Fig. 5: The net key gain per pulse \(\hat{G}\) (key rate) vs. transmissivity η of the optical channel.
From: Finite-size security of continuous-variable quantum key distribution with digital signal processing
The abscissa represents attenuation in decibel, i.e., \(-10\,{\mathrm{log}\,}_{10}\eta\). We assumed that the optical pulse that Bob receives is given by randomly displacing a coherent state to increase its variance by a factor of (1 + ξ). a The asymptotic key rate for various values of ξ. b The key rate for various values of ξ when the pulse number is finite (N = 1011). c The key rate without the excess noise (ξ = 0) along with the repeaterless bound (PLOB bound) of the secure key rate in the pure-loss channel55. d The key rate with the excess noise of ξ = 10−3.0.
