  DC measurements are made in a superconducting, persistent current qubit
structure with a time-ordered meter. The persistent-current qubit has a
double-well potential, with the two minima corresponding to magnetization
states of opposite sign. Macroscopic resonant tunneling between the two wells
is observed at values of energy bias that correspond to the positions of the
calculated quantum levels. The magnetometer, a Superconducting Quantum
Interference Device (SQUID), detects the state of the qubit in a time-ordered
fashion, measuring one state before the other. This results in a different
meter output depending on the initial state, providing different signatures of
the energy levels for each tunneling direction. From these measurements, the
intrawell relaxation time is found to be about 50 microseconds.
