Everyone talks about qubits: more qubits, better qubits. What gets less attention is that without ultra-stable control electronics, even a million qubits are useless. A small Japanese startup has now shown its controller can run for 24 hours straight without losing precision.

The Hidden Bottleneck of Quantum Computing

When you read about quantum computing breakthroughs, the headlines focus on qubit counts. IBM has its 156-qubit Heron processor, and its 1,121-qubit Condor as a scaling demonstrator. Google's Willow, announced at the end of 2024, has just 105, and the reason it mattered had nothing to do with size: it was the first chip to get below the error-correction threshold, where adding qubits makes error rates fall exponentially rather than rise. Quality over quantity. Japan's RIKEN institute, in collaboration with Fujitsu, recently unveiled a 256-qubit domestic machine.

But there's a critical piece of the puzzle that rarely makes the news: the control system, the hardware that generates, shapes, and delivers the microwave signals that actually manipulate each qubit.

Think of it like an orchestra. The qubits are the musicians, but without a conductor whose baton stays perfectly steady for hours on end, the performance falls apart. In the quantum world, even the slightest drift in signal amplitude or phase translates directly into computational errors.

What QuEL Just Achieved

QuEL, Inc., a startup born from Osaka University's Center for Quantum Information and Quantum Biology (QIQB), announced on March 27, 2026, that it has demonstrated 24-hour stable operation of its quantum bit control device, the QuEL-1 SE. The results were published in the peer-reviewed journal Review of Scientific Instruments.

Superconducting qubits are controlled by microwave signals in the GHz range, and these signals must be generated with extraordinary precision in frequency, amplitude, and phase. The problem is that analog components inside the control hardware, phase-locked loops (PLLs), amplifiers, and mixers, are sensitive to temperature fluctuations. Over hours of operation, these components cause the microwave signals to gradually drift, degrading the accuracy of quantum gate operations.

QuEL's engineering team tackled this with an approach called device-level temperature control. Instead of regulating the temperature of the entire unit, they attached individual thermistors (temperature sensors) and heaters to each temperature-sensitive component, creating independent feedback loops for PLLs, amplifiers, and mixers.

The Numbers That Matter

The team simultaneously measured microwave output from 15 channels across three QuEL-1 SE units over a full 24-hour period. The results:

  • Amplitude standard deviation: 0.09–0.22% (average 0.15%)
  • Phase standard deviation: 0.35–0.44° (average 0.39°)

Compared to operation without temperature control, the signal fluctuations were reduced by more than half. The estimated single-qubit gate errors caused by these fluctuations were approximately 2×10⁻⁶ (amplitude) and 2×10⁻⁵ (phase), well below the fault-tolerant thresholds typically required for quantum error correction (around 10⁻³ to 10⁻⁴).

In practical terms, this means the control system is so stable that it essentially disappears as a source of computational error, exactly what's needed for the next generation of quantum machines.

The experimental data also revealed that air conditioning cycles in the lab caused roughly one-hour temperature oscillations, but the device-level control successfully suppressed these disturbances.

Why Control Stability Is a Make-or-Break Issue

The biggest challenge on the path to useful quantum computing is quantum error correction. Qubits are extremely fragile, they lose their quantum states easily due to environmental noise. To perform reliable computations, engineers must use many physical qubits to encode a single "logical qubit" that can withstand errors.

IBM plans to deliver its first fault-tolerant quantum computer, called Starling, by 2029, with approximately 200 logical qubits built from around 10,000 physical qubits. Google is targeting systems with up to one million physical qubits. By the early 2030s, IBM envisions a quantum supercomputer called Blue Jay with 2,000 logical qubits and potentially over 100,000 physical qubits.

Here's the catch: as qubit counts increase, so do the number of microwave control channels, each one requiring rock-solid stability over extended periods. A 1,000-qubit system needs thousands of independently controlled microwave channels, all operating in concert without drift. If even a small fraction of these channels degrade over time, quantum error correction breaks down.

This is why QuEL's achievement matters far beyond Japan. It addresses a fundamental scaling challenge that every quantum computer builder, IBM, Google, or anyone else, must eventually solve.

Who Is QuEL?

QuEL, Inc. was founded in 2021 as a spin-off from Osaka University, making it one of the world's few companies dedicated exclusively to quantum computer control systems. While IBM and Google develop their control hardware internally as part of vertically integrated systems, most research labs and smaller quantum companies have had to build their own controllers from scratch, a time-consuming process requiring specialized expertise.

QuEL's technology has already been deployed in real quantum computers. When RIKEN launched Japan's first domestically built quantum computer in March 2023 (a 64-qubit superconducting machine), QuEL supplied the control hardware. The company has also provided controllers for quantum computers at Osaka University and handled the control electronics for the fully domestic quantum computer that came online in 2025.

Remarkably, the company has been profitable since its first year of operation. By its third year, it was selling 45 units annually and fielding inquiries from institutions both in Japan and abroad. In December 2024, CEO Yosuke Ito received the Minister of State for Science and Technology Policy Award at the Japan Venture Awards.

QuEL's CTO, Takefumi Miyoshi, holds a concurrent position as a specially appointed professor at Osaka University's QIQB, bridging the gap between academic research and commercial product development.

The Bigger Picture: Japan's Quantum Supply Chain Strategy

There's an interesting parallel between QuEL's role in quantum computing and TSMC's role in the semiconductor industry. Just as TSMC's contract manufacturing model allowed chip designers to focus on design rather than fabrication, thereby accelerating the entire semiconductor ecosystem, specialized quantum control device makers like QuEL could catalyze quantum computing development worldwide.

Currently, most quantum computing hardware outside of big tech firms relies on general-purpose laboratory instruments adapted for qubit control. Purpose-built, high-stability controllers like the QuEL-1 SE could allow quantum researchers and startups to focus on developing better qubits and algorithms rather than spending years building control infrastructure.

Japan is positioning itself strategically in this ecosystem. While it may not lead in raw qubit count, Japanese companies are developing critical supporting technologies: QuEL for control systems, ULVAC Cryogenics for dilution refrigerators, and Oxide Corporation for specialized UV lasers used in neutral-atom quantum computers. This "picks and shovels" strategy, supplying the tools that quantum computer builders need, could prove just as valuable as building the computers themselves.

What's Next

QuEL is currently developing next-generation controllers capable of handling 1,000 qubits. The company also plans to extend its technology beyond superconducting systems to support ion trap, neutral atom, and semiconductor quantum dot architectures.

The quantum computing race isn't just about who reaches the highest qubit count first. It's about who builds the most reliable, scalable infrastructure. And with its 24-hour stability milestone, QuEL has shown that Japan's approach, quiet, precise, and foundational, may be exactly what the quantum industry needs.

How is quantum computing developing in your country? Have you ever thought about the "supporting cast" technologies, like control systems and cryogenic equipment, that make quantum computers possible? Share your perspective in the comments!

References