Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2502.12651

Fully passive quantum key distribution with parametric down-conversion source

Jia‐Wei Ying, Qi Zhang, Shi‐Pu Gu, Xing-Fu Wang, Lan Zhou, Yu‐Bo Sheng

Published Feb 18, 2025• 1 citation
arXivHTMLPDF

Abstract

The fully passive source is capable of passively generating decoy states and performing passive encoding simultaneously, avoiding the side-channel risks caused by active modulation operations at the source end, thus effectively enhance the security in quantum key distribution (QKD). Existing fully passive QKD protocol and experiments exploit phase-randomized coherent pulses. In this paper, we propose a fully passive QKD protocol using parametric down-conversion source. The decoy state generation and encoding operation can be carried out passively by parameter down-conversion progress. This protocol has several advantages. First, it can also eliminate all side channels in active modulators. Second, compared with fully passive QKD protocol with phase-randomized coherent pulses, our protocol can significantly increase the key rate and extend the communication distance. Meanwhile, in terms of the transmission rate, our protocol is also closer to that of actively modulated QKD and can achieve fully passive modulation with fewer resources. Moreover, combined with measurement-device-independent (MDI) QKD, this protocol can even potentially achieve robustness against side channels in both detectors and modulators.

DOI
10.48550/arxiv.2502.12651

Related papers

Fully Passive Quantum Key Distribution

Wenyuan Wang, Rong Wang, Cheng-Qiu Hu +5 more

We propose a fully passive linear optical quantum key distribution (QKD) source that implements both random decoy-state and encoding choices with postselection only, thus eliminating all side channels in active modulators. Our source is general purpose and can be used in, e.g., BB84, the six-state protocol, and reference-frame-independent QKD. It can even potentially be combined with measurement-device-independent QKD to achieve robustness against side channels in both detectors and modulators. We also perform a proof-of-principle experimental source characterization to show its feasibility.

arXiv:2207.05916•Physical Review Letters•May 31, 2023•60 citations

Fully passive measurement-device-independent quantum key distribution

Xiang Wang, Feng-Yu Lu, Ze-Hao Wang +7 more

Measurement-device-independent quantum key distribution (MDIQKD) can resist all attacks on the detection devices, but there are still some security issues related to the source side. One possible solution is to use the passive protocol to eliminate the side channels introduced by active modulators at the source. Recently, a fully passive QKD protocol was proposed that could simultaneously achieve passive encoding and passive decoy-state modulation using linear optics. In this work, we propose a fully passive MDIQKD scheme that can protect the system from both side channels of source modulators and attacks on the measurement devices, which can significantly improve the implementation security of the QKD systems. We provide a specific passive encoding strategy and a method for decoy-state analysis, followed by simulation results for the secure key rate in the asymptotic scenario. Our work offers a feasible way to improve the implementation security of QKD systems and serves as a reference for achieving passive QKD schemes using realistic devices.

arXiv:2309.07576•Physical Review Applied•Jun 28, 2024•11 citations

Fully passive measurement-device-independent quantum key distribution

Jinjie Li, Wenyuan Wang, Hoi‐Kwong Lo

A recently proposed fully passive quantum key distribution (QKD) removes all source modulator side channels. In this work, we combine fully passive sources with measurement-device-independent (MDI) QKD to simultaneously remove side channels from source modulators and detectors. We show a numerical simulation of passive MDI QKD, and we obtain an acceptable key rate while achieving much better implementation security, as well as ease of implementation, compared with a recently proposed fully passive twin-field QKD, paving the way towards more secure and practical QKD systems. We prove that a fully passive protocol is compatible with MDI QKD and we propose a novel idea that can improve the sifting efficiency.

arXiv:2309.07673•Physical Review Applied•Jun 25, 2024•10 citations

Fully passive reference frame independent quantum key distribution

Jia‐Wei Ying, Shi‐Pu Gu, Xing-Fu Wang +2 more

Reference-frame-independent quantum key distribution (RFI QKD) significantly alleviates alignment requirements for reference frame in practical quantum communication systems. While the original protocol requires Alice to prepare six quantum states in $Z$, $X$, and $Y$ bases, its reliance on active modulation introduces inherent side-channel vulnerabilities from device imperfections. We address this security limitation by integrating a fully passive source into the RFI framework. In this paper, we propose a fully passive RFI QKD protocol. Our protocol avoids active modulation entirely, suppressing side-channel risks through passive quantum state generation. Moreover, by making full utilization of the quantum states generated by the fully passive source, we enhance the secure key rate of fully passive protocol. We establish a system model to analyze the performance of the protocol. Through the optimization of post-selection intervals and intensities, we obtain the maximum secure key transmission rate of the protocol. Under ideal circumstances, the secure key transmission rate of our protocol can reach more than 50% of that of the ideal QKD. Under practical conditions, we have considered the finite-length effect. When pulse number generated by the source reaches $10^{12}$, the maximum communication distances of the protocol can reach 167 km and 136 km with a reference frame misalignment of $0 $ and $45^{\circ} $ respectively. We believe that our protocol can contribute to the development of practical QKD systems.

arXiv:2504.15528•Apr 22, 2025•0 citations

Proof-of-principle demonstration of parametric down-conversion source-based quantum key distribution over 40 dB channel loss

Chunhui Zhang, Dong Wang, Xingyu Zhou +7 more

Quantum key distribution (QKD) offers information-theoretic security verified by quantum mechanics to share keys between legitimate users. Most of the existing QKD systems employ active decoy states based on weak coherent sources (WCS). Meanwhile, parametric down-conversion (PDC) sources are seldom used due to several of their shortcomings. In the present work, to show the superiority of PDC sources, we have accomplished a proof-of-principle demonstration of a PDC source-based QKD with over 40 dB based on the one-way BB84 protocol. In this QKD system, a novel passive decoy-state scheme-secure to coherent attacks-is proposed, using several built-in decoy states for parameter estimation. This not only avoids intensity modulating errors, but also diminishes all possible information leakage from the intensity modulating process. The experimental results show a significantly enhanced performance compared with existing PDC source-based QKD systems. In addition, it exhibits some superiority even over active decoy-state QKD systems based on WCS.

Optics Express•Sep 20, 2018•20 citations

A fully passive transmitter for decoy-state quantum key distribution

Víctor Zapatero, Wenyuan Wang, Marcos Curty

Abstract A passive quantum key distribution (QKD) transmitter generates the quantum states prescribed by a QKD protocol at random, combining a fixed quantum mechanism and a post-selection step. By circumventing the use of active optical modulators externally driven by random number generators, passive QKD transmitters offer immunity to modulator side channels and potentially enable higher frequencies of operation. Recently, the first linear optics setup suitable for passive decoy-state QKD has been proposed. In this work, we simplify the prototype and adopt sharply different approaches for BB84 polarization encoding and decoy-state parameter estimation. In particular, our scheme avoids a probabilistic post-selection step that is central to the former proposal. On top of it, we elaborate a simple and tight custom-made security analysis.

arXiv:2208.12516•Quantum Science and Technology•Feb 15, 2023•24 citations
The fully passive source is capable of passively generating decoy states and performing passive encoding simultaneously, avoiding the side-channel risks caused by active modulation operations at the source end, thus effectively enhance the security in quantum key distribution (QKD). Existing fully passive QKD protocol and experiments exploit phase-randomized coherent pulses. In this paper, we propose a fully passive QKD protocol using parametric down-conversion source. The decoy state generation and encoding operation can be carried out passively by parameter down-conversion progress. This protocol has several advantages. First, it can also eliminate all side channels in active modulators. Second, compared with fully passive QKD protocol with phase-randomized coherent pulses, our protocol can significantly increase the key rate and extend the communication distance. Meanwhile, in terms of the transmission rate, our protocol is also closer to that of actively modulated QKD and can achieve fully passive modulation with fewer resources. Moreover, combined with measurement-device-independent (MDI) QKD, this protocol can even potentially achieve robustness against side channels in both detectors and modulators.
We propose a fully passive linear optical quantum key distribution (QKD) source that implements both random decoy-state and encoding choices with postselection only, thus eliminating all side channels in active modulators. Our source is general purpose and can be used in, e.g., BB84, the six-state protocol, and reference-frame-independent QKD. It can even potentially be combined with measurement-device-independent QKD to achieve robustness against side channels in both detectors and modulators. We also perform a proof-of-principle experimental source characterization to show its feasibility.
Measurement-device-independent quantum key distribution (MDIQKD) can resist all attacks on the detection devices, but there are still some security issues related to the source side. One possible solution is to use the passive protocol to eliminate the side channels introduced by active modulators at the source. Recently, a fully passive QKD protocol was proposed that could simultaneously achieve passive encoding and passive decoy-state modulation using linear optics. In this work, we propose a fully passive MDIQKD scheme that can protect the system from both side channels of source modulators and attacks on the measurement devices, which can significantly improve the implementation security of the QKD systems. We provide a specific passive encoding strategy and a method for decoy-state analysis, followed by simulation results for the secure key rate in the asymptotic scenario. Our work offers a feasible way to improve the implementation security of QKD systems and serves as a reference for achieving passive QKD schemes using realistic devices.
A recently proposed fully passive quantum key distribution (QKD) removes all source modulator side channels. In this work, we combine fully passive sources with measurement-device-independent (MDI) QKD to simultaneously remove side channels from source modulators and detectors. We show a numerical simulation of passive MDI QKD, and we obtain an acceptable key rate while achieving much better implementation security, as well as ease of implementation, compared with a recently proposed fully passive twin-field QKD, paving the way towards more secure and practical QKD systems. We prove that a fully passive protocol is compatible with MDI QKD and we propose a novel idea that can improve the sifting efficiency.
Reference-frame-independent quantum key distribution (RFI QKD) significantly alleviates alignment requirements for reference frame in practical quantum communication systems. While the original protocol requires Alice to prepare six quantum states in ZZZ, XXX, and YYY bases, its reliance on active modulation introduces inherent side-channel vulnerabilities from device imperfections. We address this security limitation by integrating a fully passive source into the RFI framework. In this paper, we propose a fully passive RFI QKD protocol. Our protocol avoids active modulation entirely, suppressing side-channel risks through passive quantum state generation. Moreover, by making full utilization of the quantum states generated by the fully passive source, we enhance the secure key rate of fully passive protocol. We establish a system model to analyze the performance of the protocol. Through the optimization of post-selection intervals and intensities, we obtain the maximum secure key transmission rate of the protocol. Under ideal circumstances, the secure key transmission rate of our protocol can reach more than 50% of that of the ideal QKD. Under practical conditions, we have considered the finite-length effect. When pulse number generated by the source reaches 101210^{12}1012, the maximum communication distances of the protocol can reach 167 km and 136 km with a reference frame misalignment of $0 $ and $45^{\circ} $ respectively. We believe that our protocol can contribute to the development of practical QKD systems.
Quantum key distribution (QKD) offers information-theoretic security verified by quantum mechanics to share keys between legitimate users. Most of the existing QKD systems employ active decoy states based on weak coherent sources (WCS). Meanwhile, parametric down-conversion (PDC) sources are seldom used due to several of their shortcomings. In the present work, to show the superiority of PDC sources, we have accomplished a proof-of-principle demonstration of a PDC source-based QKD with over 40 dB based on the one-way BB84 protocol. In this QKD system, a novel passive decoy-state scheme-secure to coherent attacks-is proposed, using several built-in decoy states for parameter estimation. This not only avoids intensity modulating errors, but also diminishes all possible information leakage from the intensity modulating process. The experimental results show a significantly enhanced performance compared with existing PDC source-based QKD systems. In addition, it exhibits some superiority even over active decoy-state QKD systems based on WCS.
Abstract A passive quantum key distribution (QKD) transmitter generates the quantum states prescribed by a QKD protocol at random, combining a fixed quantum mechanism and a post-selection step. By circumventing the use of active optical modulators externally driven by random number generators, passive QKD transmitters offer immunity to modulator side channels and potentially enable higher frequencies of operation. Recently, the first linear optics setup suitable for passive decoy-state QKD has been proposed. In this work, we simplify the prototype and adopt sharply different approaches for BB84 polarization encoding and decoy-state parameter estimation. In particular, our scheme avoids a probabilistic post-selection step that is central to the former proposal. On top of it, we elaborate a simple and tight custom-made security analysis.