期刊
JOURNAL OF CHEMICAL PHYSICS
卷 129, 期 22, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3036114
关键词
fluctuations; perturbation theory; quantum computing; stochastic processes
资金
- National Center for Theoretical Science
- National Cheng Kung University of Republic of China [OUA 96-3-2-085]
- National Science Council of Republic of China [NSC-95-2112-M-006-001, NSC-96-2112-M-006-011-MY3]
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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