Fig. 1. Fidelity change over the gain value g between −2 and 2 with a varying amount of losses in the two-mode squeezed state.

Fig. 2. Fidelity curves over the gain value g between −2 and 2 changing as the loss rate r2 increases.

Fig. 3. Transmission fidelity of a photonic qubit with numerically optimized gains. Here, q is the squeezing parameter of the initial two-mode squeezed state; the maximum fidelity curve is numerically obtained and plotted with the thick dashed curve, and that of q=1 is plotted with the thin dotted curve. It is impossible to attain fidelity higher than the classical limit (horizontal dotted line) with loss bigger than about 11%.

Fig. 4. Log negativity of the two-mode squeezed state in terms of the loss rate r2. On the contrary to the fidelity, there is no inversion in order with increasing loss.