the resonant frequency of the isolation junction matches the [$0 \rightarrow 2$]{} transition frequency of the qubit. At high bias, the escape rates exceed the excitation rates of the noise and the total escape rate converges to $\Gamma_0$; a similar effect occurs for thermal excitations.[@Dutta04a] While noise complicates the situation, the overall behavior suggests that both [$\omega_{0 1}$]{} and [$\Gamma_{0}$]{} of the dc SQUID are described by the same one-dimensional tilted washboard potential. Also shown in Fig. \[FEnergyGamma\](b) are numerical predictions for [$\Gamma_{1}$]{} (dashed), [$\Gamma_{2}$]{} (dotted), and [$\Gamma_{3}$]{} (dashed-dotted).

We observed Rabi oscillations between the ground and first excited states by turning the microwave current [$I_{r\!f}$]{} on when $I_b$ was at the value where ${\ensuremath{\omega_{0 1}}} = {\ensuremath{\omega_{r\!f}}}$ and measuring the time-resolved escape rate while [$I_{r\!f}$]{} remained at a constant value. This serves as a simple method of monitoring the evolution of the state populations.[@Yu02a] Although the biases continued to increase during the Rabi oscillations, the ramp rates were reduced (with $d I_b / dt \approx 0.01\ {\ensuremath{{\ensuremath{\mathrm{A}}} / {\ensuremath{\mathrm{s}}}}}$) before [$I_{r\!f}$]{} was turned on, so that the level spacing ${\ensuremath{\omega_{0 1}}}$ changed by a negligible amount during the escape rate measurement. The symbols in Fig. \[F031806DGtot\] show $\Gamma$ due 