Article

Bragg spectroscopic interferometer and quantum measurement-induced correlations in atomic Bose-Einstein condensates

New Journal of Physics (Impact Factor: 3.67). 04/2012; 14(7). DOI: 10.1088/1367-2630/14/7/073057
Source: arXiv

ABSTRACT We theoretically analyze the Bragg spectroscopic interferometer of two
spatially separated atomic Bose-Einstein condensates that was experimentally
realized by Saba et al. [Science 2005 v307 p1945] by continuously monitoring
the relative phase evolution. Even though the atoms in the light-stimulated
Bragg scattering interact with intense coherent laser beams, we show that the
phase is created by quantum measurement-induced back-action on the homodyne
photo-current of the lasers, opening possibilities for quantum-enhanced
interferometric schemes. We identify two regimes of phase evolution: a running
phase regime which was observed in the experiment of Saba et al., that is
sensitive to an energy offset and suitable for an interferometer, and a trapped
phase regime, that can be insensitive to applied forces and detrimental to
interferometric applications.

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    ABSTRACT: Off-resonant optical imaging is a popular method for continuous monitoring of a Bose–Einstein condensate. However, the disturbance caused by scattered photons places a serious limitation on the lifetime of such continuously monitored condensates. In this paper, we demonstrate that a new choice of feedback control can overcome the heating effects of the measurement backaction. In particular, we show that the measurement backaction caused by off-resonant optical imaging is a multi-mode quantum-field effect, as the entire heating process is not seen in single-particle or mean-field models of the system. Simulating such continuously monitored systems is possible with the number- phase Wigner particle filter, which currently gives both the highest precision and largest timescale simulations amongst competing methods. It is a hybrid between the leading techniques for simulating non-equilibrium dynamics in condensates and particle filters for simulating high-dimensional non-Gaussian filters in the field of engineering. The new control scheme will enable long- term continuous measurement and feedback on one of the leading platforms for precision measurement and the simulation of quantum fields, allowing for the possibility of single-shot experiments, adaptive measurements and robust state- preparation and manipulation.
    New Journal of Physics 11/2013; 15(11):113060. · 3.67 Impact Factor

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