Fly a Bose-Einstein Condensate through a cavity WITHOUT mirrors
A conventional cavity is made of two parallel mirrors which reflect lights back and forth. Just like a person standing in front of a mirror or between two mirrors, two cases give rather distinct views of images. A single image vs. periodic images in front of the real person. In the exotic quantum world, physicists insert single atoms within a cavity, and learn very fundamental questions of how atoms interact with photons, namely cavity quantum electrodynamics (CQED). In Sci. Rep. 6, 35402 (2016), we investigate a cavity without mirrors where a Bose-Einstein condensate (BEC) flies through. A cavity without mirrors! How come? Actually any matter reflects photons can be used as a mirror. Along this line, we invoke two separated atomic clouds whose index of refraction is simultaneously modified by two counterpropagating control laser beams such that two clouds reflect (absorb) lights when two lasers are on (off). A dispersive cavity! This novel cavity provides the fast controls over mirrors which is out of the question for any conventional mirror. On the other hand, BEC is a very special state of matter that each individual bosonic atom in a dilute gas, cooled to temperatures very close to absolute zero by the technique called laser cooling, can be described by the same coherent wavefunction.
We demonstrate that a dispersive cavity can be used to control the interaction between photons and a BEC. When a BEC is excited in a dispersive cavity, the emitted photons will be reflected and again interact with the host BEC in a cooperative fashion, i.e., superradiance. This iterative process results in the diffraction of BEC due to the momentum conservation along the cavity long axis (a single photon carries momentum which kicks an emitting atom!). We show two methods to manipulate the diffraction of BEC by
altering the intensity of two counterpropagating control laser beams.
dynamically switching off two counterpropagating control laser beams.
Both give a novel way to control light-matter interactions.
