Slashdot Mirror
Quantum Telecloning Demonstrated?
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."
but I'm starting to get discouraged now that the already hard to grasp concepts of quantum mechanics are being infused with new more complicated forms. In the end I just want to know if we can teleport ourselves cause I'm tired of my f'ing commute.
"The difference between stupidity and genius is that genius has its limits." -- Albert Einstein
Encryption is a mathematical transformation. Quantym "encryption" has no mathematical transformation in it, it is just a way of modulating signals, i.e. a physical process! That is called "modulation" and has no security properties besides the physical signal properties. No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!
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.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
I knew this was gonna happen. I kept telling everyone it was just a matter of time.
so now we can listen in on quantum encrypted... wait a second... that doesn't exist yet.
O well, must be the FBI getting an early start.
I was just gonna say that...
:)
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...
What ramifications does this have on the heisenberg uncertainty principal? I may be no expert, but doesn't this mean that you could make a remote copy of a particle, and measure one's momentum and the other's position with great accuracy?
I'm a signature virus. Please copy me to your signature so I can replicate.
Have a nice day!
This issue is a bit more complicated than you think.
It's always bugged me that they call it quantum encryption since it's really classical encryption used in a quantum transmission role. I don't see anything "quantum" about the encryption itself. Of course, it probably sounds cooler that way...
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.)
This issue is a bit more complicated than you think.
Well, I for one welcome our quantum encryption link eavesdropping overlords...
Most of the time, I at least read TFA and make a dumb comment. This time, I read TFA and just felt dumb.
Can some explain it and use real-world examples?
As a physics major who has taken the time to look over the paper (read: barely skimmed--I am a lazy college student afterall), I would just like to offer my sincere opinion of "HUh?"
I hope that will be helpful to other Slashdotters outside the field.
When things get complex, multiply by the complex conjugate.
I love it when they come up with these totally original and ambiguous names like "mutlipartite entanglement." Why!? What EVER could that mean? Oh brother...
ok so it tries to tag a / on the end and wikipedia doesnt like it so heree
http://en.wikipedia.org/wiki/Uncertainty_principl
Comment removed based on user account deletion
Now I can be screwed in 32 different states. Kinda like Madonna.
---
When you come to a fork in the road, take it! --Yogi Berra--
if you remember: http://tinyurl.com/ozw7f
another karma abuse.
smash.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
We need to put a stop to this quantum cloning. It is immoral and wrong. Who knows where it might lead!
Just great. Now we can hack a form of encrypted transmission we don't even have yet...
It's interesting that we were just talking about this very article (well the actual release, not this article about it) in a analytical mechanics class I'm taking. One of the things that wasn't mentioned in this article was the fact that the beam of light cloned was only done so to about 66% accuracy. I'm sort of kept from going into more details about this by my own fairly limited grasp on the matrix mechanics, but as the clone wasn't perfect, the uncertainty principle was upheld. It is fairly worrisome to see this study spun much out of proportion though. The opening blurb about Captain Kirk only reinforces untrue stereotypes about the potential of quantum teleportation. Alas, if journalists were physicists...
According to the article: "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." Does this mean the eavesdropping can still be detected, but no information about the eavesdropper can be obtained?
Somehow I doubt this is cloning without disturbing the original state...
http://en.wikipedia.org/wiki/No-cloning_theorem
I just finished compiling Quantum encryption support last week, now I'll have to recompile my kernel. Any word on when the patch will be released? Which repository should I use?
I haven't read the PRL, but the linked article says: ;-))
"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."
So as far as I can tell, the parties sending and receiving the message still know that their is an eavesdropper, just not
"their identity and location." I am sure that heisenberg is still fine, a quantum state still cannot be cloned, and information cannot be sent faster than the speed of light. If this was the case, this would be the headline, and I'm guessing it would be on cnn headline news. (Maybe the world isn't that nerdy though...
I don't know if you guys read this:d =14754716
http://yro.slashdot.org/comments.pl?sid=177904&ci
But the MWOCPT also has patents on this field...
Please, our patience is running short... we don't want to shut-off the Moon's Dark Side stabilizing gravity amplifiers... Or you thought the Moon always faced this way becuase of nature???
Arghhh,
-Stitch
LOCATED at MilkyWay.Sol.3 (aka, Planet Earth)
eMail slashstich@yahoo.com
DAMMIT! Now I have encrypt my files all over again!
Hopefully that Quantum Pretangle Cloning will stay unscannable.
"Beware of he who would deny you access to information, for in his heart, he dreams himself your master."
So let me get this straight
There is a security hole in technology that hasn't even been developed yet?
Isn't someone gonna put a patch out for it?
Register the editry.
The reason that it doesn't violate the Heisenberg uncertainty principle is that the cloning is only approximate. You have one good photon, and you create two copies, neither of which are like the original. They are only somewhat like the original. This means that the evesdropper will get detected. Telecloning, just means that you clone the photon (approximately), and move it to another location (cloning+teleportation). The article claims that this means the location of the evesdropper will thus be safe, even if her attack is noticed. The article is actually about an experimental realisation of telecloning, not the discovery of telecloning itself.
Deconstruct the State
On average, I'm able to correctly decode 50% of the bits.
SCHRODINGER'S CAT FOUND HALF ALIVE
Quantum Theory Wrong
at least, half the cats are alive
You'd have to read the paper every day because it would be on the test.
Stock charts would be replaced by their formulae.
Articles would be published only after 6 month's peer review.
Articles would be written only after attaining an NSF grant.
The grant would in include USD$4 Billion for a 10-acre superconducting adjective collider (SAC) for smashing random words together in the hope of finding new, short-lived metaphors. Expected completion by 2018.
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
This article is NOT about quantum cryptography at all. Telecloning is related to quantum entanglement which is behind basic quantum cryptology, but they are two completely different subjects. Also, we don't even have basic quantum computers yet...I think it will be a long time before we're teleporting people.
I wonder if this will make porn faster to get um.....
Let me see if I can explain this in English, with minimal math. (ed: not without taking a page)
First, I should make it clear that this isn't a dramatic new idea or a new "take" on quantum physics. That being said, it's pretty neat. Like quantum teleportation or quantum computing, it's the sort of thing that you know is theoretically possible, but is still very exciting when somebody does it.
Let's talk about three things: quantum teleportation, quantum cloning, and quantum telecloning.
I'm going to talk about everything in the context of "qubits," quantum bits. As anyone reading this probably already knows, a normal bit can have the states 0 and 1; so can a qubit, though we call them |0> and |1>. Unlike a bit, a qubit can also have intermediate states, like (|0> + |1>). [*] As you also may know, whatever the qubit's state is -- |0> + |1>, |0> - |1>, 1/2 |0> + sqrt(3)/2 |1>, or whatever -- if you measure the qubit, you'll get either |0> or |1>, and no indication of what state it was in previously.
That's why we need QUANTUM TELEPORTATION. Suppose I have a qubit in state A = a|0> + b|1>, and I want to send it to you on the other side of the world. Even supposing that I knew what my state was -- and if I don't, I can't find out -- it would take a long time to transmit a and b, since they're arbitrary real numbers. Quantum teleportation is the transmission of an exact copy of A from me to you. We need to start off with some entangled qubits that we made last time we met, but for the moment we'll assume that we have those.
So what is QUANTUM CLONING, and why isn't teleportation it? Well, teleportation has the unfortunate feature that if I want you to have a copy of A, I have to destroy my copy of it in the process. Ideally, what quantum cloning would do is give you and me each a copy of A. Unfortunately, you can't do that: there's something called the No Cloning Theorem [**] that expressly forbids doing that. The best you can do with quantum cloning is make a copy that isn't only a copy; it's entangled with the original. What that means is if I measure my copy of A and get |0> or |1>, your copy is stuck with the same result: if I got |0>, you'll get |0>. Mathematically, we start with a|0>|0> + b|1>|1>, and measuring with result |1> will change that to |1>|1>. So it's a clone, but the clones' destinies are intertwined.
There's another post where someone asks about Heisenberg's Uncertainty Principle: could I use this to make two copies of A, and measure the position of one and the momentum of the other? Well, you could, but it would be exactly equivalent to just taking A and measuring its position and then its momentum. By measuring, you change the state of both copies.
So now we bring all this together, with QUANTUM TELECLONING. We're going to do quantum teleportation just like before: you and I already shared some entangled qubits ahead of time, and we want to teleport. But this time, instead of just a pair of entangled qubits, we have a triplet: I got one of the qubits, and you and my MSc supervisor Bill each got one. Now when I send A to you both, you get a copy and Bill gets a copy (and I lose mine), just like in quantum teleportation. But the copies you have are clones as I discussed above: if either of you ever makes a measurement, it will affect the other's state.
The application of this to quantum communication is that I can throw a wiretap into your communication line, and through this technique I can clone a copy of your qubit for myself -- and also let you have an exact copy of the original go through unimpeded. So what does this do to quantum cryptography? To be honest I'm not sure, but it's clearly not quite like you're just another receiver. I'm going to a lecture on this either tomorrow or Tuesday, so I'll post a followup then. You can also contact me at slashdotphysicist at geemail if you're interested in more.
[*] There should be a
Yeah
a) Experiment demonstrates previously theorized quantum telecloning which is one way to get an approximation of transmitted bits (simply, u can get X more bits correct than just guessing).
b) The quantum No Cloning Theorem is still safe and not violated, no need to get hysterical or pissed off. This is because No Cloning Theorem only forbids exact copies.
c) Fidelity was 58%
Experiment makes, without a doubt, a valuable contribution although didn't overturn fundamental theory.
Imho, Quantum cryptography still viable due to privacy enhancement techniques. Read more on that here http://www.ai.sri.com/~goldwate/quantum.html
Are we sure that this story wasn't posted by Calvin as his latest school assignment? If you have a look at the PDF with edits left in, you'll see words like "Transmogrify" crossed out all through it. I'm sure Hobbes could have put him up to it.
Theorizing that one could time travel within his own lifetime, Dr. Sam Beckett stepped into the Quantum Leap accelerator and vanished .... He woke to find himself trapped in the past, facing mirror images that were not his own and driven by an unknown force to change history for the better. His only guide on this journey is Al, an observer from his own time, who appears in the form of a hologram that only Sam can see and hear. And so Dr. Beckett finds himself leaping from life to life, striving to put right what once went wrong and hoping each time that his next leap will be the leap home.
"Oh boy.."
That reminds me of the Windows XP anticopy scheme. Long before it was even released publicly, the crack had already hit the street. Sweet.
My 0.02 cents
I've been quantum telecloning via multipartite entanglement for years with my ultra-flux quasi capacitordangle jimmy-rigged to a quanto-farscope for multi-resolution ohmage. I built this with the latest in Lego technology!
Glad to see you know more than just viruses ;)
Appreciate your stuff back in the day. I sure learnt a lot.
So, when do we send a satellite off into space with a "quantum receiver" on board? We could send it to Pluto (the planet) and have it blow up or do something drastic (you know, for the effect) which would be visible from Earth once it gets back to us at the speed of light.
Let me say "physorg sucks"
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 wannabe philosopher nonsense. Search physorg a bit - you'll see bullshit like alien crash landings and various other nonsense. And look at all the ads. Dear Lord. No scientist I know will go within 10 feet of that heaping pile.
It's a quantum party line!
(deem g/d/r implied)
Got time? Spend some of it coding or testing
Well, I guess I won't be upgrading from telnet just yet.
Could this eventually be used for a near zero latency WAN?
Of course they will have to retool the multi player capabilities of
Duke Nukem Forever to take advantage of this before it's release.
But does it run Linux? (Sorry, I had to. :D)
What day is it? Could you please tell me?
I'll feed the troll..
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 a tap in place as long as the interruption was minimal.
Around here, when there's a fiber cut, it takes hours- but I assume some of that is discovering the cut, finding a crew and getting to the site. I would suppose if you put one of the worlds top splicers right there that the interruption could be made fast enough that the techs monitoring the connection would be confused but would chalk it up to some sort of temporary bend or other error.
I am not a fiber tech, but all of that seems fairly reasonable to me.
In other words, I don't think quantum teleportation is necessary or even applicable to straight forward fiber implementations that don't depend on the orientation of photons.
Thats not even necessary though. They already have devices that bend fiber optic cables just enough to be able to detect the light comeing out the side of the thing, then they passivly read everything that passes through. No splices at all.
From the paper referenced in this PRL, Physical Review A 59 (1999), M. Murau, D. Jonathan, M.B. Plenio, V. Vendral:
"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 mechanics), which we assume to be sufficient for her purposes." (Caps are mine.)
Now I admit, the PRL is too dense for me to understand, but based on this, it lookse to me like perfect quantum clones are not allowed. In fact, this quantum no-cloning theorem follows quite directly and naturally from first principles. We won't be cloning Kirk anytime soon, at least not perfectly.
Didn't you hear? Quantum computing makes everything happen faster.
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.
hmm... what I'd like to see on the web is an introduction to quantum physics for non physicists. something that outlines the primary results of quantum physics with some graphical explanation for laymen.
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 increasing will say "quantum physics" and do a bunch of handwaving to promote psuedoscience. people don't do this with relativistic physics because most people at least understands the *domain* of relativity and know that it isn't likely to lead to inventions that say, clean your clothes better, or something along those lines. quantum physics on the other hand is sometimes quoted when selling just such products (I've seen little plastic balls that are supposed to go in washing machine along these lines) because most people just don't know what the results of quantum physics are, just that they are supposed to be powerful and profound, so charlatans play on that uncertainty.
and... anyway I think we all agree that the *public* understanding of scientific issues, on a least a basic level, is really important to the health of our society. I'm sure we can all name a couple of other issues where poor understanding of science in the public sphere and in government has led to poor decisions and general idiocy. popularization of science and science understanding seems like a goal we should be devoting more resources to.
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.'
:)
Maybe I'm missing the point here (because I'm not a theoretical physicist), but what would happen if you combined something like this (light cloning) with fiber optics (data transfer) over long distances? Would it do away with having to have tons of underground fiber? Would it create an exponential jump in bandwidth?
Just food for thought.
1 is the square root of all evil.
Please give either the original URL or a makeashorterlink URL, so there's a chance to see the real destination before going there.
The Tao of math: The numbers you can count are not the real numbers.
I was under the impression that since the cables are internally reflective, there was no translucence to the mirror finish- eg not transmissive. The way I understood it (or thought I did) was that even a slight bend would change the angle of reflection and cause the signal to fail. Presuming there was some transmission through the mirrors inside the cable, you'd have some light loss in addition to a bend.
Is there a link on Wikipedia or anywhere that might explain to me how those devices work in principle?
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 combination os states, proof there's tapping going on.
What if the tap is set up while the fiber is still dark?
"For that matter, they could afford to buy your entire planet and take it apart one atom at a time"
I wish people would look up the original press release instead of advertising the physorg tarpit.
Here.
(yes, all the stupid "teleportation" stuff was in the original)
Um, I know I got Doom 3 pretty late and have been playing late into the night but...is this a real news item?
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
It's 10 PM. Do you know if you're un-American?
The statement...
...leads to...
... not the other way around.
"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 I found articles referencing "alien" and many of the top hit were respectable articles about spitzer, hubble, etc. Couldn't find any on "alien crash", searching the readers comments provided plenty of fantasy as it would on slashdot.
I wonered for a second what other "nonesense" I could search for? I pictured an average "science, space and technology" section at the newsagent, "UFO" flashed eveywhere, three hits (one a dupe!).
PhysOrg is kinda like the "science, space and technology" section, the one big difference is that they invite general comments and would love to hear from specialists. If that seems to much effort then just rate the article or post an intelligent critisim/rebuttal. Bitching on another nerd site when these options are open to you is just crass and immature.
People are not born with the philosophy and method of science magically imprinted, much less the detail involved in graduate studies, this is doubly true for arts majors such as journalists (who BTW will pick the shit out of my scribbles).
In short, unless you have some scientific training everything from UFO's to spacetime sounds equally plausible, it's all appears to be some "smart guy's" opinion. Case in point: The slashdot summary for TFA makes an incorrect interpretation, as a heap of QM nerds have clearly pointed out. Sites like slashdot and PhysOrg are all about the discussion, if "scientists" don't go to the "lions den" and participate in "popular science", what chance do journalists have?
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
You what that means...
Actually, the big problem with quantum key distribution is that, while it allows for the possibility of the quantum channel being compromised - so that the eavesdropper can intercept the photons and send out new ones - it fails to consider that the classical channel may be compromised to the same degree.
Of course, presently encryption based on prime numbers could be used to secure the classical channel, but that makes the quantum channel superfluous anyway. QKP is intented for when Shor's algorithm is implementable in practice, so that classical encryption fails - but it still depends upon it.
nothing new...
comment first, facts later. http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
This is a result of Snell's law. When light travels from a material with a high index of refraction to one with a low index, its angle with the plane gets smaller. See http://scienceworld.wolfram.com/physics/SnellsLaw. html where they show the light going in the opposite direction.
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 rays will have a high enough angle that they escape. Note that my 'high' and 'low' are with respect to the plane, while usually when doing calculations the angle is measured against the normal.
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.
If aspiration is a virtue, achievement cannot be a vice.
Quantum Crypto was never about "oh no, the alarm tripped, someone's snooping". It was always about "assume some bits are snooped, some aren't, find and discard the snooped bits and just use the secret ones". It's a way of sharing key or one-time-pad material, not of passing meaningful data.
IOW, the "attack" is meaningless.
Could someone explain to me why exactly a man in the middle attack is impossible? As far as I can tell, it's only impossible so long as Alice and Bob have a direct connection to each other. If there is a series of hand-offs between various networks in between Alice and Bob, then quantum cryptography can't work since the particles have to be read and interacted with by the first router Alice connects to. So long as you can compromise some device in between Alice and Bob, you've got a man in the middle attack, right?
Explain how the states of the entangled photons is supposed to be preserved between Alice and Bob if they aren't directly connected to one another.
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
Well,
We have clearly reached the end of my insight into cryptography. I would like to thank you for taking the time to answer.