I know about this experiment and I am still very skeptical about this acausal interpretation. I must admit, I don’t know every steps the second photon has to pass through. Either, information pass through somehow or it is an experimental error…? I think acausality is very unlikely. Information is never lost…?

Even though someone find the Graal, all physics may have to be rewritten. This necessitates many people working together. The problem is we live in a society of specialists where everyone see the other as a potential enemy. I’m sure you know what I’m talking about…

]]>“Splitting” is just a shorthand in what I wrote for “where formerly there was one, now later there are many”. The paradox doesn’t go away with the longer form. Do ask Tegmark about the continuum objection. I have discussed that with a many-worlds advocate and got waffle about applying a measure over imaginary worlds (I asked about the origin of the measure and got no answer); I have also found the issue not to be addressed in a fair amount of writing on the subject, including Everett’s founding works. Science fiction is the kindest thing I can say about it.

]]>Yes Phillip, but there are ways of dealing with the dilemma that don’t wreck the Copenhagen view, such as decoherence, whereas with many-worlds you are stuck. And if you think that many-worlds advocates would disagree with my phrasing, where and why?

Moreover the many-worlds view cannot handle the case in which the eigenspectrum of the operator being measured includes a continuum. It is sheer science fiction.

]]>The order in which you do the measurements on the two particles in a Bell-type experiment is not Lorentz-invariant. That implies acausality at the hidden variable level. And there is Wheeler’s “delayed choice” experiment in which you decide whether to measure a wave pattern (requiring a quantum to pass through two slits) or the location of a particle (requiring the quantum to pass through just one of the slits) *after* it has passed the screen containing the slits. That is strongly suggestive of acausality at a deeper level.

]]>I don’t think you need to know the future, but you need to explore the entire universe…

]]>We should look for hidden variables because it is the vocation of physicists to improve testable prediction. If you don’t want to do that, become a gardener. (I mean no disrespect to gardeners and I don’t mean you personally.) Purported no-hidden-variable theorems merely rule out certain classes of hidden variables. Bell’s theorem ruled out local hidden variables, so they must be nonlocal as you say. Some experiments – whose results are correctly predicted by quantum mechanics – show that the hidden variables must also be acausal. That is more shocking, because it appears to show that to predict the future you must know it, in which case there really is a limit on prediction. Yes, but (1) perhaps you can still improve practical prediction from today’s level even if you can’t go all the way, and you won’t know if you don’t try; and (2) wouldn’t it be great to know the equations of the theory even if you can’t get the initial conditions? Finding the basic ontology would surely trigger some major advances.

The Copenhagen interpretation is actually a refusal to interpret. Provided it is viewed as provisional while the astonishing results of quantum theory – notably quantum computing – are explored then no harm is done. But when rationalisations for giving up are proposed, such as the many-worlds view, then one must dispute them. Now, a measurement involves an interaction between the measuring apparatus and the system, so the apparatus and system could be considered as a joint system quantum-mechanically. There would supposedly be splitting into many worlds if you treat the system as quantum and the apparatus as classical, but no splitting if you treat them jointly as quantum. Nothing privileges a measuring apparatus, so physicists are free to analyse the situation in these two differing ways – but then they disagree about whether splitting has taken place. That’s inconsistent, and many-worlds is crazy.

It is truly remarkable that in quantum mechanics you get from a many-particle description to a one-particle description by integrating the wavefunction over the coordinates of the ‘other’ particles, yet the laws of logic require you to integrate (marginalise) over probabilities, which are (roughly) the squares of wavefunctions; yet no inconsistency arises.

]]>open minded people…

]]>I agree with you, we all need to open up our mind. I think some form of non local hidden variables is a necessity to solve this puzzle though.

The first key point is from Quantum physics and it is the quantization or discretization of energy (the quantum states). The second key point comes from Einstein’s Relativity which implies that there is no absolute space and time. The third key point is just to expose a fact that people tend to forget: It takes time for a photon to go from point A to point B. Within this lapse of time, information could travel faster than light without any violation of causality, as long as no energy is exchanged faster than light.

How is it possible that we have discrete particles having discrete states with no absolute space and time? These particles are quantized in space and time. Relativity must be quantized in a quantum gravity theory.

How could quantization be the same everywhere we look in the cosmos?

Either space or time is not entirely relative and information, somehow, may be exchanged much faster than light. Experiments tend to demonstrate that space is not quantized…

Just some ideas to be shared with opened mind people…

]]>The state vector of a multiparticle system is obtained by tensor product rather than superpositional addition – although superpositions of such products often are involved too of course – and absolute phase is just as unmeasurable for such states. Superposition is about adding interfering possibilities rather than interfering waves; doing probability theory calculations rather than mechanics theory calculations.

As Ballentine says: conceptually, single particles and their “wave functions” are a real menace – a temptation into psiontology!

]]>What do you think is wrong with the first paragraph you quote?

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