# Is Cryogenic Heat Dissipation the Real Bottleneck on the Path to a Million Qubits?

**100 mW of cooling power at 500 mK.** That single specification — delivered by Absolut System's newly qualified QCube® 100-Class 3 platform — is what French silicon spin-qubit startup Quobly says unlocks the next stage of its scaling roadmap. The two companies have signed a multi-stage Industrial Partnership Declaration to co-develop cryogenic infrastructure purpose-built for Quobly's Alloy quantum processor family, with the QCube® 100-Class 3 qualification representing the first milestone under France's Cryonext program.

The commercial timeline is specific: cloud access for research users by late 2026, scaling toward 100,000 physical qubits between 2027 and 2029, and one million qubits for [fault-tolerant quantum computing](https://quantumintel.tech/glossary/fault-tolerant-quantum-computing) by 2032. Underpinning that roadmap is a €115 million Series A completed in June 2026 — one of the largest European quantum hardware rounds on record — and a supply chain that now includes Soitec, STMicroelectronics, Air Liquide, and Orano, all anchored in the Grenoble deep-tech corridor.

The core thesis: when you integrate VLSI control logic directly on-chip alongside spin-qubit processors, the limiting factor shifts from die size to how much heat you can extract from the cold stage. Quobly and Absolut System are betting that solving refrigeration at industrial scale is the critical path to mass-manufacturable quantum hardware.

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## Why the QCube® 100-Class 3 Specification Matters

The QCube® 100-Class 3 is not a conventional [dilution refrigerator](https://quantumintel.tech/glossary/dilution-refrigerator) bolted onto an existing processor. According to the source material, it provides integrated thermal, mechanical, and radio-frequency (RF) interfaces specifically designed to operate co-packaged cryogenic control electronics alongside spin-qubit processors — meaning the system was engineered from the ground up to handle Quobly's Alloy architecture, not adapted from a general-purpose lab instrument.

The 100 mW at 500 mK figure deserves context. Most current dilution refrigerators used in academic and early-commercial superconducting qubit work provide cooling power in a similar range at their mixing chamber (typically sub-20 mK for superconducting transmon systems, which have very different thermal requirements). Silicon spin qubits operate at higher temperatures — 500 mK is meaningfully warmer than the ~15 mK mixing chamber temperatures required for superconducting architectures — but the integration of cryogenic VLSI control electronics directly on the same cold stage creates a heat load problem that off-the-shelf cryostats were not designed to handle.

This is the architectural bet Quobly is making: by building on 300mm Fully Depleted Silicon-on-Insulator (FD-SOI) wafer lines in co-design with STMicroelectronics, the company integrates control logic on-chip, eliminating the wiring harnesses that create I/O bottlenecks at scale. The trade-off is that you now need to extract heat from that control electronics at cryogenic temperatures — which is precisely what the QCube® 100-Class 3 was engineered to do.

**The skeptical read:** Quobly's claim that the scaling bottleneck has shifted "from physical chip size to cryogenic heat dissipation" is architecturally coherent, but it essentially trades one hard problem for another. Achieving 100,000 physical qubits by 2029 would require a roughly three-order-of-magnitude scale-up from where any silicon spin-qubit system operates today. The QCube® qualification is a necessary condition, not a sufficient one — gate fidelity, [coherence time](https://quantumintel.tech/glossary/coherence-time), and qubit uniformity across a 300mm wafer all remain open engineering challenges that the cryogenic partnership does not address.

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## The European Supply Chain Play

Quobly's partner list reads like a deliberate attempt to vertically integrate European deep-tech capabilities:

- **STMicroelectronics** — 300mm FD-SOI fabrication, co-design of integrated control logic
- **Soitec** — Silicon-28 substrate supply (isotopically purified silicon reduces nuclear spin noise, directly improving T2 coherence times)
- **Air Liquide** — Cryogenic fluid supply chain
- **Orano** — Nuclear materials expertise (relevant for isotopic enrichment of silicon-28)
- **Absolut System** — Sub-kelvin refrigeration engineering

This is a serious industrial supply chain, not a research consortium. The involvement of Soitec for silicon-28 is particularly significant: isotopically purified silicon is a finite resource with limited global production capacity, and securing that supply chain is a genuine competitive moat, not just a technical detail.

The Grenoble cluster gives Quobly proximity to all of these partners, as well as to CEA-Leti, Europe's leading microelectronics research lab — an institutional advantage that is difficult to replicate in markets without equivalent public research infrastructure.

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## Industry Trajectory: What This Means for Silicon Spin Qubits

Silicon spin qubits have long been described as the "semiconductor-compatible" approach to quantum hardware, with the theoretical advantage of leveraging existing fab infrastructure. The gap between that theoretical advantage and practical demonstration has been wide — most silicon spin-qubit demonstrations remain in the single-digit or low tens of qubits range, with gate fidelities that are improving but still generally trail leading superconducting and trapped-ion systems.

Quobly's FD-SOI approach, co-designed with STMicroelectronics on 300mm lines, is the most credible industrial-scale silicon spin-qubit program in Europe. The €115 million Series A and the Absolut System partnership suggest that investors and industrial partners believe the manufacturing pathway is real. But the 2027–2029 window for 100,000 physical qubits is aggressive by any measure — it implies a scaling rate that has not been demonstrated by any qubit modality to date.

For enterprise buyers and investors, the near-term signal to watch is the late 2026 cloud availability commitment. If Quobly delivers a research-accessible system on that timeline, even at modest qubit counts, it validates the manufacturing pipeline and provides early fidelity and [coherence time](https://quantumintel.tech/glossary/coherence-time) data that will either support or challenge the longer-range roadmap claims.

For the broader industry, the Quobly-Absolut System partnership is a data point in a larger argument: that scaling quantum hardware is as much a cryogenic and packaging engineering problem as it is a qubit physics problem. Companies like [Bluefors](https://quantumintel.tech/companies/bluefors) have built substantial businesses on that insight in the superconducting space. Absolut System is making a comparable bet in the silicon spin-qubit segment.

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## Key Takeaways

- **QCube® 100-Class 3 qualified:** Absolut System's platform delivers 100 mW of continuous cooling at 500 mK, with integrated thermal, mechanical, and RF interfaces for co-packaged cryogenic control electronics.
- **Milestone under Cryonext:** The qualification is the first deliverable under France's Cryonext program, signaling government-backed industrial intent.
- **Quobly's roadmap:** Cloud access for research users by late 2026; 100,000 physical qubits targeted between 2027 and 2029; one million qubits for fault-tolerant computing by 2032.
- **€115M Series A:** Completed June 2026, one of Europe's largest quantum hardware rounds.
- **FD-SOI architecture:** Built on 300mm wafer lines with STMicroelectronics; integrated VLSI control logic shifts the primary scaling constraint to heat dissipation.
- **Supply chain depth:** Partners include Soitec (silicon-28), Air Liquide, Orano, and STMicroelectronics — all anchored in the Grenoble corridor.
- **Critical caveat:** Cryogenic qualification is a necessary but not sufficient condition; gate fidelity and wafer-scale qubit uniformity remain unaddressed in this announcement.

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## Frequently Asked Questions

**What is the QCube® 100-Class 3 and why does it matter for quantum computing?**
The QCube® 100-Class 3 is a sub-kelvin refrigeration platform developed by Absolut System, delivering 100 mW of continuous cooling power at 500 mK. It is specifically engineered to handle the heat load generated by Quobly's co-packaged cryogenic control electronics and silicon spin-qubit processors — a problem that becomes acute when VLSI control logic is integrated directly on-chip at cryogenic temperatures.

**How does Quobly's silicon spin-qubit approach differ from superconducting qubits?**
Silicon spin qubits encode quantum information in the spin state of individual electrons or nuclei in silicon, and can operate at higher temperatures (around 500 mK) compared to superconducting transmon qubits, which typically require mixing chamber temperatures below 20 mK. Quobly's approach uses standard 300mm FD-SOI semiconductor manufacturing processes in co-design with STMicroelectronics, targeting mass-manufacturability at semiconductor fab scale rather than bespoke quantum hardware fabrication.

**What is silicon-28 and why is Quobly securing that supply chain?**
Silicon-28 is an isotopically purified form of silicon with essentially zero nuclear spin, which dramatically reduces a key source of decoherence for spin qubits. Natural silicon contains roughly 4.7% silicon-29, which has a non-zero nuclear spin and limits T2 coherence times. Soitec is named as Quobly's silicon-28 substrate supplier — a supply chain relationship that constitutes a genuine competitive advantage given limited global production capacity.

**Is Quobly's one-million-qubit by 2032 target credible?**
The roadmap is technically coherent but historically aggressive. No qubit modality has demonstrated scaling at the rate implied by the 2027–2029 window for 100,000 physical qubits. The €115 million Series A and the industrial partner network suggest serious capital and manufacturing commitment. The near-term validation point is the late 2026 cloud availability milestone — that delivery will provide the first independent evidence of whether the manufacturing pipeline performs as claimed.

**What does this partnership mean for European quantum sovereignty?**
The Quobly-Absolut System collaboration, backed by the French Cryonext program, represents a deliberate effort to build a vertically integrated European silicon spin-qubit supply chain — from isotopic silicon substrates (Soitec) through CMOS fabrication (STMicroelectronics) to sub-kelvin cryogenic infrastructure (Absolut System). This mirrors broader EU industrial policy goals around quantum technology independence, and positions the Grenoble deep-tech cluster as a credible alternative to US and Asian quantum hardware programs.