Experimental observation of decoherence

In the 1980s, theoretical estimates showed that on macroscopic scales I decoherence occurs extremely rapidly, thus effectively precluding the observation of nonclassical I superposition states [21–23]. This immediately led to the question of how we may experimentally observe the continuous action of decoherence and thus the smooth transition from quantum to classical. Several challenges have to be overcome in the design of such experiments. The system is to be prepared in a nonclassical superposition of mesoscopically or even macroscopically distinguishable states (ISchrödinger-cat state) with a sufficiently long decoherence time such that the gradual action of decoherence can be resolved. The existence of the superposition must be verified, and a scheme for monitoring decoherence must be devised that introduces a minimal amount of additional decoherence. Starting in the mid-1990s, several such experiments have been successfully performed, using physical systems such as: