Macroscopic Quantum Entanglement

meckardt writes: "We laugh at the science fiction of such programs as Star Trek, but it can almost be stated as a truism that what is fiction today may be science tomorrow and engineering next week. Researchers at the University of Aarhus in Denmark report in the science journal Nature that they have been able to cause particles to interact over a distance using lasers. The effect, called quantum entanglement, has been observed before, but never with such large amounts of matter. Don't expect transporters next week, but it is interesting that this report hits the streets the same day that Enterprise debuts."

Clarification...?

[melquiades]

As I've understood these experiments in the past, entanglement involes splitting a particle, or taking two existing particles, and "entangling" their states -- so that, for example, if you change the spin of one electron, its partner electron's spin also changes, even at a great distance (or something to this effect).

The application to faster-than-light information transmission is obvious. But teleportation? The article doesn't give enough specifics. Can anybody shed light on this? How would this experiment lead to a teleporter??

Quantum Entanglement

[blitz77]

Quantum entanglement is basically splitting up a photon into 2 parts. These 2 parts are quantumly entangled, so when you measure one, you would get exactly the same result on the other as a result of them being entangled. The supposed ability to transport particles is not true. It is only able to allow measurements on one particle to be duplicated on the other. So, if we ever get this to work on large objects such as humans (!) you wont get teleported. There'd only be a duplicate of you on the other side. And in the act of measuring the state of all the particles of your body, you'd probably be dead too. I wouldnt care to have a duplicate of me on the other side, because you'd still be dead.

Re:Clarification...?

[lkcl]

regarding teleportation. it's simple. when you fire one photon at another, they interact [they're waves, but also particles]. in this way, you get one photon passing through another, or you get one photon imparting "mass" to another photon, and a change of direction of the two photons, conserving momentum. when you fire one photon at an "entangled" pair, if the momentums are matched, then the "fired" photon can actually disappear at the location where it hits one of the "entangled" pair, and reappear at the location of the SECOND "entangled" pair. in this way, you have instant teleportation - of photons. now make that many photons, and you have instantaneous quantum communication it's not really FTL because it's actually the same photon that happens to have more than one point-of-presence in the physical universe. now, step that up to particles, instead of just photons, and you have instantaneous teleportation. however, i theorise that this would require some _seriously_ cohesive photons, which probably implies that they must have intelligence built-in to the photons, and it's at the word "intelligence" as associated with "photons" that i diverge from current "accepted" theories regarding the nature of the universe and i'm going to shut up because there is a lot more to learn than meets the eye.

Still a big jump to teleportation

[Glorat]

As I understand Quantum Entanglement, you're not going to get teleportation with this. To create the initial entanglement, you have to perform an operation (such as shooting electrons with energy) to a pair of particles that are at the same inital location. The point of quantum entanglement is that once these particles are separated, the two particles still have this quantum connection between them.

But to get any transportation, you would need to put still need to transport(=move) one of those particles to the new location defeating the point of our transporter!

Re:A Clarification...

[jaoswald]

It doesn't necessarily "change the state" of the second particle. (It can't, since the particles cannot causally interact; the particle's state evolves according to the local environment). However, the results of measurements on the second particle are inter-dependent with the results of the measurements of the first particle, even though the acts of measurement themselves cannot be connected causally (in the sense of special relativity).

The really funky thing is that the *choice* made to determine what kind of measurement to make on the first particle affects the inter-dependence. The idea being that "somehow" the measurement apparatus is communicating its setup to the distant particle, even though it really can't. This is really disturbing, but probably doesn't have any better explanation than "that's just how it is."

Re:Not true teleportation

[Theodore Logan]

it's NOT teleporation. Teleportation involves taking an object from point A and moving it to point Z without crossing the in-between space, C through Y.

This is incorrect. Classical teleportation is defined as a scenario where the sender is given the classical description of an arbitrary quantum state while the receiver simulates any measurement on it. This is exactly what you argues it isn't. Besides, if the destinction you make is one worth making or not is an open philosophical question, i.e. one that is not resolved.

It's what I've always said: we should have a new moderation cathegory - "Incorrect".

Re:A Clarification...

[renard]

Your billiard ball example is equivalent to Einstein's "hidden variables" attempt to explain away quantum entanglement. Bell's theorem demonstrated that the predictions of quantum mechanics were actually inconsistent with such a theory - and subsequent experiments proved him right. The universe is far more mysterious than you or Einstein give it credit for.

In fact the reproduction of a quantum state - in all its particulars - is as perfect a teleportation as we might ever expect to achieve - see my accompanying comment. So I don't think your criticisms are entirely justified.

I say "not entirely" because extrapolating 13 orders of magnitude, and to real systems rather than super-cooled ones - as required for useful teleportation - still requires a bit of hutzpah. But the scientists cannot take all the blame. After all, the Trekkies were there long before...

-Renard

Are we really this smart?

[MajesticFiles]

The potentials, of course, are staggering, but I have one question. Should the ability to teleport/transport matter between two points become reality, what of that vaporous non-matter that is so imporant? Our memories, our knowledge, all that is us? How do you transport something like that? Even if it's a duplication and not a true teleportation, how do you duplicate something like that? Wouldn't we just be transporting empty shells...the skin and bones and blood...but not the soul?

In anycase I guess my commute won't be shortened anytime soon.

Re:Quantum Entanglement

[DanEsparza]

You're funny.

While I would agree that this is the classic explanation of this phenomena I think it's important to point out that the photons can't be observed directly (like under a microscope) -- and we honestly don't know what the heck is going on at this point.

The article points out Einsteins famous quote describing this phenomena is "spooky action at a distance" -- which it is. I'm sure if you asked Schroedinger (spelling?) he'd tell you that the photon 'was neither split, nor one photon' ... because we just don't know.

If you want an interesting (although hardly scientific) read on this subject, check out Michael Chricton's 'Timeline' book.

Re:Ansible

[MobyDisk]

I thought that transporting information superluminally violated causality. Remember this [slashdot.org] article about superliminal transmission of microwaves in a cesium gas? It sparked a discussion about how useful this would be for data transmission. But I understand that the general scientific opinion is that causality prevents this from actually being able to send information faster than light. The same thing happens with gravity. Gravity doesn't travel truly "instantly" in all frames of reference, so you cannot transmit information faster than light by adjusting mass.

If someone could clarify this it would be great.

Re:A Clarification...

[Rothfuss]

Your billiard ball experiment is an interesting little analogy, but shows a lack of understanding of true entanglement.

Quantum entangled states behave as unknowns from the time of entanglement and remain "unknown states" until a measurement is made. Even though you haven't looked in the bag, physically the ball *is* either black or white and has been all along. Your knowledge of it's state doesn't matter. It is definitely in one state or the other, regardless of your own knowledge of the matter.

On the other hand, the quantum entangled particles are *not* actually in a state until a measurement is made which collapses the wave packet and by various conservation reduces both particles/photons/whatever to their correct state.

If you are thinking "Well it was really just that way all along," you are fundamentally missing the coolness of Quantum Physics.

-Rothfuss

Re:A Clarification...

[vinylat33]

nothing in quantum mechanics or entanglement theory allows anything resembling faster-than-light information traveling

That is correct. However, a particle (or any other exitation in a quantumfield) may only exist when there is a solution.This solution may be over time.

example: light you see from the sun (a photon traveling from emission of the sun to absorption in your eye) only exists because it is a solution in the quantumfield. Hence it is impossible to duck for that photon, cause it would never exist if you were not there.

The problem this article, i think, is about changing states of a symmetry broken system. Symmetry broken systems are like superconductivity, but also simply said a table. Depending on the system.
I have to read the insights, but i think it is not so new as they postulate.
In fermi-systems, like liquid 3He, at temperatures below its fermi-temperature, the whole system is in *one* state, which cannot be changed with low energy, cause you have to change the whole system. Maybe this is about a change at low energies than the system.

or maybe i am bullshitting.