Aalto Researchers Build First Superconducting Heat Engine

Aalto University researchers have built the world’s first superconducting quantum heat engine, a device comprised of a transmon qubit, a resonator and a quantum refrigerator, demonstrating a physical realization rather than a theoretical model. The newly developed engine advances understanding of thermodynamics and could enable technologies crucial for building high-qubit quantum computers, similar to the impact James Watt’s steam engine had on the industrial revolution. “This is the first experimental demonstration of a cyclic quantum heat engine in superconducting circuits,” says Tuomas Uusnäkki, the study’s first author, detailing how the team harnessed minuscule heat in ultracold conditions to cyclically produce usable energy. By creating an Otto cycle within a superconducting circuit, the researchers have provided a solid proof of concept for a technology that relies on quantum phenomena like tunneling, entanglement and superposition.The realization of a functional quantum heat engine built from superconducting components marks a significant step toward scalable quantum computing and a deeper understanding of thermodynamics at the quantum level. This achievement echoes the historical impact of James Watt’s steam engine, suggesting a potential for similar advancements in energy conversion and computation.

The team, led by Professor Mikko Möttönen, engineered an Otto cycle, the same thermodynamic process found in internal combustion engines, within a superconducting circuit operating near absolute zero. “In our experiment, we built a nanofabricated heat engine using superconducting circuits and operated it in a cryostat near absolute zero. At its heart is a transmon qubit, one of the basic building blocks of modern quantum technologies,” explains Tuomas Uusnäkki, the study’s first author.Crucially, this engine doesn’t rely on separate heat sources; instead, it utilizes a single, tunable quantum refrigerator to both heat and cool the qubit, simplifying the design and increasing its versatility. The ability to harness minuscule amounts of heat in ultracold conditions to generate measurable work opens possibilities for autonomous heat engines that could drastically reduce the complexity and cost of future high-qubit quantum computers. Möttönen envisions a future where these engines could read out qubits without extensive cabling, potentially eliminating the need for millions of expensive microwave cables currently required for large-scale quantum systems. “Finland’s Quantum Technology Strategy envisions a quantum computer with one thousand logical qubits by 2035, which probably means hundreds of thousands of physical qubits,” he states, highlighting the practical implications of this research.“This is the first experimental demonstration of a cyclic quantum heat engine in superconducting circuits.”The pursuit of scalable quantum computing increasingly focuses on minimizing the infrastructure required to control and read out qubits, and recent work at Aalto University demonstrates a novel approach to power management within these systems. This achievement isn’t merely an exercise in quantum mechanics; it directly addresses the practical challenges of building larger, more complex quantum processors. The ability to control heat flow at this scale allowed the team to demonstrate the conversion of heat into measurable work, a critical step toward self-powered quantum components. This development has significant implications for future quantum computer architecture. The researchers envision a future where autonomous heat engines can perform tasks like qubit readout without the need for extensive cabling, drastically reducing cost and complexity. He notes that current technology necessitates millions of expensive microwave cables, introducing noise into the system; autonomous devices could largely eliminate this need. The study, published in Nature Communications, represents a crucial step toward more efficient and scalable quantum technologies.Researchers at Aalto University are actively pursuing designs beyond the initial demonstration of their superconducting quantum heat engine, with a focus on creating fully autonomous systems capable of streamlining quantum computer operation. Source: https://www.aalto.fi/en/news/worlds-first-superconducting-quantum-heat-engine-opens-the-path-to-larger-quantum-computers See today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals.Ivy Delaney has been working with neural networks and machine learning since the mid-nineties, back when a couple of hidden layers and a long afternoon of training counted as ambitious. She has watched the field go from academic curiosity to the thing quietly running underneath everything, and she brings that long view to quantum computing.

For Quantum Zeitgeist she covers the ground where the two fields meet. That means quantum machine learning and the variational algorithms it leans on, and it also means the less glamorous but more interesting story of classical machine learning already doing real work inside quantum machines, decoding error-correcting codes, calibrating noisy hardware and learning the error models that simulators depend on. She writes about the hardware those algorithms have to run on too, and about the post-quantum cryptography scramble that the same hardware has set off. Her stories typically start with the paper, whether that is peer-reviewed work, conference proceedings or an arXiv preprint, with the source linked so you can hold a claim up against the research it came from. She is unimpressed by benchmarks that will not say what they beat, and by demonstrations that only work in the press release.