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Quantum Telecloning Demonstrated? 195

Posted by ScuttleMonkey from the nosey-people dept.
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."
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Quantum Telecloning Demonstrated? More

Quantum Telecloning Demonstrated?

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  • I really dig this stuff... (Score:5, Funny)

    by Mark_Uplanguage ( 444809 ) on Sunday February 19, 2006 @09:52PM (#14758002)
    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.

  • It is not "encryption", it is "modulation"! (Score:4, Interesting)

    by gweihir ( 88907 ) on Sunday February 19, 2006 @09:52PM (#14758006)
    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.

    • Re:It is not "encryption", it is "modulation"! (Score:4, Informative)

      by Secret Rabbit ( 914973 ) on Sunday February 19, 2006 @10:12PM (#14758134) Journal
      No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!
      Perhaps you haven't read:

      http://www.amazon.ca/exec/obidos/ASIN/0521635039/q id%3D1140401059/701-1812336-3224355 [amazon.ca]
      I am not surprised that once again claims of perfectness by ethically challenged researchers and businesspeople have turned out to be wrong.
      Perhaps you are not aware of a phrase that states "within current theory" that is implied everytime a theorist speaks. Or weren't you aware of that?

      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.

      • Beng somewhat of a mathematician and crypto-buff, let me say this.

        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
      • Perhaps you are not aware of a phrase that states "within current theory" that is implied everytime a theorist speaks. Or weren't you aware of that?


        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.
    • No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!

      Absolutely! Because since it's quantum mechanics we're talking about, any mathematical proof *might* or *might not* be true :p

    • Re:It is not "encryption", it is "modulation"! (Score:5, Informative)

      by wwwrench ( 464274 ) on Sunday February 19, 2006 @10:16PM (#14758158) Homepage
      Wrong.
      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]
      • Thank you for forcing me to go back and re-read the article. I misread it, as did the submitter, and was extremely confused.

        The eavesdropper is still detected. The blurb is wrong.

        eavesdropping on a quantum encrypted link can now be done without [detection (wrong)] being located
      • the problem with quantum crypto is that it requires the components to be installed together and securely, if you are doing that you may as well simply use abnormally large symmetric keys.

      • Re:It is not "encryption", it is "modulation"! (Score:5, Informative)

        by tbo ( 35008 ) on Monday February 20, 2006 @12:16AM (#14758668) Journal
        Disclaimer: IAAQIS (I Am A Quantum Information Scientist).

        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.
        • 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.

          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

      • Quantum cryptography is absolutely secure as long as the laws of quantum mechanics are true.

        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)

    by Anonymous Coward
    I knew this was gonna happen. I kept telling everyone it was just a matter of time.

  • ahh yes (Score:4, Funny)

    by la htris ( 955271 ) on Sunday February 19, 2006 @09:54PM (#14758021)
    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.

    • Re:ahh yes (Score:5, Informative)

      by kebes ( 861706 ) on Sunday February 19, 2006 @11:00PM (#14758361) Journal
      I think you're confusing quantum computing [wikipedia.org] (which is still mostly theoretical... the largest experimental proof has only involved a few qbits, and for all we know a full-fledged computer will be impractical) and quantum cryptography [wikipedia.org], which actually has been experimentally demonstrated.

      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)

        by Anonymous Coward on Monday February 20, 2006 @12:05AM (#14758621)
        http://en.wikipedia.org/wiki/Quantum_entanglement [wikipedia.org]

        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.

      • quantum computing (which is still mostly theoretical... the largest experimental proof has only involved a few qbits, and for all we know a full-fledged computer will be impractical

        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

  • What? (Score:4, Insightful)

    by compuguy84 ( 886540 ) on Sunday February 19, 2006 @09:55PM (#14758027)
    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... :)

  • Heisenberg Uncertainty Principal? (Score:5, Interesting)

    by icleprechauns ( 660843 ) on Sunday February 19, 2006 @09:55PM (#14758028) Homepage
    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?
    • There IS NO Heisenburg Uncertainty Principal.

      Unless there is a school named Heisenburg Uncertainty, which would be cool.
    • I'm not sure Heisenberg is a principal either.

    • the cloning is only approximate (Score:5, Informative)

      by wwwrench ( 464274 ) on Sunday February 19, 2006 @10:47PM (#14758306) Homepage
      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.

    • Re:Heisenberg Uncertainty Principal? (Score:5, Funny)

      by Concerned Onlooker ( 473481 ) on Sunday February 19, 2006 @10:50PM (#14758317) Homepage Journal
      What ramifications does this have on the Heisenberg uncertainty principle?

      Obviously no one is quite sure.

    • Re:Heisenberg Uncertainty Principal? (Score:5, Informative)

      by da cog ( 531643 ) on Sunday February 19, 2006 @11:22PM (#14758447)
      Actually, if it could be done it wouldn't violate the Uncertainty Principle at all. A particle cannot have both a definite momentum and position, it can only have (roughly speaking) a probability distribution of each. So if you could clone a particle a zillion times, then each time you wouldn't get the same position, but rather if you looked at all of the clones together you'd get a distribution which would be identical to that of the original particle.

      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.

    • No, this doesn't mess up Heisenberg.

      If you were to measure the momentum of one, then the position of both will become fuzzy. That's what quantum entanglement does.

  • 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...
    • Although the encryption scheme itself just uses a classical key, the transmission of the key is done over a public channel using a quantum trick. Normally you would be crazy to just transmit the key over a public channel, but by using entangled particles (photons or whatever), you have a mathematically and physically rigorous proof that the transmission was sent without being intercepted. Thus, you know that the end-party received the key without anyone else getting a copy. If some third party does manage t

  • Another basic law of physics... (Score:3, Funny)

    by NotQuiteReal ( 608241 ) on Sunday February 19, 2006 @10:01PM (#14758060) Journal
    If someone says something, someone might overhear it.

    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.)

    • Thank you very much, I'll be here all week. (Mostly because I have nowhere else to go.)
      You left out the line about tipping the waitresses.

      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.
    • The RIAA and MPAA are reportedly lobbying to get that law changed, as it threatens to destroy their business model and it costs them nearly a trillion dollars in losses each year.

      -

  • Can I get this in English? (Score:5, Funny)

    by ip_freely_2000 ( 577249 ) on Sunday February 19, 2006 @10:02PM (#14758072)
    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... (Score:5, Funny)

    by physicsphairy ( 720718 ) on Sunday February 19, 2006 @10:04PM (#14758081)
    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.
    • I whole-heartedly agree with you. I was a physics major too; long long ago.

      "Remember all that stuff we told about undetectable eavesdropping on a quantum transmission being impossible by definition, well... uhhm... we just did it."

      Whatthafu?

    • 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 w
      • The statement...

        "No scientist I know will go within 10 feet of that heaping pile."

        ...leads to...

        Let me say "physorg sucks".

        ... not the other way around.

        "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
    • My formal discipline is as an artist, so let me handle the explaining.

      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
  • 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...
    • 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...

      Perhaps you meant dasterdly-mutleypartite entanglement?

      Sounds like one of Klunk's inventions that didn't quite work as expected.
      • LOL! It's like the scientist version of naming your kid "OrangeJello."
        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)

    by account_deleted ( 4530225 ) on Sunday February 19, 2006 @10:12PM (#14758137)
    Comment removed based on user account deletion

    • I remember reading about this undefeatable encryption on slashdot a few months ago. Seriously, that had to be the most short-lived security scheme ever.

      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)

    by CatWrangler ( 622292 ) on Sunday February 19, 2006 @10:16PM (#14758159) Journal
    Now I can be screwed in 32 different states. Kinda like Madonna.

  • right... (Score:3, Funny)

    by smash ( 1351 ) on Sunday February 19, 2006 @10:21PM (#14758193) Homepage Journal
    Back to IP over avian carrier? :)

    smash.

    • Yeah.. I want to booby trap the message so that if anyone tries to "clone" the message for stealth decryption... *poof* instant feather cloud :-D
      • Yeah.. I want to booby trap the message so that if anyone tries to "clone" the message for stealth decryption... *poof* instant feather cloud :-D

        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 ;-)

    • 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)

    by noidentity ( 188756 ) on Sunday February 19, 2006 @10:23PM (#14758197)
    We need to put a stop to this quantum cloning. It is immoral and wrong. Who knows where it might lead!
    • No, Human Cloning is fine, it's the human-animal hybrid programs that must stop - they'll be the ruin of us all. Ruin I say, ruiiiiiiiin!!! Won't someone of the children-puppy hybrids?
    • Oh God!

      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!

      -
  • Just great. Now we can hack a form of encrypted transmission we don't even have yet...

  • Hmm, how seredipitous... (Score:5, Interesting)

    by kopasa ( 866116 ) on Sunday February 19, 2006 @10:27PM (#14758213)
    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...
    • The opening blurb about Captain Kirk only reinforces untrue stereotypes about the potential of quantum teleportation.

      That sounds like Captain Kirk's evil twin speaking.
    • Actually, the accuracy rate may not be a big issue depending on usage. I'm really wondering what time delay (if any) there is between the signal and the eavesdropper, depending on location. Maybe telecloning will one day become a usable form of realtime intersteller communication?
    • Even a 99% accurate clone would adhere to the uncertainty principle. And 99.9999998% would still be uncertain. There is no reason that in terms of real world cloning, a "useful" copy could be made. I knew this was going to be possible -- not because I'm trained in Quantum Mechanics, but because I'm a really, really good guesser.

      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.
    • The opening blurb about Captain Kirk only reinforces untrue stereotypes about the potential of quantum teleportation.

      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)

    by Anonymous Coward
    On average, I'm able to correctly decode 50% of the bits.
  • The submission is simply wrong: the 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."
    , but the summary says "eavesdropping on a quantum encrypted link can now be done without detection", which is exactly the opposite.
  • 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

  • IIRC (Score:2, Funny)

    by alx5000 ( 896642 )
    That reminds me of the Windows XP anticopy scheme. Long before it was even released publicly, the crack had already hit the street. Sweet.

  • Ah, yes! (Score:3, Funny)

    by sonofagunn ( 659927 ) on Sunday February 19, 2006 @11:43PM (#14758531)
    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!
  • It's a quantum party line!
  • 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 me

  • huh? (Score:2, Insightful)

    by sentientbrendan ( 316150 )
    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 increasi
    • (Disclaimer: IANAP, but I do have a bachelor's in EE and a fair amount of self-study.)
      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
  • Ahem, the authors may know a lot about quantum stuff, but they don't know anything about how fiber optics work.

    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

  • I wish people would look up the original press release instead of advertising the physorg tarpit.

    Here. [york.ac.uk]

    (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
  • a new form of quantum entanglement - multipartite entanglement

    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.

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