No Quantum Process Can Explain the Existence of the Preferred Basis: Decoherence Is Not Universal

TL;DR

This paper argues that environment-induced decoherence cannot universally explain the emergence of a preferred measurement basis in quantum mechanics, implying that such a basis must be postulated rather than derived.

Contribution

It demonstrates that environment-induced decoherence does not generally lead to a preferred basis due to implicit assumptions of prior independence, challenging common explanations.

Findings

Decoherence does not guarantee a preferred basis in general.

Prior independence assumptions are invalid, preventing decoherence from selecting a basis.

The preferred basis must be postulated in quantum mechanics.

Abstract

Environment induced decoherence, and other quantum processes, have been proposed in the literature to explain the apparent spontaneous selection - out of the many mathematically eligible bases - of a privileged measurement basis that corresponds to what we actually observe. This paper describes such processes, and demonstrates that - contrary to common belief - no such process can actually lead to a preferred basis in general. The key observation is that environment induced decoherence implicitly assumes a prior independence of the observed system, the observer and the environment. However, such independence cannot be guaranteed, and we show that environment induced decoherence does not succeed in establishing a preferred measurement basis in general. We conclude that the existence of the preferred basis must be postulated in quantum mechanics, and that changing the basis for a measurement is, and must be, described as an actual physical process.