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Search Publications by

Raymond Simmonds (Fed)

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Displaying 26 - 40 of 40

Electromagnetically induced transparency in a superconducting three-level system

April 16, 2009
Mika Sillanpaa, Katarina Cicak, Fabio Altomare, Jae Park, Raymond Simmonds, Jian Li, G. S. Paraoanu, Pertti Hakonen
When a three-level quantum system is irradiated by an intense coupling field resonant with two of the three possible transitions, the resonant absorption of the system from its ground state by an additional radiation field is suppressed. This effect, where

Frequency-Tunable Josephson Junction Resonator for Quantum Computing

June 23, 2007
Kevin Osborn, Joshua Strong, Adam J. Sirois, Raymond W. Simmonds
We have fabricated and measured a high-Q Josephson junction resonator with a tunable resonance frequency. A dc magnetic flux allows the resonance frequency to be changed by over 10%. Weak coupling to the environment allows a quality factor of 7000 in the

Elimination of two level fluctuators in superconducting quantum bits by an epitaxial tunnel barrier

September 7, 2006
Seongshik Oh, Katarina Cicak, Jeffrey S. Kline, Mika Sillanpaa, Jed D. Whittaker, Raymond W. Simmonds, David P. Pappas, Kevin Osborn
Quantum computing based on Josephson junction technology is considered promising due to its scalable architecture. However, decoherence is a major obstacle. Here, we report evidence for improved Josephson quantum bits qubits using a single-crystal Al2O3

Josephson Junction Materials Research Using Phase Qubits

May 30, 2006
Raymond Simmonds, Dustin P. Hite, Robert McDermott, Matthias Steffen, Ken B. Cooper, Kristine Lang, John M. Martinis, David P. Pappas
At present, the performance of superconducting qubits is limited by decoherence. Strong decoherence of phase qubits is associated with spurious microwave resonators residing within the Josephson junction tunnel barrier [1]. In this work, we investigate

Decoherence in Josephson Qubits from Dielectric Loss

November 16, 2005
John M. Martinis, Ken B. Cooper, Robert Mcdermott, Matthias Steffen, Markus Ansmann, Kevin Osborn, Katarina Cicak, Seongshik Oh, David P. Pappas, Raymond Simmonds, Clare Yu
Dielectric loss from two-level states is shown to be a dominant decoherence source in superconducting quantum bits. Depending on the qubit design, dielectric loss from insulating materials or the tunnel junction can lead to short coherence times. We show

Epitaxial growth of rhenium with sputtering

October 6, 2005
Seongshik Oh, Dustin P. Hite, Katarina Cicak, Kevin Osborn, Raymond W. Simmonds, Robert Mcdermott, Ken B. Cooper, Matthias Steffen, John M. Martinis, David P. Pappas
We have grown epitaxial renium (0001) films on α-Al2O3(0001) substrates using sputter deposition in an ultra high vacuum system. We find that better epitaxy is achieved with DC rather than with RF sputtering. With DC sputtering, epitaxy is obtained with

Low-Leakage Superconducting Tunnel Junctions with a Single-Crystal Al2O3 Barrier

September 5, 2005
Seongshik Oh, Katarina Cicak, Kevin Osborn, Raymond Simmonds, David P. Pappas, Robert Mcdermott, Ken B. Cooper, Matthias Steffen, John M. Martinis
We have developed a two-step growth scheme for single-crystal Al2O3 tunnel barriers. The barriers are epitaxially grown on single-crystal rhenium (Re) base electrodes that are grown epitaxially on a sapphire substrate, while polycrystalline Al is used as

Simultaneous state measurement of coupled Josephson phase qubits

February 25, 2005
Robert McDermott, Raymond Simmonds, Matthias Steffen, Ken B. Cooper, Katarina Cicak, Kevin Osborn, Seongshik Oh, David P. Pappas, John M. Martinis
One of the many challenges of building a scalable quantum computer is singleshot measurement of all the quantum bits (qubits). We have used simultaneous single-shot measurement of coupled Josephson phase qubits to directly probe interaction of the qubits

Observation of Quantum Oscillations between a Josephson Phase Qubit and a Microscopic Resonator using Fast Readout

October 25, 2004
Ken Cooper, Matthias Steffen, Robert McDermott, Raymond Simmonds, Seongshik Oh, Dustin Hite, David P. Pappas, John M. Martinis
We have detected coherent quantum oscillations between Josephson phase qubits and microscopic critical current fluctuators by implementing a new state readout technique that is an order of magnitude faster than previous methods. The period of the

Conducting atomic force microscopy for Nanoscale tunnel barrier characterization

August 13, 2004
Kristine Lang, Dustin Hite, Raymond Simmonds, Robert McDermott, David P. Pappas, John M. Martinis
Increasing demands on nanometer scale properties of oxide tunnel barriers necessitate a consistent means to assess them at these lengths. Here we use conducting atomic force microscopy (CAFM) to characterize aluminum oxide (AlOx)barriers to be used in

Decoherence in Josephson Qubits from Junction Resonances

August 13, 2004
Raymond Simmonds, Kristine Lang, Dustin Hite, David P. Pappas, John M. Martinis
We present experimental data that demonstrates a large reduction in the coherence of a Josephson phase qubit from spurious microwave resonances. These resonances are believed to arise from resonant fluctuators in the tunnel junction that couple to the

Coupled Macroscopic Quantum Resonators: Entanglement and Squeezed State

Lin Tian, Raymond W. Simmonds
Linear coupling between solid-state quantum resonators generates entanglement and squeezing effectively. We study the coupled system of a nanomechanical resonator and a superconducting electrical resonator as well as two electrical resonators coupled