Entanglement. What is it, how does it work?

This thread is a split off from a thread in Alternative Theories called Bell's Theorem and Non-locality.

The question here is about Entanglement. What is it, how does it work, what does it mean to the future of quantum physics?

Here are two links referred to in that thread:
http://www.telegraph.co.uk/science/...cotty-teleportation-could-become-reality.html

http://www.independent.co.uk/news/science/scientists-achieve-quantum-teleportation-breakthrough-that-could-prove-einstein-wrong-9462053.html

 

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In all seriousness, I think that even though Einstein was wrong, his tongue-in-cheek description was nonetheless apt: spooky action at a distance.

I mean really, has anyone actually learned anything beyond that yet? All I see is further investigation into just how spooky it all is.

Not that I necessarily believe that some sort of definitive explanation is forever beyond us.

 

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It is under study of course. In Q is for Quantum, by John Gribbin, the topic of entanglement is covered under Superposition of states, where entanglement is the relationship between two particles that are in superposition. Superposition is:

A mixture of quantum states for which it is impossible to specify the physical characteristics of a quantum entity. For example, in classical physics a particle which has spin can be either spin up or spin down. But in the quantum world the particle can also exist in a mixed state, a superposition. Only when the particle is measured does it settle into a definite state and has either spin up or spin down.

 

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but how does this address the issue of distance separating the particles or "half particles" seeming to be irrelevant to the entangled spin of each?
I believe the largest distance demonstrated is about 140 kms ... [ but will need to dig up the article]

 

I don't know, but in this Wiki there is some interesting presentation of the topic, and pretty current.

http://en.wikipedia.org/wiki/Bell_test_experiments

 

Entanglement is a general term that relates to the interactions of quantum particles, i.e. bosons and fermions.

Spin entanglement is commonly discussed, but quantum particles are entangled over all their properties: position, momentum, charge, parity, or any quantum observable.

The observables can be considered as projections of a quantum state onto the measurement of that particular choice: position or momentum, say.
Entanglement is considered as a resource in quantum computation; it can be 'distilled', there is weak and strong entanglement, it can be transmitted between quantum systems like a signal of sorts. Understanding what it is could mean understanding pretty much all of QM, or you could understand it from an informational aspect and ask: "what is quantum information, and how is it different to classical information?".

 

Whatever entanglement is, it isn't restricted to the quantum level. Macro entanglement has been demonstrated in everyday objects as large as diamond crystals sitting in everyday conditions:

http://www.popularmechanics.com/tec...anglement-created-in-everyday-objects-6606439

Also the micro/macro entanglement of light:

http://www.nature.com/nphys/journal/v9/n9/full/nphys2682.html

 

The diagram shows entanglement. Because the light sphere hits the z receiver in .65 seconds, combined with the velocity of the box, and the light sphere increasing radius at c, and the x receiver is at the center point of the wall, and the light sphere must hit the x reciever at precisely the exact time. Any variable that gets in the way of that exact time will mean calculations will be incorrect. There is only 1 point in time that the light sphere can contact the x receiver, and it is indicated.

The equation for the z receiver locks in the x receiver time. It's not negotiable! Everything is locked in. There is no wiggle room!

None!

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Well, because there is nothing that makes it relevant. In physics you need a reason that something is relevant before you can claim it can affect a process. In EM radiation, for example, the effects of propagation and dispersion are well understood, which is why distance attenuates EM signals. But nothing like that operates on entangled particles.

 

I'm with you.

I would take that to mean we don't know the properties until we measure them, and measurement gives us a part of the picture, but not the whole picture.

Yes, a part of the picture based on what we were specifically measuring.

I see, and can that transmission of a signal of sorts be faster than light, i.e. instantaneous maybe?

Do we understand the mechanics of entanglement? Or is it more appropriate to say there are no mechanics to it, it is just not understood well enough to say what the particulars are of how multiple states can be superimposed into a mixed state?

 

No, you have to 'encode' the entangled state somehow and send it, i.e. it takes energy and energy cannot be transmitted faster than light. In fact using light to transmit entanglement is the limit.

It's understood well enough that quantum logic exists, in the same way electronics is understood well enough that logic circuits exist.

I take it you haven't looked into the subject that hard?

 

Sure. I guess I thought you were asking about the underlying or mediating mechanism(s) involved as that's where all the mystery is.

 

Arfa brane says it is not a mystery.

 

Thread moved:
Due to the subject being Fringe (The border of Scientific achievement with a whole case of "There be Dragons") this thread has been moved to the Alternative Theories section (which isn't the correct definition for it but the closest available). This shouldn't be any reason to degrade the discussion and will likely cast far less resistance than if attempting to exist in the Physics and Mathematics sub-forum that tends to keep to a consensus of empirically proven Science.

 

I agree with that decision. I broke it off of the Bell's Theorem and Nonloclity thread because CptBork said entanglement was proven fact, not theory. If it is fringe, I think that falsifies his belief that it is fact and not theory.

 

Entanglement is a fact, peoples interpretation of what entanglement means is what drives it to the fringe area.

 

If the interpretation is that there is FTL communication between entangled particles, is that a theory or a fact?

Also, did you see this post?

Do you agree that entanglement involves superposition? Can we observe a particle in superposition? Doesn't that make entanglement a theory and not a fact?

 

It is neither fact nor theory, the idea of communicating at FTL speed using entangled particles is one of the misconception that pushes these discussion into the fringe sections!

Nope.

I do not know if entaglement involves superposition. Superposition is a theory or hypothesis describing how the fact of entanglement works. Just like we have a theory of gravity, which may or may not be 100% correct, but it has no bearing on the fact of gravity.

 

http://physics.about.com/od/quantumphysics/f/QuantumEntanglement.htm

One important thing to remember is that in quantum physics, the original uncertainty about the particle's quantum state isn't just a lack of knowledge. A fundamental property of quantum theory is that prior to the act of measurement, the particle really doesn't have a definite state, but is in a superposition of all possible states. This is best modeled by the classic quantum physics thought experiment, Schroedinger's Cat, where a quantum mechanics approach results in an unobserved cat that is both alive and dead simultaneously.

http://rationalwiki.org/wiki/Quantum_entanglement

Quantum entanglement or the 'quantum non-local connection' is the quantum mechanical property of a multi-object system that means that the quantum state of one of the objects cannot be described without describing the entire system as a whole. When two particles are entangled whatever change is made to one has an immediate effect on the other no matter how far apart the two particles are. It has some use in quantum computing and teleportation, although it cannot be used to violate the law that information and energy cannot exceed the speed of light.

 

It's a proven fact:

http://www.livescience.com/27920-quantum-action-faster-than-light.html


Entanglement has even been show to operate from the future to the past:

http://www.livescience.com/19975-spooky-quantum-entanglement.html