Quantum noise, scaling, and domain formation in a spinor Bose-Einstein condensate

George I. Mias, Nigel R. Cooper, and S. M. Girvin
Phys. Rev. A 77, 023616 – Published 14 February 2008

Abstract

In this paper we discuss Bose-Einstein spinor condensates for F=1 atoms in the context of R87b, 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 N atoms in a pure F=1, mF=0 state are described in analogy to the two-mode squeezing of quantum optics in terms of an su(1,1) algebra. In this system the initial mF=0 condensate acts as a source (pump) for the creation pairs of mF=1,1 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 mF=+1 degree of freedom, obtained by tracing out the mF=1,0 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.

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  • Received 12 November 2007

DOI:https://doi.org/10.1103/PhysRevA.77.023616

©2008 American Physical Society

Authors & Affiliations

George I. Mias1,*, Nigel R. Cooper2,†, and S. M. Girvin1,‡

  • 1Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520-8120, USA
  • 2TCM Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom

  • *george.mias@aya.yale.edu
  • nrc25@cam.ac.uk
  • steven.girvin@yale.edu

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Vol. 77, Iss. 2 — February 2008

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