Computational Complexity of Present Schemes of Reverse Reconciliation Continuous Variable Quantum Key Distribution

The continuous variable quantum key distribution has been considered to have the potential to provide high secret key rate. However, in present experimental demonstrations, the secret key can be distilled only under very small loss rates. Here, by calculating explicitly the computational complexity with the channel transmission, we show that under high loss rate it is hard to distill the secret key in present reverse reconciliation continuous variable scheme and one of its advantages, the potential of providing high secret key rate, may therefore be limited. To overcome this problem, new protocols need to be explored.