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

Optical Fiber Communication Conference

Daylight Operation of a High-Speed Free-Space Quantum Key Distribution using Silica-based Integration Chip and Micro-Optics-based Module

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

Published Jan 1, 2019• 5 citations
Publisher

Abstract

We developed a high-speed quantum key distribution (QKD) system integrated with a compact self-developed silica-based planar lightwave circuit chip and a micro-optics-based polarization module. Also, we demonstrated that our system can generate average secure keys at the rate of 701.22 kbps over a free-space link of 275 m in daylight by using effective noise filtering systems in the temporal, spectral, and spatial domains. Real-time beam tracking system was adopted to stabilize the fluctuation of the beam position.

DOI
10.1364/ofc.2019.m4f.2

Related papers

Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics

M. Avesani, L. Calderaro, Matteo Schiavon +16 more

Abstract The future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions.

arXiv:1907.10039•npj Quantum Information•Jun 8, 2021•172 citations

High-speed free-space quantum key distribution system for urban daylight applications

María-José García-Martínez, Natalia Denisenko, D. Soto +3 more

We report a free-space quantum key distribution system designed for high-speed key transmission in urban areas. Clocking the system at gigahertz frequencies and efficiently filtering background enables higher secure key rates than those previously achieved by similar systems. The transmitter and receiver are located in two separate buildings 300 m apart in downtown Madrid and they exchange secure keys at rates up to 1 Mbps. The system operates in full bright daylight conditions with an average secure key rate of 0.5 Mbps and 24 h stability without human intervention.

Applied Optics•May 6, 2013•35 citations

Time-frequency Quantum Key Distribution over a Free-Space Optical Link

Jasper Rödiger, Nicolas Perlot, Oliver J. Benson +1 more

We present an implementation of the time-frequency (TF) quantum key distribution (QKD) protocol realized mainly with standard telecommunication components at 1550 nm. TF-QKD is implemented with modulations in time and frequency, namely pulse position modulation (PPM) and frequency shift keying (FSK). The time-frequency uncertainty relation ensures the security of the protocol. We further demonstrate free-space optical QKD transmission over a 388-m distance. Since the QKD setup is single-mode fiber (SMF) -based, precise coupling in and out of the SMFs is crucial. Thus, we implemented an optical tracking system. The QKD signal is wavelength-multiplexed with a strong beacon for optical tracking. Strong spectral filtering is necessary to separate beacon and QKD signal. Together with spatial filtering caused by the SMF most background light is filtered, enabling daylight QKD transmission.

arXiv:2112.04306•Dec 8, 2021•0 citations

Silicon photonics-based experimental daylight free-space quantum key distribution at telecom wavelength (Conference Presentation)

Marco Avesani, Luca Calderaro, Matteo Schiavon +14 more

The future global-scale quantum communication network will require free-space and satellite links able to work in daylight conditions and compatible with the telecom fiber infrastructure. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps. The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource for future satellite missions.

•Mar 10, 2020•0 citations

Quantum photonic chip for practical high-rate continuous-variable quantum key distribution

Lin Cao, Sijin Li, Hao Yu +12 more

Quantum key distribution (QKD) is a quantum communication technology that offers absolute security. Among its various implementations, continuous-variable (CV) QKD has garnered significant attention due to its high secret key generation rates and compatibility with conventional optical telecommunication infrastructure, which operates under ambient conditions. However, chip-based integration is crucial for realizing practical and scalable CV-QKD networks, and photonic integrated circuit technology is a potential solution, leveraging the on-chip integration of essential optical components onto silicon photonic circuits. Therefore, this work presents a compact, stable, and cost-effective quantum photonic CV-QKD system on a chip. Our architecture combines time- and polarization-multiplexing with high-extinction-ratio pulse generation to mitigate excess noise. At the same time, a real-time feedback control mechanism compensates for polarization drift, ensuring robust system performance. Fiber-based evaluations reveal secret key generation rates of 2.55 Mbps over 25 km and 0.737 Mbps over 50 km with 12 h stable operation, establishing, to our knowledge, a new benchmark for integrated photonic CV-QKD systems with both the transmitter and receiver on-chip. These results mark a significant milestone in on-chip quantum communication, paving the way for widespread adoption of photonic integrated circuits in future metropolitan quantum-secure networks.

Photonics Research•Mar 13, 2026•2 citations

Daylight quantum key distribution over free-space optics for future security networks

Peide Zhang, Romerson Deiny Oliveira, Zoe C. M. Davidson +7 more

As the demand for better security and higher capacity grows, quantum key distribution (QKD) using free-space optics (FSO) presents an innovative solution for 5G networks and beyond. The Innovate-UK AirQKD project explores how FSO–QKD could enable quantum-secure connections at a metropolitan scale, focusing on the critical “last-mile” of connectivity. However, implementing FSO–QKD in the real world brings several engineering challenges, spanning software, hardware, system integration, and security. This paper dives into the complexities of system architecture and integration, QKD transmission over FSO, and the post-processing of keys. We showcase a cohesive system design that blends the quantum and classical domains, incorporating cutting-edge FSO–QKD hardware and software. The system’s functionality is demonstrated for key processes such as transmission, post-processing, network control, and key management. As a case study, we tested an FSO–QKD link over 135 m at BT’s Adastral Park in Suffolk, UK. The setup achieved a photon count rate of up to 585 kcps through a channel with 15.9 dB of loss and 12 kHz of background noise, resulting in a security key rate (SKR) of up to 84.3 kbps using two detectors. We also conducted simulations to estimate the SKR and compared them with the experimental results. Both approaches confirm the system’s ability to generate keys and successfully transmit orthogonal polarization states, highlighting its potential for practical application.

Journal of Optical Communications and Networking•Mar 24, 2025•8 citations
We developed a high-speed quantum key distribution (QKD) system integrated with a compact self-developed silica-based planar lightwave circuit chip and a micro-optics-based polarization module. Also, we demonstrated that our system can generate average secure keys at the rate of 701.22 kbps over a free-space link of 275 m in daylight by using effective noise filtering systems in the temporal, spectral, and spatial domains. Real-time beam tracking system was adopted to stabilize the fluctuation of the beam position.
Abstract The future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions.
We report a free-space quantum key distribution system designed for high-speed key transmission in urban areas. Clocking the system at gigahertz frequencies and efficiently filtering background enables higher secure key rates than those previously achieved by similar systems. The transmitter and receiver are located in two separate buildings 300 m apart in downtown Madrid and they exchange secure keys at rates up to 1 Mbps. The system operates in full bright daylight conditions with an average secure key rate of 0.5 Mbps and 24 h stability without human intervention.
We present an implementation of the time-frequency (TF) quantum key distribution (QKD) protocol realized mainly with standard telecommunication components at 1550 nm. TF-QKD is implemented with modulations in time and frequency, namely pulse position modulation (PPM) and frequency shift keying (FSK). The time-frequency uncertainty relation ensures the security of the protocol. We further demonstrate free-space optical QKD transmission over a 388-m distance. Since the QKD setup is single-mode fiber (SMF) -based, precise coupling in and out of the SMFs is crucial. Thus, we implemented an optical tracking system. The QKD signal is wavelength-multiplexed with a strong beacon for optical tracking. Strong spectral filtering is necessary to separate beacon and QKD signal. Together with spatial filtering caused by the SMF most background light is filtered, enabling daylight QKD transmission.
The future global-scale quantum communication network will require free-space and satellite links able to work in daylight conditions and compatible with the telecom fiber infrastructure. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps. The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource for future satellite missions.
Quantum key distribution (QKD) is a quantum communication technology that offers absolute security. Among its various implementations, continuous-variable (CV) QKD has garnered significant attention due to its high secret key generation rates and compatibility with conventional optical telecommunication infrastructure, which operates under ambient conditions. However, chip-based integration is crucial for realizing practical and scalable CV-QKD networks, and photonic integrated circuit technology is a potential solution, leveraging the on-chip integration of essential optical components onto silicon photonic circuits. Therefore, this work presents a compact, stable, and cost-effective quantum photonic CV-QKD system on a chip. Our architecture combines time- and polarization-multiplexing with high-extinction-ratio pulse generation to mitigate excess noise. At the same time, a real-time feedback control mechanism compensates for polarization drift, ensuring robust system performance. Fiber-based evaluations reveal secret key generation rates of 2.55 Mbps over 25 km and 0.737 Mbps over 50 km with 12 h stable operation, establishing, to our knowledge, a new benchmark for integrated photonic CV-QKD systems with both the transmitter and receiver on-chip. These results mark a significant milestone in on-chip quantum communication, paving the way for widespread adoption of photonic integrated circuits in future metropolitan quantum-secure networks.
As the demand for better security and higher capacity grows, quantum key distribution (QKD) using free-space optics (FSO) presents an innovative solution for 5G networks and beyond. The Innovate-UK AirQKD project explores how FSO–QKD could enable quantum-secure connections at a metropolitan scale, focusing on the critical “last-mile” of connectivity. However, implementing FSO–QKD in the real world brings several engineering challenges, spanning software, hardware, system integration, and security. This paper dives into the complexities of system architecture and integration, QKD transmission over FSO, and the post-processing of keys. We showcase a cohesive system design that blends the quantum and classical domains, incorporating cutting-edge FSO–QKD hardware and software. The system’s functionality is demonstrated for key processes such as transmission, post-processing, network control, and key management. As a case study, we tested an FSO–QKD link over 135 m at BT’s Adastral Park in Suffolk, UK. The setup achieved a photon count rate of up to 585 kcps through a channel with 15.9 dB of loss and 12 kHz of background noise, resulting in a security key rate (SKR) of up to 84.3 kbps using two detectors. We also conducted simulations to estimate the SKR and compared them with the experimental results. Both approaches confirm the system’s ability to generate keys and successfully transmit orthogonal polarization states, highlighting its potential for practical application.