back to article Boffins pack more info onto photon for faster quantum key distro

Researchers have packed extra information onto single photons to speed up quantum key distribution (QKD) systems. QKD uses a characteristic of quantum mechanics to protect keys used to encrypt data using classical crypto schemes: if Eve tries to snoop on the key Alice is sending Bob, the quantum state/s a photon carries are …

  1. Mark 85

    Interesting that DARPA is looking into and funding research into better encryption and certain agencies are trying to ban it or make it breakable. At what point do the agencies start a pissing contest against DARPA in Congress?

    1. Anonymous Coward
      Anonymous Coward

      At what point do the agencies start a pissing contest against DARPA in Congress?

      Never. You forgot the "D" in the DARPA's name. There is no contradiction between wanting unbreakable crypto for your military forces' and government's use, and denying it to your population and the "aliens" (who are obviously too stupid to understand the math behind it themselves).

      1. Charles 9

        Yes there is. Simply put, what YOY can make, someone else can copy or re-make, simply because you proved it possible. IOW, never make something you're not prepared to have turned against you.

      2. Anonymous Coward
        Anonymous Coward

        here is no contradiction between wanting unbreakable crypto for your military forces' and government's use, and denying it to your population

        Until you are more worried about your own military / government than your population.

        I suspect you want to eavesdrop on congress more than on Joe Doe

    2. Shaha Alam

      oh its fine, they're not against the concept of unbreakable encryption. they're against you* having unbreakable encryption.

      *you means anyone outside the power elite^

      ^outside the power elite means you

      1. Charles 9

        But my point still stands. ANYTHING they can make can leak out. Few things don't leak out, particularly if they're of unbreakable encryption. The fact it's public knowledge (rather than black--deny it even exists) indicates they don't seem to care too much about it these days.

  2. John Smith 19 Gold badge
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    So it's a pulse position modulation scheme

    Given that system timing can easily be down to the picosecond a 1 mbs signal could have a million states in it. PPM is an old school tech used in old radio control model radio systems.

    That tradeoff is probably a bit excessive but suggests there's a fair bit of stretch in this technology.

    BTW DARPA's motto is "Creating and avoiding strategic surprise."

    IOW Knowing everything our enemies will do before they do it while ensuring they have no idea what what (or when) we are doing something.

  3. DainB Bronze badge

    Are we there yet ?

    I mean can we reliably produce entangled photons on demand and not at the rate of 1 in a few millions ?

    1. deconstructionist

      Re: Are we there yet ?

      Only linear optics provide accurate timings , hence why the Oil and pharmaceutical industry are still using BNC so I am not sold on this yet , and entanglement fields are still experimental musings rather than anything of practical use yet.

  4. Flakk

    “Using a four dimensional (d = 4) state space represented by four distinct time bins and its conjugate state space in the Fourier transform domain, we realise a QKD that generates an ultra-high secret key rate.”

    I read this once, and it made absolutely no sense. I re-read it, and again I had difficulty coming to grips with the concepts presented. The third time I read it, I used the voice of ST:TNG's Commander Data to carry the words into my mind. As I am conditioned to simply accept the incomprehensible techno-gibberish spoken by that character, I was able to move on.

  5. Jim Mitchell


    "qudit"? I would think that qubyte would be the obvious upgrade in capacity from qubit.

    1. Flakk

      Re: qudit?

      Are you sure that wouldn't be a quibble?

  6. DCFusor


    There are far too many "ifs" in their thinking.

    First... Shannon - they need to do some reading about bit rate vs signal to noise. Even if they had an actually-new approach, it'd be covered there. Shame these young'ns don't know history of a field they claim to have some command of.

    Second, this would all be "if" they could produce suitable photons on a tight time schedule, which I hear is still quite an issue, maybe not even theoretically soluble.

    If your feet hurt, it's probably the spikes on my lawn, and there's an easy way to avoid those.

  7. John Smith 19 Gold badge
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    multi bits were a thing even in the days of dial up modems.

    How did you think they got 56kbs over a voice grade phone line with an analog bandwidth of about 3KHz.?

    TBH I had not realized that "time in slot" was a parameter that could be safely manipulated.

    However making this work in a quantum context is still a major achievement.

    Well done to the team involved, especially for using more or less OTS hardware to do so.

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