COHERENT EVOLUTION AND QUANTUM TRANSITIONS IN A 2-LEVEL MODEL OF A SQUID RING

Using a quantum mechanical model for a frictionless superconducting qu antum interference device ring subjected to a time varying external ma gnetic flux we solve the time-dependent Schrodinger equation for the r ing and calculate the time-averaged energy and screening current expec tation values. We demonstrate by computation that (subject to constrai nts on the applied field frequency and amplitude) the ring can be trea ted as a two level system. We also show that for certain regions of th e bias flux, the time-averaged energy expectation value appears to jum p between the time-averaged energies of the adiabatic ground and first excited states of the ring. (C) 1998 Academic Press.