From the fact of observation of squeezed light follows the possibility of a nonperturbing or nondemolition measurement (observation) of a single microscopic object in a widely distributed quantum-mechanical state. Macroscopic bodies—objects of classical mechanics—are usually found in states with narrow wave packets, although quantum mechanics does not forbid them to be in states with wide wave packets. The absence of macroscopic bodies in such states requires explanation. In this article it is shown that in virtue of a special, geometrical nature of the gravitational field the absence in nature of macroscopic bodies in widely distributed states can be due to the focusing action of the self-gravitational field of a macroscopic body on its wave packet. Thus, the gravitational field can play an important role in the relaxation of the classical limit of quantum mechanics.
We demonstrate a breakdown in the macroscopic (classical-like) dynamics of wave-packets in complex microscopic and mesoscopic collisions. This breakdown manifests itself in coherent superpositions of the rotating clockwise and anticlockwise wave-packets in the regime of strongly overlapping many-body resonances of the highly-excited intermediate complex. These superpositions involve $\ensuremath{\sim}{10}^{4}$ many-body configurations so that their internal interactive complexity dramatically exceeds all of those previously discussed and experimentally realized. The interference fringes persist over a time-interval much longer than the energy relaxation-redistribution time due to the anomalously slow phase randomization (dephasing). Experimental verification of the effect is proposed.
A semiclassical approximation is presented which uses the wave-pocket formulation of collision theory. First an appropriate semiclassical approximation is derived by assuming that the wave packet is and remains narrow during the passage of the interaction region. After this, a process is devised to decompose a macroscopic wave packet into narrow wave packets. The wave function, after the collision, is obtained by summing up the contributions from all the narrow wave packets into which the macroscopic wave packet was decomposed. Finally, using this function, the
S matrix and the scattering cross section are calculated.