Intrinsic dephasing in one-dimensional ultracold atom interferometers
-
Edited by Paul C. Martin, Harvard University, Cambridge, MA, and approved April 27, 2007 (received for review October 9, 2006)
Abstract
Quantum-phase fluctuations prevent true long-range phase order from forming in interacting 1D condensates, even at zero temperature. Nevertheless, by dynamically splitting the condensate into two parallel decoupled tubes the system can be prepared with a macroscopic relative phase, facilitating interferometric measurement. Here, we describe a dephasing mechanism whereby the quantum-phase fluctuations, which are so effective in equilibrium, act to destroy the macroscopic relative phase that was imposed as a nonequilibrium initial condition. We show that the phase coherence between the condensates decays exponentially with a dephasing time that depends on intrinsic parameters: the interaction strength, sound velocity, and density. Interestingly, significant temperature dependence appears only above a cross-over scale T∗. In contrast to the usual phase diffusion, which is essentially an effect of confinement and leads to Gaussian decay, the exponential dephasing caused by fluctuations is a bulk effect that survives the thermodynamic limit.
Footnotes
- ‡To whom correspondence should be addressed. E-mail: rafi.bistritzer{at}weizmann.ac.il
-
Author contributions: R.B. and E.A. designed research, performed research, contributed new reagents/analytic tools, analyzed data, and wrote the paper.
-
The authors declare no conflict of interest.
-
This article is a PNAS Direct Submission.
-
↵ § This length scale may be obtained by solving the GP boundary problem in which the wave function increases from zero at x = 0 to its bulk value at x → ∞ (19).
-
↵ ¶ The interaction is activated by using U(t) = U[1 + tanh(λt)]/2, where λ controls the degree of adiabaticity.
- Abbreviations:
- TWA,
- truncated Wigner approximation;
- GP,
- Gross–Pitaevskii.
- © 2007 by The National Academy of Sciences of the USA
