Coherence time of a Bose-Einstein condensate

A. Sinatra, Y. Castin, and E. Witkowska
Phys. Rev. A 80, 033614 – Published 16 September 2009

Abstract

Temporal coherence is a fundamental property of macroscopic quantum systems, such as lasers in optics and Bose-Einstein condensates in atomic gases and it is a crucial issue for interferometry applications with light or matter waves. Whereas the laser is an “open” quantum system, ultracold atomic gases are weakly coupled to the environment and may be considered as isolated. The coherence time of a condensate is then intrinsic to the system and its derivation is out of the frame of laser theory. Using quantum kinetic theory, we predict that the interaction with noncondensed modes gradually smears out the condensate phase, with a variance growing as At2+Bt+C at long times t, and we give a quantitative prediction for A, B, and C. Whereas the coefficient A vanishes for vanishing energy fluctuations in the initial state, the coefficients B and C are remarkably insensitive to these fluctuations. The coefficient B describes a diffusive motion of the condensate phase that sets the ultimate limit to the condensate coherence time. We briefly discuss the possibility to observe the predicted phase spreading, also including the effect of particle losses.

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  • Received 6 July 2009

DOI:https://doi.org/10.1103/PhysRevA.80.033614

©2009 American Physical Society

Authors & Affiliations

A. Sinatra and Y. Castin

  • Laboratoire Kastler Brossel, Ecole Normale Supérieure, UPMC and CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France

E. Witkowska

  • Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warszawa, Poland

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Issue

Vol. 80, Iss. 3 — September 2009

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