Experimentally optimizing QKD rates via nonlocal dispersion compensation

Year: 2021

Authors: Neumann SP., Ribezzo D., Bohmann M., Ursin R.

Autors Affiliation: Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, Boltzmanngasse 3, A-1090 Vienna, Austria; Vienna Ctr Quantum Sci & Technol, Boltzmanngasse 5, A-1090 Vienna, Austria; Ist Nazl Ottica, Largo Enrico Fermi 6, I-50125 Florence, Italy.

Abstract: Quantum key distribution (QKD) enables unconditionally secure communication guaranteed by the laws of physics. The last decades have seen tremendous efforts in making this technology feasible under real-life conditions, with implementations bridging ever longer distances and creating ever higher secure key rates. Readily deployed glass fiber connections are a natural choice for distributing the single photons necessary for QKD both in intra- and intercity links. Any fiber-based implementation however experiences chromatic dispersion which deteriorates temporal detection precision. This ultimately limits maximum distance and achievable key rate of such QKD systems. In this work, we address this limitation to both maximum distance and key rate and present an effective and easy-to-implement method to overcome chromatic dispersion effects. By exploiting entangled photons’ frequency correlations, we make use of nonlocal dispersion compensation to improve the photons’ temporal correlations. Our experiment is the first implementation utilizing the inherently quantum-mechanical effect of nonlocal dispersion compensation for QKD in this way. We experimentally show an increase in key rate from 6.1 to 228.3 bits/s over 6.46 km of telecom fiber. Our approach is extendable to arbitrary fiber lengths and dispersion values, resulting in substantially increased key rates and even enabling QKD in the first place where strong dispersion would otherwise frustrate key extraction at all.

Journal/Review: QUANTUM SCIENCE AND TECHNOLOGY

Volume: 6 (2)      Pages from: 25017-1  to: 25017-10

More Information: We acknowledge European Union’s Horizon 2020 Programme Grant agreement No. 857156 (OpenQKD) and the Austrian Academy of Sciences. We also want to thank Josef Vojtech of CESNET (Prague) for providing us with dispersion compensation equipment, Siddarth Koduru Joshi of NSQI (Bristol) for lending us a DWDM device and Soren Wengerowsky of IQOQI (Vienna) for fruitful discussions.
KeyWords: quantum cryptography; quantum key distribution; quantum communication; nonlocal dispersion compensation; fiber telecommunication; chromatic dispersion; photonic entanglement
DOI: 10.1088/2058-9565/abe5ee

Citations: 16
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