Epistemology of Wave Function Collapse in Quantum Physics

TL;DR

This paper mathematically demonstrates that in GRW and similar quantum theories, there are fundamental limits to what inhabitants can know about their universe, including the impossibility of precisely measuring certain collapse events.

Contribution

It provides a formal analysis of epistemic limitations in spontaneous collapse theories and compares these with other interpretations like Bohmian mechanics and orthodox quantum mechanics.

Findings

Inhabitants cannot reliably measure the number of collapses during a time interval.

Certain factual questions about the universe are empirically undecidable in GRW.

The limitations are similar across different collapse and no-collapse quantum theories.

Abstract

Among several possibilities for what reality could be like in view of the empirical facts of quantum mechanics, one is provided by theories of spontaneous wave function collapse, the best known of which is the Ghirardi-Rimini-Weber (GRW) theory. We show mathematically that in GRW theory (and similar theories) there are limitations to knowledge, that is, inhabitants of a GRW universe cannot find out all the facts true about their universe. As a specific example, they cannot accurately measure the number of collapses that a given physical system undergoes during a given time interval; in fact, they cannot reliably measure whether one or zero collapses occur. Put differently, in a GRW universe certain meaningful, factual questions are empirically undecidable. We discuss several types of limitations to knowledge and compare them with those in other (no-collapse) versions of quantum mechanics, such as Bohmian mechanics. Most of our results also apply to observer-induced collapses as in orthodox quantum mechanics (as opposed to the spontaneous collapses of GRW theory).