Experimental study of quantum chaos using atom optics technique

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The project aims to solve the problem of quantum chaos using electromagnetically manipulated atoms. Summarized below are the outcomes of our research carried out toward this goal.1. We predicted that classical motion of atoms trapped in a magnetic potential becomes chaotic when the magnetic field is periodically modulated. Rb atoms were once laser-cooled to 10 μ K, then parametrically heated on the video-tape atom chip. The observed spectrum is well reproduced by numerical simulations based on Newton's equations of motion, showing that atoms behave as classical particles. We numerically demonstrated cooling or heating of the atom cloud without changing their internal energy. These researches were carried out in cooperation with Center for Cold Matter, Imperial College London.2. The transverse motion of atoms optically guided in a hollow-core fiber becomes chaotic when the light intensity is periodically modulated. For laser-cooling of the incident atoms, we stabilized the frequency of the newly introduced diode laser. Construction of a magneto-optical trap is now in progress. We have also developed a novel method of frequency stabilization that uses electromagnetically induced transparency.3. Two types of optical traps, both of which use counter propagating laser beams, were developed for micro-sized particles. Laser trapping of hexagonal ice crystals was demonstrated for the first time. In the CO_2 laser trap, air flow counteracts gravity and prolongs the trap time.4. Based on the shooting method, we developed a novel algorithm to search periodic orbits of a non-integrable system. Its feasibility was tested on the anisotropic Kepler problem and a hydrogen atom in electromagnetic fields. CPU time was remarkably saved.