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

Impact of Laser Frequency Noise on a Heterodyne Continuous Variable Quantum Key Distribution System

Max Rückmann, Sebastian Kleis, Christian Schaeffer

Published May 8, 2019• 0 citations
OpenAlex

Abstract

We experimentally investigate the impact of laser frequency noise on the achievable key rate and distance of a heterodyne continuous variable quantum key distribution system using different lasers at the transmitter site.

Related papers

1 GBaud Continuous Variable Quantum Key Distribution Using Pilot Tone Assisted Heterodyne Detection

Max Rückmann, Sebastian Kleis, Christian Schaeffer

The major drawbacks of current CV-QKD systems are the achievable secret key rate or transmission distance. Moreover, most of the CV-QKD systems are based on homodyne detection and use a remotely transmitted local oscillator in time or polarization multiplex. This enhances the complexity of the transmitter and the receiver, limits the transmission distance and leaves a security loophole for a potential eavesdropper performing for example a local oscillator calibration attack. In this article, a CV-QKD system using a discrete 8-state phase modulation and a symbol rate of 1 GBd as well as a heterodyne detection with a real local oscillator is experimentally demonstrated. The excess noise, a crucial parameter limiting the achievable key rate and transmission distance, is studied.

•Jun 11, 2018•4 citations

1 GBaud Heterodyne Continuous Variable Quantum Key Distribution over 26 km Fiber

Max Rückmann, Christian G. Schaeffer

We experimentally demonstrate a 1 GBaud heterodyne continuous variable quantum key distribution system based on standard telecom components capable to achieve a key rate of 1.71 Mbit/s over 26 km of fiber.

Conference on Lasers and Electro-Optics•Jan 1, 2019•4 citations

Laser Linewidth Effects in Continuous-Variable QKD: Simulation-Based Analysis and Optimization Guidelines for Defense-Grade Secure System

Seyed Saman Mahjour, F.M.A. Moreira

Continuous-Variable Quantum Key Distribution (CV-QKD) offers practical advantages for secure communication, but laser linewidth-induced phase noise remains a critical performance limitation. This work presents a comprehensive simulation-based analysis quantifying the impact of laser linewidth on secret key rate (SKR) in Gaussian-modulated coherent-state CV-QKD systems. We develop a detailed noise model incorporating detector electronics, Raman scattering, phase recovery, ADC quantization, and laser relative intensity noise. Through systematic parameter sweeps spanning linewidths from 10 Hz to 250 kHz, modulation variances from 1 to 20 SNU, and fiber distances up to 100 km, we identify three distinct operational regimes and optimization strategies for both transmitted local oscillator (TLO) and local–local oscillator (LLO) configurations under homodyne and heterodyne detection. Results show that metropolitan-scale links (50 km) require linewidths below 5 kHz to maintain secure operation, with performance decreasing beyond 25 kHz. We demonstrate that modulation variance must be jointly optimized with laser quality, with optimal values decreasing from 3–4 SNU at narrow linewidths to 2–2.5 SNU at moderate linewidths. The analysis reveals asymmetric sensitivity in LLO systems where local oscillator linewidth degrades performance more strongly than signal laser linewidth. These quantitative findings provide practical design guidelines for achieving secure CV-QKD operation over metropolitan distances with realistic hardware constraints, supporting deployment of defense-grade quantum communication networks.

Photonics•Apr 27, 2026•0 citations

Improving the maximum transmission distance of continuous-variable quantum key distribution with noisy coherent states using a noiseless amplifier

Tianyi Wang, Song Yu, Yichen Zhang +2 more

Physics Letters A•Aug 1, 2014•19 citations

Detector Asymmetry in Continuous Variable Quantum Key Distribution

Bartlett, Jennifer O, Wilson, Alfie J Myers, Christopher J. Chunnilall +1 more

In Local-local Oscillator (LLO) based Continuous-Variable Quantum Key Distribution (CV-QKD), the phase reference of the transmitter and receiver, Alice and Bob, are naturally de-correlated due to their use of individual lasers. A phase reference signal is used, whose measurement is critical for estimating the phase difference and correcting the raw QKD data. We observed that asymmetry in the quadrature measurements of the shot noise-limited heterodyne detector affects the accuracy of the reference signal's phase estimation and thereby reduces the achievable transmission distance and key rate of the CV-QKD system. We quantify the effect and propose a method to counteract the effect of detection asymmetry. We also evaluate the effects of detection asymmetry using quantum optical tomography.

arXiv:2510.17419•Oct 20, 2025•0 citations

Self-heterodyne Technique for measuring Linewidth of Laser for applications in Continuous Variable Quantum Key Distribution

Yagublu, Kanan

•Sep 1, 2022•0 citations
The major drawbacks of current CV-QKD systems are the achievable secret key rate or transmission distance. Moreover, most of the CV-QKD systems are based on homodyne detection and use a remotely transmitted local oscillator in time or polarization multiplex. This enhances the complexity of the transmitter and the receiver, limits the transmission distance and leaves a security loophole for a potential eavesdropper performing for example a local oscillator calibration attack. In this article, a CV-QKD system using a discrete 8-state phase modulation and a symbol rate of 1 GBd as well as a heterodyne detection with a real local oscillator is experimentally demonstrated. The excess noise, a crucial parameter limiting the achievable key rate and transmission distance, is studied.
Continuous-Variable Quantum Key Distribution (CV-QKD) offers practical advantages for secure communication, but laser linewidth-induced phase noise remains a critical performance limitation. This work presents a comprehensive simulation-based analysis quantifying the impact of laser linewidth on secret key rate (SKR) in Gaussian-modulated coherent-state CV-QKD systems. We develop a detailed noise model incorporating detector electronics, Raman scattering, phase recovery, ADC quantization, and laser relative intensity noise. Through systematic parameter sweeps spanning linewidths from 10 Hz to 250 kHz, modulation variances from 1 to 20 SNU, and fiber distances up to 100 km, we identify three distinct operational regimes and optimization strategies for both transmitted local oscillator (TLO) and local–local oscillator (LLO) configurations under homodyne and heterodyne detection. Results show that metropolitan-scale links (50 km) require linewidths below 5 kHz to maintain secure operation, with performance decreasing beyond 25 kHz. We demonstrate that modulation variance must be jointly optimized with laser quality, with optimal values decreasing from 3–4 SNU at narrow linewidths to 2–2.5 SNU at moderate linewidths. The analysis reveals asymmetric sensitivity in LLO systems where local oscillator linewidth degrades performance more strongly than signal laser linewidth. These quantitative findings provide practical design guidelines for achieving secure CV-QKD operation over metropolitan distances with realistic hardware constraints, supporting deployment of defense-grade quantum communication networks.
In Local-local Oscillator (LLO) based Continuous-Variable Quantum Key Distribution (CV-QKD), the phase reference of the transmitter and receiver, Alice and Bob, are naturally de-correlated due to their use of individual lasers. A phase reference signal is used, whose measurement is critical for estimating the phase difference and correcting the raw QKD data. We observed that asymmetry in the quadrature measurements of the shot noise-limited heterodyne detector affects the accuracy of the reference signal's phase estimation and thereby reduces the achievable transmission distance and key rate of the CV-QKD system. We quantify the effect and propose a method to counteract the effect of detection asymmetry. We also evaluate the effects of detection asymmetry using quantum optical tomography.