Macroscopic resonant tunneling in extremely asymmetric superconducting qubits

We predict surprisingly strong macroscopic resonant tunneling (MRT) effects in extremely asymmetric double well superconducting qubits. Observable signatures include a complex pattern of 1-100 MHz splittings in the energy level spectra, arising from the quantum coherent tunnel coupling between states in a shallow upper well and highly excited states in a very deep lower well. Probing quantum tunneling in these devices provides a new test of macroscopic quantum mechanics under extreme asymmetric conditions. Moreover, if our predictions are confirmed, they will have important implications for double well phase qubits.