



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/0806.4711v200946nas a2200133   4500008004100000245009000041210006900131260001400200490000700214520050400221100002700725700002300752856003700775       2008                        eng d00aTheoretical analysis of perfect quantum state transfer with  superconducting qubits
0 aTheoretical analysis of perfect quantum state transfer with supe  c2008/9/240 v783 a  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.
1 aStrauch, Frederick, W.1 aWilliams, Carl, J.  uhttp://arxiv.org/abs/0708.0577v301425nas a2200169   4500008004100000245006800041210006700109260001400176490000700190520091100197100002701108700001801135700001901153700002301172700002301195856003701218       2008                        eng d00aTunneling phase gate for neutral atoms in a double-well lattice0 aTunneling phase gate for neutral atoms in a doublewell lattice  c2008/5/120 v773 a  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.
1 aStrauch, Frederick, W.1 aEdwards, Mark1 aTiesinga, Eite1 aWilliams, Carl, J.1 aClark, Charles, W.  uhttp://arxiv.org/abs/0712.1856v1