Making Better Sense of Quantum Mechanics

There is an interesting, pithy and polemical paper on the arXiv by David Mermin, with the abstract:

We still lack any consensus about what one is actually talking about as one uses quantum mechanics. There is a gap between the abstract terms in which the theory is couched and the phenomena the theory enables each of us to account for so well. Because it has no practical consequences for how we each use quantum mechanics to deal with physical problems, this cognitive dissonance has managed to coexist with the quantum theory from the very beginning. The absence of conceptual clarity for almost a century suggests that the problem might lie in some implicit misconceptions about the nature of scientific explanation that are deeply held by virtually all physicists, but are rarely explicitly acknowledged. I describe here such unvoiced but widely shared assumptions. Rejecting them clarifies and unifies a range of obscure remarks about quantum mechanics made almost from the beginning by some of the giants of physics, many of whom are held to be in deep disagreement. This new view of physics requires physicists to think about science in an unfamiliar way. My primary purpose is to explain the new perspective and urge that it be taken seriously. My secondary aims are to explain why this perspective differs significantly from what Bohr, Heisenberg, and Pauli had been saying from the very beginning, and why it is not solipsism, as some have maintained. To emphasize that this is a general view of science, and not just of quantum mechanics, I apply it to a long-standing puzzle in classical physics: the apparent inability of physics to give any meaning to “Now” — the present moment.

The `new perspective’ Mermin espouses is a form of `QBism (i.e. `Quantum Bayesianism’)‘. You can download the full article for free here.

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3 Responses to “Making Better Sense of Quantum Mechanics”

  1. For me, QBism has more to do with quantum computers and psychology than it has to do with the fundamental laws of physics. Though it represents a certain reality and it may be helpful; in the end, it is emergent and phenomenological. What problems does it solve?

  2. I mean what problem does it solve really?

  3. Anton Garrett Says:

    David Mermin deserves respect. He is a clear writer who has published outstandingly good expositions of the GHZ and Hardy scenarios, which tighten and shed light on Bell’s theorem; of the remarkable Kochen-Specker result in quantum mechanics; and of quantum computing, at book length. But I don’t believe that this present paper is one of his useful contributions. It seems to have been inspired by the view that probability is the degree of belief which it is justified for someone to have in a proposition, in the light of other propositions held to be true. The word “belief” of course means that someone is doing the believing. I prefer the definition that p(A|B) is how strongly the (assumed) truth of proposition B implies the truth of proposition A. In all problems in which uncertainty is involved, this quantity is what we actually want; and from the (Boolean) calculus of propositions it can be shown that the p’s, which have propositions as their arguments, obey the well-known sum and product rules.

    This is of course moving back towards impersonalism – the wrong direction according to Mermin. But his paper raises other questions. If someone is doing the believing and cannot be eliminated from the analysis, then the laws of physics – which are quantum – can also be applied to that someone. We get the familiar problem: when is an interaction a measurement, and how can we reconcile the description of “system + observer” with “interaction described quantum-mechanically”? The usual infinite regression problem looms. It seems to me that Mermin is terminating it by insisting on the role of consciousness, but without saying so explicitly. Yet what is consciousness? s a dog conscious? A fish? An amoeba? A virus?

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