Extracting work from quantum systems

Abstract

We consider the task of extracting work from quantum systems in the resource theory perspective of thermodynamics, where free states are arbitrary thermal states, and allowed operations are energy conserving unitary transformations. Taking as our work storage system a 'weight' we prove the second law and then present simple protocols which extract average work equal to the free energy change of the system - the same amount as in classical thermodynamics. Crucially, for systems in 'classical' states (mixtures of energy eigenstates) our protocol works on a single copy of the system. This is in sharp contrast to previous results, which showed that in case of almost-deterministic work extraction, collective actions on multiple copies are necessary to extract the free energy. This establishes the fact that free energy is a meaningful notion even for individual systems in classical states. However, for non-classical states, where coherences between energy levels exist, we prove that collective actions are necessary, so long as no external sources of coherence are used.

15 pages

References in corpus (6)

• The Resource Theory of Quantum States Out of Thermal Equilibrium
• The Physics and Mathematics of the Second Law of Thermodynamics
• The thermodynamic meaning of negative entropy
• Reversible transformations from pure to mixed states, and the unique measure of information
• Virtual qubits, virtual temperatures, and the foundations of thermodynamics
• The work value of information

Cited by in corpus (18)

• Description of quantum coherence in thermodynamic processes requires constraints beyond free energy
• The second laws of quantum thermodynamics
• Quantum heat engines and refrigerators: Continuous devices
• Catalytic Coherence
• Quantum coherence, time-translation symmetry and thermodynamics
• Fully quantum fluctuation theorems
• A short note on passivity, complete passivity and virtual temperatures
• Beyond heat baths: Generalized resource theories for small-scale thermodynamics
• Thermal machines beyond the weak coupling regime
• Quantum thermodynamics of correlated-catalytic state conversion at small-scale
• Coherence and asymmetry cannot be broadcast
• How an autonomous quantum Maxwell demon can harness correlated information
• Reexamination of Pure Qubit Work Extraction
• Fundamental limitations on photoisomerization from thermodynamic resource theories
• Toward physical realizations of thermodynamic resource theories
• Key Issues Review: Useful autonomous quantum machines
• Energy requirement for implementing unitary gates on energy-unbounded systems
• Work extraction from heat-powered quantized optomechanical setups