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Universal work extraction in quantum thermodynamics
Kaito Watanabe1, Ryuji Takagi2
1Department of Basic Science, The University of Tokyo, Meguro-ku, Tokyo, Japan. watanabe715@g.ecc.u-tokyo.ac.jp.
Nature Communications
|March 3, 2026
Summary
Researchers developed a quantum channel to extract maximum work from unknown quantum states, matching previous methods that required full state knowledge. This advances quantum thermodynamics by removing operational restrictions for work extraction.
Area of Science:
- Quantum Thermodynamics
- Quantum Information Theory
Background:
- Extracting maximum work from nanoscale quantum systems is a key challenge.
- Prior methods required knowing the quantum state's description, limiting practical applications.
Purpose of the Study:
- To demonstrate work extraction without prior knowledge of quantum input states.
- To remove operational restrictions in quantum thermodynamics.
Main Methods:
- Construction of a novel quantum channel.
- Analysis of work extraction efficiency for unknown input states.
Main Results:
- Achieved optimal work extraction quantified by free energy, without needing input state information.
- The method applies even to infinite-dimensional quantum systems.
- Optimal asymptotic work extraction is unaffected by input state knowledge.
Conclusions:
- The developed quantum channel enables state-independent work extraction.
- This significantly broadens the applicability of quantum thermodynamics principles.
- The findings resolve a fundamental limitation in nanoscale energy harvesting.
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