On the limits of quantum theory: contextuality and the quantum-classical cut

TL;DR

This paper explores the limitations of quantum theory at higher levels, emphasizing the role of contextuality and top-down causation in the quantum-classical transition, challenging traditional views on measurement and the Heisenberg cut.

Contribution

It introduces a framework based on assumptions about layered reality and contextuality, showing that higher-level laws are generally non-unitary and that quantum theory's applicability is limited beyond the fundamental level.

Findings

Higher-level effective laws are non-unitary.

Quantum measurement involves top-down causal effects.

The quantum-classical cut is influenced by contextuality and emergence.

Abstract

This paper is based on four assumptions: 1. Physical reality is made of linearly behaving components combined in non-linear ways. 2. Higher level behaviour emerges from this lower level structure. 3. The way the lower level elements behaves depends on the context in which they are imbedded. 4. Quantum theory applies to the lower level entities. An implication is that higher level effective laws, based in the outcomes of non-linear combinations of lower level linear interactions, will generically not be unitary; hence the applicability of quantum theory at higher levels is strictly limited. This leads to the view that both state vector preparation and the quantum measurement process are crucially based in top-down causal effects, and helps provide criteria for the Heisenberg cut that challenge some views on Schroedinger's cat.