Dephasing by an Asymetric Environment

Abstract

The crossover from coherent quantum mechanical behavior in microscopic systems to classical dynamics in macroscopic ones has long generated interest. With the advent of microfabrication techniques and cryogenic technology, such discussions are no longer simply speculative, but have bearing on practical measurements. For example, experiments have shown that as the temperature is lowered, nonlocal effects can be seen in transport measurements in some systems due to the wave nature of the electron (Webb et al., 1985; Chandrasekhar et al., 1985). It has been shown theoretically that such interference effects can be suppressed when a quantum mechanical system interacts with an environment (Schmid, 1982; Caldeira and Leggett, 1983a, 1983b, 1985; Hakim and Ambegaokar, 1985). However, it must be stressed that not all interactions destroy such interference. It is perfectly possible [and has indeed been experimentally demonstrated (Badurek et al., 1983)] for a quantum system to exchange energy with its environment and still display interference. Thus it is incorrect to simply equate an inelastic scattering time with the characteristic time over which the system loses phase coherence or “dephasing time”, τϕ.