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We illustrate the equivalence between the non-unitary evolution of an open quantum system governed by a Markovian master equation and a process of continuous measurements involving this system. We investigate a system of two coupled modes, only one of them interacting with external degrees of freedom, represented, in the first case, by a finite number of harmonic oscillators, and, in the second, by a sequence of atoms where each one interacts with a single mode during a limited time. Two distinct regimes appear, one of them corresponding to a Zeno-like behavior in the limit of large dissipation.

We model a feasible experiment involving two interacting microwave cavities with very different quality factors. An excitation is initially present in the high Q cavity. Modeling the environment as linearly coupled oscillators, we find a Zeno-like behavior which should occur when the dissipation constant is large enough as compared to the unitary coupling.

We investigate the conditions for the existence of states less exposed to the environment and decoherence-free subspaces (DFS) for two oscillators subjected to reservoirs at any temperature. We show that the main effect of the temperature is to fasten the decoherence process. However, the DFS found for zero temperature remain protected. A solution for diffusive environments is presented.

A quantum phase transition, characterized by an accumulation of energy levels in the espectrum of the model, is associated with a qualitative change in the corresponding classical dynamic obtained upon generalized coherent states of angular momentum.

The extension of the Caldeira–Leggett model to two oscillators coupled to a reservoir predicts an environment induced interaction between the two oscillators, which may lead to decoherence-free subspaces. A quantitative analysis of the parameter's strength of the model is therefore important. We propose here an experiment capable of deciding this question.

We show that the well-known geometric phase, the Gouy phase in optics can be defined for matter waves in vacuum as well. In particular we show that the underlying physics for the “matter waves” Gouy phase is the generalized Schrodinger–Robertson uncertainty principle, more specifically, the off diagonal elements of the covariance matrix. Recent experiments involving the diffraction of fullerene molecules and the uncertainty principle are shown to be quantitatively consistent with the existence of a Gouy phase for matter waves.