Researchers at the National Institute of Standards and Technology (NIST) have "teleported" or transferred quantum information carried in light particles over 100 kilometers (km) of optical fiber, four times farther than the previous record.
The experiment confirmed that quantum communication is feasible over long distances in fiber. Other research groups have teleported quantum information over longer distances in free space, but the ability to do so over conventional fiber-optic lines offers more flexibility for network design.
...
"Only about 1 percent of photons make it all the way through 100 km of fiber," NIST's Marty Stevens says. "We never could have done this experiment without these new detectors, which can measure this incredibly weak signal."Until now, so much quantum data was lost in fiber that transmission rates and distances were low. The new NTT/NIST teleportation technique could be used to make devices called quantum repeaters that could resend data periodically in order to extend network reach, perhaps enough to eventually build a "quantum internet." Previously, researchers thought quantum repeaters might need to rely on atoms or other matter, instead of light, a difficult engineering challenge that would also slow down transmission.
Related Stories
For the first time in the history of quantum mechanics, scientists have been able to transmit a black and white image without having to send any physical particles. The phenomenon can be explained using the Zeno effect, the same effect that explains that movement itself is impossible.
The journal article is in Proceedings of the National Academy of Sciences of the United States of America (DOI: 10.1073/pnas.1614560114)
Wikipedia has an article about the quantum Zeno effect.
Related stories:
Physicists Break Distance Record for Quantum Teleportation
First Covert Communication System with Lasers
Long-Range Secure Quantum Communication System Developed
China's "Quantum-Enabled Satellite" Launches
How to Outwit Noise in Quantum Communication
(Score: 4, Insightful) by Anonymous Coward on Wednesday September 23 2015, @03:55AM
They really need to stop using the word teleportation for the same reasons AT&T needs to stop using the word unlimited.
(Score: 1) by Some call me Tim on Wednesday September 23 2015, @04:44AM
I would call information sent over fiber "transmission" and through free space "teleportation".
Questioning science is how you do science!
(Score: 2) by davester666 on Wednesday September 23 2015, @05:23AM
Normal people call it "light". Or electromagnetic radiation.
(Score: 1, Interesting) by Anonymous Coward on Wednesday September 23 2015, @10:04AM
Obligatory. [xkcd.com]
(Score: 2) by jasassin on Wednesday September 23 2015, @05:49AM
First, let me state for the record I know didly shit about quantum mechanics. I keep hearing about quantum encryption and any interception of photons being detectable and hosing shit up. So how can repeaters be used? So confused.
jasassin@gmail.com GPG Key ID: 0xE6462C68A9A3DB5A
(Score: 2) by Beryllium Sphere (r) on Wednesday September 23 2015, @06:32AM
You're asking the right questions. In any other communications field a "repeater" would be something that copies a signal. If quantum states could be arbitrarily copied, you could make two copies of a particle's state and measure the position of one and the momentum of the other.
(Score: 2) by FatPhil on Wednesday September 23 2015, @07:35AM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Wednesday September 23 2015, @10:07AM
If you don't know about it, why don't you just keep silent, or at least state that you just write down your speculation, instead of pretending to write down facts when you actually are wrong?
(Score: 1, Informative) by Anonymous Coward on Wednesday September 23 2015, @09:47AM
The information in quantum teleportation is not in the transmitted quantum states. That's the whole point in the quantum teleportation scheme (and why it is called "teleportation" to begin with): Basically you can put it into two steps:
Step 1: Alice and Bob establish a shared entangled state. That's what the quantum channel is needed for. In essence, the entangled pair is for quantum encryption what the one-time pad is for classical encryption, with the difference that all entangled pairs are the same, and only the subsequent measurement introduces the randomness (so if you just measure the entangled states, it's essentially a nonlocal one-time pad generation). Indeed, to know the entangled state Alice and Bob share, Eve would not even have to eavesdrop; she just has to look into the protocol description. The actual transmitted information is then generated by Alice by a combined measurement of her particle and the state she wants to sent, and that information is sent over a normal classical channel; however that classical information is useless if you don't have the other part of the entangled pair, just as it would be for a classical OTP if you don't have the OTP. It's just random bits, uncorrelated to the information you want to send.
Now the obvious attack would be that Eve would just catch the photon sent to bob, and use that to decode the classical information. But Bob then would not receive a photon, and therefore would tell Alice that he didn't get a photon so she can't send him anything, thus Eve won't get anything to decode.
Now the counter strategy for Eve seems obvious: She might simply send another photon to Bob. However if that photon is not entangled with Alice's photon, Alice will not be able to send to Bob; moreover, Alice and Bob can run explicit tests whether their photons are entangled or not. So Eve cannot just send an arbitrary photon.
But wait, what if Eve creates another photon that is also entangled with Alices photon, and sends that to Bob? Then Bob and Eve both have a photon that is entangled with Alice's photon, and thus both can decrypt the information from the classical system, right? Well, there's just one problem with this: It is not possible. Any entanglement between Alice's and Eve's particel will correspondingly degrade the entanglement between Alice's and Bob's particle; that property is known as monogamy of entanglement. So even if Eve has first intercepted the photon, Alice and Bob know that as long as their photons are entangled with each other, they cannot be entangled with anything Eve has, and thus Eve cannot decrypt their communication.
OK, now how can quantum repeaters work? Well, they work exactly because they do not retain any entanglement for themselves. If they did (and therefore could decrypt the messages), they couldn't pass it on. Indeed, they don't even have to "pass it on" in a literal sense; all that matters is that in the end, Alice and Bob end up sharing a maximally entangled pair (and thus can be sure that there's no one else sharing entanglement with them, no matterwhat happened in between). I don't know what repeaters do in detail, but I guess it's a combination of entanglement distillation (basically, taking several pairs with degraded entanglement, and collecting their entanglement in pairs that are maximally entangled) and entanglement swapping (which essentially is quantum teleportation of states that themselves are part of an entangled pair).
And let me remind you again that all this happens before the actual information is sent. So any attempt on eavesdropping this process will not obtain that information any more than obtaining an OTP before the information is sent will give you information about the OTP. In essence, entanglement acts as a copy-protected OTP. If you have it, you know nobody else has it, and if you don't have it, you can easily check that you don't have it.
(Score: 0) by Anonymous Coward on Wednesday September 23 2015, @10:14AM
Err … should read "are maximally entangled with each other". Of course in practice it will be "sufficiently", because even if Eve's can get some correlation with the message, as long as it is low enough (say, in 50.01% of all cases the correct bit is returned, instead of 50% as for purely random guessing) it won't matter anyway.
(Score: 2) by Gaaark on Wednesday September 23 2015, @11:27AM
That's it, you two... keep talking dirty to me. What are you, Alice and Bob wearing?
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Wednesday September 23 2015, @03:35PM
I think Alice wears Eve's dropped clothes. :-)