High fidelity, modular and scalable receiver modules are recognised as the enabling technology for entangled based quantum key distribution, which is essential for distributed quantum computing and the transmission of quantum states in quantum internet. To address this need, the MARCONI project will develop and demonstrate two new OEM quantum key distribution receivers based on different technologies and interchangeable at the point of optical connection. They will be built with UK components: \*For smaller set-ups and short distance communications, a four channel single photon avalanche detector system using novel SPADs from Phlux, packaged by Bay Photonics \*For larger, long-distance applications, a unique 64 channel superconducting nanowire single photon detector system using enhanced SNSPDs from the University of Glasgow cooled by novel 1K system by Chase Cryogenics and coupled with a new compact 64-channel timetagger from Redwave Labs. Redwave Labs will optimise the control electronics and timetaggers for both systems, which will be coupled with Fraunhofer's optical receiver module. The University of Cambridge will demonstrate the receivers in entanglement based discrete variable-quantum key distribution transmission in both metro and long-haul networks. Secure keys will be generated using the BBM92 protocol. A Strategic Advisory Board of end-users and service providers will help direct the R&D and path to commercialisation.

Superconducting quantum technology, currently regarded worldwide as the leading candidate architecture for the creation of a quantum computer, requires ultra-low temperatures close to 10 milliKelvin. Access to such low temperatures has until now relied on large research-scale cryogenic platforms that typically occupy several tens of square meters of floorspace, and require either Helium liquefaction plant or high-power 3-phase electricity and water cooling. These cost and infrastructure requirements are significant barriers to the marketisation of quantum computing technologies. Commercial cryocooler systems reaching temperatures below 4K are now available in a compact, mobile format that requires only single-phase domestic electrical supply. This creates the technical opportunity to access ultra-low temperatures using compact add-on modules to provide the next-step cooling from 4K down to milliKelvin temperatures. All necessary technological solutions are, in principle, already available for such 'desktop' quantum technology, but they have never before been integrated together into a low-power, low-cost cooling platform designed for quantum computing applications. Demonstrating the feasibility of such a product is the central aim of this project. By dramatically cutting both the capital and operational cost of quantum computing, this development would hugely accelerate its deployment, for example, in hospitals, banks, ports and airports, in both fixed and 'mobile' field-based applications. The project leaders, Chase Research Cryogenics (CRC) are leading world experts in self-contained cryocooler modules operating from 1K to 0.1K and have an established track record of designing and manufacturing instruments for academics, research institutions and quantum technology companies around the world. CRC will work closely with project partners SeeQC.UK, a company specialising in the development of a cryogenic qubit controller that forms the core of practical quantum computing resources. CRC and SeeQC.UK will together explore and demonstrate the feasibility of operating the SeeQC.UK quantum technology on CRC's novel cooling platform. Meeting the major challenge of extending CRC's current cooling technology to millikelvin temperatures will require us to unlock the deep specialist knowledge currently residing in the world-leading low-temperature research groups in UK universities, and transfer their know-how into the commercial world. This project will therefore bring together, for the first time, academic and commercial partners in a unique team, encompassing a unique range of knowledge, skills and expertise that could revolutionize the potential for commercialisation of quantum computing.