Entangling Alliances: Photons and Charge Oscillations in Josephson Arrays David Stroud Ohio-State University A Josephson junction is a superconducting device in which an applied dc current can produce an ac voltage. Since the currents are charged, they can couple strongly to any nearby electromagnetic field. In this talk, I will first review some recent experiments by Barbara and collaborators, in which arrays of junctions couple to the modes of an electromagnetic cavity, producing voltage steps and remarkably strong coherent radiation into the cavity. I will then present a model which can explain this behavior and predict additional novel effects. Finally, I will discuss what happens in the quantum limit of very small junctions. In this case, one may observe novel entangled quantum-mechanical states between the cavity photons and the charge states of the Josephson junctions.