>>44
The flux in a SQUID loop can tunnel between two minima. This implies that the degenerate ground state energy of the SQUID is split by a difference in energy ΔW related to the tunneling matrix element, and those two states are regarded as mixed energy states.
Therefore, if the coherence of such a mixture can be maintained sufficiently long, the magnetic flux will oscillate back and forth between those two states at a frequency ΔW / 2πh .
