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Displaying 101 - 125 of 204

Effect of metal/substrate interfaces on radio-frequency loss in superconducting coplanar waveguides

November 8, 2010
Author(s)
David S. Wisbey, Jiansong Gao, Fabio C. da Silva, Jeffrey S. Kline, Michael Vissers, David P. Pappas, Leila R. Vale
Microscopic two-level systems (TLSs) are known to contribute to loss in resonant superconducting microwave circuits. This loss increases at low power and temperatures as the TLSs become unsaturated. We find that the loss is dependent on both the substrate

Remote sensing and control of phase qubits

September 10, 2010
Author(s)
Dale Li, Fabio C. Da Silva, Danielle Braje, Raymond W. Simmonds, David P. Pappas
We demonstrate a remote sensing design of phase qubits by separating the control and readout circuits from the qubit loop. This design improves measurement reliability because the control readout chip can be fabricated using more robust materials and can

Direct Observation of Coherent Population Trapping in a Superconducting Artificial Atom

April 20, 2010
Author(s)
David P. Pappas, Jeffrey S. Kline, Willim R. Kelley, Zachary Dutton, Thomas A. Ohki, john Schlafer, Bashkar Mookerji
The phenomenon of coherent population trapping (CPT) of an atom (or solid state artificial atom ), and the associated effect of electromagnetically induced transparency (EIT), are clear demonstrations of quantum interference due to coherence in multilevel

Thin lm dielectric microstrip kinetic inductance detectors

March 8, 2010
Author(s)
David P. Pappas, Jiansong Gao, Benjamin Mazin, Daniel Sank, Erik Lucero, John M. Martinis, Andrew Merrill, Sunil Golwala, David Moore, Jonas Zmuidzinas
Microwave Kinetic Inductance Detectors, or MKIDs, are a type of low temperature detector that exhibit intrinsic frequency domain multiplexing at microwave frequencies. We present theory and measurements on a new type of MKID based on a microstrip

Normal-state conductance used to probe superconducting tunnel junctions for quantum computing

March 3, 2010
Author(s)
David P. Pappas, Jeffrey S. Kline, Seongshik Ohy, Carlos Chapraro, Richard Bavier, Yong Kim, Eunyoung Kim
Here we report normal-state conductance measurements of three different types of superconducting tunnel junctions that are being used or proposed for quantum computing applications: p-Al/a-AlO/p-Al, e-Re/e-AlO/p-Al, and e-V/e-MgO/p-V, where p stands for

Model of magnetic impurities within the Josephson junction of a phase qubita

December 23, 2009
Author(s)
David P. Pappas, R. P. Erickson
We consider a superconducting phase qubit consisting of a monocrystalline sapphire Josephson junction with symmetry axis perpendicular to the junction interfaces. Via the London gauge we present a theoretical model of Fe3+ magnetic impurities within the

Oersted Field Induced Magnetization Scissoring In Permalloy Bars

December 10, 2009
Author(s)
Lu Yuan, Fabio C. da Silva, Sean Halloran, Hamid Z. Fardi, David P. Pappas
We have systematically studied the magnetization behavior induced by the applied current in the permalloy (Ni81Fe19) bars using second and third harmonic analysis. Three types of sample were studied with layer structures of Al30/NiFe10, NiFe5/Al30/NiFe5

Magnetic Noise in a Low-Power Picotesla Magnetoresistive Sensor

October 25, 2009
Author(s)
Stephen E. Russek, Lu Yuan, Sean Halloran, Fabio C. da Silva, David P. Pappas, John M. Moreland, Sy-hwang Liou, Rui Zhang
We present a design of a low power, compact, magnetoresistive sensor. The key features of the design are(1) decreasing the noise by the use of a 64 element magnetic tunnel junction (MTJ) bridge,(2) reducing the magnetic noise by annealing the MTJ sensors

Modification of magnetotransport properties across patterned GaMnAs nanoconstrictions by application of high current densities

July 17, 2009
Author(s)
David P. Pappas, Fabio Cesar Da Silva, Teresa Osminer, Sung Un Cho, Hyung Choi, Chan Yang, Yun Park
We report on the modification of magnetotransport properties across patterned GaMnAs nanoconstrictions by the application of high current densities (< 107 A/cm2). We observe controllable changes in the electrical resistance with the direction of the bias

Josephson phase qubit circuit for the evaluation of advanced tunnel barrier materials

November 21, 2008
Author(s)
Jeffrey S. Kline, Haohua Wang, Seongshik Oh, John M. Martinis, David P. Pappas
We have found that crystalline Josephson junctions have critical current density control problems which decrease circuit yield. We present a qubit circuit designed to accommodate a factor-of-five variation in critical current density for the evaluation of

A z-component magneto-resistive sensor

April 8, 2008
Author(s)
Fabio C. da Silva, Sean Halloran, Lu Yuan, David P. Pappas
A thin-film sensor is described that measures the component of the magnetic field perpendicular to the plane of the substrate (also called the z-component field.) The sensors are fabricated on anisotropically etched, V-shaped groves on Si(100) substrates

Dependence of noise in magnetic tunnel junction sensors on annealing field and temperature

March 7, 2008
Author(s)
Stephen E. Russek, David P. Pappas, Sean Halloran, Lu Yuan, Sy-Hwang Liou, Rui Zhang
The minimum detectable field of magnetoresistive sensors is limited by their intrinsic noise. Magnetization fluctuations are one of the crucial noise sources and are related to the magnetization alignment at the antiferromagnetic – ferromagnetic interface