Posted on 06/16/2004 1:54:18 PM PDT by vannrox
TED: 2:55 pm EDT June 16, 2004
UPDATED: 3:03 pm EDT June 16, 2004
In a step toward making ultra-powerful computers, scientists have transferred physical characteristics between atoms by using a phenomenon so bizarre that even Albert Einstein called it spooky.
Such "quantum teleportation" of characteristics had been demonstrated before between beams of light.
The work with atoms is "a landmark advance," H.J. Kimble of the California Institute of Technology in Pasadena, Calif., and S.J. van Enk of Bell Labs in Murray Hill, N.J., declare in Thursday's issue of the journal Nature.
Two teams of scientists report similar results in that issue. One group was led by David J. Wineland of the National Institute of Standards and Technology in Boulder, Colo., and the other by Rainer Blatt of the University of Innsbruck in Austria.
Teleportation between atoms could someday lie at the heart of powerful quantum computers, which are probably at least a decade away from development, Wineland said. Although his work moved information about atomic characteristics only a tiny fraction of an inch, that's in the ballpark for what would be needed inside a computer, he said.
His work involved transmitting characteristics between pairs of beryllium atoms, while the Austrian work used pairs of calcium atoms. Each atom's "quantum state," a complex combination of traits, was transmitted to its counterpart.
Key to the process was a phenomenon called entanglement, which Einstein derided as "spooky action at a distance" before experiments showed it was real.
Basically, researchers can use lab techniques to create a weird relationship between pairs of tiny particles. After that, the fate of one particle instantly affects the other; if one particle is made to take on a certain set of properties, the other immediately takes on identical or opposite properties, no matter how far away it is and without any apparent physical connection to the first particle.
Well, I'll have to wait until one of our resident experts shows up to help out. I pinged them in my last post.
Earth (July 4) -------> WormholeA (July 4) -------> WormholeB (July 4) -------> Starship (July 3)
Earth (July 4) <------- WormholeA (July 4) <------- WormholeB (July 4) <------- Starship (July 3)
WormholeA and WormholeB represent the opposite ends of the wormhole with their respective timeframes. The symmetry is broken because the ansible is not locally time-dilated relative either the Earth or the Starship, but the Starship is time-dilated relative the inertial frame of the Earth. The Starship is receiving the communication in a time-dilated manner, but the Earth is not!
BTW, this works even if the two ends of the wormhole are both moving at relativistic speeds so long as their respective ansibles are operating on the same inertial frame, but it becomes much more complex to depict. The important thing to remember is that ends of a wormhole (ansible) are always synchronized even if their locations are not!
A wormhole is displaced in both space and time!
You cannot treat the ansible communication as if the persons communicating are doing so telepathically. You cannot ignore the intermediary conduit that way. The original set-up in your post #119 treats the "instantaneous" communication as if the speakers have some telepathic link. The ansible is also instantaneous, but it's not analogous to that "instantaneous"!
Quantum entanglement is divorced from special relativity!
I guess I'm prejudiced against wormholes. Let's wait until one of the experts arrives.
Well, my suspicion is that we are all right but that we are talking about different phenomena. If we ever get on the same page, then we will be even more right than we were before! =)
The one part I'm not 100% certain about is what happens if you have two starships communicating with one another using an ansible operating on a different inertial plane than either starship. To be honest, I haven't really thought about that because my life is complicated enough already.
Waiting commenced. Make it so!
In the first instance, we are simply assuming that information may be transmitted via quantum entanglement regardless of whether that is ever proven true in actuality.
Well, don't assume that, because it is definitively known that entanglement cannot be used to transmit information. But I know what you mean: we'll put our foot down, like Ursula LeGuin, and say "an ansible exists! Now what?"
Now as for the second issue, I simply want to reiterate that quantum mechanics and special relativity are not a unified theory; the two cannot be encompassed within a single known mathematical framework. The very phenomenon of quantum entanglement underscores that discrepancy and indeed its conjectured existence first made that clear. We cannot use the discordance between quantum mechanics and special relativity
Stop right there. There is no discrepancy between special relativity and quantum mechanics. Entanglement does not violate SR, because it cannot lead to non-causal physical behaviors. It's just a correlation.
[Geek alert: The famed discrepancy between relativity and quantum mechanics is between General Relativity and Quantum Field Theory. You see, in QFT, the forces are described by the exchange of particles called bosons. The physical quantities we calculate are based on a superposition of all possible boson exchanges; this infinite sum is kept finite by a method called renormalization. It works incredibly well for all forces besides gravity. Now, what about gravity? Because of the geometry of the Einstein Field Equations, the bosons of any quantized gravity force would be spin-2, meaning that each boson would carry twice as much angular momentum as a photon (a boson of electromagnetism). Here's the problem: spin-2 forces aren't renormalizable in the 4-dimensional spacetime we observe. In fact, there are only two spaces in which a spin-2 force can be finite: one space has 26 dimensions, and the other space has 11. (Sound familiar?)]
OK, well I can accept that. But my understanding is that quantum entanglement is generally thought to be invariant within special relativity. That is what I meant. Is this incorrect?
Geek alert:
Indeed!! j/k =)
Relativistic, Causal Description of Quantum Entanglement and Gravity
I admittedly don't fully understand what the author is getting at, precisely, but the basic phenomenon I'm referring to is alluded to throughout. The abstract and introductory paragraph should make it clear and you'll almost certainly follow it much better than I!
I think he means that the instantaneous communications system establishes (or exists in) a non-relativistic Galilean frame of reference that includes the sending and receiving ends, notwithstanding that the sender and receiver are in motion with respect to each other, and are otherwise in different frames of reference.
You might want to be a bit more careful with your language, because "invariant" has a specific technical meaning in relativity.
That said, your comment doesn't make much sense. The "spooky action at a distance" doesn't reside in any specific inertial frame. It is a correlation between events, and I might also add that events don't belong to any specific inertial frame.
An inertial frame is a point of view--a coordinate system. Any event that occurs takes place in all inertial frames; nobody is prevented from observing, in principle, any event, no matter how fast they are going, or in what direction. Nobody can be said to be "at rest" with respect to an event, as the mere fact of an event's occurrence means that momentum has been transferred from something to something else. (When a bullet hits a target, does that impact event take place in the bullet's frame, or the target's?)
There is a more detailed scientific article on the matter here:
OK, let me make a few comments with regards to how you're going about this, and I hope you'll take them kindly. It seems that you have an idea in your head about how things are "supposed" to behave, and you're going to cling to it, whether or no. When you are told that your basic idea is wrong, you reject that, and assume that the disagreement is the result of your failure to articulate your thought, and not because your thought is wrong. Then, in order to bolster your case, you cast about for things on the internet that (according to your reading) support your position.
Step back a moment. Start from scratch. Forget about wormholes and pilot waves and time travel and FTL communication. Don't link papers you can't read. Those are advanced topics, and you haven't understood the basics. Get the basic mechanics right, and then you can ponder the weird stuff.
You don't need to cast about on the internet. Most of the stuff you'll find out there is wrong, anyhow (although sharpblue's stuff is A-OK). At least one of your interlocutors is a professional physicist who really does understand this stuff at the level you require.
One last thing. I try my level best not to "pull rank" on these threads, and say things like "I'm a physicist and you're not, so I know what I'm talking about and you don't, thus I'm right and you're wrong, now shut up". That said, if I say something that doesn't jibe with your understanding, do at least stop and consider that I probably have a very good reason for saying it.
Well, there's much to say about all that, but rather little worth saying, so I won't bother saying it!
Your impression of me and my approach is quite wrong, though. Quite the disappointment, really.
Have a g'day!
To my understanding, it is generally held that quantum entanglement between all degrees of freedom is invariant across different Lorentz frames. Therefore, assuming that one could apply this entanglement to quantum information processing, it could be said to establish a non-relativistic Galilean frame of reference that includes both the sending and receiving ends.
Stated differently, the entangled particles always see one another as if they are on the same inertial frame, even when they are seen to be in different frames of reference by the communicators. This would have the same mathematical properties as a wormhole in the sense that the 'clock' of the entangled quanta is always synchronized; it is not subject to special relativity.
Anyhow, thanks for understanding the point I've been conveying. Assuming that this is incorrect and quantum entanglement is subject to special relativity in that way, then my hypothetical ansible falls apart. We could still discuss the topic at hand (causality, etc) but we would have to focus on wormholes per se and cut quantum entanglement out of the picture.
It's possible my analogy was ill-considered and incorrect, but I'm not yet certain that's the case. Anyhow, you are prejudiced against wormholes and it seems that you're not the only one! I agree comfort zones are a wonderful thing. =)
Been off for a bit. BTTT for later read.
As an aside, since you actually seem interested and fairly comfortable with speculative physics, you may find this Everett FAQ quite fascinating. If not, that's OK too!
Not only am I prejudiced against wormholes, but I'm really prejudiced against the "many worlds" hypothesis (or more properly, wild conjecture). Anyway, let's give the causality thing a break for a while ... unless RadioAstronomer has a new viewpoint to contribute.
There are things we know that we know. Then there are known unknowns. That is to say, there are things that we now know we don't know. But there are also unknown unknowns. There are things we don't know we don't know. So when we do the best we can and we pull all this information together, and we then say well that's basically what we see as the situation, that is really only the known knowns and the known unknowns.
And each year, we discover a few more of those unknown unknowns.
The one thing I'm quite confident of is that we know less than what we don't know!
I don't quite understand how any information has been transmitted. In order to determine a quantum state, it has to be measured - and the act of measuring causes the quantum state to collapse. So the "sender" at point A causes a quantum state change, the "receiver" at point B has to make a measurement to determine the quantum state, and B could do that prematurely, causing the quantum state at A to resolve... Quantum entanglement works both ways.
My understanding is that the answer involves Quantum Error Correction, so that link may provide some insight.
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