h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

No, you misunderstand me. I understand the QM completely, but you are assuming QM is correct when interpretting the results, there is no way to test if it is, at least not directly.

Tango

You are right, Tango. No-one has yet proven QM. The EPR systems just INDICATE that the stuff works (i.e. the cat is BOTH dead and alive). I don't think I state that QM is proven by EPR experiments in the Entry. The title is also pointing that QM is at its limit, when it comes to the interpretations of working EPR systems. I give two possibilities: QM folks would like to believe in non-locality. Determinists will point to the hidden variables. Whatever... BOTH are right. No-one will ever know.

I thought you were saying, in one of your previous posts, that the cat is EITHER dead or alive in the box when it's closed. Sorry for the confusion.

Later...

HELL

Well, that was what i was saying, really. You say in the entry the these experiments prove (as much as anything can prove stuff in science, which is not at all, technichally, but you know what i mean) that the photons are entangled, which implies that QM is right. The experiments show that either they are entangled, or QM is wrong. If you assume QM is right, then your entry is fine, but you can't really do that. Maybe a footnote would shut me up? Who knows?

Tango

Well. The phptpns ARE entangled. This IS proven. And it does work.

However, that is no final proof for QM or against Einstein, Podolski and Rosen. Like I said: It could be hidden variables or non-locality.

"The experiments show that either they are entangled, or QM is wrong."

I hope that this is not written down like that in the Entry. The experiments show, demonstrate and prove that certain particles ARE entangled, and that these particles behave like proposed by QM. It just defuses Einstein, Podolski and Rosen's argument against QM. And therefore just *indicates* that QM is right. But it's - of course - no proof.

Maybe I'll add something to 'shut you up', Tango. Thanks for discussing these nits with me. I think it is important to get the correct message across.

HELL

Hi all... Hi, Tango.

I've just re-read the Entry, and I found many passages where you will find something in the lines of "QM is not proven by EPR systems". I state explicitly right in the beginning that QM is incomplete, and that many people are trying to prove it wrong, or find shortcommings (without success so far). Furthermore, you will find that the EPR-experiments do not DEMAND QM to work, for example if you use hidden variables.

I don't think I need to add more to 'shut you up' - as you say, Tango. Maybe you would have a more specific suggestion?

HELL

What i don't understand is very simple:

How can you tell the difference between particles that are in a state of flux yet entangled, and particles that aren't in a state of flux at all. Isn't the whole point of the flux thing that you cannot tell, because as soon as you observe them they will stop being in flux anyway?

Tango

OK... So, to start, I don't understand what you mean with a 'state of flux'.

Let us assume entangled particles flowing from a central point (i.e./e.g. where the 'mother' photon got down-converted into two 'daughter' photons) to A and to B. Nobody knows which one (vertical or horizontal) is going to A and which one is going to B (vertical or horizontal). If you set the detectors in A and in B at 45 degrees you will get the following result:

A: h-v-h-h-v-h-v-v
B: v-h-v-v-h-v-h-h

A and B are complementary.

If I have a flux of oppositely polarized, but non-entangled photons flowing to A and to B (with 45° detectors) the picture goes like this (suppose I send the same pattern as above to both A and B):

SA:h-v-h-h-v-h-v-v (the photons I send to A)
SB:v-h-v-v-h-v-h-h (the photons I send to B)

A: h-h-h-v-v-h-v-v (scrambled up sequence because of 45° detector)
B: h-h-v-h-v-v-h-h (scrambled up sequence because of 45° detector)

A and B are NOT complementary. (each photon can decide separately what to do at the 45° detector)

I think that is the proof. No?

HELL

by "state of flux" i just mean the state before they have been observed.

I understand the experiment. You've used the term "complimentary" rather than entangled in your latest explanation, photons can be complimentary without being entangled, if they were never in a "state of flux", as i called it, at all.

Tango

I'm in the process of reading 'The Dancing Wu Li Masters' which is all about this stuff.

I loved the description (I think it was Newton's) of the universe being like a watch that you couldn't get the cover off. You could propose all sorts of reasons to explain what was going on under the cover including the ticking and the hands moving round, but you couldn't be sure and you would never be able to take the cover off.

It was about this subject that Einstein said famously, 'God doesn't play dice with the universe', which you've paraphrased, but not credited to him. He didn't like the idea of chance explaining anything.

One of the explanations was that the photons were sentient/organic.

Anyway, where are we with this entry?

Are the discussions resolved?

Might be good to mention the Everett-Wheeler-Graham theory too!

I don't know how relevent it is, but recently they have been having some sucess with looking at hardy's paradox, using something called "weak measurement", which lets them look at quantum states without disrupting them.

Hmm nice suggestions, but I think that adding Hardy's and Graham's would be out of scope. I was really trying to focus on the EPR paradox and not ALL limits of QM...

anyways, maybe a slight mention would be in order, right.

I'll come up with something soon-ish

HELL

Let us know when you've done it.

Ahem.

Hello,

Sorry, been in Holland w/ family. Am looking at Entry right now.

HELL

Hi ZSF,

I have re-read the Entry thoroughly (it's good to come back with a distance) and I have rephrased many passages to make things clearer. However, I did not find anything big to redo. I think it's good like it is now. The discussion with Tango, in this thread, was fruitful (ended up giving us the two paragraphs on non-locality and hidden variables). It could go on forever, though, and too far off the main point of this Entry which was to present the EPR paradox.

So, I think this might be good to go.

Hugs,

HELL

Are you still working on this, Hell?

Hi Hell,

I know it's late, but I just saw this entry in PR. How's it going? I haven't been around much lately. Anyway, I like the entry - a lot. But I think it's not giving a fair picture to talk about EPR, and QM being incomplete, without at least mentioning Bell's inequality, and the implications of his results. According to what I've read, Bell's work essentially killed all of the work that was being done on "hidden variable" theories that were trying to replace QM.

I don't have the book in front of me which I learned about Bell & EPR from, so I can't go into detailed work on it, but I'd be glad to get it and work on it if you want.

On a side note, I had a crazy thought the other day. The idea was based on the fact that I don't know what the density requirement is for something to be blackhole. Do protons,electrons and other sub-atomic particles exceed this density requirement? (probably not, but I'm asking the question anyway). If they do, then these particles fit into what einstein described as "singularities" - items which have "event horizons". Now, the event horizon in laymans terms is a location in space-time beyond which an outside observer can have no knowledge...isn't this beginning to sound like the fundamentals of quantum mechanics?

What if sub-atomic particles are singularities, and the fact that they have event horizons which they routinely interact with leads to the observed probabilities and knowledge restrictions of QM? What if instead of singularities in mass, they are singular in charge? Is that possible? If electrons/protons aren't singular, than what about quarks?

Just some thoughts. I'm throwing these out in the hopes that a real phsicist will read them and be able to shoot them down quickly and painlessly.

dave

The Wu Li Dancing Masters? Great title, great book!