Physics

A Matter of Extended Coherence

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Science  21 Mar 2008:
Vol. 319, Issue 5870, pp. 1590
DOI: 10.1126/science.319.5870.1590d

The splitting and subsequent re-overlapping of a coherent light beam provides the basis for exquisitely sensitive detection of path-length differences; this technique of optical interferometry finds applications ranging from stellar observations to holographic imaging and characterization of optical components. Analogously, the cooling of a cloud of bosonic atoms into a Bose-Einstein condensate, a state in which all the atoms share the same quantum state, is described in terms of a coherent matter wave. Because atoms sense gravity, the interference of matter waves can then be used to provide a sensitive gravity detector, with a comparably diverse set of applications ranging from testing relativity to detecting underground bunkers. Unlike photons, however, which do not interact much with each other, the atoms in the trapped cloud do interact by way of collisions. These collisions then give rise to losses and induce shifts in the phase of the matter wave, thereby limiting the sensitivity of any atom interferometer. Gustavsson et al. and Fattori et al. present setups in which the interaction strength between the atoms in the condensate (cesium and potassium, respectively) is tuned via magnetic field so that the scattering between the atoms is significantly reduced. The resulting extension of the matter-wave coherence time leads to improved sensitivity of the atom interferometers. — ISO

Phys. Rev. Lett. 100, 080404; 080405 (2008).

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