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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.
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.
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--
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!
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...
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."
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
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!
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.
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.
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.