



@article {1305,
	title = {Multilevel effects in the Rabi oscillations of a Josephson phase qubit},
	journal = {Physical Review B},
	volume = {78},
	year = {2008},
	month = {2008/9/15},
	abstract = {  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.
},
	doi = {10.1103/PhysRevB.78.104510},
	url = {http://arxiv.org/abs/0806.4711v2},
	author = {S. K. Dutta and Frederick W. Strauch and R. M. Lewis and Kaushik Mitra and Hanhee Paik and T. A. Palomaki and Eite Tiesinga and J. R. Anderson and Alex J. Dragt and C. J. Lobb and F. C. Wellstood}
}
@article {1300,
	title = {Quantum behavior of the dc SQUID phase qubit},
	journal = {Physical Review B},
	volume = {77},
	year = {2008},
	month = {2008/6/13},
	abstract = {  We analyze the behavior of a dc Superconducting Quantum Interference Device
(SQUID) phase qubit in which one junction acts as a phase qubit and the rest of
the device provides isolation from dissipation and noise in the bias leads.
Ignoring dissipation, we find the two-dimensional Hamiltonian of the system and
use numerical methods and a cubic approximation to solve Schrodinger{\textquoteright}s equation
for the eigenstates, energy levels, tunneling rates, and expectation value of
the currents in the junctions. Using these results, we investigate how well
this design provides isolation while preserving the characteristics of a phase
qubit. In addition, we show that the expectation value of current flowing
through the isolation junction depends on the state of the qubit and can be
used for non-destructive read out of the qubit state.
},
	doi = {10.1103/PhysRevB.77.214512},
	url = {http://arxiv.org/abs/0805.3680v1},
	author = {Kaushik Mitra and F. W. Strauch and C. J. Lobb and J. R. Anderson and F. C. Wellstood and Eite Tiesinga}
}
