INTERFERENCE AND TRANSMISSION OF QUANTUM FLUXONS THROUGH A JOSEPHSON RING

The influence of quantum interference on the transmission of a fluxon through an ideal long circular Josephson junction (a ''Josephson ring' ') is studied. In the low-temperature regime the transmission is a per iodic function of a gauge charge applied along the ring with a period 2e. Around points of full period of both the gauge charge and the opti cal path, the transmission shows resonances as a function of the gauge charge and ''antiresonances'' as a function of the optical path. Thes e resonances and antiresonances are associated with energy levels of t he circular junction and with short dwelling time of the fluxon in the ring. In the high-temperature regime the interaction with plasmons de phases the fluxon wave function completely. The transmission probabili ty in this regime is calculated in a stationary picture and in a dynam ical picture and two different results are obtained. The discrepancy b etween the two pictures is explained via the ratio of the dwelling tim e to the time the thermal bath needs to change the plasmons' microscop ical state. A general method that retrieves the two results is present ed.