Talk:Copenhagen interpretation

Teller Copenhagen interpretation

Anybody have scholarly sources for Edward Teller's Copenhagen interpretation? I find it very convincing but I'd prefer a formal treatment instead of the colloquial explanation he gives on Web of Stories:

With one special remark; if you make a measurement which defines the position precisely, this measurement does not require an observer. Indeed, it is entirely independent. Something might happen a billion years ago and I can find in the geological remains that this or that has happened, no observer. What happens in a measurement is what is called - excuse me for introducing a new concept, which I will explain - something must happen which is called an Irreversible Process. And I will show you an irreversible process right here. Here is this hopefully empty cup and I drop it. Now, what happens in physics forward can also happen backward. The equations are so constructed that everything that happens one way can happen also the opposite way. So therefore, having stopped this- dropped this cup, I stand here with my hand open and wait for the cup to rise again, not as I do it, lifting it, but of its own accord, redoing the whole thing and landing in my hand. You all know that if that can happen at all you have to have a lot of patience, a patience greatly exceeding the age of the universe which is about as good as saying it never can happen. And the interference phenomenon, a peculiar thing in quantum mechanics, will show up its consequences in whatever else I do with this object. Because from the end state, I can reconstruct the initial state, except if there is an irreversible process. A measurement is not defined by Eugene Wigner knowing about it, or anybody else, it is defined by an irreversible process which does not allow the original state to be reconstructed from the final state. It is in this sense that Heisenberg should be understood. And he's talking of it- about an observer. It's simply justified as a didactic device, as a device to explain things, so people understand more easily what an observer is than to say what an irreversible process is.

References

It appears Teller eliminates the observer and the wavefunction collapse out of the Copenhagen interpretation and replaces them with a statistically "irreversible" wavefunction, which doesn't appear to be formally irreversible, just that it has a near zero probability. HueSurname (talk) 16:47, 1 January 2021 (UTC)

He is describing the process we now call decoherence, that a "measurement" in quantum mechanics which converts a superposition into a unique classical state, which is described in the Copenhagen interpretation as "wavefunction collapse", may actually occur by a thermodynamically irreversible process, like the dropped coffee cup. All "measurements" or "observations" in quantum mechanics are irreversible processes, which is what causes apparent wavefunction collapse. For example, in the Schrodinger's cat experiment, the detection of the atomic particle by the geiger counter, and the amplification of the signal by the electronics to actuate the release of the poison, are irreversible processes. It is this irreversible entanglement of the quantum superposition with the wavefunction of a large number of particles, the "external world", that causes the different components ("eigenstates") of the superposition ("live cat" and "dead cat" in Schro's experiment) to become mutually unobservable, so it appears that only one of the possibilities has occurred.

This process wasn't really recognised in the Copenhagen Interpretation, the wavefunction of the external world wasn't considered. In the CI, the world is divided into the "experiment", which is described quantum mechanically, and the "observer", "measuring apparatus" or "external world", which is described classically. As you say, in this 1998 speech Teller replaces the outside world by its wavefunction, but this wasn't his own idea. The effect of the entanglement of the apparatus wavefunction with the world's wavefunction had been discovered Heinz-Dieter Zeh in the 1970s. The fact that the irreversibility of the measuring apparatus increased the state space occupied by the entangled wavefunction, causing decoherence which resulted in only one eigenstate being observable, was first published in a 1970 paper by Zeh. This isn't part of the Copenhagen Interpretation, or any interpretation. --Chetvorno^TALK 00:23, 11 April 2021 (UTC)

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The miscellaneous quotations added in this edit do not, in my view, contribute clarity to the article. We already summarize the serious scholarship by Howard and others that indicates how ahistorical invocations of "the" Copenhagen interpretation are. Questioning the unity of "the" Copenhagen interpretation is at least as old as Jammer's book in 1974, or in other words, only about twenty years younger than the use of "Copenhagen interpretation" in print. The lengthy quotation from Beller is orthogonal to the question of how the term originated, and the others are repetitive, seemingly chosen at random, and do not convey additional information. (An offhand mention in a book about falling cats? It's a fine book — I've read it — but really?) The lengthy quotation from Stone is mostly tangential as well, and pushes a POV that plenty of physicists have disagreed with, from Heisenberg on; I mean, how easy is it to visualize a wave function for more than one particle? For a finite-dimensional Hilbert space bigger than a single qubit? And while the term "wave mechanics" might be mostly used these days to talk about the history of quantum physics, it didn't vanish entirely; it's still in use, being roughly synonymous with "Schrödinger picture". XOR'easter (talk) 20:15, 25 November 2021 (UTC)

Lead vs Body on the origin and meaning of topic.

As the section on Origin points out, the "Copenhagen interpretation" is not a characterization espoused by any of the principals listed in the lead paragraph. An encyclopedic approach to the topic should start with what "it" is and "it" is a name coined in the mid-1950s for ideas partly traceable to Bohr and Heisenberg, but also Born Dirac and von Neumann, and many others. In fact the breadth contributors to the "Copenhagen interpretation" is exactly why it is the most commonly taught. Johnjbarton (talk) 22:30, 10 August 2023 (UTC)

I've tried adjusting the intro. Faye's article in the Stanford Encyclopedia of Philosophy lists Born right up there with Bohr and Heisenberg; Dirac and maybe Pauli could potentially be mentioned too. XOR'easter (talk) 22:32, 11 August 2023 (UTC)

Thanks

Resolved

Johnjbarton (talk) 00:24, 12 August 2023 (UTC)

The Heisenberg cut

I renamed a section to The Heisenberg cut. This section is confusing. It mixes up quantum discontinuity, measurement, and quantum system definition, plus some goop about observers and cosmology, with a dollop of mind projection fallacy. Johnjbarton (talk) 00:27, 12 August 2023 (UTC)

We can probably tidy it up and maybe move some stuff around, but I'm not sure what's intrinsically confusing about it. There's a cluster of related complaints about the Copenhagen interpretation(s), sometimes phrased as having to make a division between quantum and classical, or between microscopic and macroscopic, reversible and irreversible, etc. Quantum cosmology is then claimed to be a setting where the Copenhagen interpretation(s) can't work, because there is no "outside". XOR'easter (talk) 00:40, 12 August 2023 (UTC)