Virtual particles and entanglement

ahrkron
Staff Emeritus
Gold Member
Originally posted by subtillioN
It is still an effect of a change in the state of knowledge of an event.

Not at all. If there was no entanglement, the measurements would be different.

For instance, in Fermilab we are also working towards the measurement of Sin2Beta. Due to the fact that we collide protons vs antiprotons (which, being a quark mess, have a very different physics than that of electron-positron collisions), the
B meson pairs are not quantum-entangled. As a result, the asymmetry behaves in a different way than those in BaBar and Belle.

There is a somewhat simple way to show that the observed properties of spin are incompatible with the idea of a well determined value, hidden from observation. It was published some three years ago by David Mermin (I think). I'll try to find the complete reference.

Another, somewhat older, proof that classical thinking is incompatible with the (experimentally) observed behavior of quantum systems is called the "Kocher-Specker paradox". I'm not sure about the spelling,... I'll check on the net later.

[Edit: I just checked: Kochen-Specker theorem]

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subtillioN
Originally posted by ahrkron
Not at all. If there was no entanglement, the measurements would be different.

Not if they stem from the same process. In such a case the corelation can come from the causal interaction in the past.

ahrkron
Staff Emeritus
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Originally posted by subtillioN
Not if they stem from the same process. In such a case the corelation can come from the causal interaction in the past.

Can you elaborate?

Also, I surfed for it a little: it was a paper by David N. Mermin. I still don't find the complete reference, but will keep trying.

subtillioN
Originally posted by ahrkron
Can you elaborate?

I can if you give me a good idea of what you know is physically happening in this particular experiment. I am assuming that you are actually working in the lab? I have never done the experiments and seen the results firsthand so your deeper firsthand knowledge-base will be very helpful in fleshing out the causal root.

ahrkron
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Originally posted by subtillioN
I can if you give me a good idea of what you know is physically happening in this particular experiment.

Do you mean the CP violation experiment?

The basic idea of the experiment is quite simple: B0 mesons (particles that contain quarks anti-b and d) decay differently (in time) than their counterparts (b and anti-d). When you subtract the two plots (number of decays vs time), you see an oscillation.

(if matter and antimatter behaved the same, you would get zero when doing the subtraction, since both plots would be identical).

When they are created in a e+e- collision, B mesons are entangled, so that the behavior of one of them depends on the measurements you do on the other one. If you decide to measure what flavor one of them was, the other is forced into being the opposite flavor at that moment (this is the "collapse"). From then on, it starts to do its usual stuff.

If such collapse didn't happen, you would not find the asymmetry, or the process would be quite different. I'll try to find a decent webpage about this for you later.

subtillioN
Originally posted by ahrkron
If you decide to measure what flavor one of them was, the other is forced into being the opposite flavor at that moment (this is the "collapse").

What do you mean when you say "forced"? Do you actually see something different happen to the other meson? Or do you mean that its flavor was indeterminate until the moment of the collapse? If the latter then how do we know it wasn't already this flavor before its partner was measured? How does one measure "flavor"?

Can you give me a time breakdown of this experimental procedure?

Originally posted by elas
One science correspondent recently reported that he had made serious enquiries as to why Hawking's has never received a Noble Prize. The answer was that none of his (Hawking's) work could be related to reality. One should take purely theorectical work with the same caution shown by the committee.

Hi elas,
I couldn't agree with you more. However, the criterion that Nobel Laurelhood is proof of some kind of genius is pretty well strained when you see how many false theories that defy understanding have resulted in fraudulently granted prizes. So-called "thought experiments" since the time of Kepler have been accepted as laws of physics mostly because peer reviews come from theory collabrolators. Too often, Computer-aided science methods have resulted in potential peers, (including so-called think tanks) using borrowed "software".

Notice the contributors of this string have birthdays that are called N/A (meaning that they are possibly pre-teen "trekies") and two who are not N/As are less than twenty years old. You are over seventy and are my junior by seven years. I am normally reluctant to join strings that are concerned with arguable topics. But your clear channel posting deserved some cheering from your peers. Cheers, Jim Osborn

Originally posted by jcsd
No, Tail they DO NOT both become real, the particle that fulls into the hole represents negative energy flowing into the black hole.
I don't see the contradiction there. It becomes real AND represents the negative energy.

Originally posted by wimms
Is it free? What happens with escaped particle when fallen antiparticle annihilates with some matter inside BH? Would entangled particle receive all properties of that its pair encountered?
Initially, "there was" 1 particle (in BH), then, pair appears, total 3. One goes off to earth, other falls into BH where it interacts with its destined one. End-result - 1 real particle on way to earth. If conservation laws hold, then it must have all properties of initial particle inside BH?

That's exactly right. The anti-particle that goes into the black hole and annihilates with a particle exactly opposite itself, and not only THAT particle is opposite of the antiparticle, the one that escapes also is. They are very much the same.

I don't hope anything practial about that info. Still, some remote estimates about BH-internal environment could be extracted in principle, i guess. Thus some observational evidence.
No, no, no.
If I think of abstraction where only instant is viewed when anti-energy interacts inside BH, that happens after it has traveled some distance into BH and its matter-pair has traveled away, then picture arises that energy of poor particle inside BH effectively travels at 2c to outside...
It CANNOT travel faster than light. And mass is just concentrated energy.

Originally posted by jcsd
Basically a measurement on one of the virtual particles defines the properties of the other so they are entangled.
I agree that 'a measurement on one of the virtual particles defines the properties of the other', but they're still not entangled. It's like in basic maths, you can add 1 if you also subtract 1. In this case also they are exactly the opposite of the other, but it has NOTHING to do with entanglement.

subtillioN
Originally posted by Tail
And mass is just concentrated energy.

And what is energy? The ability to do work? How can the ability to do work be concentrated?

Energy is a mystery to the Standard Model. It is no wonder that 99% of the Universe is supposedly made of "dark matter/energy"?

Mystery indeed.

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jcsd
Gold Member
Originally posted by Tail
I don't see the contradiction there. It becomes real AND represents the negative energy.

Well, you can't talk about the particle being real once it is beyond the event horizion.

Okay it is silly to talk in terms of virtual particles and entanglement, but clearly they demonstrtae entangled behaviour in this instance, In otherwords they have a combined wave function that will collapse when one is subject to a quantum measurement.

elas
I think you're interpreting that response wrong. The comment about not relating to reality is not a snide remark that addresses the reliability of the work in any way. Rather, what they mean is more likely that there are no direct applications of the work at this time

I did not intend my observation to be taken as a snide remark, but as a factual statement. My point being that subscribers are using a purely theoretical work to comment on experiments when the relationship between Hawking's theory and reality has not been established.
With regard to relativity, Einstein used so much of other peoples work that he requested the publishers that the work be published without any mention of an author. For this reason the committee felt Einstein could not be awarded a prize for Relativity and selected one of his other works.
My own view is that Newton, Einstein and Hawking are amongst the greatest mathematicians that ever lived, but whether they are also great scientist is open to question, given that only a predictive interpretation can be placed on their work; the questions 'how' and 'why' are still with us.
I blame Newton for this state of affairs he invented the name 'gravity' when the term 'vacuum' allows an explanation of 'how' and 'why'. Creating undefinable new names remains in fashion to this day, Lord Ockham is writhing in his grave!.

ahrkron
Staff Emeritus
Gold Member
Originally posted by subtillioN
What do you mean when you say "forced"? Do you actually see something different happen to the other meson?

It is not something you can "see" directly, especially because we are talking about the effect on the unmeasured side. However, the behavior you find is just as predicted by QM, with its "collapse" and all.

This is somewhat difficult to explain without the math (Fourier analysis in particular). I don't have much time now, but I'll try to come back with some illustration of it.

Or do you mean that its flavor was indeterminate until the moment of the collapse?

The moment you measure the flavor of one, the other collapses into the opposite flavor. It is not just a matter of our knowledge.

If the latter then how do we know it wasn't already this flavor before its partner was measured?

Because QM says so :)

No, really. Because if we decided to measure something else, then the other side would show a different behavior, which is incompatible with that of a different measurement selection.

Remember I mentioned the article by Mermin? I wrote to him and got the reference:

Hidden Variables and the Two Theorems of John Bell'', Revs. Mod. Phys. 65, 803-815 (1993).

I'll try to summarize the main idea here later.

How does one measure "flavor"?

It basically means determining if the particle was a B0 or an anti-B0. The difficulty arises from two factors: 1. both are neutral states (hence no trace left, and it decays in the same number of positive and negative particles), and 2. They oscillate into each other!

Can you give me a time breakdown of this experimental procedure?

Here's a link to a pdf presentation. I know it is a bit technical and sketchy, but it may be helpful (also, it includes something about the detectors and analysis). Look at page 13 (21 has a sketch also).

Janus
Staff Emeritus