Oxford Quantum Circuits (OQC) is a superconducting quantum computing company spun out of the University of Oxford in 2017. It was founded by Dr Peter Leek, whose Oxford research group developed the company's core intellectual property, including the Coaxmon 3D qubit architecture. OQC builds quantum computers engineered for commercial use and provides access to them through cloud services, direct access and systems colocated in data centres. It describes itself as Europe's first Quantum-Compute-as-a-Service provider. Its proprietary dual-rail Dimon qubit design supports the generation of logical, error-corrected qubits, and its published roadmap targets 200 logical qubits by 2028 and 50,000 by 2034.

OQC's systems are deployed in London, Tokyo, New York City and Spain. The New York system sits in a Quantum-AI data centre run by Digital Realty and built with NVIDIA GH200 Grace Hopper Superchips. The company has benchmarked a two-qubit gate speed of 25 nanoseconds. Its customers and partners span financial services, defence and security, and pharmaceuticals. Collaborations include JPMorganChase and AMD on a quantum-AI platform in London, Citi and the UK National Quantum Computing Centre on derivative pricing research, Trust Base on financial risk workloads, Mastercard on quantum-enhanced fraud detection, QinetiQ on a defence application, Fraunhofer EMFT on fabrication, and Classiq on quantum software.

OQC has raised more than $490M. Its funding includes a £38M Series A in July 2022, co-led by Lansdowne Partners and the University of Tokyo Edge Capital Partners, a $100M Series B in November 2023 led by SBI Investment, and a £260M Series C in June 2026 led by Bullhound Capital. The Series C, which included a £100M investment from the British Business Bank, was described as the largest private quantum computing funding round in Europe. The company has also received UK Research and Innovation grants. In 2024 Dr Leek was appointed Chief Scientific Officer, and Gerald Mullally was appointed CEO in 2025.