v1.1 · published 6 September 2026 · supersedes v1.0 (9 August 2026) · CC BY 4.0
Download the Monitor (PDF) · PPTX · Monitor home · doi:10.5281/zenodo.21860767
Superconductor electronics (SCE) — digital logic, memory and mixed-signal circuits built from Josephson junctions, whose largest branch is single-flux-quantum (SFQ) logic — is a genuine outlier. It holds the outright digital speed record, a 770 GHz toggle flip-flop that no technology has beaten, and it switches at roughly 2×10⁻¹⁹ J, about 1,000× below CMOS before the cryogenic cooling tax and a conditional 10–30× after it.
Its limitations are equally plain, though. It is not dense — about 2×10⁴× behind CMOS as demonstrated, with a physics ceiling still three to four orders of magnitude below it. It is memory-poor: the 4 K RAM record is 64 kb, set in 2013, and the largest all-junction memory ever built holds 202,280 bits. And its tooling is uneven — a commercial physical-verification layer exists, from a single supplier, but above RTL nothing is licensable. Memory, not tooling, is the lowest gating subsystem.
Why this warrants its own monitor
SCE sits on three critical paths at once.
It is an enabler and a multiplier for superconducting quantum computing. Room-temperature control tops out at roughly a thousand lines into a cryostat; at 10⁵–10⁶ qubits, control electronics has to move inside it. SFQ is the only logic family that has demonstrated qubit-control waveform synthesis at millikelvin — up to 99.9% single-qubit fidelity in 2026, now from three independent parties — and demonstrated digital demultiplexing that breaks one-line-per-qubit scaling. Control and readout are also where a quantum processor meets the classical machine around it, so the same cold-side position places SCE directly on the interface between quantum computing and HPC.
It is one of the plausible futures of HPC itself. Wall-plug energy per unit of work is now the binding constraint on large-scale computing, and the projected system figures sit well below current datacenter accelerators even after the cooling tax is paid. Those are vendor projections, not silicon.
It is very nearly the only route to computing at hundreds of gigahertz. The outright digital speed record in any technology is an SFQ flip-flop, and Josephson-junction physics supports switching approaching a terahertz. Complex circuits run at tens of gigahertz today; no other digital family is credibly in that conversation.
What v1.1 changed
The publication is renamed to the field’s own umbrella term: SFQ is the largest branch of superconductor electronics, not the whole of it. The edition adds a twenty-two-family taxonomy, a density page — the gap, the four levers and the fabs that hold them — a fab × technology matrix, and fourteen fab profiles that the matrix rows link through to.
It also corrects eight claims of v1.0, itemised on the edition’s page 32. Every scenario band, scenario weight and absolute market figure is unchanged and was re-verified anchor by anchor.
Cite as
Neeman, R., “Superconductor Electronics Monitor 2026,” v1.1, Qodeh, 2026 · qodeh.com/sfq-monitor · doi:10.5281/zenodo.21860767
The all-versions DOI always resolves to the current edition; to pin this edition cite 10.5281/zenodo.22537315. v1.0 remains citable at 10.5281/zenodo.21860768.
Factual corrections are welcome: raveh.neeman@qodeh.com