Fig. 3
From: Experimental measurement-device-independent quantum digital signatures
Secure key rates vs. distance. MDI-QKD (top diagram) and QKD (centre and bottom diagrams) secure key rates for a Z (X) basis probability equal to 80% (20%) and a security parameter \({\epsilon _{{\rm{sec}}}}\) ≲ 10−10 are shown as a function of distance. Because the reconfigurable scheme is symmetrically deployed, the distance between Alice and Bob (top) is approximately twice the distance between Alice and Charlie (centre) and Bob and Charlie (bottom). All the distances have been calculated assuming 0.2 dB/km attenuation on the channel, except for the data points indicated by stars, where a real fibre was used. The projected time to attain the shown key rates is 25 h of which 3 min are spent on QKD and the rest on MDI-QKD, to balance their key rates. The fitting lines are the result of a numerical simulation with the parameters mentioned above and the following additional ones: Charlie’s insertion loss, 1.1 dB; detectors’ efficiency and temperature, 20% and 0°, respectively; afterpulsing, 4%; dark count probability per gate, 1.6 × 10−5; error correction coefficient, 1.16
