A "Garden of Forking Paths" - the Quantum Mechanics of Histories of Events

TL;DR

This paper surveys the ETH approach to quantum events, clarifying the concept of events in quantum mechanics and exploring their role in the evolution of isolated systems, supported by a simple mesoscopic model.

Contribution

It introduces and explains the ETH approach to quantum events, providing a clear conceptual framework and illustrating it with a concrete mesoscopic system model.

Findings

Clarification of the notion of quantum events.

Outline of a theory for observations and recordings of events.

Application to a simple mesoscopic quantum system.

Abstract

We present a short survey of a novel approach, called "ETH approach", to the quantum theory of events happening in isolated physical systems and to the effective time evolution of states of systems featuring events. In particular, we attempt to present a clear explanation of what is meant by an "event" in quantum mechanics and of the significance of this notion. We then outline a theory of direct (projective) and indirect observations or recordings of physical quantities and events. Some key ideas underlying our general theory are illustrated by studying a simple quantum-mechanical model of a mesoscopic system.