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SPIE Conference on Quantum and Nonlinear Optics

Multirate and multiprotocol OFDM-based multicarrier continuous-variable quantum key distribution

Ting Ye, Qingsong Jia, Heng Wang, Yan Pan, Yaodi Pi, Yun Feng Shao, Yang Li, Tao Zhang, Wei Huang, Bingjie Xu

Published Oct 11, 2024• 0 citations
Publisher

Abstract

In this paper, we propose a multi-rate and multi-protocol CV-QKD scheme based on the orthogonal-frequencydivision- multiplexing (OFDM) technology. The proposed OFDM-based multi-carrier CVQKD scheme only requires one transmitter and one receiver to realize QKD with different modulation protocols and different key rates in one communication. More importantly, the multiple subcarriers with different modulation protocols have different excess noise tolerances in the same transmission channel, which can achieve the flexible QKD service even in long-distance and high-disturbance fiber channel. In order to verify the proposed scheme, 5 subcarriers with QPSK, 64QAM, 256QAM, 1024QAM and Gaussian modulation protocols are evaluated by the SDP and no-switch Gaussian security analysis method at different transmission distances. The simulation results show the proposed OFDM-based multi-carrier scheme allows various QKDs with different modulation protocols and different key rates in one communication. Moreover, according to the obtained 5 SKRs, we can choose the optimal modulation protocol of the subcarriers to meet different needs of quantum network operators. In addition, the scheme also can choose much more subcarriers and different symbol rates to flexibly achieve the QKD in different quantum secure communication scenarios. Therefore, the proposed scheme changes the modulation protocol, subcarrier number and symbol rate to achieve the interoperability, flexibility and compatibility.

DOI
10.1117/12.3035917

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In this paper, we propose a multi-rate and multi-protocol CV-QKD scheme based on the orthogonal-frequencydivision- multiplexing (OFDM) technology. The proposed OFDM-based multi-carrier CVQKD scheme only requires one transmitter and one receiver to realize QKD with different modulation protocols and different key rates in one communication. More importantly, the multiple subcarriers with different modulation protocols have different excess noise tolerances in the same transmission channel, which can achieve the flexible QKD service even in long-distance and high-disturbance fiber channel. In order to verify the proposed scheme, 5 subcarriers with QPSK, 64QAM, 256QAM, 1024QAM and Gaussian modulation protocols are evaluated by the SDP and no-switch Gaussian security analysis method at different transmission distances. The simulation results show the proposed OFDM-based multi-carrier scheme allows various QKDs with different modulation protocols and different key rates in one communication. Moreover, according to the obtained 5 SKRs, we can choose the optimal modulation protocol of the subcarriers to meet different needs of quantum network operators. In addition, the scheme also can choose much more subcarriers and different symbol rates to flexibly achieve the QKD in different quantum secure communication scenarios. Therefore, the proposed scheme changes the modulation protocol, subcarrier number and symbol rate to achieve the interoperability, flexibility and compatibility.
We experimentally demonstrated a high-performance multi-protocol continuous-variable quantum key distribution (CV-QKD) using one transceiver. The demonstrated multi-protocol CV-QKD system can simultaneously distribute 5 subcarriers with Gaussian, 4QAM, 16QAM, 64QAM, and 1024QAM modulation protocols based on orthogonal-frequency-division-multiplexing (OFDM) technology. Moreover, the modulation variance and probability distribution factor of 5 subcarriers are carefully optimized to maximize their respective SKRs. Besides, we innovatively design an effective OFDM-based DSP scheme and a precise dual-stage phase noise compensation scheme to realize a low excess noise for each subcarrier operating at a 2 GHz symbol rate. Thus, the multi-protocol CV-QKD achieves multiple SKRs of 48.79, 7.58, 23.67, 32.93, and 36.78 Mbps over a typical transmission distance of 50 km within a single transmission. Therefore, our work provides a practical solution to achieve highly efficient, interoperable, flexible, and secure QKDs for high-speed quantum secure communication.
Multi-carrier continuous-variable quantum key distribution (CV-QKD) is considered to be a promising way to boost the secret key rate (SKR) over the existing single-carrier CV-QKD scheme. However, the extra excess noise induced in the imperfect multi-carrier quantum state preparation process of N subcarriers will limit the performance of the system. Here, a systematic modulation noise model is proposed for the multi-carrier CV-QKD based on the orthogonal frequency division multiplexing (OFDM). Subsequently, the performance of multi-carrier CV-QKD with arbitrary modulation protocol (e.g. QPSK, 256QAM and Gaussian modulation protocol) can be quantitatively evaluated by combining the security analysis method of the single-carrier CV-QKD. Under practical system parameters, the simulation results show that the SKR of the multi-carrier CV-QKD can still be significantly improved by increasing the carrier number N even with imperfect practical modulations. Specifically, the total SKR of multi-carrier CV-QKD can be optimized by carefully choosing N. The proposed model provides a feasible theoretical framework for the future multi-carrier CV-QKD experimental implementation.
In this paper, a multi-carrier Gaussian modulated continuous variable quantum key distribution (CV-QKD) scheme has been proposed based on orthogonal frequency division multiplexing (OFDM) for distributing multiplexing independent secret keys encoded on N subcarriers within a single fiber channel. However, the performance of the system will be significantly influenced by the extra modulation noise in the multi-carrier quantum state preparation. Therefore, a modulation noise model is analyzed in more compact for multi-carrier Gaussian modulated CV-QKD system. Specifically, the gain imbalance and quadrature skew in IQ modulation and the third-order intermodulation effect in N subcarrier modulation are systematically analyzed in the OFDM-based multi-carrier CV-QKD with Gaussian modulation. That is, the IQ imbalance noise and the intermodulation noise are modeled as the modulation noise of the multi-carrier Gaussian modulated CV-QKD system. Moreover, the secure performances of the multi-carrier Gaussian modulated CVQKD are evaluated based on the proposed modulation noise model. Besides, the simulation results show the SKRs are greatly increased by N independent quantum state preparation, which indicates that the multi-carrier CV-QKD system gets rid of the asymptotic SKR limit of single-carrier CV-QKD system for future high-rate CV-QKD deployment in broadband access network.
Quantum key distribution (QKD) is an effective solution to ensure the secure transmission of information. However, for the large-scale application of QKD, the interoperability and flexibility of the transmitter and receiver are urgent issues to be solved. Here, for the first time, to the best of our knowledge, we experimentally verify the feasibility of one continuous-variable (CV) QKD system to achieve multiple protocols and rates. The flexibility of the system comes from the modulator realizing multiple protocols and a broadband coherent detector realizing multiple symbol rates. The results show that this system can switch between different rates and protocols to generate the secure key, and reveal its similarity to classical optical communication. Therefore, It can be adjusted according to user needs and provides a system-level solution for building a flexible quantum network.
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 propose a continuous-variable quantum key distribution (CVQKD) scheme at terahertz (THz) bands based on multicarrier multiplexing (MCM) technology. In this scheme, multiple Gaussian modulated subcarriers are coupled to transmit multipath superposed thermal Gaussian states. At the receiver, optical discrete Fourier transform (ODFT) is used to demultiplex the received subcarriers, and the keys can be generated in parallel by homodyne detection and post processing. We analyze the security of the scheme against the optimal collective Gaussian attack under indoor environment and in inter-satellite links respectively. Results indicate that by using MCM technology, each subchannel may be affected by crosstalk, resulting in slight shortening of the maximal transmission distance while the total secret key rate can be greatly increased. We also verify the feasibility of higher key rate and longer distance THz-QKD by using MCM technology in inter-satellite links communication. We expect this work will provide an efficient path to build a global quantum communication network.