A team in Japan has harnessed non-thermal quantum states to break classical thermodynamic limits, converting waste heat into electricity with record efficiency. Credit: Stock
Researchers have discovered a method to surpass traditional thermodynamic limits in converting waste heat into electricity.
Japanese researchers have discovered a way to overcome long-standing thermodynamic limits, such as the Carnot efficiency, by using quantum states that do not undergo thermalization. Their innovative method employs a non-thermal Tomonaga-Luttinger liquid to transform waste heat into electrical energy with greater efficiency than conventional systems. This advancement could lead to more energy-efficient electronics and future progress in quantum computing.
Energy harvesters are devices that collect power from surrounding environmental sources, offering a means to improve the efficiency of modern electronics and industrial operations. Waste heat is produced continuously by everyday technologies, including computers, smartphones, and factory machinery, as well as by large-scale systems like power plants. Energy-harvesting techniques make it possible to reclaim this otherwise lost heat and convert it into usable electricity, reducing dependence on traditional energy supplies.
Traditional energy-harvesting technologies, however, remain limited by the fundamental principles of thermodynamics. Systems that operate under thermal equilibrium face strict boundaries on how much heat can be turned into electrical power. The ratio between generated electricity and the heat drawn from a waste source is defined by the Carnot efficiency. Additional constraints, such as the Curzon-Ahlborn efficiency (which represents the efficiency achievable at maximum power output), have further restricted how much practical energy can be recovered from waste heat.
This infographic depicts a simplified diagram of the novel energy-harvesting technique using the TL liquid. Implementation of this strategy in practice could help in the conversion of waste heat generated from electronic devices into usable power. Credit: Institute of Science Tokyo
Now, a research team led by Professor Toshimasa Fujisawa from the Department of Physics at Institute of Science Tokyo (Science Tokyo), Japan, in collaboration with Senior Distinguished Researcher Koji Muraki from NTT Basic Research Laboratories, Japan, has found a way to bypass this barrier. In their paper published in Communications Physics on September 30, 2025, the team introduced a novel energy-harvesting technique that uses unique quantum states to achieve efficiencies that go beyond the conventional thermodynamic limits.
A Quantum Solution from Japan
Instead of relying on traditional thermal states, the researchers harnessed the properties of a non-thermal Tomonaga-Luttinger (TL) liquid. This is a special type of one-dimensional electron system that, due to its quantum nature, does not thermalize. This means that when heat is introduced, the system holds onto its non-thermal, high-energy state rather than spreading the energy out evenly, as happens in a conventional thermal system.
The research team designed an experiment to demonstrate the potential of this concept. They injected waste heat from a quantum point contact transistor—a device that controls electron flow—into a TL liquid. This non-thermal heat was transported several micrometers to a quantum-dot heat engine, which is a microscopic device that converts heat into electricity through quantum effects. The researchers found that this unconventional heat source produced a significantly higher electrical voltage and achieved higher conversion efficiency, performing much better than a conventional, quasi-thermalized heat source. “These results encourage us to utilize TL liquids as a non-thermal energy resource for new energy-harvesting designs,” says Fujisawa.
Subsequently, the researchers developed a model based on a binary Fermi distribution to provide a description of non-thermal electron states in the proposed system. Using it, they showed that their technique surpasses not only the Carnot efficiency but also the Curzon-Ahlborn efficiency, which describes the efficiency at maximum power output of conventional heat engines.
Overall, this research opens the door to a new generation of energy harvesting, leveraging non-thermal quantum states. “Our findings suggest that waste heat from quantum computers and electronic devices can be converted into usable power via high-performance energy harvesting,” remarks Fujisawa. With any luck, further efforts in this field will make future technologies more powerful and sustainable.
Reference: “Efficient heat-energy conversion from a non-thermal Tomonaga-Luttinger liquid” by Hikaru Yamazaki, Masashi Uemura, Haruhi Tanaka, Tokuro Hata, Chaojing Lin, Takafumi Akiho, Koji Muraki and Toshimasa Fujisawa, 30 September 2025, Communications Physics.
DOI: 10.1038/s42005-025-02297-6
Funding: Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology
