Research Project: Single-photon Enhanced Quantum Optical Network Detector (SEQOND)
About Optica
21 March 2025
Research Project: Single-photon Enhanced Quantum Optical Network Detector (SEQOND)
Collaborating with project lead RedWave Labs, Covesion and the Fraunhofer Centre for Applied Photonics are working on the Innovate UK-funded Single-photon Enhanced Quantum Optical Network Detector (SEQOND) project. This initiative aims to develop high-fidelity, modular, and scalable receiver modules that serve as a critical enabling technology for entanglement distribution—an essential component for quantum key distribution, scalable quantum computing, and the transmission of quantum states across the quantum internet. By introducing cutting-edge Original Equipment Manufacturer (OEM) receiver modules for entangled network systems, SEQOND aims to maximise performance and unlock new quantum memory and qubit link capabilities.
Currently, quantum networks rely on Single-Photon Avalanche Diode (SPAD) modules, which, while compact and cost-effective, face performance limitations at the required 1550 nm telecom wavelength. The industry-standard InGaAs SPADs suffer from high dark count rates, lower efficiency, increased afterpulsing, and longer deadtimes. Additionally, the commercial availability of InGaAs SPADs is limited. These constraints hinder the widespread deployment of quantum networks. SEQOND will overcome these barriers by developing a novel 1550 nm SPAD solution based on upconversion technology. This approach will provide a unique, commercially viable alternative to InGaAs SPADs, and enhance the reliability and scalability of quantum networks.
The SEQOND project builds on Covesion’s proven PPLN (Periodically Poled Lithium Niobate) waveguide solutions, which have demonstrated upconversion efficiencies of 70%. By harnessing this technology, the project will convert 1550 nm photons into the visible/near-infrared spectrum to enable efficient detection using silicon SPADs. It will integrate the PPLN waveguide and silicon SPADs into a compact module, optimised through RedWave Labs’ expertise in optoelectronics, and demonstrate the complete system within a functional quantum network environment—validating its real-world performance. Beyond quantum networking, additional market opportunities exist in infrared single-photon counting for sensing applications and photonic quantum computing, where high-fidelity photon detection is crucial.
SEQOND aims to accelerate the adoption of quantum networks by enhancing capabilities and eliminating technological barriers. The project will develop a supply chain for high-performance single-photon detectors to lower costs and enhance accessibility, while also demonstrating commercial viability through integration into quantum networks and collaboration with industry partners.
RedWave Labs specialises in OEM subsystems for spectroscopy and quantum technologies. As the project lead, RedWave will develop the detector module, integrate the electronics, and conduct extended optoelectronic testing. Covesion brings high-efficiency upconversion technology to the project. Our expertise in periodically poled materials and waveguide development provides optimal performance in photon conversion and detection. Fraunhofer CAP contributes extensive experience in non-linear waveguide characterisation and high-speed quantum networking demonstrations. SEQOND will also collaborate with major industry players such as BT and Vodafone, ensuring the technology aligns with commercial needs and undergoes real-world testing at the project’s conclusion.
The SEQOND project represents a transformative leap in quantum networking technology, addressing critical supply chain vulnerabilities while enhancing performance and scalability. By developing an innovative upconversion-based single-photon detector solution, SEQOND will unlock new possibilities for secure communication, quantum computing, and broader quantum technology applications.
The project is scheduled to run from April 2025 to April 2026 for a duration of twelve months.
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Further Information:
The organisations involved in the SEQOND project include:
- RedWave Labs Limited
- Covesion Limited
- The Fraunhofer Centre for Applied Photonics
Covesion Ltd is a UK manufacturer of Periodically Poled Lithium Niobate (PPLN) materials, including Magnesium Doped Periodically Poled Lithium Niobate (MgO:PPLN). Their proprietary PPLN poling process creates high-fidelity grating periods for high-efficiency wavelength conversion. Covesion provides bulk crystals, waveguides, and associated components for integration into optical systems.
Website: www.covesion.com
Covesion:
Corin Gawith
Chief Technology Officer
Covesion
Tel: +44-(0)1794 521638
Email: corin.gawith@covesion.com
Marketing and Press Information:
Katherine Bourne
Director
Accelerate Associates
Tel: +44(0)1785 747102
Mobile: +44(0)7904 594485
Email: katherine@accelerate-associates.co.uk
