Quantum Cryptography Improves by Factor of 100; Ready for Primetime?

By Andrew Moseman | April 20, 2010 4:13 pm

confidential secret documentsA quantum-encrypted future is a step closer this week after researchers announced a great advancement in speed: from fast enough to encrypt voice transmissions to fast enough to encrypt video.

For decades now scientists have tried to develop reliable quantum cryptography systems that take advantage of the quirks of quantum mechanics. Thanks to the Heisenberg Uncertainty Principle, for example, we know that you can’t measure a photon of light without altering it. Thus, the thinking goes, if you encode information into photons of light, no hacker could intercept the information without giving themselves away. In 2008, we covered the scientists who orchestrated a secure video conference by using a quantum key, a security key derived from the patterns of arriving photons. Now, the Toshiba Research Lab in Cambridge [England] has reported a secure bit rate of 1 MB/sec, which is over 100 times better than previously achieved, making it suitable for commercial application [Nature]. The team outlines this research in Applied Physics Letters.

Research leader Andrew Shields says the key to this advance in quantum key distribution (QKD) is the marvelously named “semiconductor avalanche photodiodes,” in which a photon hits a bit of semiconductor to trigger an “avalanche” of electric charge. It takes time for that avalanche to build and pass, which limits the detector’s rate. New photodiodes can sense smaller avalanches and, hence, run faster, Shields says [ScienceNOW]. There’s also a stabilization system to adjust for the fiber-optic cables heating up.

The encryption method is considered to be perfect because it uses extremely long encryption keys only once and so cannot be cracked using crypto-analysis [Computer Weekly]. That big claim will be put to the test in October in Japan, when a quantum key distribution demonstrator will test the secure key across a wider “metropolitan network”, which may ultimately lead to the technology becoming commercially available [Wired.co.uk]. Someday many scientists hope to expand to an entire computer network employing quantum mechanics, including the possibility of messages encrypted with quantum entanglement. But now that researchers are surmounting some of the technical challenges, the next problem is, naturally, cost.

Related Content:
80beats: Quantum Cryptography Takes a Step Toward Mainstream Use
80beats: Harnessing Quantum Weirdness To Make Spy-Proof Email
DISCOVER: Future Tech: The quantum cryptography race is on

Image: iStockphoto

CATEGORIZED UNDER: Physics & Math, Technology
  • ChH

    Why couldn’t a hacker intercept, measure and divert photons, then retransmit them based on the measurements?

  • Brian Too

    Although this is progress and I applaud that, remember the iron-clad rule of security. Make one part of the system more secure (perfect, even) and the attacks will simply move elsewhere.

    These days that seems to be the people; legitimate users can often be conned into doing something they should not do. Security systems are often rendered totally useless by authorized clients making a wrong decision and bypassing all controls. There are even plenty of users who think that security is an Information Technology problem and if they expose a system to risk, it’s still someone else’s responsibility!

  • John

    ChH I think the problem is one of the measured state of the photons when they leave the senders device. These quantam states can not be duplicated by any means. The receivers’ device is expecting a this specific quantum state. When the hacker measures the photons the quantum state must change by the nature of the Heisenberg Uncertainty Principle. This is the beauty of the system.

  • dO_ob

    In 2008, concerned students at MIT worked to develop a way to hack into the photon stream itself using theororetical mechanical transferrance. Late last year they succeeded. The secret to hacking the stream is to twist the


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