…We simulate the dynamics of the system by using a stochastic phase space technique known as the truncated Wigner (TW) method, which has previously been used to model the dynamics of quantum gases [40][41][42][43], and unlike the GPE, can be used to model non-classical particle correlations [44][45][46]. The derivation of the TW method has been described in detail elsewhere [40,47,48].…”

Spontaneous spin squeezing in a rubidium BEC

“…If, on the other hand, the overlap of the components is significantly reduced, the collisional interaction between the two states U 12 reduces accordingly so that U 12 =U 11 , U 22 , i.e., U 12 no longer compensates the interaction of each state with itself. As a result, a sizeable nonlinear interaction now arises even for identical scattering lengths [4,13,19].…”

“…The condensate is initially prepared in 1ñ | and subjected to a π/2 pulse on the 1 2 ñ « ñ | | transition. The subsequent free evolution in the cigar-shaped trap leads to demixing of the two components [13,20,[23][24][25], initiating the squeezing dynamics (figure 1). By applying a second pulse to close the spin interferometer when the 1ñ | component oscillates back into overlap with 2ñ | , we indeed observe not only a contrast revival, but also a simultaneous reduction of spin projection noise, yielding metrological spin squeezing.…”

“…Both methods have led to spectacular results, but come at the price of a considerably more complex setup. Here we describe an experiment where spin squeezing occurs spontaneously after an internal state quench, the dynamics being initiated simply by an initial π/2 pulse [13] applied to a rubidium BEC in a harmonic trap.…”

Squeezed-light-enhanced atom interferometry below the standard quantum limit

“…These are based on phenomena as diverse as molecular dissociation [23], spin-exchange collisions [24][25][26], atomic four-wave mixing [27][28][29][30], and atomic Kerr squeezing [31][32][33][34][35][36][37]. However, all these schemes require large interatomic interactions, small atom number, and give little control over the motional atomic state.…”