C. Ryu, A. A. Blinova, P. W. Blackburn, M. G. Boshier
We report the creation of ideal Josephson junctions in a toroidal dilute gas Bose-Einstein condensate (BEC). The demonstrated configuration of a pair of junctions on a multiply-connected BEC is the cold atom analog of the well-known dc Superconducting Quantum Inteference Device (SQUID). We measure the critical current of the junctions, observe Josephson effects, and find dynamic behavior that is in good agreement with the simple Josephson equations for an ideal tunnel junction with a sinusoidal current-phase relation. The junctions and toroidal trap are created with the Painted Potential, a time-averaged optical dipole potential technique which will allow scaling to more complex BEC circuit geometries than the single Atom-SQUID case reported here. Since rotation plays the same role in the Atom SQUID as magnetic field does in the dc SQUID magnetometer, the device has potential as a compact rotation sensor. It may also be useful for creating macroscopic Schr\"odinger Cat states.
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http://arxiv.org/abs/1304.8095
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