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

Compact GHz-Gated InGaAs/InP SPAD Arrays for Quantum Key Distribution

Louise Wells, Joseph A. Dolphin, Rosemary O. E. Scowen, D. J. P. Ellis, Abbie Lowe, B. Ramsey, J. I. Davies, A. J. Shields, Taofiq K. Paraïso, R. M. Stevenson

Published Jan 1, 2026• 0 citations
Publisher

Abstract

This work addresses scalable photonic integration of non-cryogenic detectors for quantum key distribution. Using GHz-gated InGaAs/InP SPAD arrays and silica waveguides, we achieve secure key rates over 15 kbps across 100 km.
DOI
10.1364/ofc.2026.w4k.5

Related papers

Hybrid-integrated InGaAs/InP SPAD arrays for quantum communications

Joseph A. Dolphin, Rosemary O. E. Scowen, Louise Wells +7 more

Photonic integration is a promising route to miniaturise the hardware of quantum key distribution (QKD), yet the monolithic integration of single-photon detectors remains a significant challenge. QKD receiver chips integrating superconducting detectors have been demonstrated, but their requirement for cryogenic cooling restricts their practical applications. High-frequency gated single-photon avalanche diodes (SPADs) provide a mature non-cryogenic alternative, and their fabrication into compact arrays would enable scalable hybrid integration. However, this faces several challenges related to efficient GHz array gating, inter-pixel crosstalk, and scalable waveguide coupling, which to date remain unaddressed. Here, we overcome the key challenges and develop GHz-gated InGaAs/InP SPAD arrays with performance viable for QKD and negligible inter-pixel crosstalk. We combine the arrays with low-loss silica waveguide chips to produce compact hybrid QKD receivers and perform BB84 protocol experiments, achieving secure key rates over 2 Mbps at short distances and 15 kbps over 100 km of fibre. Our work provides a method for flexible and scalable integration of waveguide-coupled SPADs for quantum information processing applications.

arXiv:2509.05134•Optica Quantum•Nov 20, 2025•1 citation

The application of hybrid integrated photonics to quantum communication systems

Joseph A. Dolphin

Quantum key distribution (QKD) is a rapidly maturing quantum photonic technology that allows for the distribution of secure cryptographic keys under no assumptions of the attacker's computing power. A key hurdle for its large-scale adoption is the reduction of its hardware size and cost, for which photonic integration is a promising solution. However, there exists no perfect material platform for this task, and for QKD this leads to either design compromises or core functionalities left off-chip. This thesis makes the assertion that hybrid integrated photonics, where one combines two chip materials into one structure, can resolve some of these issues. Firstly, we present an edge-coupled hybrid transceiver that combines a silicon nitride waveguide chip with an indium phosphide modulator chip. Secondly, we pursue the hybrid integration of the single photon detectors. However, the appropriate solution of fast-gated telecom-wavelength avalanche diodes did not exist, and so in the second experimental chapter of this thesis we develop and characterise a linear array of GHz-gated InGaAs/InP SPADs. Finally, we demonstrate a hybrid integrated QKD receiver, consisting of a silica waveguide chip with the aforementioned SPAD array. This represents the first integrated QKD receiver without requiring either external single photon detectors or cryogenic cooling. The results support the benefits of hybrid integration for quantum key distribution, but also more widely for quantum photonic technology as it continues to emerge.

•Sep 30, 2025•0 citations

Practical Quantum Key Distribution Over 100 km Using Sinusoidally Gated InGaAs/InP Avalanche Photodiodes

Naoto Namekata, Hiroki Takesue, Toshimori Honjo +2 more

We report on the quantum key distribution experiment using ultra-low-noise 2-GHz sinusoidally gated InGaAs/InP avalanche photodiodes. The detectors enabled us to distribute secure keys over 100 km with a bit rate of 24 kbps.

Conference on Lasers and Electro-Optics•Jan 1, 2011•0 citations

High-rate quantum key distribution over 100 km using ultra-low-noise, 2-GHz sinusoidally gated InGaAs/InP avalanche photodiodes

Naoto Namekata, Hiroki Takesue, Toshimori Honjo +2 more

We have demonstrated quantum key distribution (QKD) over 100 km using single-photon detectors based on InGaAs/InP avalanche photodiodes (APDs). We implemented the differential phase shift QKD (DPS-QKD) protocol with electrically cooled and 2-GHz sinusoidally gated APDs. The single-photon detector has a dark count probability of 2.8 × 10(-8) (55 counts per second) with a detection efficiency of 6 %, which enabled us to achieve 24 kbit/s secure key rate over 100 km of optical fiber. The DPS-QKD system offers better performances in a practical way than those achieved using superconducting single-photon detectors. Moreover, the distance that secure keys against the general individual attacks can be distributed has been extended to 160 km.

Optics Express•May 16, 2011•84 citations

2.23 GHz gating InGaAs/InP single-photon avalanche diode for quantum key distribution

Jun Zhang, Patrick Eraerds, Nino Walenta +3 more

We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose a useful way to characterize the afterpulsing distribution for rapid gating that allows for easy comparison with conventional gating regimes. We compare the performance of this rapid gating scheme with free-running detector and superconducting single-photon detector (SSPD) for the coherent one-way quantum key distribution (QKD) protocol. The rapid gating system is well suited for both high-rate and long-distance QKD applications, in which Mbps key rates can be achieved for distances less than 40km with 50 ns deadtime and the maximum distance is limited to ~190km with 5 μs deadtime. These results illustrate that the afterpulsing is no longer a limiting factor for QKD.

arXiv:1002.3240•Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Apr 20, 2010•68 citations

Fully integrated InGaAs/InP single-photon detector module with gigahertz sine wave gating

Xiao-Lei Liang, Jian-Hong Liu, Quan Wang +6 more

InGaAs/InP single-photon avalanche diodes (SPADs) working in the regime of GHz clock rates are crucial components for the high-speed quantum key distribution (QKD). We have developed for the first time a compact, stable, and user-friendly tabletop InGaAs/InP single-photon detector system operating at a 1.25 GHz gate rate that fully integrates functions for controlling and optimizing SPAD performance. We characterize the key parameters of the detector system and test the long-term stability of the system for continuous operation of 75 h. The detector system can substantially enhance QKD performance and our present work paves the way for practical high-speed QKD applications.

arXiv:1208.0127•Review of Scientific Instruments•Aug 1, 2012•39 citations
Photonic integration is a promising route to miniaturise the hardware of quantum key distribution (QKD), yet the monolithic integration of single-photon detectors remains a significant challenge. QKD receiver chips integrating superconducting detectors have been demonstrated, but their requirement for cryogenic cooling restricts their practical applications. High-frequency gated single-photon avalanche diodes (SPADs) provide a mature non-cryogenic alternative, and their fabrication into compact arrays would enable scalable hybrid integration. However, this faces several challenges related to efficient GHz array gating, inter-pixel crosstalk, and scalable waveguide coupling, which to date remain unaddressed. Here, we overcome the key challenges and develop GHz-gated InGaAs/InP SPAD arrays with performance viable for QKD and negligible inter-pixel crosstalk. We combine the arrays with low-loss silica waveguide chips to produce compact hybrid QKD receivers and perform BB84 protocol experiments, achieving secure key rates over 2 Mbps at short distances and 15 kbps over 100 km of fibre. Our work provides a method for flexible and scalable integration of waveguide-coupled SPADs for quantum information processing applications.
Quantum key distribution (QKD) is a rapidly maturing quantum photonic technology that allows for the distribution of secure cryptographic keys under no assumptions of the attacker's computing power. A key hurdle for its large-scale adoption is the reduction of its hardware size and cost, for which photonic integration is a promising solution. However, there exists no perfect material platform for this task, and for QKD this leads to either design compromises or core functionalities left off-chip. This thesis makes the assertion that hybrid integrated photonics, where one combines two chip materials into one structure, can resolve some of these issues. Firstly, we present an edge-coupled hybrid transceiver that combines a silicon nitride waveguide chip with an indium phosphide modulator chip. Secondly, we pursue the hybrid integration of the single photon detectors. However, the appropriate solution of fast-gated telecom-wavelength avalanche diodes did not exist, and so in the second experimental chapter of this thesis we develop and characterise a linear array of GHz-gated InGaAs/InP SPADs. Finally, we demonstrate a hybrid integrated QKD receiver, consisting of a silica waveguide chip with the aforementioned SPAD array. This represents the first integrated QKD receiver without requiring either external single photon detectors or cryogenic cooling. The results support the benefits of hybrid integration for quantum key distribution, but also more widely for quantum photonic technology as it continues to emerge.
We have demonstrated quantum key distribution (QKD) over 100 km using single-photon detectors based on InGaAs/InP avalanche photodiodes (APDs). We implemented the differential phase shift QKD (DPS-QKD) protocol with electrically cooled and 2-GHz sinusoidally gated APDs. The single-photon detector has a dark count probability of 2.8 × 10(-8) (55 counts per second) with a detection efficiency of 6 %, which enabled us to achieve 24 kbit/s secure key rate over 100 km of optical fiber. The DPS-QKD system offers better performances in a practical way than those achieved using superconducting single-photon detectors. Moreover, the distance that secure keys against the general individual attacks can be distributed has been extended to 160 km.
We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose a useful way to characterize the afterpulsing distribution for rapid gating that allows for easy comparison with conventional gating regimes. We compare the performance of this rapid gating scheme with free-running detector and superconducting single-photon detector (SSPD) for the coherent one-way quantum key distribution (QKD) protocol. The rapid gating system is well suited for both high-rate and long-distance QKD applications, in which Mbps key rates can be achieved for distances less than 40km with 50 ns deadtime and the maximum distance is limited to ~190km with 5 μs deadtime. These results illustrate that the afterpulsing is no longer a limiting factor for QKD.
InGaAs/InP single-photon avalanche diodes (SPADs) working in the regime of GHz clock rates are crucial components for the high-speed quantum key distribution (QKD). We have developed for the first time a compact, stable, and user-friendly tabletop InGaAs/InP single-photon detector system operating at a 1.25 GHz gate rate that fully integrates functions for controlling and optimizing SPAD performance. We characterize the key parameters of the detector system and test the long-term stability of the system for continuous operation of 75 h. The detector system can substantially enhance QKD performance and our present work paves the way for practical high-speed QKD applications.