Decoherence, the measurement problem, and interpretations of quantum mechanics

Quantum decoherence plays a pivotal role in the dynamical description of the quantum-to-classical transition and is the main impediment to the realization of devices for quantum information processing. This paper gives an overview of the theory and experimental observation of the decoherence mechanism. We introduce the essential concepts and the mathematical formalism of decoherence, focusing on the picture of the decoherence process as a continuous monitoring of a quantum sy...

This paper aims to show how adoption of a pragmatist interpretation permits a satisfactory resolution of the quantum measurement problem. The classic measurement problem dissolves once one recognizes that it is not the function of the quantum state to describe or represent the behavior of a quantum system. The residual problem of when, and to what, to apply the Born Rule may then be resolved by judicious appeal to decoherence. This can give sense to talk of measurements of ph...

This is a preliminary version of an article to appear in the forthcoming Ashgate Companion to the New Philosophy of Physics. I don't advocate any particular approach to the measurement problem (not here, at any rate!) but I do focus on the importance of decoherence theory to modern attempts to solve the measurement problem, and I am fairly sharply critical of some aspects of the "traditional" formulation.

This thesis has three aims: (1) to clarify in detail the relation between the decoherence mechanism and the problem of definite outcomes, (2) to dispel common misconceptions about the measurement problem in quantum mechanics, and (3) to present some recent alternative approaches in the quest for a satisfactory solution of the definite outcomes problem.

Endeavoring to formulate an exhaustive solution to the measurement problem in view of the theory of decoherence leads to a better understanding of the status of the collapse and of the emergence of classicality, thanks to a precise definition of the measurement and some new vocabulary to speak about quantum mechanics. Considering the latter as a probabilistic theory all along allows us to avoid the usual probability problem of the many-worlds interpretations. A thorough verif...

A short critical review of the concept of decoherence, its consequences, and its possible implications for the interpretation of quantum theory is given.

We introduce and investigate a simple model of conditional quantum dynamics. It allows for a discussion of the information-theoretic aspects of quantum measurements, decoherence, and environment-induced superselection (einselection).

We show that the quantum description of measurement based on decoherence fixes the bug in quantum theory discussed in [D. Frauchiger and R. Renner, {\em Quantum theory cannot consistently describe the use of itself}, Nat. Comm. {\bf 9}, 3711 (2018)]. Assuming that the outcome of a measurement is determined by environment-induced superselection rules, we prove that different agents acting on a particular system always reach the same conclusions about its actual state.

The roles of decoherence and environment-induced superselection in the emergence of the classical from the quantum substrate are described. The stability of correlations between the einselected quantum pointer states and the environment allows them to exist almost as objectively as classical states were once thought to exist: There are ways of finding out what is the pointer state of the system which utilize redundancy of their correlations with the environment, and which lea...

I offer a few selected reflections on the decoherence program, with an emphasis on Zeh's role and views. First, I discuss Zeh's commitment to a realistic interpretation of the quantum state, which he saw as necessary for a consistent understanding of the decoherence process. I suggest that this commitment has been more fundamental than, and prior to, his support of an Everett-style interpretation of quantum mechanics. Seen through this lens, both his defense of Everett and th...