Abstract
In this paper we discuss Bose-Einstein spinor condensates for atoms in the context of , as studied experimentally by the Stamper-Kurn group [L. E. Sadler et al., Nature (London) 443, 312 (2006)]. The dynamical quantum fluctuations of a sample that starts as a condensate of atoms in a pure , state are described in analogy to the two-mode squeezing of quantum optics in terms of an algebra. In this system the initial condensate acts as a source (pump) for the creation pairs of atoms. We show that even though the system as a whole is described by a pure state with zero entropy, the reduced density matrix for the degree of freedom, obtained by tracing out the degrees of freedom, corresponds to a thermal state. Furthermore, these quantum fluctuations of the initial dynamics of the system provide the seeds for the formation of domains of ferromagnetically aligned spins.
3 More- Received 12 November 2007
DOI:https://doi.org/10.1103/PhysRevA.77.023616
©2008 American Physical Society