Decoherence Through Interaction with the Environment

Abstract

The observation that all objects in our universe interact with each other to a greater or lesser degree seems rather trivial at first sight. The strength, and thereby the consequences, of interactions vary enormously, depending on the situation considered. Sometimes, even in the framework of classical physics, surprising results have been found. A prominent example, already mentioned in Sect. 2.3, is the influence of a small mass of a few grams, as far away as the star Sirius, on the trajectories of air molecules here on earth (Borel 1914a, Brillouin 1964) . This example demonstrates that even a coupling which is considered as weak (as gravity certainly is over such distances) can have a great influence on systems that are sensitive enough to this kind of interaction, “The representation of gaseous matter... composed of molecules with positions and velocities which are rigorously determined at a given instant is therefore a pure abstract fiction;... as soon as one supposes the indeterminacy of the external forces, the effect of collisions will very rapidly disperse the trajectory bundles which are supposed to be infinitely narrow, and the problem of the subsequent movement of the molecules becomes, within a few seconds, very indeterminate, in the sense that an enormously large number of different possibilities are a priori equally probable.”1 (Borel 1914b)