Slashdot Mirror

← Back to Stories (view on slashdot.org)

Theoretical Breakthrough For Quantum Cryptography

Posted by Soulskill on from the add-qutrits-to-your-super-scrabble-words dept.

KentuckyFC writes "Quantum cryptography uses the quantum properties of photons to guarantee perfect secrecy. But one of its lesser known limitations is that it only works if Alice and Bob are perfectly aligned so that they can carry out well-defined polarization measurements on the photons as they arrive. Physicists say that Alice and Bob must share the same reference frame. That's OK if Alice and Bob are in their own ground-based labs, but it's a problem in many other applications, such as ground-to-satellite communications or even in chip-to-chip communications, because it's hard to keep chips still over distances of the order of the wavelength of light. Now a group of UK physicists have developed a way of doing quantum cryptography without sharing a reference frame. The trick is to use entangled triplets of photons, so-called qutrits, rather than entangled pairs. This solves the problem by embedding it in an extra abstract dimension, which is independent of space. So, as long as both Alice and Bob know the way in which all these abstract dimensions are related, the third provides a reference against which measurements of the other two can be made. That allows Alice and Bob to make any measurements they need without having to agree ahead of time on a frame of reference. That could be an important advance enabling the widespread use of quantum cryptography."

7 of 116 comments (clear)

  1. Stay away from this by Anonymous Coward · · Score: 5, Funny

    One thing, with quantum crypto, the code changes when you look at it. In other words, you have to know the key before seeing it.

    Two, it kills a LOT of cats! You get the code right, and BAM! dead cat.

    PETA will be against this!

  2. You lost me at hello... by PPalmgren · · Score: 4, Funny

    Boy am I glad I didn't pursue that physics major. The only thing I got out of that is that Alice and Bob needed a marriage counselor to reconcile their differences.

    Anyone mind converting that attempt in layman's terms to something useful, like a car analogy?

    1. Re:You lost me at hello... by mrsurb · · Score: 5, Informative

      I'll give it a shot.

      Alice wants to get out of her car and into Bob's car. In laboratory conditions both cars are perfectly still so it's easy. Out on the freeway travelling at high speeds it's a recipe for disaster.

      But these clever engineers have come up with a wonderful design for a semi-trailer that both cars can sit on while being driven down the freeway. Now Alice and get out of her car and into Bob's car for that secret rendezvous. In the middle of the freeway.

    2. Re:You lost me at hello... by JaneTheIgnorantSlut · · Score: 4, Funny

      Do Carol and Ted know about this?

  3. "This solves the problem by embedding it...." by Conspiracy_Of_Doves · · Score: 5, Insightful

    "This solves the problem by embedding it in an extra abstract dimension, which is independent of space."

    Has it occurred to anyone else how UNBELIEVABLY FRIGGIN' COOL it is that a line like that shows up in an article that is talking about building an actual, physical device?

    --

    Technoli
    1. Re:"This solves the problem by embedding it...." by K.+S.+Kyosuke · · Score: 4, Funny

      Has it occurred to anyone else how UNBELIEVABLY FRIGGIN' COOL it is that a line like that shows up in an article that is talking about building an actual, physical device?

      I can vividly see the label on the unit packaging: "Dimensions: 0.45 x 0.3 x 0.25 x 1.7 m"

      --
      Ezekiel 23:20
  4. Re:Just wondering .. by ElAurian · · Score: 4, Funny

    They'd have to reroute the plasma flow and depolarise the graviton matrix first. Duh.