Figure 1

(a) EB scheme based on Alice heterodyning one-half of the mode of the Einstein-Podolsky-Rosen (EPR) [23] state and Bob homodyning the other half, with Eve only attacking the signal. (b) LOIA consisting of attacking the signal beam with a general Gaussian collective attack and attacking LO with intensity attenuation by a non-changing phase attenuator A such as a beam splitter whose transmission is variable. U is unitary operation and $X_E$ is Eve's intercepted mode. (c) LOIA with U being a beam-splitter transformation and Eve's ancilla modes $X_{E0}$ and $X_{E2}$ being the EPR pairs with variance $N$, and $X_{E1}$ is the intercepted mode. This signal attack is also called an entangling cloner attack.Reuse & Permissions

Figure 2

Reverse reconciliation pseudosecret key rate and the truly secret one vs channel transmission $T$ under LOIA. Solid lines are secret key rate estimated by Bob without monitoring LO intensity and dashed lines are the truly secret ones. Colored lines correspond to the LO transmissions $\eta$ as labeled. Here Alice's modulation variance $V_S=20$.Reuse & Permissions

Figure 3

Reverse reconciliation pseudosecret key rate (dashed lines) and intercepted one (solid lines) by Eve without being found vs LO intensity fluctuation rate $(1-\eta )$ with different transmission distances. From top to bottom the transmission distances are labeled, and the fiber loss is 0.2 dB/km. Inset is an amplified graph with $(1-\eta )$ between $0\sim 0.16$. Here Alice's modulation variance $V_S=20$.Reuse & Permissions

Figure 4

Direct reconciliation pseudosecret key rate and truly secret one vs channel transmission $T$ under LOIA. Solid lines are secret key rates estimated by Bob without monitoring LO intensity and dashed lines are the truly secret ones. Colors correspond to the LO transmissions as labeled. Here Alice's modulation variance $V_S=20$.Reuse & Permissions

Figure 5

Direct reconciliation pseudosecret key rate (dashed lines) and intercepted one (solid lines) by Eve without being found vs LO intensity fluctuation rate $(1-\eta )$ with different transmission distances. From top to bottom the transmission distances are labeled, and the fiber loss is 0.2 dB/km. Here Alice's modulation variance $V_S=20$.Reuse & Permissions