Data postprocessing for the one-way heterodyne protocol under composable finite-size security

The performance of a practical continuous-variable quantum key distribution protocol depends significantly, apart from the loss and noise of the quantum channel, on the postprocessing steps which lead to the extraction of the final secret key. A critical step is the reconciliation process, especially when one assumes finite-size effects in a composable framework. Here, we focus on the Gaussian-modulated coherent-state protocol with heterodyne detection in a high signal-to-noise ratio regime. We simulate the quantum communication process and we postprocess the output data by applying parameter estimation, error correction (using high-rate, nonbinary low-density parity-check codes) and privacy amplification. This allows us to study the performance for practical implementations of the protocol and optimize the parameters connected to the steps above. We also present an associated Python library performing the steps above.

Automated summary

This article focuses on the performance of a practical continuous-variable quantum key distribution protocol, particularly on the postprocessing steps involving finite-size effects in the reconciliation process. The quantum communication process is simulated and output data is postprocessed using parameter estimation, error correction, and privacy amplification, aiming to optimize the protocol's practical implementations.