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Irreversibility and Dephasing from Vacuum Fluctuations

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Published in Skjeltorp, Arne T. and Vicsek, Tamas. NATO Advanced Study Institute : Complexity from Microscopic to Macroscopic Scales: Coherence and Large Deviations. Geilo (Norway) - 17-27 April 2001 - Dordrecht: Kluwer Academic. 2002, p. 21-47
Collection NATO Science Series II: Mathematics, Physics and Chemistry; 63
Abstract We investigate the role of vacuum (zero-point) fluctuations in generating decoherence in a number of simple models. First we discuss a harmonic oscillator coupled to a semi-infinite elastic string and discuss the irreversible nature of such a bath. We investigate the fluctuations in energy of the oscillator and discuss the trace the oscillator leaves in the bath. Most of the work deals with two-level systems coupled to a bosonic bath (a transmission line). For two-level systems with a Hamiltonian that commutes with the total Hamiltonian (system plus coupling plus bath) the ground state is a pure state. The energy of the system is a constant of motion. For the general case, the energy of the two-level system fluctuates, and the ground state is only partially coherent. A particular realization of such a two level system consists of a mesoscopic ring with a quantum dot coupled capacitively to a transmission line. In the presence of an Aharonov-Bohm flux this system exhibits a persistent current. This current is a measure of the coherence of the ground state. As a function of the coupling strength the ground state undergoes a crossover from a state characterized by a time-averaged persistent current which is much larger than its time-averaged mean squared fluctuations to a state characterized by a persistent current with an average amplitude that is much smaller than its mean squared fluctuations.
Keywords Mesoscopic systems and quantum hall effectCondensed matter
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ISBN: 978-1-4020-0634-0
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BUTTIKER, Markus. Irreversibility and Dephasing from Vacuum Fluctuations. In: Skjeltorp, Arne T. and Vicsek, Tamas (Ed.). NATO Advanced Study Institute : Complexity from Microscopic to Macroscopic Scales: Coherence and Large Deviations. Geilo (Norway). Dordrecht : Kluwer Academic, 2002. p. 21-47. (NATO Science Series II: Mathematics, Physics and Chemistry; 63) https://archive-ouverte.unige.ch/unige:4479

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Deposited on : 2009-12-01

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