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 …
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).
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
But my point still stands. ANYTHING they can make can leak out. Few things don't leak out, particularly if they're of value...like 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.
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.
“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.
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.
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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