Cracking commercial quantum cryptography: how we did it, in pictures

We used the same attack to crack systems from two vendors; here is one of them. Below you can see the secure communicating boxes with their internals exposed, Alice at left and Bob at right. In a typical installation they get separated by tens of kilometers of fiber. Our main interest in this attack was to gain control of the single-photon detector in Bob; the next picture shows a close-up of its electronics board.

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