Loss of quantum coherence in a system coupled to a zero-temperature   environment
  We discuss the influence of a zero-temperature environment on a coherent quantum system. First, we calculate the reduced density operator of the system in the framework of the well-known, exactly solvable model of an oscillator coupled to a bath of harmonic oscillators. Then, we propose the sketch of an Aharonov--Bohm-like interferometer showing, through interference measurements, the decrease of the coherence length of the system due to the interaction with the environment, even in the zero temperature limit. 
A. Ratchov (LPM2C), F. Faure (LPM2C), F. W. J. Hekking (LPM2C)