Quantum Darwinism and Computability Theory

TL;DR

This paper explores whether unitary evolution alone can explain the emergence of classical reality, concluding that additional mechanisms are needed as unitarity alone cannot account for measurement and observation.

Contribution

It analyzes the limitations of unitarity in quantum mechanics using computability theory, highlighting the necessity of additional processes for measurement and classical emergence.

Findings

Unitary evolution alone cannot produce measurement outcomes.

Computability theory shows quantum machines cannot halt or observe states.

Additional mechanisms are required for the emergence of classicality.

Abstract

This paper examines whether unitary evolution alone is sufficient to explain emergence of the classical world from the perspective of computability theory. Specifically, it looks at the problem of how the choice related to the measurement is made by the observer viewed as a quantum system. In interpretations where the system together with the observers is completely described by unitary transformations, the observer cannot make any choices and so measurement is impossible. From the perspective of computability theory, a quantum machine cannot halt and so it cannot observe the computed state, indicating that unitarity alone does not explain all matter processes. Further it is argued that the consideration of information and observation requires an overarching system of knowledge and expectations about outcomes.