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Quantum Cryptography Slowed by "Dead Times"

Posted by CmdrTaco on from the what-i-call-the-time-before-my-first-cup-of-coffee dept.

coondoggie writes "Researchers at the National Institute of Standards and Technology and the Joint Quantum Institute said today that technological and security issues will stall maximum transmission rates at levels comparable to that of a single broadband connection, such as a cable modem, unless researchers reduce "dead times" in the detectors that receive quantum-encrypted messages."

75 comments

  1. Use a cat! by Anonymous Coward · · Score: 1, Funny

    Then maybe it won't be dead!

    1. Re:Use a cat! by Anonymous Coward · · Score: 0

      Why are all first posts marked as redundant? It's the first post, it can't be redundant!

    2. Re:Use a cat! by sveard · · Score: 1

      I think some people reason that it is not contributing anything useful to the discussion so they mod it redundant.

    3. Re:Use a cat! by 91degrees · · Score: 1

      Well, of course it's the first post. Telling you so is superfluous information.

    4. Re:Use a cat! by maxwell+demon · · Score: 1

      But in this case, the first post doesn't state it's the first post. It tries to make a joke based on Schrödinger's cat.

      --
      The Tao of math: The numbers you can count are not the real numbers.
    5. Re:Use a cat! by 91degrees · · Score: 2, Funny

      Ah. In that case I put it down to a reflex action. Or maybe slashcode has been altered so that it always mods down the first post as redundant as a matter of principle.

    6. Re:Use a cat! by Anonymous Coward · · Score: 0

      But wouldn't that just be offtopic?

  2. This could be a problem ... by ScrewMaster · · Score: 1

    "Quickly, Bones! Transmit the quantum-encrypted packet!"

    "I can't ... it's DEAD, Jim!"

    --
    The higher the technology, the sharper that two-edged sword.
    1. Re:This could be a problem ... by Anonymous Coward · · Score: 0

      Am I the only one who thought this post would have better read:

      "Quickly, Kiff! Transmit the quantum-encrypted packet!"
      "I can't ... it's DEAD, sir!"

    2. Re:This could be a problem ... by Frumious+Wombat · · Score: 1

      Basically, this translates to 'Engineers, put down the Halo controller and get back to work". Early telephones were nothing to call home about either, now they don't even need wires, are small enough for the dog to swallow, and have settings for any feature you can imagine, except possibly "Stun". (note, I'm not sure about this, as I'm still reading the manual that came with my last phone) Improvements will be made, and in a few years you'll look at your old hyperthreaded multi-core biege box and wonder why you ever put up with it.

      --
      the more accurate the calculations became, the more the concepts tended to vanish into thin air. R. S. Mulliken
  3. I have no clue what this is about by Wannabe+Code+Monkey · · Score: 4, Insightful

    I read the summary and didn't understand a single part of it, but it sounded interesting and I though, "The article must explain things better." But after reading the article I still have no idea what is going on. Is there someone else that could maybe help explain what this story is all about?

    --
    We always knew Comcast was corrupt, here's the proof: http://tech.slashdot.org/comments.pl?sid=1909890&cid=34545432
    1. Re:I have no clue what this is about by Anonymous Coward · · Score: 5, Funny

      hardware which may or may not exist yet is going to run slowly unless said hardware is improved at some time in the future when it may or may not exist.

    2. Re:I have no clue what this is about by Anonymous Coward · · Score: 0, Informative

      The problem comes when researchers attempt to observe the time their predictions are based on. As the waveform collapses from a simultaneous dead and non-dead state to reveal its true underlying characteristic, novel techniques created by S. King et al. become necessary to fill the volume of space between the two sides.

    3. Re:I have no clue what this is about by mangu · · Score: 1

      Maybe you need a quantum decrypter to understand it...

    4. Re:I have no clue what this is about by ShakaUVM · · Score: 1

      Don't understand? This lolcat will explain everything: http://www.thecheezburgerfactory.com/completestore/128351432363906250OHHAIIcollap.jpg

    5. Re:I have no clue what this is about by kmac06 · · Score: 3, Informative

      Most single photon detectors are a reverse biased photodiode. When a photon strikes it, it creates an electron-hole pair, which then collide with other electrons creating more pairs, making an avalanche effect that results in a pulse, indicating a photon. After this pulse, there is some "dead time" before everything is settled down back to its original state. During this dead time, if a photon hits the detector it will not be detected. Typical dead time is about ~50 ns, limiting the device to about 20M counts/second.

    6. Re:I have no clue what this is about by Anonymous Coward · · Score: 0

      hardware which may or may not exist yet

      No no no. It both exists and doesn't exist at the same time, until someone opens the box.
    7. Re:I have no clue what this is about by TheRaven64 · · Score: 2, Funny
      Einstein explained radio like this:

      You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat. Quantum cryptography is the same, the only difference is that the absence of cat may or may not be alive.
      --
      I am TheRaven on Soylent News
    8. Re:I have no clue what this is about by vininim · · Score: 1

      Dead-time is the period of time in which single-photons detectors are recovering from an avalanche(the process wich amplifies the current induced by the photon), and can not detect another photon. This time was neglible to the speed QKD was being tested, but the researchers now have found that it is a limiting issue with current improvements. It's just that conventional detectors made of silicon are showing to be not useful beyond some transmission speed.

    9. Re:I have no clue what this is about by jne_oioioi · · Score: 0

      ..at which point it might or might not transmutate into a cat ?

    10. Re:I have no clue what this is about by Anonymous Coward · · Score: 0

      that was very succinct pause not.

    11. Re:I have no clue what this is about by zildgulf · · Score: 1

      It's all because the Heisenberg cats are controlling the transmission. They control the horizontal, the vertical, and the outer limits of them there quantum encrypted packets, but all these cats want to do is lick themselves and sleep.

    12. Re:I have no clue what this is about by zippthorne · · Score: 1

      I think you may have conflated diode detectors with photomultiplier tubes.

      --
      Can you be Even More Awesome?!
    13. Re:I have no clue what this is about by kmac06 · · Score: 1

      I don't think I did...did I say something wrong? Photomultiplier tubes are another type of single photon detector, but I was describing an APD.

    14. Re:I have no clue what this is about by UnHolier+than+ever · · Score: 1

      State-of-the-art really expensive detectors have dead time of about 50ns. Typical dead times are more like 10us.

    15. Re:I have no clue what this is about by kmac06 · · Score: 1

      It's good to be in a well-funded research group :)

    16. Re:I have no clue what this is about by UnHolier+than+ever · · Score: 1

      *grumble grumble*

      yeah, well....my laser is bigger than yours!!!!!

      (It probably is - in volume.)

    17. Re:I have no clue what this is about by n3tcat · · Score: 1

      Should we call this Schroedingers Law of technology?

  4. How do they know it's dead? by pathological+liar · · Score: 1

    You changed the outcome by measuring it!

  5. How can you have security issues? by LiquidCoooled · · Score: 1

    How can you have security issues with quantum tech?

    Anyone would think this whole industry was smoke and mirrors.

    Additionally, isn't it possible to multiplex the connections and gain parallel speedups?
    My current understanding of quantum tech is the data still goes by traditional means but they use a quantum *handwaving* thing to ensure the bits sent traditionally haven't been messed with.

    --
    liqbase :: faster than paper
    1. Re:How can you have security issues? by ScrewMaster · · Score: 3, Funny

      but they use a quantum *handwaving* thing to ensure the bits sent traditionally haven't been messed with.

      It's a Force thing. The quantum circuits say, "you don't need to see his information" and anyone trying to listen in simply waves the information on its way.

      --
      The higher the technology, the sharper that two-edged sword.
    2. Re:How can you have security issues? by The+Standard+Deviant · · Score: 0

      . . .They use a quantum *handwaving* thing. . . I think you'll find the technical term is a hand-wave function.
    3. Re:How can you have security issues? by SocratesJedi · · Score: 2, Informative

      My current understanding of quantum tech is the data still goes by traditional means but they use a quantum *handwaving* thing to ensure the bits sent traditionally haven't been messed with. It works under a simple principle: Bits coming down a traditional wire from Alice to Bob can be intercepted by Eve, read and then re-generated down the wire so that neither Alice nor Bob know that Eve has read the message. Quantum cryptography exploits a property of a quantum system that says that if you measure a system: (a) you change the system and (b) you can't get all of the original information about the system back out [think Heisenberg Uncertainty Principle: if you know position accurately, you don't know velocity accurately; there are other pairs of physical quantities that have this relationship too]. (a) and (b) together imply that Eve can't measure a signal and then re-create it and send it on it's way without Alice and Bob noticing a problem with the statistics they expect to observe. The benefit of quantum cryptography is that Alice and Bob know that there was an interceptor if there was one and can react accordingly. Because it is relatively low-throughput, usually only some garbage data like a key is exchanged and then more traditional means of cryptography can be used.

      IAAUP (I am an undergraduate physicist), but if YAAP and know better, please correct me if I'm at all wrong.
  6. meta by TheSHAD0W · · Score: 4, Insightful

    So use the quantum cryptography to exchange a large classic private key.

    1. Re:meta by Ctrl-Z · · Score: 1

      Why? Who cares if you can exchange keys safely if the cryptosystem is broken?

      --
      www.timcoleman.com is a total waste of your time. Never go there.
    2. Re:meta by maxwell+demon · · Score: 1

      Why? Who cares if you can exchange keys safely if the cryptosystem is broken? The solution is simple: Use a non-broken cryptosystem.
      --
      The Tao of math: The numbers you can count are not the real numbers.
    3. Re:meta by itsdapead · · Score: 2, Informative

      So use the quantum cryptography to exchange a large classic private key.

      AFAIK that's basically how it works - the quantum link can't transmit any actual "information" - it just allows Alice and Bob to exchange a big random number in a way that allows them to detect whether Eve is listening in. Even that requires a "conventional" information link and several rounds of back-and-forth commuinication to "agree" on the key.

      I guess the other problem is that to be 100% guanranteed uncrackable the key needs to be the same length as the plaintext - "cycling" the key introduces redundancy that could be open to a "brute force" attack, and part of the motivation behind quantum cryptography is that the guys in the next lab are trying to build quantum computers that could eat that sort of calculation for breakfast...

      --
      In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
    4. Re:meta by Teresita · · Score: 1

      AFAIK that's basically how it works - the quantum link can't transmit any actual "information" - it just allows Alice and Bob to exchange a big random number in a way that allows them to detect whether Eve is listening in

      A Britney song is just a big random number, and Alice could be RIAA and Bob could be the Britney fan, and this technology will allow RIAA to know if Bob is siphoning off data to an un-DRM'd format such as MP3. Expect to see millions of dollars pouring into this research soon.

    5. Re:meta by Anonymous Coward · · Score: 0

      That's how public key cryptography has always worked. Sheesh, please mod parent down or I'll lose my faith in the moderation system here. Overrated.

    6. Re:meta by X0563511 · · Score: 1

      OK, lets see your algorithms, which cannot be defeated by quantum computing.

      Oh, harder than it sounds, isn't it?

      --
      For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
    7. Re:meta by owlstead · · Score: 1

      AES-256 is thought to be quite indifferent to quantum computing. It's mostly the regular asymmetric algorithms that are targeted by quantum computing.

    8. Re:meta by TheSHAD0W · · Score: 1

      It's really only cryptosystems with public/private key combinations which are subject to quantum analysis. "What two numbers multiplied make up this number?" This is the sort of question best posed to a quantum computer. Trying to do redundancy analysis on a high-grade key, even with a quantum computer backing you up, isn't going to work very well.

    9. Re:meta by Anonymous Coward · · Score: 0

      If AES-256 works, I'll take Serpent-256. Very similar to AES but has 32 rounds rather than AES's 10, 12 or 14 (depending on key size), and somewhat faster than AES-256. (AES wins speed with a smaller key)

    10. Re:meta by itsdapead · · Score: 1

      A Britney song is just a big random number

      I know it is a depressing thought, but no - its not random, its pre-determined. However, any random number could be a Britney song (if an infinite number of monkeys can type the works of Shakespeare then Britney should be a cinch!) so any random number generator is a potentially infringing device under the DMCA.

      If God does play dice with the universe he better not roll the HD-DVD encryption key...

      --
      In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
    11. Re:meta by SwordsmanLuke · · Score: 1
      Three words: One time pad.

      It seems to me that this is exactly the type of encryption the GP was referring to when he referenced a "private key." In any case, there already exists unbreakable[1] encryption through OTPs. The problem is coordinating them between parties, which is the problem public-key encryption solves. If (in this case through quantum crypto) we can safely transmit OTPs, we can have perfectly secure communication over any channel of our choosing.

      [1] "...if the key is truly random, never reused, and kept secret, the one-time pad provides perfect secrecy."
      http://en.wikipedia.org/wiki/One_time_pad/

      --
      Any plan which depends on a fundamental change in human behavior is doomed from the start.
    12. Re:meta by Anonymous Coward · · Score: 0

      which in turn can be broken by quantum computer in 2 sec.

  7. Is this really a problem? by Anonymous Coward · · Score: 1, Informative

    Most of these implementations (like http://www.idquantique.com/products/vectis.htm) use quantum mechanics only for key exchange and not for generating a one time pad.

  8. Organization often confussed with... by Nezer · · Score: 4, Funny

    It should be noted that the Joint Quantum Institute does *entirely different* research than the Quantum Joint Institute located in Amsterdam.

    1. Re:Organization often confussed with... by Anonymous Coward · · Score: 0

      splitters!

    2. Re:Organization often confussed with... by Anonymous Coward · · Score: 1, Funny
      It should be noted that the Joint Quantum Institute does *entirely different* research than the Quantum Joint Institute located in Amsterdam.

      The latter, presumably, conducting most of their meetings in coffee shops.

    3. Re:Organization often confussed with... by Anonymous Coward · · Score: 0

      Short-term memory loss tends to dominate the itinerary of every meeting.

    4. Re:Organization often confussed with... by Anonymous Coward · · Score: 0

      Duuuuude.... I think my wavefunction is talking to me!

  9. Quantum encrypted messages is nonsense by temcat · · Score: 2, Informative

    The only quantum thing in quantum cryptography is key distribution, or key generation, to be more precise.

  10. Amazing! by neiko · · Score: 2, Insightful

    Quantum transmission speeds will be slow until someone figures out how to speed it up.

  11. Dead time in scientific instruments by confused_demon · · Score: 5, Informative
    I've got some clue what's meant by dead time for scientific measurements. Basically, dead time is the amount of time after an event is measured that it takes for the detector system to reset. For example, if you're using a Spectroscopy Amplifier (or another shaping amplifier) dead time comes from two signals coming too close to each other. Shaping amplviers are setup so that a square wave (or a step) would produce a characteristic shape (usually a flat-topped Gaussian shape, or a trapazoid). The purpose of the shaping is to allow for the imperfections in detector to be integrated into a single measurement which is easier to process (signal being generated slowly or slowly getting through prior parts of the circuit). If a second signal occurs while the shaping is still taking place it will be integrated into the output of the shaping amplifier resulting in a garbled output for both inputs.

    The net result is that as you send more and more signals to a spectroscopy system, the dead time increases and eventually you get no output because the electronics are constantly saturated. A well put together system will include a measurement of dead time so you know how many signals you're loosing.

    1. Re:Dead time in scientific instruments by Anonymous Coward · · Score: 0

      A well put together system will include a measurement of dead time so you know how many signals you're loosing.

      AARUARAARRAGH!

      I can't take it anymore!

      "lose" = "to misplace, to fail to keep track of"
      "loose" = "to set free, to give slack"

      Thanks for the nice explanation--it truly is useful. But this word usage thing is driving me crazy! It's not just you--it's a lot of people.

    2. Re:Dead time in scientific instruments by Anonymous Coward · · Score: 0

      Some kind of grammatically-aware-on-the-fly-spellchecking Firefox plugin is perhaps in your future.

      After all, what have you got to loose!

  12. Tell God you support Quantum Neutrality by Anonymous Coward · · Score: 2, Funny

    That fucker is just trying to throttle bandwidth unless the matter-energy providers and Waveform Collapsing Union pay his exorbitant Higgs access fees.

  13. So much for... by MeditationSensation · · Score: 1, Insightful

    ...spooky action at a distance and breaking the speed of light barrier. ;-)

  14. Quantum cryptography is a sham by Anonymous Coward · · Score: 0

    Who cares how fast or slow it is?

    Quantum crypto **does not address trust**. Without trust encryption is pointless, useless and just plain stupid.

    Without trust the security properties of the 'non-classical' portion of the system are useless as there is no way to crypographically bind the classic and quantum channels.

    Quantum crypto rocks in that it does provide the ultimate in forward secrecy for OTP systems..but at the same time its useless.

  15. Latency. by ZwJGR · · Score: 1

    It sounds to me like they mean:
    The read latency of the quantum receiver is/will be too high.
    Hence throughput speeds will be limited.

    Therefore someone should find a way to reduce this latency, such that transmission speeds can be increased.

    --
    There is no psychiatrist in the world like a puppy licking your face - Ben Williams
  16. store it by Arthur+B. · · Score: 2, Interesting

    If you plan to be sending encrypted data to someone, you can exchange a one time pad the size of the data through the quantum channel. When you need to communicate, just use the one time pad at a speed not limited by quantum cryptography.

    You can continuously refill this one time pad thus the real limitation is
      - your average rate of encrypted data over the year
      - disk space (but that's very cheap)

    peak speed of encrypted data transmission is not constrained

    --
    \u262D = \u5350
    1. Re:store it by kestasjk · · Score: 1

      With quantum cryptography you can read data off the link, but by reading it you change it.
      So someone could read the whole one time pad and decrypt it as it's sent via conventional means, and the person receiving wouldn't know the one time pad had been read until they had the incorrect encrypted message.

      You could checksum the random pad, but it doesn't inspire much confidence. (I'm only barely starting quantum physics in uni so I'm a layman)

      --
      // MD_Update(&m,buf,j);
  17. Amazing... by packetmon · · Score: 0, Offtopic

    You know, I'm glad someone explained this all. Critical network and security functions through a flexible content driven, media friendly derivative with parallel facing vector approaches which may or may not be hindered by dead times. This is an extremely proficient alternative to the traditional approach of deploying modular - forward facing designs and parallel vectors. The ramifications of parallelizations are altogether to high to ignore. So yes, I didn't understand it either. Did you?

    --
    Infiltrated dot Net
  18. We demand an immediate release of the cat by 140Mandak262Jamuna · · Score: 3, Funny

    The Society for the prevention of cruelty to Animals vehemantly condemns subjecting animals to needless cruelty in the name of scientific experiments. Release Schrodinger's Cat Now!

    --
    sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
    1. Re:We demand an immediate release of the cat by maxwell+demon · · Score: 1

      We'd do, but opening the box might kill it.

      --
      The Tao of math: The numbers you can count are not the real numbers.
    2. Re:We demand an immediate release of the cat by JonnyRo · · Score: 1

      Haha, you reminded me of this crazed LolCat

      --
      blog.jonnyro.com - Jeep/IT blog
    3. Re:We demand an immediate release of the cat by Rick+Genter · · Score: 1

      Too late...

      Or maybe not...

      --
      Don't underestimate the power of The Source
  19. I don't think this is that important by Omnifarious · · Score: 1

    AFAIK, there are no quantum computing algorithms that do more than effectively halve the effective key length for symmetric key cryptography (things like AES, DES and Blowfish). This means that if you use quantum cryptography to exchange symmetric keys, you should then be able to continue on using these kinds of ciphers in a normal communications channel.

    --
    Need a Python, C++, Unix, Linux develop
  20. Confucius says... by flyingfsck · · Score: 1

    Quantum encryption is to be slowing unless some is to be speeding it up.

    --
    Excuse me, but please get off my Pennisetum Clandestinum, eh!
  21. most insightful by Anonymous Coward · · Score: 0

    most insightful +5 funny post ever.

    (in this lowly AC's opinion)

  22. That Explains It..... by IHC+Navistar · · Score: 1

    I guess that explains the horrible connection speeds at the county cemetary.....

    Ok. Ok. Ok..... Mod -1 BadJoke

    --
    Knowing Google's lust for data collection, the Soviet Union is still alive and well inside the psyche of Sergey Brin....
  23. Security is irrelvant by Anonymous Coward · · Score: 0

    Unless someone's found a way to eavesdrop on quantum entanglement.

    Didn't think so...

  24. Ah, now I get it... by bwcbwc · · Score: 1

    Quantum Vaporware. In fact, isn't vaporware in general a quantum phenomenon? A software maker pre-announces a product, but we are unable to tell if the product actually exists until it is released...

    --
    We are the 198 proof..