Quantum Decoherence of Single-Photon Counters
  The interaction of a quantum system with the environment leads to the so-called quantum decoherence. Beyond its fundamental significance, the understanding and the possible control of this dynamics in various scenarios is a key element for mastering quantum information processing. Here we report the quantitative probing of what can be called the quantum decoherence of detectors, a process reminiscent of the decoherence of quantum states in the presence of coupling with a reservoir. We demonstrate how the quantum features of two single-photon counters vanish under the influence of a noisy environment. We thereby experimentally witness the transition between the full-quantum operation of the measurement device to the "semi-classical regime", described by a positive Wigner function. The exact border between these two regimes is explicitely determined and measured experimentally. 
Virginia D'Auria (LKB - Jussieu), Noriyuki Lee (LKB - Jussieu),   Taoufik Amri (LKB - Jussieu), Claude Fabre (LKB - Jussieu)...
quant-ph