Quantum jump as an objective process of nature

We study the time evolution of a linear superposition of two spatially separated wave packets, and we focus on the entanglement of the two distinct branches of the state vector with the environment. We focus in particular on the dynamics of a dissipative oscillator under the influence of objective processes of wave-function collapse, the continuous spontaneous localizations (CSL) recently proposed by Ghirardi et al. [G. C. Ghirardi, P. Pearle, and A. Rimini, Phys. Rev. A 42, 78 (1990)]. We prove that the entanglement of the system of interest with the environment induces an accumulation of spontaneous wave-function collapses denoted by us as the environment-enhanced CSL process. This process of CSL accumulation is triggered by the same mechanism of interaction between the quantum system and the environment as that responsible for relaxation and dissipation. In agreement with the predictions of a preceding paper of our group [D. Vitali, L. Tessieri, and P. Grigolini, Phys. Rev. A 50, 967 (1994)], the CSL processes are shown to produce negligible effects at the statistical level. However, if we assume the attitude stimulated by the recent literature on optical quantum jumps, which is forcing us to adopt individual-system pictures, we show that the single runs are characterized by processes of wave-function collapses occurring at times compatible in principle with the experimental observation.