Figure 1

(a) Beam-splitter model with signal attenuation. An extra EPR state is presented and one mode of which is coupled with the signal mode to introduce the source noise. This is similar to the conventional detector model [11]. (b) Beam-splitter model with signal amplification. The extra EPR state intervenes through coupling the mode sent to Alice and parameters are adjusted so that the EB scheme is equivalent to the PM scheme. (c) Our model. A neutral party Fred is presented who implements a unitary Gaussian transformation to introduce the source noise to the signal. The capital letters represent quantum states at each position.Reuse & Permissions

Figure 2

Secret key rate as a function of the transmittance of the channel in no-switching protocol with reverse reconciliation. The solid line stands for our model, dashed line for the beam-splitter model, and dotted line for the untrusted source noise model. Data are acquired under the variance of $V=20$, and the channel’s excess noise is chosen to be $\epsilon =0.04$. (a) Signal attenuation with source parameter $T_A=0.9$ and ${\epsilon }_A=0.1$. (b) Signal amplification with source parameter $T_A=1.1$ and ${\epsilon }_A=0.1$.Reuse & Permissions

Figure 3

Secret key rate as a function of the transmittance of the channel in no-switching protocol with direct reconciliation. The solid line stands for our model, dashed line for the beam-splitter model, and dotted line for the untrusted source noise model. Data are acquired under the variance of $V=20$, and the channel’s excess noise is chosen to be $\epsilon =0.04$. (a) Signal attenuation with source parameter $T_A=0.9$ and ${\epsilon }_A=0.1$. (b) Signal amplification with source parameter $T_A=1.1$ and ${\epsilon }_A=0.1$.Reuse & Permissions