S-Transistors, a Finnish startup developing superconducting transistors for quantum computer control systems, has raised €2.6 million in a pre-seed round led by Lifeline Ventures with participation from an undisclosed angel investor, the company announced on August 31. The funding comes as the quantum computing industry confronts a thorny engineering challenge: how to control thousands of fragile qubits without drowning them in heat and cables.
CEO Heorhii Bohuslavskyi, who spent over a decade at VTT Technical Research Centre of Finland before spinning out S-Transistors, describes the problem plainly. Superconducting qubits operate at temperatures colder than outer space, measured in millikelvins. Today's control electronics sit at room temperature. Every coaxial cable threading into the refrigerator-sized cryostat carries unwanted heat and consumes precious space.
IBM has publicly acknowledged the constraint. The company has outlined a modular cryogenic architecture that will feature 12 times more wiring volume than earlier designs, explicitly to accommodate control lines for thousands of qubits. IBM has set ambitious targets: more than 1,000 programmable qubits per cryostat by 2027, and a fault-tolerant system by decade's end.
The physics forces a choice. Either you accept the cable sprawl and engineer around it, or you move the control electronics inside the freezer.
Several companies have chosen the latter path, each with a different technical approach. SEEQC, a U.S.-U.K. venture, published results in Nature Electronics in March showing superconducting digital logic co-packaged with qubits at millikelvin temperatures. The company's single-flux-quantum circuits achieved single-qubit fidelities approaching 99.9 percent while using digital demultiplexing to reduce the number of control lines needed. IBM and Google, meanwhile, have been researching cryo-CMOS controllers operating at 4 Kelvin and above, according to research papers published over the past year.
S-Transistors is wagering on a different primitive altogether. The company's voltage-controlled superconducting transistors can switch signals at near-zero power dissipation, or so the founders claim, while operating at the same millikelvin temperatures as the qubits themselves. That's a meaningful distinction. Heat is the enemy in these systems; even a few microwatts can destabilize qubits.
The core technology rests on graphene Josephson field-effect transistors fabricated on 150-millimeter wafers. A paper in Applied Physics Letters, co-authored by researchers from VTT and Aalto University, detailed the devices: wet-transferred CVD graphene layered with atomic-layer-deposited aluminum oxide gate dielectrics and titanium-aluminum superconducting contacts. The research team reported approximately 90 percent room-temperature yield and tunable critical current across all devices tested at low temperatures. Crucially, they say the fabrication stack is compatible with standard CMOS foundry processes.
"The real vision is the quantum motherboard operating at millikelvin temperatures, and controlling the operation of qubit-based QPU," said CTO Andrey Generalov in the company's announcement.
Bohuslavskyi holds a doctorate and logged more than 12 years in cryogenic electronics, quantum computing, and AI hardware as a VTT senior scientist and quantum sensing lead. Generalov brings 15 years in advanced manufacturing and superconducting integrated circuits. Lead engineer Markus Lehtisalo previously handled process and fabrication of superconducting devices at VTT. The founding advisor is Mikko Möttönen, an Aalto University professor who has already spun out two other VTT-linked quantum ventures: IQM and QMiLL.
VTT has become something of a quantum startup factory. Arctic Instruments, which raised €2.35 million in March for superconducting microwave amplifiers, and SemiQon, which builds cryo-CMOS control platforms for in-cryostat RF switching and multiplexing, both trace their lineage to the research center.
The convergence on in-cryostat control is happening along multiple technical vectors. IBM's cryo-CMOS hybrid, announced in March, pairs room-temperature RF electronics with a cryogenic controller on the company's 156-qubit Heron R2 processor. Google has published work on 28-nanometer bulk-CMOS cryogenic pulse modulators and unit-cell controllers. Researchers have even floated photonic-CMOS hybrids operating at 4 Kelvin, according to a preprint that appeared on arXiv.
S-Transistors positions its superconducting transistors as complementary to these efforts rather than competitive: near-zero dissipation switches, multiplexers, and logic elements that can sit alongside qubits without adding to the heat budget. "Superconducting transistors can become a critical part of the hardware stack that makes scaling possible," said Jyri Engeström, a partner at Lifeline Ventures.
The €2.6 million will go toward building a cryogenic laboratory, setting up a pilot manufacturing line for superconducting-transistor integrated circuits, developing multiple product prototypes for cryogenic signal control, and expanding the team. The first product—a superconducting-transistor-based cryogenic multiplexer—is slated to ship to early customers and partners within a year. The company's technology page displays photos of 150-millimeter wafers dotted with thousands of prototype devices. In promotional materials, S-Transistors hints at a longer-term vision extending beyond quantum into energy-efficient computing for AI workloads.
The funding arrives as Europe accelerates quantum hardware infrastructure. The EU selected the SUPREME consortium, coordinated by VTT, to build a superconducting quantum device pilot line with a total budget near €50 million, split roughly evenly between EU funds and national contributions, Fraunhofer announced in February. SUPREME is planned to launch in early 2026 and aims to open to external users by 2027. Partners include Fraunhofer, TNO, IQM, and component suppliers such as QuantWare, QphoX, and Single Quantum. Five additional EU pilot lines cover semiconductor qubits, ion traps, photonics, diamond, and neutral atoms. A European Commission document from mid-2026 previewed a Quantum Chips Industrialisation Roadmap.
NIST has launched a parallel cryogenic integrated circuits program, highlighting work on cryo low-noise amplifiers in 16-nanometer FinFET nodes operating at 4 milliwatts, according to the agency's program materials.
The commercial picture is shifting. A McKinsey Quantum Technology Monitor report from April noted that more than 300 global companies are now adopting quantum technologies and framed the sector as nearing a commercial tipping point. BCG estimated enterprise quantum spending at approximately $550 million in recent years and published updated market scenarios extending to 2030.
That upward trajectory has attracted regulatory scrutiny. The U.S. Bureau of Industry and Security lists quantum control components and cryogenic refrigeration systems, including dilution refrigerators, as export-controlled items for Russia under EAR Part 746. The EU added or updated controls covering quantum computers, cryogenic electronics, parametric amplifiers, and cryogenic wafer probers to its dual-use list in 2025.
Cryogenic infrastructure itself faces supply constraints. A Center for a New American Security report cited helium-3 at $2,500 to $3,000 per liter with long lead times, and dilution refrigerator lead times stretching six to 12 months. A GAO report flagged ongoing risks to DOE stewardship of critical isotopes, helium-3 among them. Bluefors, a major dilution-refrigerator vendor that acquired Cryomech in 2023 and now employs more than 700 people, has announced preconfigured systems with four-month order-to-install timelines.
A March paper in EPJ Quantum Technology highlighted helium-3 scarcity, concentrated dilution-refrigerator vendors, and talent shortages as critical dependencies. Integrated cryogenic control could reduce cable count and heat load, potentially easing thermal-budget constraints even as helium supplies tighten.
"S-Transistors' superconducting transistor technology will allow us to reach the point where quantum computers finally provide real-world value," said Erja Turunen, executive vice president at VTT.
The startup declined to disclose headcount or identify the angel investor. Lifeline Ventures closed a €150 million fifth fund in 2023.
Whether superconducting transistors emerge as the winning architecture or simply one option in a diverse hardware ecosystem remains an open question. What's certain is that the wiring problem won't solve itself, and the race to build practical quantum computers now turns, at least in part, on refrigerator real estate.
