Model for an irreversible bias current in the superconducting qubit measurement process

Hutchinson, G. D., Holmes, C. A., Stace, T. M., Spiller, T. P., Milburn, G. J., Barrett, S. D., Hasko, D. G. and Williams, D. A. (2006) Model for an irreversible bias current in the superconducting qubit measurement process. Physical Review A, 74 6: 062302-1-062302-17. doi:10.1103/PhysRevA.74.062302

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Author Hutchinson, G. D.
Holmes, C. A.
Stace, T. M.
Spiller, T. P.
Milburn, G. J.
Barrett, S. D.
Hasko, D. G.
Williams, D. A.
Title Model for an irreversible bias current in the superconducting qubit measurement process
Journal name Physical Review A   Check publisher's open access policy
ISSN 1050-2947
Publication date 2006-12-01
Year available 2006
Sub-type Article (original research)
DOI 10.1103/PhysRevA.74.062302
Open Access Status File (Publisher version)
Volume 74
Issue 6
Start page 062302-1
End page 062302-17
Total pages 17
Place of publication College Park, MD, United States
Publisher American Physical Society
Language eng
Abstract The superconducting charge-phase "quantronium" qubit is considered in order to develop a model for the measurement process used in the experiment of Vion [Science 296, 886 (2002)]. For this model we propose a method for including the bias current in the readout process in a fundamentally irreversible way, which to first order is approximated by the Josephson junction tilted-washboard potential phenomenology. The decohering bias current is introduced in the form of a Lindblad operator and the Wigner function for the current-biased readout Josephson junction is derived and analyzed. During the readout current pulse used in the quantronium experiment we find that the coherence of the qubit initially prepared in a symmetric superposition state is lost at a time of 0.2 ns after the bias current pulse has been applied, a time scale that is much shorter than the experimental readout time. Additionally we look at the effect of Johnson-Nyquist noise with zero mean from the current source during the qubit manipulation and show that the decoherence due to the irreversible bias current description is an order of magnitude smaller than that found through adding noise to the reversible tilted-washboard potential model. Our irreversible bias current model is also applicable to persistent-current-based qubits where the state is measured according to its flux via a small-inductance direct-current superconducting quantum interference device.
Keyword Optics
Physics, Atomic, Molecular & Chemical
Macroscopic Quantum States
Experimental Realization
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Physical Sciences Publications
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Created: Thu, 20 Sep 2007, 04:04:51 EST