Figure 3

Evolution of (a) the estimated channel transmission, given by (20), (b) Bob’s shot noise estimate, given by (21), (c) the estimated excess noise, given by (22), and (d) the estimated key rate, given by (23), as a function of Bob’s photo detector imbalance. We have used \({T=0.1}\), \({g_{\text{TIA}}=10^{4}}\text{ V/A}\), \({\varepsilon _{\text{th}}=1.44\times 10^{-4}}\text{ Vrms}\), \({|\alpha _{\text{A}}|^{2}=1.25\times 10^{8}}\text{ s}^{-1}\), \({|\alpha _{\text{B}}|^{2}=1.56\times 10^{17}}\text{ s}^{-1}\), \({T_{s}=4}\text{ ns}\), \({dt=31.25}\text{ ps}\) and \({\text{RIN}^{\text{A}}_{\Delta f}=\text{RIN}^{\text{B}}_{\Delta f}= \text{RIN}_{\Delta f}=3\times 10^{-15}}\text{ Hz} ^{-1}\). The point corresponding to the balanced system, i.e. the “real” value, is identified by a star