- cross-posted to:
- phys@rss.ponder.cat
- Melllvar ( @charonn0@startrek.website ) English9•26 days ago
What exactly are they trying to accomplish? The article talks about sending entangled photons down a fiber optic… but that just sounds like ordinary fiber with extra steps.
- Che Banana ( @The_Che_Banana@beehaw.org ) English4•25 days ago
Extra quantum steps
- YtA4QCam2A9j7EfTgHrH ( @YtA4QCam2A9j7EfTgHrH@infosec.pub ) English2•25 days ago
I’m guessing for quantum cryptography. It would allow you to have perfect crypto (assuming the non quantum hardware isn’t hacked (a big if)).
- Sekoia ( @Sekoia@lemmy.blahaj.zone ) English1•25 days ago
You can have post-quantum cryptography using classical computation, though
(“Simply” pick a problem with no quantum acceleration. I think Elliptic Curves Cryptography works, but I’m not an expert)
- YtA4QCam2A9j7EfTgHrH ( @YtA4QCam2A9j7EfTgHrH@infosec.pub ) English3•25 days ago
Quantum crypto is different than cracking encryption with a quantum computer. The point of quantum crypto is that the key exchange is perfectly secret. If it is observed, the people exchanging keys will know due to entanglement bs that I’m too dumb to understand.
But you basically get the perfect uncrackable encryption of one time pads without having to manage one time pads.
- Sekoia ( @Sekoia@lemmy.blahaj.zone ) English3•25 days ago
Oh yeah, that. My bad, mixed 'em up.
The original algorithm doesn’t use entanglement, though! Just the fact that measurements can change the state. You can pick an axis to measure a quantum state in. If you pick two axes that are diagonal to each other, measuring a state in the “wrong” axis can give a random result (the first time), whereas the “right” one always gives the original data.
So the trick is to have the sender encode their bits into a randomly-picked axis per bit (the quantum states), send the states over, and then the receiver decodes them along a random axis as well. On average, half the axes will match up and those bits will correspond. The other bits are junk (random). They then tell each other the random axes they picked, which identifies the right bits!
They can compare a certain amount of their “correct” bits: if there’s an eavesdropper, they must have measured in the wrong state half the time (on average). Measurement changes the state into its own axis, so the receiver gets a random bit instead of the right one half the time. 25% of the time, the bits mismatch, when they should always correspond.