DELFT, Netherlands, BERKELEY, Calif. and OXFORDSHIRE, United Kingdom, May 06 2025 -- QphoX B.V., a Dutch quantum technology startup developing leading frequency conversion systems for quantum applications, Rigetti Computing, Inc., a pioneer in full-stack quantum-classical computing, and the National Quantum Computing Centre (NQCC), the UK’s national lab for quantum computing, today announced that they have been awarded a multinational grant to perform readout of superconducting qubits using light transmitted over optical fiber.

In a recent demonstration, QphoX and Rigetti validated the potential of this technique by optically reading out the state of a single superconducting qubit. Optical readout is made possible by microwave-to-optical transduction at the base temperature of the cryostat. This transduction process converts the information contained in the microwave readout pulse into an optical signal carried over optical fiber. This approach could eventually replace conventional microwave amplifiers and coaxial wiring as part of the qubit signal processing chain and thereby offer considerable scaling advantages due to the comparatively low dissipation of the transducer and the negligible passive heat loads from telecommunications optical fiber.

QphoX, Rigetti and the NQCC are partnering to take the next step in this research to realize optical readout of a fully-fledged superconducting quantum computer. In this multinational collaboration, QphoX will scale its optical qubit readout system that will interface with Rigetti’s 9-qubit Novera QPU, enabling optical readout of all qubits in the processor. The combined system will be installed and operated at the NQCC.

“Using light to readout the state of a superconducting qubit will remove a significant amount of heat load on cryogenic systems and therefore allow to overcome one of the critical bottlenecks in building a universal quantum computer. We are excited to take our developments to the next level and work with our partners in demonstrating this critical technology at scale,” says Simon Groeblacher, CEO of QphoX.

"This innovative solution to a well-known scaling challenge is made possible by an open and modular system architecture," says Dr. Subodh Kulkarni, Rigetti CEO. "Integrating our partners’ technology with our QPU enables us to benefit from even more expertise to accelerate our work towards fault tolerance."

“Demonstrating optical qubit readout at the system level represents an important step in our mission to advance scalable quantum computing, and we are delighted to host this collaborative work at the NQCC with such innovative project partners,” commented Dr. Michael Cuthbert, Director of NQCC.

The 33-month program is funded by the Rijksdienst voor Ondernemend Nederland (RVO) and Innovate UK via the Eureka network, an intergovernmental organization for research and development funding and coordination.