QUANTUM ERROR CORRECTION IN SUPERCONDUCTING AND SPIN QUBIT PLATFORMS: EUROPEAN AND SWISS APPROACHES TO FAULT-TOLERANT QUANTUM COMPUTING

Abstract

Quantum error correction (QEC) is essential for achieving scalable and fault-tolerant quantum computing. Superconducting qubits and spin qubits represent the two most advanced and experimentally validated hardware platforms capable of supporting large-scale logical qubit architectures. This review presents a comprehensive analysis of QEC techniques implemented in these platforms, emphasizing contributions from leading European and Swiss research institutions. We examine dominant noise mechanisms, coherence limitations, fidelity constraints, and control challenges that necessitate robust error-correction strategies across diverse physical qubit modalities. Stabilizer codes, surface codes, bosonic encodings, and emerging low-density parity-check (LDPC) codes are evaluated with respect to their feasibility for current hardware capabilities, integration requirements, and long-term scalability toward million-qubit systems. Special attention is given to the work of ETH Zürich, EPFL, IBM Research Zürich, IMEC, CEA-Leti, Chalmers University, and TU Delft, as well as key initiatives under the EU Quantum Flagship, which collectively advance logical qubit demonstrations, cryogenic control electronics, error-mitigated architectures, and CMOS-compatible fabrication technologies. By synthesizing experimental progress with national and regional research roadmaps, this review identifies realistic pathways toward fault-tolerant quantum systems and outlines critical engineering and theoretical challenges that must be addressed to reach the error-correction thresholds required for practical quantum advantage in scientific and industrial applications.

Keywords : Quantum error correction, superconducting qubits, spin qubits, fault-tolerant quantum computing, surface codes, stabilizer codes, LDPC codes, coherence times, European quantum technologies, Swiss quantum research.