Squeezing and non-equilibrium dynamics in a multi-component Bose condensate
A pendulum prepared perfectly inverted and motionless is a prototype of unstable equilibria and corresponds to an unstable fixed point in the dynamical phase space. In many-body quantum systems, mean-field approximations fail in the vicinity of these points and lead to dynamics driven by quantum fluctuations. In this talk, I will discuss our measurements of non-equilibrium quantum spin dynamics of a spin-1 atomic Bose condensate. The condensate is initialized to a minimum uncertainty spin state corresponding to a unstable (hyperbolic) fixed point of the phase space, and quantum fluctuations lead to non-linear spin evolution along a separatrix. At early times, we measure squeezing in spin-nematic variables up to -8 dB . At longer times, we observe quantum spin mixing characterized by non-Gaussian probability distributions that are in good agreement with exact quantum calculations . These results show that spin dynamics in multi-component condensates provide a powerful tool to generate highly correlated and robust quantum many-body states of the type required for quantum enhanced metrology and continuous variable quantum information processing.
 Hamley, C.D., Gerving, C.S., Hoang, T.M., Bookjans, E.M., and Chapman, M.S., Nature Phys.8, 305--308 (2012).
 Gerving, C.S., Hoang, T.M., Land, B.J., Anquez, M., Hamley, C.D., and Chapman, M.S., arXiv:1205.2121v1 [cond-mat.quant-gas].