Effects of a resonant cavity on macroscopic quantum tunneling of fluxons in long Josephson junctions

Abstract

We investigate the effects of high-Qc resonant cavity on macroscopic quantum tunneling (MQT) of fluxon both from a metastable state to continuum and from one degenerate ground-state of a double-well potential to the other. By using a set of two coupled perturbed sine-Gordon equations, we describe the tunneling processes in linear long Josephson junctions (LJJs) and find that MQT in the resonant cavity increases due to potential renomalization, induced by the interaction between the fluxon and cavity. Enhancement of the MQT rate in the weak-coupling regime is estimated by using the experimantally accessible range of the model parameters. The tunneling rate from the metastable state is found to increase weakly with increasing junction-cavity interaction strength. However, the energy splitting between the two degenerate ground-states of the double-well potential increases significantly with increasing both the interaction strength and frequency of the resonant cavity mode. Finally, we discuss how the resonant cavity may be used to tune the property of Josephson vortex quantum bits.

Development of a Josephson vortex two-state system based on a confocal annular Josephson junction

“…As the annulus aspect ratio approaches unity, the factor c tends to the ring radius and equation (2) reduces to the well known perturbed sine-Gordon equation of a circular annular JTLs [28]. We stress that, for CAJTJs in a uniform in-plane magnetic field, the component of the applied magnetic field normal to the junction perimeter varies very smoothly, guaranteeing an accurate modeling at variance with other proposed geometries for a JVQ based on the δ-like behavior of the normal field or of the local critical current density [12,34,35].…”