Technology / Hardware / Superconducting circuits
Superconducting circuits
Microwave-controlled electrical circuits at millikelvin temperatures.
The tradeoff
Strengths: Fast gates; Semiconductor-style fabrication; Mature ecosystem.
Challenges: Cryogenics; Wiring; Crosstalk; Coherence.
Maturity: early-commercial (cloud access); fault tolerance in progress.
Specific gate speeds, fidelities and qubit counts are not published here, they change quarterly. Verify against each company's latest technical publications, not press releases.
Who is pursuing it
IBM
The largest superconducting program: processors on the cloud since 2016, an open software stack (Qiskit), and a public roadmap toward error-corrected systems.
public · IBM
Google Quantum AI
Alphabet's superconducting effort. The 2019 supremacy-benchmark claim and prominent below-threshold error-correction demonstrations.
subsidiary · GOOGL (Alphabet)
Rigetti Computing
A public pure-play building superconducting chips and full systems, with its own fabrication facility and cloud access.
public · RGTI
IQM
Europe's largest superconducting startup, selling on-premise systems to research centers and building co-design processors.
private
Fujitsu / RIKEN
A Japanese industrial-academic partnership producing domestic superconducting systems and hybrid quantum-classical platforms.
research-lab
AWS (Amazon)
Amazon's hardware effort focuses on error-corrected cat-qubit architectures, alongside the Braket cloud service offering other vendors' machines.
subsidiary · AMZN (Amazon)
Alice & Bob
French startup building 'cat qubits'. Superconducting qubits designed to suppress bit-flip errors by construction, aiming to shrink error-correction overhead.
private