David Ibberson

David joined the spin qubit community in 2017 while pursuing his PhD at University of Bristol, during which he worked closely with the Hitachi Cambridge Laboratory. He joined Quantum Motion in 2021, where he continues experimental research on the scale-up of foundry-fabricated silicon quantum processors.

Constance started her PhD in 2022 at UCL in collaboration with Quantum Motion, working on spin qubits with a focus on experiments for qubit readout and control. In 2025, she joined Quantum Motion as a quantum theorist to bring her qubit expertise to error correction and architecture

Stabiliser cycles and logical encoding in a cloud-accessible four-qubit electron spinquantum processor

Quantum error detection will be essential to mitigate qubit physical errors and enablefault-tolerant quantum computing. Stabiliser cycles, which regularly measure the parities ofmultiple qubits via ancillas in order to identify errors and stabilise states, are particularlychallenging as they require high gate and measurement fidelities while competing withdecoherence. In this work, we operate a linear four-qubit silicon MOS QPU fabricated on a300 mm wafer process and deployed full-stack on a cloud platform. We demonstrate multiplestabiliser cycles with mid-circuit-measurement, enabling the generation of entangled statesvia stabiliser measurements, noise purification where injected bit-flip errors are reducedthrough syndrome post-selection, and logical encoding in a two-data-qubits subspace. Thisperformance is achieved by leveraging the qubit topology to implement various circuitsincluding those with data-on-data gates in the spirit of recent ‘middle-out' or ‘code morphing’ideas1, further optimised through simulation. At the device level, gate fidelities are enhancedby operating two-qubit geometric phase gates2 available between all neighbours (mean 2Qduration 426 ns) and single-qubit gates by ESR (mean 1Q duration 1100 ns). To mitigatesingle-qubit crosstalk, which can be particularly challenging when qubits have similarresonance frequencies (separated by <2MHz), we employ pulse engineering3. This workrepresents the first demonstration of quantum error detection in a silicon MOS device,opening pathways for accessible quantum algorithm testing and error correction protocols.