Non-Markovian suppression of charge qubit decoherence in the quantum point contact measurement

Ming Tsung Lee, Wei-Min Zhang

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

A nonequilibrium theory describing the charge qubit dynamics measured by a quantum point contact is developed based on Schwinger-Keldysh's approach. Using the real-time diagrammatic technique, we derive the master equation to all orders in perturbation expansions. The non-Markovian processes in the qubit dynamics is naturally taken into account. The qubit decoherence, in particular, the influence of the tunneling-electron fluctuation in the quantum point contact with a longer correlation time comparing to the time scale of the qubit dynamics, is studied in the framework. We consider the Lorentzian-type spectral density to characterize the channel mixture of the electron-tunneling processes induced by the measurement, and determine the correlation time scale of the tunneling-electron fluctuation. The result shows that as the quantum point contact is casted with a narrower profile of the spectral density, tunneling electrons propagate in a longer correlation time scale and lead to the non-Markovian processes of the qubit dynamics. The qubit electron in the charge qubit can be driven coherently. The quantum point contact measurement with the minimum deviation of the electron-tunneling processes prevents the qubit state from the decoherence.

Original languageEnglish
Article number224106
JournalJournal of Chemical Physics
Volume129
Issue number22
DOIs
Publication statusPublished - 2008 Dec 22

Fingerprint

Electron tunneling
Point contacts
electron tunneling
retarding
Spectral density
deviation
perturbation
expansion
Electrons
profiles
electrons

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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abstract = "A nonequilibrium theory describing the charge qubit dynamics measured by a quantum point contact is developed based on Schwinger-Keldysh's approach. Using the real-time diagrammatic technique, we derive the master equation to all orders in perturbation expansions. The non-Markovian processes in the qubit dynamics is naturally taken into account. The qubit decoherence, in particular, the influence of the tunneling-electron fluctuation in the quantum point contact with a longer correlation time comparing to the time scale of the qubit dynamics, is studied in the framework. We consider the Lorentzian-type spectral density to characterize the channel mixture of the electron-tunneling processes induced by the measurement, and determine the correlation time scale of the tunneling-electron fluctuation. The result shows that as the quantum point contact is casted with a narrower profile of the spectral density, tunneling electrons propagate in a longer correlation time scale and lead to the non-Markovian processes of the qubit dynamics. The qubit electron in the charge qubit can be driven coherently. The quantum point contact measurement with the minimum deviation of the electron-tunneling processes prevents the qubit state from the decoherence.",
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Non-Markovian suppression of charge qubit decoherence in the quantum point contact measurement. / Lee, Ming Tsung; Zhang, Wei-Min.

In: Journal of Chemical Physics, Vol. 129, No. 22, 224106, 22.12.2008.

Research output: Contribution to journalArticle

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