Direct Observation of Photonic Josephson Effects in Weakly Linked Microcavities Containing Ultracold Atoms

The interaction of light and matter has always fascinated physicists and layman as well. Recently a group of researchers led by Dr. W. M. Liu from Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS published their findings on Josephson effect for photons in Physical Review Letters.

The Josephson effect is the phenomenon of current flow across two weakly coupled superconductors, separated by a very thin insulating barrier. It has important applications in quantum-mechanical circuits, such as superconducting quantum interference devices.

Dr. W. M. Liu and his team successfully designed and built an optical system that allows for direct observation of the photonic Josephson effects in two weakly linked microcavities containing ultracold two-level atoms. By moving the ultracold atoms within one cavity, they simulated an analogous superconducting circuit and realized both the alternating- and direct-current (ac and dc) photonic Josephson effects.

The research provides a strategy for constructing novel interference devices of coherent photons and enables new investigations of the effect of many-body physics in strongly coupled atom-cavity systems.