Abstract
In this paper, a practical continuous-variable quantum key distribution system is developed and it runs in the real-world conditions with 25 MHz clock rate. To reach high-rate, we have employed a homodyne detector with maximal bandwidth to 300 MHz and an optimal high-efficiency error reconciliation algorithm with processing speed up to 25 Mbps. To optimize the stability of the system, several key techniques are developed, which include a novel phase compensation algorithm, a polarization feedback algorithm, and related stability method on the modulators. Practically, our system is tested for more than 12 hours with a final secret key rate of 52 kbps over 50 km transmission distance, which is the highest rate so far in such distance. Our system may pave the road for practical broadband secure quantum communication with continuous variables in the commercial conditions.
Highlights
Rate and output a final secret key rate about 52 kbps over 50 km fiber channel
Our system is implemented based on the well-known GMCS Quantum key distribution (QKD) protocol[17], and several novel techniques are developed, including the broadband homodyne detection, precise phase compensation, and high-rate multidimensional reconciliation
It is worth noting that this paper has presented a practical CVQKD system with highest secret key rate at the secure distance of 50 km over a standard telecom fiber, our CVQKD system may pave the road for broadband secure quantum communication with continuous variables in practical applications
Summary
Comparing to the results in theoretical regime, i.e., the infinite data block, a realistic block length limits the secure distance and one cannot remove this uncertainties completely This is the finite-size effects which are mainly associated with the excess noise and privacy amplification. 50% of the optical pulses were used for generating the key and the rest were used for parameter estimation and frame overhead We anticipate that the CVQKD with our technologies should remain effective for longer transmission distance by further controlling the excess noises in the practical CVQKD system
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