To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measur...To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measurement. We send a low-frequency repeat optical pulse synchronized with associated quantum signals on the receiver's side by using a time-to-digital converter(TDC)module, the time intervals between quantum signals, and synchronization signals measured and converted to corresponding temporal orders to complete the synchronization.We state the principle of the synchronization scheme in detail and then verify it in an actual QKD test bed. The test results show that our TDC-GPX-based synchronization can obtain a time resolution better than 100 ps, and the proposed scheme shows full feasibility for an actual QKD system.展开更多
We investigate the crosstalk noise, especially the spontaneous Raman scattering, in the optical fiber of a copropagation system between quantum key distribution(QKD) and classical communications. Although many methods...We investigate the crosstalk noise, especially the spontaneous Raman scattering, in the optical fiber of a copropagation system between quantum key distribution(QKD) and classical communications. Although many methods have been proposed, such as increasing the wavelength spacing and narrowband filtering technique, to suppress Raman scattering noise, these methods greatly affect the performance of QKD. One way to solve the obstacle restricting the coexistence is to decrease the classical signal power. Based on the high gain of the gated avalanche photodiode and pulse position modulation, we demonstrate that the co-propagation system works effectively with only a small effect on long-haul fibers, which has great significance for the practical widespread commercialization of QKD.展开更多
Due to the vulnerability of fibers in optical networks, physical- layer attacks targeting photon splitting, such as eavesdrop- ping, can potentially lead to large information and revenue loss. To enhance the existing ...Due to the vulnerability of fibers in optical networks, physical- layer attacks targeting photon splitting, such as eavesdrop- ping, can potentially lead to large information and revenue loss. To enhance the existing security approaches of optical networks, a new promising technology, quantum key distribu- tion （QKD）, can securely encrypt services in optical networks, which has been a hotspot of research in recent years for its characteristic that can let clients know whether infomlation transmission has been eavesdropped or not. In this paper, we apply QKD to provide secret keys for optical networks and then introduce the architecture of QKD based optical net- work. As for the secret keys generated by QKD in optical net- works, we propose a re-transmission mechanism by analyzing the security risks in QKD-based optical networks. Numerical results indicate that the proposed re-transmission mechanism can provide strong protection degree with enhanced attack protection. Finally, we illustrated some future challenges in QKD-based optical networks.展开更多
We demonstrate a three-node active quantum key distribution(QKD)network with our previous two-way QKD system.An optical switch is used as a router to connect the two nodes.Adjacent nodes are connected by a 25 km optic...We demonstrate a three-node active quantum key distribution(QKD)network with our previous two-way QKD system.An optical switch is used as a router to connect the two nodes.Adjacent nodes are connected by a 25 km optical fiber.The test over 11 h shows that our system can reduce the Raleigh backscattering efficiently in the absence of the storage fiber.Furthermore,the obtained average sifted key is about 1.2 kbps in the network,with high visibility and low quantum bit error rate in the long-time test.展开更多
Silica-based planar lightwave circuit(PLC)devices can reduce transmission loss and cost in a quantum key distribution(QKD)system,and have potential applications in integration and production.A PLC-based quantum decodi...Silica-based planar lightwave circuit(PLC)devices can reduce transmission loss and cost in a quantum key distribution(QKD)system,and have potential applications in integration and production.A PLC-based quantum decoding integrated chip for multi-protocols is designed and fabricated,which is composed of variable optical splitters(VOSs),asymmetric Mach-Zehnder interferometers(AMZIs),and variable directional couplers(VDCs).Balanced pulse-pairs of four outputs are obtained simultaneously with measured delay times of 405 ps and 402 ps,respectively.The chip has advantages in achieving high interference visibility and low quantum bit error rate(QBER).展开更多
In this communication, we report results of running tests on standard telecommunication metropolitan network 1550 nm fiber applied to a quantum channel to EPR S405 Quelle prototype systems installed in National Labora...In this communication, we report results of running tests on standard telecommunication metropolitan network 1550 nm fiber applied to a quantum channel to EPR S405 Quelle prototype systems installed in National Laboratory for Quantum Technologies WUT and in CompSecur Wroclaw. Testing was carried out by means of the original design by us and applied special data card collecting parameters of functioning system allowing for assessment of quality of quantum channel. We have performed several trials using various configurations of standard 1550 nm fiber patch-cord up to length of 6.5 km with additional usage of various patch-cords with weldings and connectors which typically present in already installed commercial metropolitan communication networks. The implementation of this testing indicated that the rigorous maintenance of photon polarization is required for quantum information exchange upon EPR S405 Quelle functioning. The polarization of optical signal turned out to be, however, very unstable for the tested connection which resulted in very rapid QBER rise precluding practical usefulness of this connection for secure quantum exchange of cryptographic key over practically significant distances. We have identified that the main obstacle was the polarization decoherence caused by weldings and connectors in standard patch-cords and accidental strains in fibers as well as generally poor transmitting properties of 1550 nm fiber for much shorter wave-length photons used by the Quelle system. To maintain the quantum channel active, very frequent manual corrections of polarization control were required. So we expect that by design and application of an automatic polarization control module, one would stabilize visibility ratio and lower QBER to an acceptable level conditioning possible future implementation of entangled QKD system in commercial networks.展开更多
基金supported by National Natural Science Foundation of China (Nos. 11375195, 11375263 and 11105143)National Magnetic Confinement Fusion Energy Development Research (No. 2013GB104003)
文摘To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measurement. We send a low-frequency repeat optical pulse synchronized with associated quantum signals on the receiver's side by using a time-to-digital converter(TDC)module, the time intervals between quantum signals, and synchronization signals measured and converted to corresponding temporal orders to complete the synchronization.We state the principle of the synchronization scheme in detail and then verify it in an actual QKD test bed. The test results show that our TDC-GPX-based synchronization can obtain a time resolution better than 100 ps, and the proposed scheme shows full feasibility for an actual QKD system.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61605248 and 61505261)
文摘We investigate the crosstalk noise, especially the spontaneous Raman scattering, in the optical fiber of a copropagation system between quantum key distribution(QKD) and classical communications. Although many methods have been proposed, such as increasing the wavelength spacing and narrowband filtering technique, to suppress Raman scattering noise, these methods greatly affect the performance of QKD. One way to solve the obstacle restricting the coexistence is to decrease the classical signal power. Based on the high gain of the gated avalanche photodiode and pulse position modulation, we demonstrate that the co-propagation system works effectively with only a small effect on long-haul fibers, which has great significance for the practical widespread commercialization of QKD.
基金supported in part by NSFC project(Grant No.61571058and 61601052)Science and Technology Project of State Grid Corporation of China:The Key Technology Research of Elastic Optical Network(Grant No.526800160006)+1 种基金China Postdoctoral Science Foundation Project(2016M600970)ZTE Industry-Academia-Research Cooperation Funds
文摘Due to the vulnerability of fibers in optical networks, physical- layer attacks targeting photon splitting, such as eavesdrop- ping, can potentially lead to large information and revenue loss. To enhance the existing security approaches of optical networks, a new promising technology, quantum key distribu- tion （QKD）, can securely encrypt services in optical networks, which has been a hotspot of research in recent years for its characteristic that can let clients know whether infomlation transmission has been eavesdropped or not. In this paper, we apply QKD to provide secret keys for optical networks and then introduce the architecture of QKD based optical net- work. As for the secret keys generated by QKD in optical net- works, we propose a re-transmission mechanism by analyzing the security risks in QKD-based optical networks. Numerical results indicate that the proposed re-transmission mechanism can provide strong protection degree with enhanced attack protection. Finally, we illustrated some future challenges in QKD-based optical networks.
基金Supported by the National Natural Science Foundation of China Grant No 61072071.
文摘We demonstrate a three-node active quantum key distribution(QKD)network with our previous two-way QKD system.An optical switch is used as a router to connect the two nodes.Adjacent nodes are connected by a 25 km optical fiber.The test over 11 h shows that our system can reduce the Raleigh backscattering efficiently in the absence of the storage fiber.Furthermore,the obtained average sifted key is about 1.2 kbps in the network,with high visibility and low quantum bit error rate in the long-time test.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFA0306403)the National Nature Science Foundation of China(Grant No.61805232).
文摘Silica-based planar lightwave circuit(PLC)devices can reduce transmission loss and cost in a quantum key distribution(QKD)system,and have potential applications in integration and production.A PLC-based quantum decoding integrated chip for multi-protocols is designed and fabricated,which is composed of variable optical splitters(VOSs),asymmetric Mach-Zehnder interferometers(AMZIs),and variable directional couplers(VDCs).Balanced pulse-pairs of four outputs are obtained simultaneously with measured delay times of 405 ps and 402 ps,respectively.The chip has advantages in achieving high interference visibility and low quantum bit error rate(QBER).
文摘In this communication, we report results of running tests on standard telecommunication metropolitan network 1550 nm fiber applied to a quantum channel to EPR S405 Quelle prototype systems installed in National Laboratory for Quantum Technologies WUT and in CompSecur Wroclaw. Testing was carried out by means of the original design by us and applied special data card collecting parameters of functioning system allowing for assessment of quality of quantum channel. We have performed several trials using various configurations of standard 1550 nm fiber patch-cord up to length of 6.5 km with additional usage of various patch-cords with weldings and connectors which typically present in already installed commercial metropolitan communication networks. The implementation of this testing indicated that the rigorous maintenance of photon polarization is required for quantum information exchange upon EPR S405 Quelle functioning. The polarization of optical signal turned out to be, however, very unstable for the tested connection which resulted in very rapid QBER rise precluding practical usefulness of this connection for secure quantum exchange of cryptographic key over practically significant distances. We have identified that the main obstacle was the polarization decoherence caused by weldings and connectors in standard patch-cords and accidental strains in fibers as well as generally poor transmitting properties of 1550 nm fiber for much shorter wave-length photons used by the Quelle system. To maintain the quantum channel active, very frequent manual corrections of polarization control were required. So we expect that by design and application of an automatic polarization control module, one would stabilize visibility ratio and lower QBER to an acceptable level conditioning possible future implementation of entangled QKD system in commercial networks.
