01777nas a2200241 4500008004100000245007500041210006900116260001400185490000700199520107300206100001801279700002701297700001801324700001901342700001701361700002101378700001901399700002101418700002001439700001701459700002201476856003701498 2008 eng d00aMultilevel effects in the Rabi oscillations of a Josephson phase qubit0 aMultilevel effects in the Rabi oscillations of a Josephson phase c2008/9/150 v783 a We present Rabi oscillation measurements of a Nb/AlOx/Nb dc superconducting
quantum interference device (SQUID) phase qubit with a 100 um^2 area junction
acquired over a range of microwave drive power and frequency detuning. Given
the slightly anharmonic level structure of the device, several excited states
play an important role in the qubit dynamics, particularly at high power. To
investigate the effects of these levels, multiphoton Rabi oscillations were
monitored by measuring the tunneling escape rate of the device to the voltage
state, which is particularly sensitive to excited state population. We compare
the observed oscillation frequencies with a simplified model constructed from
the full phase qubit Hamiltonian and also compare time-dependent escape rate
measurements with a more complete density-matrix simulation. Good quantitative
agreement is found between the data and simulations, allowing us to identify a
shift in resonance (analogous to the ac Stark effect), a suppression of the
Rabi frequency, and leakage to the higher excited states.
1 aDutta, S., K.1 aStrauch, Frederick, W.1 aLewis, R., M.1 aMitra, Kaushik1 aPaik, Hanhee1 aPalomaki, T., A.1 aTiesinga, Eite1 aAnderson, J., R.1 aDragt, Alex, J.1 aLobb, C., J.1 aWellstood, F., C. uhttp://arxiv.org/abs/0806.4711v2