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Irreversibility and Dephasing from Vacuum Fluctuations

ContributorsButtiker, Markus
Presented at Geilo (Norway), 17-27 April 2001
PublisherDordrecht : Kluwer Academic
Collection
  • NATO Science Series II: Mathematics, Physics and Chemistry; 63
Publication date2002
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 effect
  • Condensed matter
Citation (ISO format)
BUTTIKER, Markus. Irreversibility and Dephasing from Vacuum Fluctuations. In: 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)
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ISBN978-1-4020-0634-0
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