Deep inside a lab at Aalto University in Finland, researchers have built something that sounds like a contradiction: a quantum heat engine. It's the first of its kind in the world, and it could one day make quantum computers much cheaper and easier to build.
Heat engines are everywhere in everyday life. They power car engines, ships, planes, and most power plants that generate electricity. The famous steam engines that started the Industrial Revolution in the 1700s were heat engines. Now, Professor Mikko Möttönen's team at Aalto has shrunk that idea down to the quantum scale—smaller than atoms—using superconducting circuits cooled to near absolute zero, the coldest temperature possible.
The device is incredibly small. At its heart is something called a transmon qubit, one of the basic building blocks of quantum computers. The team connected it to a quantum-circuit refrigerator they designed, which acts as both a heat source and a cooling source. By sending carefully timed control pulses through the system, they ran what's called an Otto cycle—the same type of process that powers car engines—and watched as quantum-scale heat converted into measurable work.
"This is the first experimental demonstration of a cyclic quantum heat engine in superconducting circuits," said Tuomas Uusnäkki, the study's first author. "Using a single controllable quantum refrigerator as both the hot and cold environment of the engine makes it simpler and more versatile."
The research, published in Nature Communications on July 13, 2026, matters because quantum computers are notoriously difficult and expensive to build. Finland's Quantum Technology Strategy aims for a quantum computer with 1,000 logical qubits by 2035. That would probably require hundreds of thousands of physical qubits. Current technology needs millions of microwave cables to control all those qubits, and each cable costs thousands of euros. They also introduce unwanted noise into the system.
The team hopes their quantum heat engine could eventually work as an autonomous device—reading out qubit information without needing all those cables. That could dramatically cut costs and complexity for the powerful quantum computers of the future.