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:1706.08705 · Optics Express

Critical side channel effects in random bit generation with multiple semiconductor lasers in a polarization-based quantum key distribution system

Heasin Ko, Byung‐Seok Choi, Joong‐Seon Choe, Kap‐Joong Kim, Jong-Hoi Kim, Chun Ju Youn

Published Aug 10, 2017• 20 citations
arXivHTMLPDF

Abstract

Most polarization-based BB84 quantum key distribution (QKD) systems utilize multiple lasers to generate one of four polarization quantum states randomly. However, random bit generation with multiple lasers can potentially open critical side channels that significantly endangers the security of QKD systems. In this paper, we show unnoticed side channels of temporal disparity and intensity fluctuation, which possibly exist in the operation of multiple semiconductor laser diodes. Experimental results show that the side channels can enormously degrade security performance of QKD systems. An important system issue for the improvement of quantum bit error rate (QBER) related with laser driving condition is further addressed with experimental results.

DOI
10.1364/oe.25.020045

Related papers

High-speed and high-performance polarization-based quantum key distribution system without side channel effects caused by multiple lasers

Heasin Ko, Byung‐Seok Choi, Joong‐Seon Choe +3 more

Side channel effects such as temporal disparity and intensity fluctuation of photon pulses caused by random bit generation with multiple laser diodes in high-speed polarization-based BB84 quantum key distribution (QKD) systems can be eliminated by increasing DC bias current condition. However, background photons caused by the spontaneous emission process under high DC bias current degrade the performance of the QKD systems. In this study, we investigated, for the first time, the effects of spontaneously emitted photons on the system performance in a high-speed QKD system at a clock rate of 400 MHz. Also, we further show improvements of system performance without side channel effects by utilizing temporal filtering technique with real-time FPGA signal processing.

arXiv:1711.08255•Photonics Research•Feb 28, 2018•20 citations

Experimental demonstration of the time-dependent source side-channel and countermeasures in polarization-based BB84 QKD systems

Wanli Zhang, Cong Jiang, Fei Zhou +3 more

High-speed is one development tendency of the practical and commercial quantum key distribution (QKD) systems, and the gain-switched semiconductor laser (GSSL) and Sagnac interferometer have been popular components for high-speed commercial polarization-based BB84 QKD systems thanks to their stability, compactness and low cost. However, due to the finite extinction ratio (ER) of the GSSL, the time-dependent source side-channel, which is theoretically presented in [Phys. Rev. A106(6): 062618 (2022)10.1103/PhysRevA.106.062618], also exists in these QKD systems. In this article, we experimentally investigate this side-channel in the polarization-based BB84 QKD system. The results show an obvious correlation in the output polarization states between the weak leakage light and its adjacent pulses, which will cause information to leak. More importantly, we have proposed several countermeasures, retested the side channel, and developed a mathematical framework to quantitatively assess the impact of the time-dependent side channel and these countermeasures on the secure key rate. Finally, we offer a trade-off analysis that considers defense effectiveness, pulse impact, and cost for various countermeasures in QKD. This provides a practical recommendation for improving the security of QKD systems.

Optics Express•Sep 23, 2024•4 citations

Impact of Physical Channel Impairments and Detector Noise on BB84 Quantum Key Distribution: A Python-Based Simulation Study

Avinash Upadhyay, Shashwat Saxena, Ritu Raj Singh +3 more

The absence of real single-photon sources is a significant limitation to the experimental implementation of the BB84 quantum key distribution (QKD) protocol. When substantially attenuated laser pulses are substituted for ideal sources in practical systems, the outcome is weak coherent states where each pulse has a nonzero probability of having multiple photons rather than pure single-photon emission. To evaluate quantum bit error rate (QBER), key generation rate and overall system security it is essential to describe the exact impact of the optical and physical system on such pulses. This practical tradeoff presents additional issues. It is crucial to understand how QBER is impacted by attenuation, loss, dispersion, depolarisation and detector properties particularly in adversarial scenarios such as photon number splitting (PNS) and beam-splitting attacks. Although a significant amount of research has been conducted on algorithmic simulations of BB84, there are few complete frameworks that can physically explain these effects and their impact on QBER. This work models the BB84 protocol at the physical level by developing a Python-based simulation platform that takes into account all significant channel impairments and system inefficiencies. The framework supports both theoretical and practical optimisation of QKD systems by further isolating the effects of different optical losses and eavesdropping techniques on QBER and secure key generation.

National Conference on Communications•Feb 26, 2026•1 citation

Performance analysis of polarization coding BB84 quantum key distribution system under non-Markovian channel

Wei Liu, Changhua Zhu, Zhang Linxi +1 more

The characteristics of quantum channel play important roles on designing a high performance quantum communication system. In this paper, we analyze the fidelity of polarization state travelling through a non-Markovian optical fiber depolarizing quantum channel with color noise environment. The quantum bit error rate (QBER) of a polarization coding BB84 quantum key distribution (QKD) system under non-Markovian depolarizing channel is also discussed. Analysis results show that there are several security regions caused by the fluctuation of QBER in such a non-Markovian channel. These will provide references for designing polarization compensation scheme and estimating of secure distance.

International Conference on Computer, Information and Telecommunication Systems•Jul 1, 2017•1 citation

Differential-phase-shift quantum key distribution experiment using fast physical random bit generator with chaotic semiconductor lasers

Toshimori Honjo, Atsushi Uchida, Kazuya Amano +6 more

A high speed physical random bit generator is applied for the first time to a gigahertz clocked quantum key distribution system. Random phase-modulation in a differential-phase-shift quantum key distribution (DPS-QKD) system is performed using a 1-Gbps random bit signal which is generated by a physical random bit generator with chaotic semiconductor lasers. Stable operation is demonstrated for over one hour, and sifted keys are successfully generated at a rate of 9.0 kbps with a quantum bit error rate of 3.2% after 25-km fiber transmission.

Optics Express•May 14, 2009•45 citations

Side-channel-free quantum key distribution source using a KTP polarization modulator and a broadband laser

Tahereh Rezaei, Andrew Conrad, Philip R. Battle +2 more

We present progress on demonstrating a side-channel-free, decoy-state quantum key distribution (QKD) source based on a polarization-modulator and a wavelength-stable attenuated pulsed laser. By modulating the polarization of the quantum state, a three-state QKD protocol is achieved. The polarization-modulator-based QKD source improves security by removing several sources of side-channel attacks that exist when multiple sources are used to generate different QKD states. Here we present our single-source design, as well as an evaluation of critical subsystems characterized by the quantum bit error rate (QBER), quantum state tomography, and achievable key rates. The QKD source is intended to operate using minimal size, weight, and power (SWaP). In our system, we use a custom KTP waveguide modulator designed and fabricated by AdvR. Our QKD source can be operated using both narrow-band and broadband lasers, and we present characterization data using a He-Ne laser, and a diode laser, respectively. The polarization-modulator-based QKD source has applications in future mobile quantum networks incorporating unmanned aerial vehicles (UAV) and autonomous vehicles, as well as fiber-based quantum networks.

Quantum Computing, Communication, and Simulation•Jan 24, 2023•0 citations
Most polarization-based BB84 quantum key distribution (QKD) systems utilize multiple lasers to generate one of four polarization quantum states randomly. However, random bit generation with multiple lasers can potentially open critical side channels that significantly endangers the security of QKD systems. In this paper, we show unnoticed side channels of temporal disparity and intensity fluctuation, which possibly exist in the operation of multiple semiconductor laser diodes. Experimental results show that the side channels can enormously degrade security performance of QKD systems. An important system issue for the improvement of quantum bit error rate (QBER) related with laser driving condition is further addressed with experimental results.
Side channel effects such as temporal disparity and intensity fluctuation of photon pulses caused by random bit generation with multiple laser diodes in high-speed polarization-based BB84 quantum key distribution (QKD) systems can be eliminated by increasing DC bias current condition. However, background photons caused by the spontaneous emission process under high DC bias current degrade the performance of the QKD systems. In this study, we investigated, for the first time, the effects of spontaneously emitted photons on the system performance in a high-speed QKD system at a clock rate of 400 MHz. Also, we further show improvements of system performance without side channel effects by utilizing temporal filtering technique with real-time FPGA signal processing.
High-speed is one development tendency of the practical and commercial quantum key distribution (QKD) systems, and the gain-switched semiconductor laser (GSSL) and Sagnac interferometer have been popular components for high-speed commercial polarization-based BB84 QKD systems thanks to their stability, compactness and low cost. However, due to the finite extinction ratio (ER) of the GSSL, the time-dependent source side-channel, which is theoretically presented in [Phys. Rev. A106(6): 062618 (2022)10.1103/PhysRevA.106.062618], also exists in these QKD systems. In this article, we experimentally investigate this side-channel in the polarization-based BB84 QKD system. The results show an obvious correlation in the output polarization states between the weak leakage light and its adjacent pulses, which will cause information to leak. More importantly, we have proposed several countermeasures, retested the side channel, and developed a mathematical framework to quantitatively assess the impact of the time-dependent side channel and these countermeasures on the secure key rate. Finally, we offer a trade-off analysis that considers defense effectiveness, pulse impact, and cost for various countermeasures in QKD. This provides a practical recommendation for improving the security of QKD systems.
The absence of real single-photon sources is a significant limitation to the experimental implementation of the BB84 quantum key distribution (QKD) protocol. When substantially attenuated laser pulses are substituted for ideal sources in practical systems, the outcome is weak coherent states where each pulse has a nonzero probability of having multiple photons rather than pure single-photon emission. To evaluate quantum bit error rate (QBER), key generation rate and overall system security it is essential to describe the exact impact of the optical and physical system on such pulses. This practical tradeoff presents additional issues. It is crucial to understand how QBER is impacted by attenuation, loss, dispersion, depolarisation and detector properties particularly in adversarial scenarios such as photon number splitting (PNS) and beam-splitting attacks. Although a significant amount of research has been conducted on algorithmic simulations of BB84, there are few complete frameworks that can physically explain these effects and their impact on QBER. This work models the BB84 protocol at the physical level by developing a Python-based simulation platform that takes into account all significant channel impairments and system inefficiencies. The framework supports both theoretical and practical optimisation of QKD systems by further isolating the effects of different optical losses and eavesdropping techniques on QBER and secure key generation.
The characteristics of quantum channel play important roles on designing a high performance quantum communication system. In this paper, we analyze the fidelity of polarization state travelling through a non-Markovian optical fiber depolarizing quantum channel with color noise environment. The quantum bit error rate (QBER) of a polarization coding BB84 quantum key distribution (QKD) system under non-Markovian depolarizing channel is also discussed. Analysis results show that there are several security regions caused by the fluctuation of QBER in such a non-Markovian channel. These will provide references for designing polarization compensation scheme and estimating of secure distance.
A high speed physical random bit generator is applied for the first time to a gigahertz clocked quantum key distribution system. Random phase-modulation in a differential-phase-shift quantum key distribution (DPS-QKD) system is performed using a 1-Gbps random bit signal which is generated by a physical random bit generator with chaotic semiconductor lasers. Stable operation is demonstrated for over one hour, and sifted keys are successfully generated at a rate of 9.0 kbps with a quantum bit error rate of 3.2% after 25-km fiber transmission.
We present progress on demonstrating a side-channel-free, decoy-state quantum key distribution (QKD) source based on a polarization-modulator and a wavelength-stable attenuated pulsed laser. By modulating the polarization of the quantum state, a three-state QKD protocol is achieved. The polarization-modulator-based QKD source improves security by removing several sources of side-channel attacks that exist when multiple sources are used to generate different QKD states. Here we present our single-source design, as well as an evaluation of critical subsystems characterized by the quantum bit error rate (QBER), quantum state tomography, and achievable key rates. The QKD source is intended to operate using minimal size, weight, and power (SWaP). In our system, we use a custom KTP waveguide modulator designed and fabricated by AdvR. Our QKD source can be operated using both narrow-band and broadband lasers, and we present characterization data using a He-Ne laser, and a diode laser, respectively. The polarization-modulator-based QKD source has applications in future mobile quantum networks incorporating unmanned aerial vehicles (UAV) and autonomous vehicles, as well as fiber-based quantum networks.