Quantum Confusions, Cleared Up (or so I hope)

Sabine Hossenfelder · 21 Sept 2023 · arxiv.org ↗

4 korrents from this paper

In plain words

Looking at quantum mechanics only as a prediction tool shows common claims about its interpretations fail, especially on locality. This cleans up confusions so debates focus on physics instead of word meanings. It is an argument investigating those claims that builds on a classification of interpretations and pushes against ideas that collapse is optional or many worlds is local.

Our summary of the paper, not the authors' words — written to be readable without the field's vocabulary, from the stored copy of the paper and nothing else. Drafted with xai:grok-4.5 and checked by a person. The authors' own sentences are the quotes below.

Sabine Hossenfelder did not write this page.

Every claim below was made in this piece, quoted word for word and numbered in the order the piece makes them, so you can read it there rather than take our word for it. The sentence above each quote is our reading of the claim, not their wording. Each quote was checked against a stored copy of the page at build time; where the two differ, the quote is the fact.

Our reading
The Copenhagen interpretation is not locally causal in Bell's sense.

Their wordsThe Copenhagen Model-and because of that, the Copenhagen Interpretation-is not locally causal in Bell's sense.

Interesting
Our reading
Violations of Bell inequalities reveal only properties of models, not of nature itself.

Their wordsSince Local Causality is a property of a model, observing violations of Bell's inequality cannot tell us anything about nature itself, but merely about the properties of the model that we use to describe nature.

Interesting
Our reading
Decoherence has not yet satisfactorily solved the measurement problem and does not restore local causality.

Their wordswhile decoherence has the potential to solve this aspect of the measurement problem, it hasn't yet been satisfactorily done. Decoherence also certainly does not return us to Local Causality.

Interesting
Our reading
The collapse postulate cannot simply be discarded without replacement instructions for measurements.

Their wordsAs we just saw, one cannot just discard the Collapse Postulate. For this reason, if one does calculations in any Many Worlds approach, one must effectively replace the Collapse Postulate by other assumptions, notably about what happens to observers and/or measurement devices when worlds branch.

Interesting