Quantum states rewrite the limits of heat-to-power conversion
by Riko Seibo
Tokyo, Japan (SPX) Oct 06, 2025

Harnessing quantum states that resist thermalization, scientists in Japan have discovered a way to break through conventional thermodynamic efficiency barriers such as the Carnot limit. The study, led by Professor Toshimasa Fujisawa at the Institute of Science Tokyo in collaboration with Koji Muraki from NTT Basic Research Laboratories, introduces a new strategy for harvesting waste heat using a non-thermal Tomonaga-Luttinger liquid - a one-dimensional quantum electron system that does not equilibrate like normal materials.

By injecting heat from a quantum point contact transistor into this non-thermal state, the researchers enabled the transfer of high-energy electrons over several micrometers to a quantum-dot heat engine, which converts heat into electricity through quantum effects. This setup achieved electrical conversion efficiencies exceeding those of traditional, thermal-based systems. "These results encourage us to utilize TL liquids as a non-thermal energy resource for new energy-harvesting designs," said Fujisawa.

The team modeled the non-thermal electron distribution using a binary Fermi model, confirming that their method surpasses both the Carnot and Curzon-Ahlborn efficiency limits - the latter defining the maximum efficiency at peak power for conventional engines. The findings point toward a new frontier in low-power electronics and quantum computing, where waste heat can be directly recycled into usable energy.

Research Report:Efficient heat-energy conversion from a non-thermal Tomonaga-Luttinger liquid

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