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Search Publications by: Joe Aumentado (Fed)

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Displaying 76 - 88 of 88

Banishing Quasiparticles From Josephson-Junction Qubits: Why and How To Do It

June 1, 2003
Author(s)
Kristine Lang, Sae Woo Nam, Joe Aumentado, John M. Martinis, C Urbina
Current-biased Josephson junctions are prime candidates for the implementation of quantum bits; however, a present limitation is their coherence time. In this paper we qualitatively describe the role of quasiparticles in decoherence. We discuss two methods

Counting Errors in a Voltage-Biased Electron Pump

April 30, 2003
Author(s)
Xavier Jehl, Mark W. Keller, Richard L. Kautz, Joe Aumentado, John M. Martinis
We have measured the counting errors of a 7-junction electron pump when charge is pumped against a voltage difference. At voltages above about 50 υV, we find that the errors increase exponentially with both pump voltage and temperature, in agreement with

Decoherence of a Superconducting Qubit due to Bias Noise

March 25, 2003
Author(s)
John M. Martinis, Sae Woo Nam, Joe Aumentado, Kristine Lang, C Urbina
We calculate for the current-biased Josephson junction the decoherence of the qubit state from noise and dissipation. The effect of dissipation can be entirely accounted for through a noise model of the current bias that appropriately includes the effect

A Seven Junction Cooper Pair Pump

February 15, 2003
Author(s)
Joe Aumentado, Mark W. Keller, John M. Martinis
We have measured current-voltage curves and individual charge transfer events in single-Cooper-pair pumps. We observe clear charge pumping in units of 2e, but this behavior is accompanied by significant effects from unwanted quasiparticles.

Single-Cooper-Pair Transistors: Requirements for Robust 2e Periodicity

January 3, 2003
Author(s)
Joe Aumentado, Mark W. Keller, John M. Martinis
The superconducting analog of the single-electron transistor (SET), the single-Cooper-pair transistor (SCPT), is comprised of two ultrasmall tunnel junctions in series forming an island (see Figure 1(a)). Transport through the SCPT depends on the

Rabi Oscillations in a Large Josephson Junction Qubit

September 9, 2002
Author(s)
John M. Martinis, Sae Woo Nam, Joe Aumentado, C Urbina
We have designed and operated a circuit based on a large-area current-biased Josephson junction whose two lower energy quantum levels could be used to implement a solid-state qubit. The circuit allows measurement of the qubit states with a fidelity of 85%