Quantum Telecloning Demonstrated? 195
An anonymous reader writes "According to Physorg eavesdropping on a quantum encrypted link can now be done without detection. From the article: 'The scientists have succeeded in making the first remote copies of beams of laser light, by combining quantum cloning with quantum teleportation into a single experimental step. Telecloning is more efficient than any combination of teleportation and local cloning because it relies on a new form of quantum entanglement - multipartite entanglement.' There is also a PDF of a related paper available here for background material."
I really dig this stuff... (Score:5, Funny)
Re:I really dig this stuff... (Score:5, Funny)
Well, don't they need a pre-publication license? (Score:2)
another karma abuse.
Re:Well, don't they need a pre-publication license (Score:2)
That's because... (Score:2)
Re:I really dig this stuff... (Score:2)
In Soviet Russia, the uncertainty breaks you !
Re:I really dig this stuff... (Score:3, Funny)
By no means can two perfect copies of people be allowed to exist at the same time. It would rip apart the very fabric of space time as we know it. Therefore...
1. Materialize two pugil sticks into the data stream, one for each person. Let them duke it out American Gladiator style. Loser gets fed into a tree shredder (provided by Soylent Green Technologies).
2. Insert shark teeth and monkey tail DNA into the copy. He would be slightly different, and slightly coo
Re:I really dig this stuff... (Score:2)
Re:I really dig this stuff... (Score:2)
Re:I really dig this stuff... (Score:2)
Re:I really dig this stuff... (Score:2, Funny)
Re:I really dig this stuff... (Score:2)
Re: (Score:2)
Re:I really dig this stuff... (Score:2)
Re:I really dig this stuff... (Score:2)
Re:I really dig this stuff... (Score:2)
It is not "encryption", it is "modulation"! (Score:4, Interesting)
Since all previous claims of security rested on not yet well understood physical principles, I am not surprised that once again claims of perfectness by ethically challenged researchers and businesspeople have turned out to be wrong.
Re:It is not "encryption", it is "modulation"! (Score:4, Informative)
http://www.amazon.ca/exec/obidos/ASIN/0521635039/
Or how about all those classical encryption schemes that were thought to be secure for long periods of time, but them turned out to be [near] trivial to break.
New attacks are created all the time. It doesn't mean the the researcher is ethically challenged. It just means that he thought he was right at the time, given the information at hand.
This is cutting edge research. Get a clue. Or at least your head out of your ass.
Re:It is not "encryption", it is "modulation"! (Score:2, Interesting)
Firstly, it IS encryption, there is data being hidden in a non-obvious format,
Dictionary.com says this about the term "Encrypt"
encrypt
tr.v. encrypted, encrypting, encrypts
1. To put into code or cipher.
2. Computer Science. To alter (a file, for example) using a secret code so as to be unintelligible to unauthorized parties.
I see nothing about mathematical transforms there. In fact, many ciphers are n
Re:It is not "encryption", it is "modulation"! (Score:2)
yes a physical manipulation is mathematical, there is geometry , graph theory, and discrete math involved.
Re:It is not "encryption", it is "modulation"! (Score:2)
Re:It is not "encryption", it is "modulation"! (Score:3, Insightful)
Wouldn't that be steganography, rather than encryption?
Re:It is not "encryption", it is "modulation"! (Score:2)
Just because somthing can be done without any knowledge of math it means that it is not math? I guess then that all criptography is done in a similar way, people use hard core cripto with their browsers almost everyday, but most of them have no idea of what is happening, so I guess those are not math either.
Just becuase somtheing is simple enouth dosen't mean it isn't math, people calculate change and it is simple and it is math. People do those c
No, he's right. (Score:2)
That's pretty obvious. I'm quite sure the grandparent poster was aware of it. However, that does not invalidate his point: that it's unethical to present a theory as a fact.
Re:It is not "encryption", it is "modulation"! (Score:2)
Absolutely! Because since it's quantum mechanics we're talking about, any mathematical proof *might* or *might not* be true
Re:It is not "encryption", it is "modulation"! (Score:5, Informative)
All the article claims is that the Evesdropper's location will be undetected. The fact that someone is attempting to eavesdrop will still be detected, and there are several well known proofs of security of this fact.
FTF Press Release
"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."
Quantum cryptography is absolutely secure as long as the laws of quantum mechanics are true. And even if the laws of quantum mechanics are false, one can still do secure cryptography from some very weak assumptions (it follows from violating Bell's inequalities and no-signalling) see this [lanl.gov]
Re:It is not "encryption", it is "modulation"! (Score:3, Insightful)
The eavesdropper is still detected. The blurb is wrong.
eavesdropping on a quantum encrypted link can now be done without [detection (wrong)] being located
Re:It is not "encryption", it is "modulation"! (Score:2)
Re:It is not "encryption", it is "modulation"! (Score:5, Informative)
The parent poster (wwwrench) is completely, 100% correct. Is this really Slashdot, or did I type the wrong URL?
Seriously, though, the parent poster is bang-on. To elaborate a bit, quantum cryptography would be more informatively called quantum key distribution (although both names are common in practice). All it does is allow you to distribute a key for a one-time pad in a secure method, given that the laws of quantum mechanics are at least partially correct (one-time pads are information-theoretic secure, provided the key is not compromised or re-used). If somebody tries to eavesdrop, you can detect it, and respond accordingly. That response could be privacy amplification (if the information the eavesdropper gained was only partial), re-trying the protocol, or bombing the eavesdropper to smithereens. That last possibility is why quantum telecloning might be useful.
One other hitch is that quantum key distribution requires a small shared secret in order to authenticate the two parties trying to generate a key. Thus, quantum key distribution is not a complete replacement for public-key cryptography.
Re:It is not "encryption", it is "modulation"! (Score:2)
And in public key cryptography, you have to have a trusted party to provide you the public key, and have to authenticate with that party.
No secure communication is possible without sharing an initial small secret. You cannot in principle say whom you are communicating with if you share no prior secret information with him. This is the way things are in this wo
Re:It is not "encryption", it is "modulation"! (Score:2)
Nope. All quantum "cryptography" tells is that you are the sole recipient of a message. However anyone could have transmitted the photons you received. Before you can trust the photons, you have to confirm the data they carried, using a conventional message authentication code. The overall system is no stronger than that code. TANSTAAFL.
In theory, quantum "cryptography" does raise the bar by stopping passive ea
saw it coming (Score:2, Funny)
ahh yes (Score:4, Funny)
O well, must be the FBI getting an early start.
Re:ahh yes (Score:5, Informative)
Amazing as it may sound, researchers have used commercially available fiber-optics to send quantum encrypted signals. There are even companies that will sell devices, although right now the tech is not quite ready for prime-time. Still, it has been shown in a laboratory many times, and it's not fanciful to say that it may be deployed within our lifetimes (just depends on when the technology becomes affordable, compared to its benefits).
Also, as others have pointed out, this new result actually doesn't show that quantum crypto is breakable... it only shows that under some circustances the eveasdropper can remain anonymous... but the users of the channel will still know that it has been compromised, and will thus not use the keys that have been generated. That is, quantum crypto is still mathematically unbreakable when properly implemented (assuming that Quantum Mechanics is correct, that is).
Re:ahh yes (Score:4, Informative)
If the composite system is in this state, it is impossible to attribute to either system A or system B a definite pure state. Instead, their states are superposed with one another. In this sense, the systems are "entangled".
Now suppose Alice is an observer for system A, and Bob is an observer for system B. If Alice performs the measurement A, there are two possible outcomes, occurring with equal probability:
1. Alice measures 0, and the state of the system collapses to |0\rangle_A |1\rangle_B
2. Alice measures 1, and the state of the system collapses to |1\rangle_A |0\rangle_B.
If the former occurs, any subsequent measurement of B performed by Bob always returns 1. If the latter occurs, Bob's measurement always returns 0. Thus, system B has been altered by Alice performing her measurement on system A., even if the systems A and B are spatially separated. This is the foundation of the EPR paradox [wikipedia.org].
The outcome of Alice's measurement is random. Alice cannot decide which state to collapse the composite system into, and therefore cannot transmit information to Bob by acting on her system. (There is a possible loophole: if Bob could make multiple duplicate copies of the state he receives, he could obtain information by collecting statistics. This loophole is closed by the no cloning theorem, which forbids the creation of duplicate states.) Causality is thus preserved, as claimed above.
http://en.wikipedia.org/wiki/No_cloning_theorem [wikipedia.org]
The no cloning theorem is a result of quantum mechanics which forbids the creation of identical copies of an arbitrary unknown quantum state. It was stated by Wootters, Zurek, and Dieks in 1982, and has profound implications in quantum computing and related fields.
Note that the state of one system can be identically entangled with the state of another system, such as by using a CNOT gate, but this does not constitute cloning since the systems will always yield the same value upon measurement. The no cloning theorem describes the inability to make separately measurable states.
Re:ahh yes (Score:2)
I don't see any reason to think it's impractical, beyond perfecting the technology and economies of scale. DVD-RWs were very hard to produce at one time, and VERY costly, but that's no reason to think they'll be impractical in the long-run, given their utility. If any new technology has utility enough to make it worth developin
news flash! (Score:2, Funny)
Quantum Theory Wrong
at least, half the cats are alive
What? (Score:4, Insightful)
Seriously though, no matter how much I learn/study/pay tuition, there're always posts that make me realize how little I know about anything.
It's both humbling and inspiring.
Off topic, but someone had to say it...
Don't worry... (Score:5, Funny)
Have a nice day!
Heisenberg Uncertainty Principal? (Score:5, Interesting)
Re:Heisenberg Uncertainty Principal? (Score:3, Funny)
Unless there is a school named Heisenburg Uncertainty, which would be cool.
Re:Heisenberg Uncertainty Principal? (Score:5, Funny)
Just as you think you know where your next lesson is you rush to get there to realise you've already missed it.
Finding out if the lecturers are still alive after opening the classroom door is an entirely different and wholey worrying scenario unto itself.
Re:Heisenberg Uncertainty Principal? (Score:2, Funny)
Re:Heisenberg Uncertainty Principal? (Score:2, Funny)
Dude! I love that place. They moved everybody out and gave me the front room
Are you sure? (Score:2)
Re:Heisenberg Uncertainty Principal? (Score:2)
the cloning is only approximate (Score:5, Informative)
Re:Heisenberg Uncertainty Principal? (Score:5, Funny)
Obviously no one is quite sure.
Re:Heisenberg Uncertainty Principal? (Score:5, Informative)
Having said that, cloning a particle perfectly is nonetheless forbidden by the No Cloning Theorem [wikipedia.org]. Basically (as I understand it) what this says is that there is an underlying principle of Quantum Mechanics that you can never know what position distribution a particle originally had, since the moment you measure it you focus it at that point and kill the original distribution. Cloning the particle would be a way of "cheating" that would let you get the distribution of the particle without destroying it, so it ends up being forbidden.
Now, even though you cannot perfectly clone a particle, you can imperfectly clone it, which is what these guys have claimed to have done. If you look at the abstract, you will note that they are only claiming a fidelity of 58% +/- 1%. (The theoretical limit is five-sixths (83%) according to this article in New Scientist [newscientist.com].)
A non-perfect fidelity, however, isn't so bad. Alice and Bob probably can't get their own optimal fidelity when using Quantum Cryptography anyways; in theory they should expect to see 50% of the bits get through, and then worry if they see it goes down below that -- even, say, to 49%. In practice, their equipment might only be able to get 40% of the bits through, and sometimes even less than that, so they'll tolerate lower rates than 50% since they are figuring that eavesdropping would lower this rate all the way down to 25%, and that is something that they'd surely notice. However, by using the techniques like those discussed in the article you can apparently eavesdrop less than perfectly in a way that, while still lowering the bit transmission, does not make it as bad as 25%. Thus, if Alice and Bob were naive they'd just assume that their equipment was faulty and not that there was an eavesdropper.
So the moral of this story is that from now on Alice and Bob will have to make their apparatus work much more reliably so that they can expect a success rate of say, 45-50% rather than 35-50%, and thus be more likely to notice a slight degradation in the signal due to an eavesdropper.
Re:Heisenberg Uncertainty Principal? (Score:2)
If you were to measure the momentum of one, then the position of both will become fuzzy. That's what quantum entanglement does.
Quantum Transmission (Score:2, Insightful)
Re:Quantum Transmission (Score:2)
Another basic law of physics... (Score:3, Funny)
I just made that up, but the obvious corollary is this; If you don't want something to be known, don't say it!
Thank you very much, I'll be here all week. (Mostly because I have nowhere else to go.)
Re:Another basic law of physics... (Score:2)
They hate it when the 'funny' guy forgets to do that. When they're not happy, management isn't happy, and when management isn't happy... well, lets just say you should probably find someone else to go.
I hear Kuro5hin is looking for some new talent.
Re:Another basic law of physics... (Score:2)
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Can I get this in English? (Score:5, Funny)
Can some explain it and use real-world examples?
Re:Can I get this in English? (Score:3, Informative)
As a physics major... (Score:5, Funny)
I hope that will be helpful to other Slashdotters outside the field.
Re:As a physics major... (Score:2)
"Remember all that stuff we told about undetectable eavesdropping on a quantum transmission being impossible by definition, well... uhhm... we just did it."
Whatthafu?
As a physics graduate student... (Score:2)
This particular quote made me particularly amused...
Telecloning combines cloning (or copying) with teleportation (i.e., disembodied transport). (emphasis mine)
Disembodied transport? WHAT? Quantum teleportation is NOTHING like the star trek fantasy these idiots are building it up to. This isn't some matter/energy conversion to move physical objects - it's FRICKIN LASER BEAMS. Fuck do I hate physorg.
Look at the comments, it's all Jim McCanney electric universe and couch potato w
Devil's advocate... (Score:2)
"No scientist I know will go within 10 feet of that heaping pile."
Let me say "physorg sucks".
"And look at all the ads."
Yes they look like they are selected by google and amazon robots, AI has a long way to go! If you want a real laugh go to any serious article anywhere on the web that has the word "evolution" and google ads.
"Search physorg a bit - you'll see bullshit like alien crash landings and various other nonsense."
Well
Re:As a physics major... (Score:2)
Uncertainty means you can't know a quantum particles location and speed absolutely. When you fix the position, the speed is unknown -- but you can make estimates and predictions of some reliability.
I'm pretty sure the "cloning" means transferring a quantum state. Say like spin direction -- you can know the speed and the clone the spin to another quantum particle by means of entanglement. Entanglement is a fancy word meaning; "hanging out
uh-huh (Score:2)
Re:uh-huh (Score:2)
Perhaps you meant dasterdly-mutleypartite entanglement?
Sounds like one of Klunk's inventions that didn't quite work as expected.
Re:uh-huh (Score:2)
I can just see the guy, "We're calling it 'multipartite entanglement!'" And his colleagues going, "Is that a technical term?"
Comment removed (Score:4, Funny)
Re:Quantum Encryption (Score:2)
Quantum cryptography (more accurately, quantum key distribution) has been around a bit longer than that -- there was an article in the July 1992 issue of Scientific American discussing work Charles Bennet was already doing with it then. A quick search shows there was a short thread about it on Usenet [google.com] shortly after publication (though I'll admit, it pro
This is great (Score:4, Funny)
Re:This is great (Score:2)
right... (Score:3, Funny)
smash.
Re:right... (Score:2)
Re:right... (Score:2)
Damn, Dude, as if being stuck fucking pigeons wasn't punishment enough.
You're a mean vindictive person.
I find your ideas intriguing and would like to subscribe to your newsletter
*sigh* (Score:2)
Back to IP over avian carrier?
Oh great. As if the botnets and spam and phishing and all the other nonsense aren't enough to drive a simple sysadmin mad, now I'm going to have to wory about bird flu as well?
--MarkusQ
Cloning is immoral! (Score:3, Funny)
Re:Cloning is immoral! (Score:2)
Re:Cloning is immoral! (Score:2)
I *so* want to go up to Bush in front of a gaggle of reporters and ask him if he supports legislation to terminate the federal funding of Quantum Cloning research!
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Great! (Score:2)
Hmm, how seredipitous... (Score:5, Interesting)
Re:Hmm, how seredipitous... (Score:2)
That sounds like Captain Kirk's evil twin speaking.
Re:Hmm, how seredipitous... (Score:2)
Re:Hmm, how seredipitous... (Score:2)
The uncertainty principle merely guarantees that no clones of Captain Kirk will be good -- they may look like him, but they will end up with a goatee and be evil.
Re:Hmm, how seredipitous... (Score:2)
No, that's not fair. Theoretical physicists have already proven that it is possible to teleport people. Building a device to do it is merely an engineering problem, and of course the theoretical physicists have handed responsibility of that part over to the wrench monkeys (engineers).
P.S.
Reversing the spin of the earth so that the sun rises in the west and sets in the east is also merely an e
I have a long distance quantuum eavesdropper (Score:2, Funny)
ScuttleMonkey didn't read TFA, clearly... (Score:2)
Calvin's work? (Score:2, Funny)
Quick summary of quantum theory (Score:2, Funny)
IIRC (Score:2, Funny)
Ah, yes! (Score:3, Funny)
Missing the point (Score:2)
A word about quantum telecloning (Score:2, Informative)
"In this paper, we investigate the following scenario. Alice holds an unknown one-qubit quantum state |Phi> and wishes to transmit identical copies of it to M associates (Bob, Claire, etc.). OF COURSE, THE QUANTUM NO-CLONING THEOREM IMPLIES THAT THESE COPIES CANNOT BE PERFECT. The best Alice can do is to send optimal quantum clones of her state (the most faithful copies allowed by quantum me
huh? (Score:2, Insightful)
most people with an interest in physics, whether they be physics majors who have taken modern physics classes or not, have some intuitive ideas about what relativistic physics means. however, when it comes to quantum physics, people just think "black magic happens here"...
what's worse is that people increasi
Re:huh? (Score:2)
If you know what a probability distribution is, the basics aren't that hard. Shankar's [amazon.com] list of the basic postulates of QM as compared to classical mechanics is helpful. The following refer to a particle in one space dimension:
1. Classical: The state of a particle at any given time is specified by two variables x(t) and p(t), i.e., as points in a two-dimensional phase space.
Translation: Every particle's "state" (that is, wh
Totally silly, fixable with $1500 tool (Score:2)
If somebody is tapping the line, strongly enough to intercept photons, it's easily determined by using a TDR (time-domain reflectometer)-- basically optical radar. Even a 1% discontinuity in amplitude or length can be detected. All it takes is a little handheld gadget.
AND if they're tapping and resending the signal, it's lost all its entangled properties, so the other end won't get the right c
Original press release. (Score:2)
Here. [york.ac.uk]
(yes, all the stupid "teleportation" stuff was in the original)
Excuse me? (Score:2)
Have we now moved into an era in which even NON-EXISTENT technology is already being OBSOLETED before it becomes real?
This just in: hydrogen fuel is officially obsolete; dilithium crystal is the fuel of the future
made by humans, broken by humans (Score:2)
I Think, Therefore It Is! (Score:2)
Because I'm pedantic, I'd like to log a clarification to this. It's not a new form of quantum entanglement. It's presumably been around since the beginning of time. What it is is a newly discovered form of quantum entanglement. This is not a case where human thoughts created something. You are not a figment of my imagination.
Re:What it all really means (Score:3, Funny)
Hopefully that Quantum Pretangle Cloning will stay unscannable.
Re:What it all really means (Score:2, Interesting)
Feasibly, someone that had access to the cables could cut them, put a receiver, a transmitter, and a computer that receives, records and retransmits everything in and splice everything up properly when done- aside from a temporary and puzzling outage- no one would be the wiser.
It can be determined from reflectometry exactly where the break is, and someone would go out and check the cable eventually with an ROV or something and find the splice, but I'd imagine for a while you could have
Re:What it all really means (Score:2)
If you go at a low enough angle, you get reflection. Inside a fiber optic cable, all the light rays are going at a low enough angle to have reflection (and they reflect at the same angle). But if you bend the cable a bit, some