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arXiv:2111.12356 · European Conference on Optical Communication

High-Rate Continuous Variable Quantum Key Distribution Based on Probabilistically Shaped 64 and 256-QAM

François Roumestan, Amirhossein Ghazisaeidi, Jérémie Renaudier, Luis Trigo Vidarte, Eleni Diamanti, Philippe Grangier

Published Sep 13, 2021• 27 citations
arXivHTMLPDF

Abstract

We designed a CV-QKD system with off-the-shelf components and established the feasibility of distributing 67.6 and 66.8 Mb/s secret key rates on average over a 9.5 km SMF link, using respectively probabilistically shaped 64 and 256 QAM, and relying on a novel analytical security proof.
DOI
10.1109/ecoc52684.2021.9606013

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Quantum key distribution (QKD), providing a way to generate secret keys with information-theoretic security, is arguably one of the most significant achievements in quantum information. The continuous-variable QKD (CV-QKD) offers the potential advantage of achieving a higher secret key rate (SKR) within a metro area, as well as being compatible with the mature telecom industry. However, the SKR and transmission distance of state-of-the-art CV-QKD systems are currently limited. Here, based on the proposed orthogonal-frequency-division-multiplexing (OFDM) CV-QKD protocol, we demonstrate a high-rate multi-carrier (MC) CV-QKD with a 10 GHz symbol rate that achieves Gbps SKR within 10 km and Mbps SKR over 100 km in the finite-size regime under composable security against collective attacks. The results are achieved by suitable optimization of subcarrier number and modulation variance, well-controlled excess noise induced by both the OFDM mechanism and the efficient DSP scheme, and high-performance post-processing capacity realized by the heterogeneous computing scheme. The composable finite-size SKR reaches 1779.45 Mbps@5 km, 1025.49 Mbps@10 km, 370.50 Mbps@25 km, 99.93 Mbps@50 km, 25.70 Mbps@75 km, and 2.25 Mbps@100 km, which improves the SKR by two orders of magnitude and quintuples the maximal transmission distance compared to the most recently reported CV-QKD results [ Nat. Commun. 13 , 4740 ( 2022 ) NCAOBW 2041-1723 10.1038/s41467-022-32161-y ]. Interestingly, it is experimentally verified that the SKR of the proposed MC CV-QKD can approach five times larger than that of the single-carrier CV-QKD with the same symbol rate without additional hardware costs. Our work constitutes a critical step toward future high-speed quantum metropolitan and access networks.
We have been intensively studying quantum noise stream cipher (QNSC) transmission technique using quadrature amplitude modulation (QAM) with a view to realizing a high-speed and long-distance secure communication system [1]. In this talk, we describe our recent demonstration of an on-line 70 Gbit/s, 128 QAM/QNSC transmission over 100 km with a continuous variable quantum key distribution (CV-QKD) system [2], in which a shared key is transmitted online via the CV-QKD so that the key is shared for a certain time period with absolutely no risk of being eavesdropped.
Abstract Quantum key distribution (QKD) is one quantum technology that can provide secure encryption keys for data transmission. The secret key rate (SKR) is a core performance indicator in QKD, which directly determines the transmission rate of enciphered data. Here, for the first time, we demonstrate a high-key-rate Gaussian-modulated continuous-variable QKD (CV-QKD) using telecom optical components. The framework of CV-QKD over these components is constructed. Specifically, the high-rate low-noise Gaussian modulation of coherent states is realized by a classical optical IQ modulator. High-baud low-intensity quantum signals are received by an integrated coherent receiver under the shot-noise limit. A series of digital signal processing algorithms are proposed to achieve accurate signal recovery and key distillation. The system can yield a high asymptotic SKR of 10.37 Mbps within 20 km standard telecom fiber, and the secure distance can exceed 100 km. This result confirms the feasibility of CV-QKD with state-of-the-art performance using telecom optical components. Besides, due to the ease of integrating these discrete components, it provides a high-performance and miniaturized QKD solution for the metropolitan quantum network.