Multi-level Parameter Estimation for Receiver Noise in CV-QKD

We present an experimental method for continuous-variable quantum key distribution (CV-QKD) that removes the need for conventional receiver noise calibration. By exploiting Multi-Level Parameter Estimation (MLPE) with controlled attenuation at the receiver, our approach directly estimates the total receiver noise, including contributions from the local oscillator, while simultaneously extracting channel-induced excess noise. This calibration-free technique allows continuous operation without halting quantum transmissions, increasing experimental throughput and robustness. We implement the method in a dual-polarization, local-local oscillator CV-QKD system multiplexed with a classical communication channel, demonstrating precise receiver noise estimation. Our results highlight MLPE as a practical tool for scalable, real-time CV-QKD deployment.