dorsal/arxiv
View SchemaA Model for an Irreversible Bias Current in the Superconducting Qubit Measurement Process
| Authors | G. D. Hutchinson, C. A. Holmes, T. M. Stace, T. P. Spiller, G. J. Milburn, S. D. Barrett, D. G. Hasko, D. A. Williams |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0610074 |
| URL | https://arxiv.org/abs/quant-ph/0610074 |
| DOI | 10.1103/PhysRevA.74.062302 |
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 et. al. [Science 296 886 (2002)]. For this model we propose a method for including the bias current in the read-out 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 read-out Josephson junction is derived and analyzed. During the read-out 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 nanoseconds after the bias current pulse has been applied. A timescale which 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 the persistent current based qubits where the state is measured according to its flux via a small inductance direct current superconducting quantum interference device (DC-SQUID).
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"abstract": "The superconducting charge-phase `Quantronium\u0027 qubit is considered in order\nto develop a model for the measurement process used in the experiment of Vion\net. al. [Science 296 886 (2002)]. For this model we propose a method for\nincluding the bias current in the read-out process in a fundamentally\nirreversible way, which to first order, is approximated by the Josephson\njunction tilted-washboard potential phenomenology. The decohering bias current\nis introduced in the form of a Lindblad operator and the Wigner function for\nthe current biased read-out Josephson junction is derived and analyzed. During\nthe read-out current pulse used in the Quantronium experiment we find that the\ncoherence of the qubit initially prepared in a symmetric superposition state is\nlost at a time of 0.2 nanoseconds after the bias current pulse has been\napplied. A timescale which is much shorter than the experimental readout time.\nAdditionally we look at the effect of Johnson-Nyquist noise with zero mean from\nthe current source during the qubit manipulation and show that the decoherence\ndue to the irreversible bias current description is an order of magnitude\nsmaller than that found through adding noise to the reversible tilted washboard\npotential model. Our irreversible bias current model is also applicable to the\npersistent current based qubits where the state is measured according to its\nflux via a small inductance direct current superconducting quantum interference\ndevice (DC-SQUID).",
"arxiv_id": "quant-ph/0610074",
"authors": [
"G. D. Hutchinson",
"C. A. Holmes",
"T. M. Stace",
"T. P. Spiller",
"G. J. Milburn",
"S. D. Barrett",
"D. G. Hasko",
"D. A. Williams"
],
"categories": [
"quant-ph"
],
"doi": "10.1103/PhysRevA.74.062302",
"title": "A Model for an Irreversible Bias Current in the Superconducting Qubit Measurement Process",
"url": "https://arxiv.org/abs/quant-ph/0610074"
},
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