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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."
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 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.
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!
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."
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".
"If you think education is expensive, try ignorance" - Derek Bok
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
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.
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I thought that transporting information superluminally violated causality. Remember this 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.
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
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.