What classicality? Decoherence and Bohr's classical concepts

TL;DR

This paper examines the relationship between decoherence-induced classicality and Bohr's classical concepts, clarifying their differences and exploring how decoherence relates to Bohr's philosophical views on classicality.

Contribution

It offers a detailed analysis of classicality in decoherence theory and its philosophical implications for Bohr's classical concepts, clarifying their distinctions and connections.

Findings

Decoherence describes a dynamical process leading to classical behavior.

Bohr's classical concepts are philosophical and foundational, not derived from decoherence.

The paper suggests nuanced ways to understand the relation between decoherence and Bohr's views.

Abstract

Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In the context of the decoherence program, on the other hand, it has become fashionable to talk about the "dynamical emergence of classicality" from the quantum formalism alone. Does this mean that decoherence challenges Bohr's dictum -- for example, that classical concepts do not need to be assumed but can be derived? In this paper, we'll try to shed some light down the murky waters where formalism and philosophy mingle. To begin, we'll clarify the notion of classicality in the decoherence description. We'll then discuss Bohr's and Heisenberg's takes on the quantum-classical problem and reflect on the different meanings of the terms "classicality" and "classical concepts" in the writings of Bohr and his followers. This analysis will allow us to put forward some tentative suggestions for how we may better understand the relation between decoherence-induced classicality and Bohr's classical concepts.