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25 MHz clock continuous-variable quantum key distribution system over 50 km fiber channel.

Wang C, Huang D, Huang P, Lin D, Peng J, Zeng G - Sci Rep (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Key Laboratory on Navigation and Location-based Service, and Center of Quantum Information Sensing and Processing, Shanghai Jiao Tong University, Shanghai 200240, China.

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.

No MeSH data available.


Related in: MedlinePlus

Diagram of the phase compensation with SNR = 0.9.The red points indicate the transmitted data at Alice’s side, and the blue points indicate the received data at Bob’s side. (a) The uncompensated waveform, (b) The compensated waveform.
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f2: Diagram of the phase compensation with SNR = 0.9.The red points indicate the transmitted data at Alice’s side, and the blue points indicate the received data at Bob’s side. (a) The uncompensated waveform, (b) The compensated waveform.

Mentions: Now we consider the phase drift in the CVQKD system, which is inevitable due to variation of temperature and vibrations in the environment. The phase shifts may lead to low probability of error correction. Since the reconciliation algorithm could recover only the original signal from the signal which overlaid by addictive white Gaussian noise (AWGN), the phase shifts will hinder the data reconciliation process, resulting in secret key rate. To overcome the phase drift in low signal-to-noise ratio condition, we propose a simple phase compensation algorithm to estimate the value of phase drift (see Methods). Making use of this algorithm, the continuous variables shared by Alice and Bob have few discrepancies on phase and linear scale. The main difference, which can be solved by reconciliation, is that Bob’s data is overlaid by AWGN. We test the phase compensation in practice, the results are shown in Fig. 2. The precision can reach 0.1° for each frame, which quite eliminates the excess noise from phase shift.


25 MHz clock continuous-variable quantum key distribution system over 50 km fiber channel.

Wang C, Huang D, Huang P, Lin D, Peng J, Zeng G - Sci Rep (2015)

Diagram of the phase compensation with SNR = 0.9.The red points indicate the transmitted data at Alice’s side, and the blue points indicate the received data at Bob’s side. (a) The uncompensated waveform, (b) The compensated waveform.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588593&req=5

f2: Diagram of the phase compensation with SNR = 0.9.The red points indicate the transmitted data at Alice’s side, and the blue points indicate the received data at Bob’s side. (a) The uncompensated waveform, (b) The compensated waveform.
Mentions: Now we consider the phase drift in the CVQKD system, which is inevitable due to variation of temperature and vibrations in the environment. The phase shifts may lead to low probability of error correction. Since the reconciliation algorithm could recover only the original signal from the signal which overlaid by addictive white Gaussian noise (AWGN), the phase shifts will hinder the data reconciliation process, resulting in secret key rate. To overcome the phase drift in low signal-to-noise ratio condition, we propose a simple phase compensation algorithm to estimate the value of phase drift (see Methods). Making use of this algorithm, the continuous variables shared by Alice and Bob have few discrepancies on phase and linear scale. The main difference, which can be solved by reconciliation, is that Bob’s data is overlaid by AWGN. We test the phase compensation in practice, the results are shown in Fig. 2. The precision can reach 0.1° for each frame, which quite eliminates the excess noise from phase shift.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Key Laboratory on Navigation and Location-based Service, and Center of Quantum Information Sensing and Processing, Shanghai Jiao Tong University, Shanghai 200240, China.

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.

No MeSH data available.


Related in: MedlinePlus