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IEEE Communications Letters

Experimental demonstration of an active quantum key distribution network with over gbps clock synchronization

Lijun Ma, Alan Mink, Xu Hai, Oliver Slattery, Xiao Hong Tang

Published Dec 1, 2007• 22 citations
Publisher

Abstract

We demonstrate a three-node QKD network that allows multiple users to share secure keys. This QKD network operates on the 850 nm and 1550 nm wavelengths at 1.25 Gbps clock rate. The communication route is controlled by MEMS optical switches. In this paper, we report the network structure and experimental results including the performance of the optical switch, polarization recovery, and timing alignment technology during switching. This demonstration experimentally shows that QKD can be extended to active multi-node networks.

DOI
10.1109/lcomm.2007.071477

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We demonstrate a three-node QKD network that allows multiple users to share secure keys. This QKD network operates on the 850 nm and 1550 nm wavelengths at 1.25 Gbps clock rate. The communication route is controlled by MEMS optical switches. In this paper, we report the network structure and experimental results including the performance of the optical switch, polarization recovery, and timing alignment technology during switching. This demonstration experimentally shows that QKD can be extended to active multi-node networks.
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Secure networks composed of optical networks and quantum key distribution (QKD) are considered in this paper. A network layer structure is defined to focus on issues important with respect to the QKD network layer that controls QKD links and supplies a secure key for message transmission. A multiple-user QKD network layer can be constructed with timing synchronization, secure key sharing between indirectly connected nodes with switched QKD systems and key relays, and key management to control the volume of key generation and supply in response to the demand from optical network nodes.
We report on the design and field validation of a fully connected entanglement-based quantum key distribution (QKD) network employing a time-shared photon-pair source and reconfigurable optical switching. The system eliminates the need for trusted relay nodes and enables any-to-any secure connectivity among users over metropolitan-scale fiber infrastructure. We present a three-node prototype network operating in the O-band(1310/1316nm)(1310 / 1316 \text{nm})(1310/1316nm)which demonstrates key generation sufficient to provide pairwise 10 G encrypted connections between 32 users, and confirming practical feasibility for telecom integration.
Quantum key distribution (QKD) enables unconditional physical layer security for the distribution of cryptographic key material. However, most experimental demonstrations have relied on simple point-to-point optical links. In this paper we investigate the compatibility of QKD with reconfigurable optical networks. By performing the first tests of QKD transmission through optical switches, we study if there are impairment mechanisms other than switch insertion loss that impact the sifted and error corrected secret bit yield. Three types of transparent optical switch elements are investigated including lithium niobate (LiNbO/sub 3/), microelectromechanical systems (MEMS), and optomechanical. We show that QKD can be extended beyond point-to-point links to switched multinode architectures including protected ring networks to enhance quantum channel availability.
Quantum key distribution (QKD), which promises secure key exchange between two remote parties, is now moving toward the realization of scalable and secure QKD networks (QNs). Fully connected, trusted node-free QNs have been realized based on entanglement distribution, in which the low key rate and the large overhead make their practical application challenging. Here, we experimentally demonstrate a fully connected multi-user QKD network based on a wavelength-multiplexed measurement-device-independent (MDI) QKD protocol. By combining the MDI-QKD protocol with integrated optical frequency combs, we achieve an average secure key rate of 267 bits per second for about 30 dB of link attenuation per user pair—more than three orders of magnitude higher than previous entanglement-based works. More importantly, we realize communication between two different pairs of users simultaneously. Our work paves the way for the realization of large-scale QKD networks with full connectivity and simultaneous communication capability among multiple users.
We have demonstrated the exchange of sifted quantum cryptographic key over a 730 meter free-space link at rates of up to 1.0 Mbps, two orders of magnitude faster than previously reported results. A classical channel at 1550 nm operates in parallel with a quantum channel at 845 nm. Clock recovery techniques on the classical channel at 1.25 Gbps enable quantum transmission at up to the clock rate. System performance is currently limited by the timing resolution of our silicon avalanche photodiode detectors. With improved detector resolution, our technique will yield another order of magnitude increase in performance, with existing technology.