Quantum Annoyance (EPR and Bell's Inequality related).

[Fra]

Also, I thought Heisenberg's Uncertainty Principle worked only because the photon that's doing the observing perturbs the particle (system), thus altering it. Is this idea correct? In this light I can see how the more we know about momentum, the less we know about position, and vise-versa. In other words, we have to measure momentum of a system using a photon (or some other unit of quanta). When we do that, the position becomes unknown, as the photon that did the observing interacted with the system, altering it.

This understanding of mine of the HUP seems to have a good, classical feel to it. Is it accurate? Or am I just that clueless?

I don't think that bounce picture is very good choice of abstraction. It is a typical realist-abstraction.

In the non-realist view, the idea is to only speak about what's known to the observer. The observer has a particular information. And the QM time evolution predicts how this information is expected to evolve. To ask to what extent the information is "correct" in some ultimate sense is IMO undefinable, because the only way to verify any information, is to put it to test by interaction. The feedback from interaction continously gives feedback to the observer.

To me the meaning of locality I think makes sense is that the possible actions of an observer is only affected by information at hand. This maintains a strong locality ideal, but totally does away with realism. This makes it plausible why particles behaves as a superposition of possiblities rather than just one of them. Because the actions of all parties of the game, are determined by their local information.

This doesn't have to be twisted, it can be quite intuitive - look at game theory. It doesn't matter what the real state of affairs are like, because each players acts upon the information at hand only. I think the best route to find some intuition into QM is game theory. And real life is full of these things. Games, stock markets and society. As is well known, there is not always a realist base for the value of company stocks, this value is rather collectively determined by the expectations of the players on the market. If everybody has the information that this company is doing good and will grow, the stock values rise regardless of the "real state of affairs". And to the stock market player sitting behind his desk speculating, these volatile expecation games is indistinguishable from the real thing! All players acts upone THEIR information, the information of the other players are not known.

They way I see HUP. Once you define the operator of momentum, the HUP follows from that definition and the rest of the axioms of QM. It's like usual wavedecomposition analogy. The Fourier components of a wavepacket are by construction infinitely extended in space, and from there follows that a localized wavepacket requires a large number of cordinated Fourier components.

That's the obvious part.

The question IMHO, is rather, what is so special about the Fourier transform relating two different distributions in x to p space? Or how come that the axioms the build QM, are so successful in describing reality? How was these axioms emergent?

One problem I am trying to solve is more focued in finding the question, to which the Fourier transform is the unique answer. I expect it's an optimation problem. Consider that an observer has limited information capacity, then clearly if they can find a transformation that allows them to be more predictive w/o expanding their memory that seems like a good evolutionary trait? I think this is already strongly correlated to the emergence of the complex amplitude formalism, and the origin of the "superposition statistics" that is really what makes QM different.

I expect to understand how the "momentum space" spontaneously is formed from the "configuration space" and the data from this two views - realted by a particular transformation - results in non-commutativity since you can not both encode the original data AND the transformed data (due to limited representation capacity). The nature of the information feed into the system (ie degree of periodicity) should determine which dominates. When the system is very massive relative to the observer, the uncertainty is not resolvable and we get to the classical domain.

Is there a deeper reason, why we the complex amplitude formalism works so well, whos insight could help take QM to the next level and understand it's connection to gravity?

This is what is the interesting question to me and I think the future holds some kind of answer, and to me the closest option is some new realational information theories. Ordinary QM is not fully a relational theory IMO, but it "should be". Perhaps that missing link is also why it's so hard to make sense of.

IMO, the interesting parts of this is really more than just interpretations. I think the problems to unify interactions and also gravity is even more inflamed by our own lack of deeper understanding of QM. So I think the proof of success or any point of view, or reinterpretation of QM is the one who finds the necessary advantages to also solve some real problems.

/Fredrik

 

[DrChinese]

Also, I thought Heisenberg's Uncertainty Principle worked only because the photon that's doing the observing perturbs the particle (system), thus altering it. Is this idea correct?

Adding to what Fra already said:

No, that idea is definitely not correct. It was an older analogy that helped people picture the situation a long time ago, but it is not accurate.

The uncertainty is NOT imparted by the measuring apparatus, which is the implication. The uncertainty derives from the acquisition of knowledge, however received. That could be from observing an entangled twin, for example. If the uncertainty came from the apparatus, then how is it that any apparatus always creates uncertainty according to the HUP? Some apparati, such as polarizers, impart no change in momentum yet do alter the polarization. Once re-polarized, the photon is otherwise undisturbed! And now there is complete uncertainty in the diagonal (45 degree) orientation in accordance with the HUP.

 

[DrChinese]

Why can particles only become entangled under carefully controlled conditions and only with the use of exotic crystals? Why can't we entangle particles with the ease with which we diffract particles?

The purpose of the "exotic" crystal is to provide a high output of entangled photon twins. "High" being a relative measure, as only a very very small percentage of input photons are down-converted. If you waited (and could look closely enough), you would actually see entangled pairs occasionally coming out of ordinary glass as well because they have a non-zero probability even there. The BBO crystals are cut to enhance down conversion at particular frequencies. They are somewhat akin to resonant cavities as an analogy, or perhaps acoustical harmonics. The key element to the entanglement is that there is conservation of total momentum, spin, etc.

Also, all virtual photon pairs are entangled, not that you could see them directly.

The point being that entanglement used for experiments requires favorable and controlled circumstances. Entanglement has been demonstrated in probably dozens of ways, on a wide variety of particle systems.