Detecting entanglement of quantum channels

Chaojian Li,Bang-Hai Wang,Bujiao Wu,Xiao Yuan

Figure 2. Entanglement witness values for the noisy CNOT and SWAP gates as a function of the noise parameter p. Since the witnesses have different normalization, we only plot different witness values under normalization. In particular, for the noisy CNOT gate, the second and third witnesses have the same value after proper normalization. For the noisy SWAP gate, they all have the same value after normalization.