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arXiv:1212.0033 · Physical Review X

Coexistence of High-Bit-Rate Quantum Key Distribution and Data on Optical Fiber

K. A. Patel, J. F. Dynes, I. Choi, A. W. Sharpe, A. R. Dixon, Zhiliang L. Yuan, Richard V. Penty, Andrew J. Shields

Published Nov 20, 2012• 259 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) uniquely allows the distribution of cryptographic keys with security verified by quantum mechanical limits.Both protocol execution and subsequent applications require the assistance of classical data communication channels.While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber.However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates.Here, we exploit a novel temporal-filtering effect for noisephoton rejection.This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb=s data communications.With a high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10-Gbit Ethernet, QKD is a significant step closer toward wide-scale deployment in fiber networks.

DOI
10.1103/physrevx.2.041010

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Quantum key distribution (QKD) uniquely allows the distribution of cryptographic keys with security verified by quantum mechanical limits.Both protocol execution and subsequent applications require the assistance of classical data communication channels.While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber.However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates.Here, we exploit a novel temporal-filtering effect for noisephoton rejection.This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb=s data communications.With a high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10-Gbit Ethernet, QKD is a significant step closer toward wide-scale deployment in fiber networks.
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Quantum key distribution (QKD) provides information-theoretic security based on the laws of quantum mechanics. The desire to reduce costs and increase robustness in real-world applications has motivated the study of coexistence between QKD and intense classical data traffic in a single fiber. Previous works on coexistence in metropolitan areas have used wavelength-division multiplexing, however, coexistence in backbone fiber networks remains a great experimental challenge, as Tbps data of up to 20 dBm optical power is transferred, and much more noise is generated for QKD. Here we present for the first time, to the best of our knowledge, the integration of QKD with a commercial backbone network of 3.6 Tbps classical data at 21 dBm launch power over 66 km fiber. With 20 GHz pass-band filtering and large effective core area fibers, real-time secure key rates can reach 4.5 kbps and 5.1 kbps for co-propagation and counter-propagation at the maximum launch power, respectively. This demonstrates feasibility and represents an important step towards building a quantum network that coexists with the current backbone fiber infrastructure of classical communications.
We demonstrate quantum key distribution (QKD) with bidirectional 10 Gb/s classical data channels in a single fiber using dense wavelength division multiplexing. Record secure key rates of 2.38 Mbps and fiber distances up to 70 km are achieved. Data channels are simultaneously monitored for error-free operation. The robustness of QKD is further demonstrated with a secure key rate of 445 kbps over 25 km, obtained in the presence of data lasers launching conventional 0 dBm power. We discuss the fundamental limit for the QKD performance in the multiplexing environment.
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We demonstrate the realization of quantum key distribution (QKD) when combined with classical optical communication, and synchronous signals within a single optical fiber. In the experiment, the classical communication sources use Fabry-Pérot (FP) lasers, which are implemented extensively in optical access networks. To perform QKD, multistage band-stop filtering techniques are developed, and a wavelength-division multiplexing scheme is designed for the multi-longitudinal-mode FP lasers. We have managed to maintain sufficient isolation among the quantum channel, the synchronous channel and the classical channels to guarantee good QKD performance. Finally, the quantum bit error rate remains below a level of 2% across the entire practical application range. The proposed multiplexing scheme can ensure low classical light loss, and enables QKD over fiber lengths of up to 45 km simultaneously when the fibers are populated with bidirectional FP laser communications. Our demonstration paves the way for application of QKD to current optical access networks, where FP lasers are widely used by the end users.