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.
BTW, none of this is really addressing the concept of superluminal quantum entanglement communication between 'stationary' (for practical purpose) locales - such as, say, Earth and a planet orbiting Alpha Centauri. That eliminates much of this time dilation issue in the course of two-way communication, although one still confronts causality issues when contemplating some theoretic third reference frame interacting with those two.
One point that is worth noting that's been on my mind is that we could very well be dealing with issues of: it works, but we don't know how and why it works. That's been the case with almost all of the quantum entanglement research in actuality. Again, as Einstein said, quantum mechanics may well be an incomplete theory. Also, as others have hypothesized, quantum mechanics may not function 'in sync' with special relativity in our observable universe. In other words, it may be that each is locally applicable but that neither is universally applicable.
Which brings us to another interesting concept: would quantum entanglement experience the effects of time dilation in the first place. It may very well not - in effect cancelling them out in communication!
The very first sentence is, "One of the most striking aspects of special relativity is that faster than light travel is equivalent to time travel." Couldn't have said it better myself.
That is the flaw in your logic. The USA would be partying.
Yes, but nothing is travelling faster than light in the course of our scenario. You seem to have a (understandable!) mental block on that point. The action at a distance appears to have you spooked.. =)
BTW, the graphics work fine for me, though there seems to be a bit of lag between loading the page and when they pop up. In any case, everything is described in the exposition although it's significantly diminished without the visuals (which themselves are unavoidable approximations).
So let me get this straight: you expect that a transmission that traverses the universe in a nanosecond will behave in a grossly different way from something that traverses it instantly?
No, as a matter of fact I do not. However, I do expect it to behave in a grossly different way from something that does not traverse the universe at all.
Maybe the key is to just do what we can do in practice without regard to the theoretic paradoxes. Let God deal with the hypothetical causality violations.. =)
While waiting for Physicist to comment, I'll play with this one. While I agree that travel into the future raises no causality issues, it's also irrelevant to FTL communications. As has been pointed out, such communications are always received (by the recipient) before the sender's transmission date, and thus they always involve travel into the past. (This is in the context of the ship and the earth being two different frames of reference.) This isn't a "presuposition," as you suggested. Rather, it's an inevitable conclusion of the way we now think the universe is put together.
But "travel into the past" does not raise causality issues unless it is into a past prior to the time of the transmission being replied to! That's the whole point: you need a second inertial frame (i.e., a third reference frame) in order to produce that phenomenon (based on current theory).
Yes, but they are recieved by the recipient after the recipient's preceding transmission date!
That's exactly what would happen. Re-read my post 119, where I pointed out:
Now you get on the supspace radio and send your condolences back to earth: "So sorry to learn of the July 4th assasination of President Hillary Clinton." Ah, but here comes the catch. You are sending this message on your July 3d. Because of your acceleration away from earth, from your point of view -- which is just as valid as earth's viewpoint -- it's earlier on earth than it is on your ship. So your message travels instantly and gets to earth on July 2nd. Earth's July 2nd. And they now know of the event before it happened.
True. The recipient isn't time-traveling (not in that sense). No one says otherwise.
Well then you don't have a causality violation! Anyhow, the July 2 arrival date for the second transmission is simply wrong! Time dilation causes the perception of the passage of time at the other end to 'slow down' for the object in motion, it does not cause time to reverse! Since both ends experience the time dilation effect relative to the other end, all transmitted replies arrive locally after the local time at which the transmission replied to departed. The transmitted reply may arrive in the transmitter's "past" but it gets received in the recipient's "future"..
There is no causality loop within a single inertial frame!
Nor would it constitute a "striking feature" of special relativity.
Please, please, please read the page you linked.
Not quite. The recipient is always getting messages earlier (in the recipient's frame) than the date of the sender's reference frame. Always. So if the ship gets the July 4 message (earth date) on July 3 (ship date), and then the ship responds (on July 3, ship date) it will arrive on earth earlier than the ship's date! The recipient always gets the message earlier (recipient's date) than the transmission according to the sender's date.
There is no causality loop within a single inertial frame!
True. But when you're receiving messages from a different frame ...
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