High Efficiency Postprocessing for Continuous-variable Quantum Key Distribution: Using All Raw Keys for Parameter Estimation and Key Extraction

Understand

High efficiency postprocessing of continuous-variable quantum key distribution system has a significant impact on the secret key rate and transmission distance of the system.

• Currently, the postprocessing mainly contains four steps in the following order: sifting, parameter estimation, information reconciliation, and privacy amplification.
• For a quantum channel with unknown prior characteristics, part of the raw keys (typically half) have to be sacrificed to estimate the channel parameters, which is used to assist in error correction (part of information reconciliation) and estimate the secret key rate.
• This introduces a tradeoff between the secret key rate and the accuracy of parameter estimation when considering the finite-size effect.