%0 Journal Article
%J Physical Review B
%D 2008
%T Multilevel effects in the Rabi oscillations of a Josephson phase qubit
%A S. K. Dutta
%A Frederick W. Strauch
%A R. M. Lewis
%A Kaushik Mitra
%A Hanhee Paik
%A T. A. Palomaki
%A Eite Tiesinga
%A J. R. Anderson
%A Alex J. Dragt
%A C. J. Lobb
%A F. C. Wellstood
%X 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.
%B Physical Review B
%V 78
%8 2008/9/15
%G eng
%U http://arxiv.org/abs/0806.4711v2
%N 10
%! Phys. Rev. B
%R 10.1103/PhysRevB.78.104510
%0 Journal Article
%J Physical Review B
%D 2008
%T Theoretical analysis of perfect quantum state transfer with superconducting qubits
%A Frederick W. Strauch
%A Carl J. Williams
%X Superconducting quantum circuits, fabricated with multiple layers, are proposed to implement perfect quantum state transfer between nodes of a hypercube network. For tunable devices such as the phase qubit, each node can transmit quantum information to any other node at a constant rate independent of the distance between qubits. The physical limits of quantum state transfer in this network are theoretically analyzed, including the effects of disorder, decoherence, and higher-order couplings.
%B Physical Review B
%V 78
%8 2008/9/24
%G eng
%U http://arxiv.org/abs/0708.0577v3
%N 9
%! Phys. Rev. B
%R 10.1103/PhysRevB.78.094516
%0 Journal Article
%J Physical Review A
%D 2008
%T Tunneling phase gate for neutral atoms in a double-well lattice
%A Frederick W. Strauch
%A Mark Edwards
%A Eite Tiesinga
%A Carl J. Williams
%A Charles W. Clark
%X We propose a new two--qubit phase gate for ultra--cold atoms confined in an experimentally realized tilted double--well optical lattice [Sebby--Strabley et al., Phys. Rev. A {\bf 73} 033605 (2006)]. Such a lattice is capable of confining pairs of atoms in a two--dimensional array of double--well potentials where control can be exercised over the barrier height and the energy difference of the minima of the two wells (known as the ``tilt''). The four lowest single--particle motional states consist of two pairs of motional states in which each pair is localized on one side of the central barrier, allowing for two atoms confined in such a lattice to be spatially separated qubits. We present a time--dependent scheme to manipulate the tilt to induce tunneling oscillations which produce a collisional phase gate. Numerical simulations demonstrate that this gate can be performed with high fidelity.
%B Physical Review A
%V 77
%8 2008/5/12
%G eng
%U http://arxiv.org/abs/0712.1856v1
%N 5
%! Phys. Rev. A
%R 10.1103/PhysRevA.77.050304