Recent content by Demystifier

I would say that the swap operation implies the A/D entanglement. The difference is that "implication" is logical rather than physical, and does not assume any temporal order.

Just a minor notational nitpicking. Is this your own notation, or have you seen it somewhere else? Wouldn't it be more common to use the notation ##\rho_{\psi} = \ket{\psi}\bra{\psi}##? Actually I like your notation, but I just haven't seen it before.

One more point, that points to the core of the confusion. To decide whether a certain state in the Hilbert space ##{\cal H}## is entangled or not, one first has to decompose ##{\cal H}## into a product of two or more subspaces. The notion of entanglement depends on this decomposition, so the...

If I have to choose one of those, I choose i). You cannot actually observe the A/D correlation before you do the swap. The data from which the correlation is extracted was there before the swap, but you can see this correlation only after the swap. In this sense, the correlation happens after...

I think now the real issue is this. If the interaction between B and C happens after the measurement of A and D, are A and D entangled or not at the time of their measurement? The answer is the following. Entanglement is a property of the wave function (not of the Bohmian particles), so to...

@PeterDonis you are right, the word "spurious" was not appropriate.

There is no action to the past. Suppose that at time ##t_1## you measure A and D, and later at ##t_2>t_1## put B and C into the interaction. Since you look for correlations, you actually do all this with many copies of the system, so that you can analyse your data statistically. At ##t_1## you...

In the other thread, @DrChinese says: "Show me any Bohmian step by step explanation of the mechanics - in precise time order as required by Bohmian theory. These experiments clearly defy Bohmian cause and effect concepts, which specifically require instantaneous action at a distance in a forward...

If particles no longer exist, then something else absorbed their energy, momentum and quantum information. For example, a photon is absorbed by an electron, so the energy, momentum and quantum information of the photon is now encoded in the electron. Instead of photons A and D, now we have...

Since the recent thread on Bohmian mechanics (BM) is now closed, I open a new thread in which I want to explain something that bothers @DrChinese for a long time. How can BM explain the entanglement swapping? But I want to make this explanation simple and intuitive, rather than technical. I want...

Yes, but the effective collapse refers to the effective wave function, not to the fundamental wave function. For various notions of "wave function" in BM, see e.g. my lecture http://thphys.irb.hr/wiki/main/images/e/e6/QFound4.pdf pages 23-24.

This nonlocal change refers to the velocity of the Bohmian particles, not to the properties of the wave function (aka pilot wave). So is there a nonlocal change of the spin? It depends on what do you mean by "spin". If you mean a property of the wave function, then there is no such nonlocal...

Here Norsen considers an idealized situation, in which any interaction in the Hamiltonian (that governs the evolution of wave function through the Schrodinger equation) describes a measurement. Under this idealization, he is right. But this is an idealization. More realistically, there are...

On these matters I agree on almost everything with Norsen, as well as with @PeterDonis . On the other hand, I find very difficult to understand what exactly @DrChinese finds problematic.

Ah, I think I understand now what's the main source of confusion. In BM there is no collapse, and yet one can talk about collapse in BM. How can that be? The key, made particularly clear by Bell, is that, in BM, one needs to distinguish exact statements from FAPP (for all practical purposes)...