Virtual qubits, virtual temperatures, and the foundations of thermodynamics
Open accessAbstract
We argue that thermal machines can be understood from the perspective of "virtual qubits" at "virtual temperatures": The relevant way to view the two heat baths which drive a thermal machine is as a composite system. Virtual qubits are two-level subsystems of this composite, and their virtual temperatures can take on any value, positive or negative. Thermal machines act upon an external system by placing it in thermal contact with a well-selected range of virtual qubits and temperatures. We demonstrate these claims by studying the smallest thermal machines. We show further that this perspective provides a powerful way to view thermodynamics, by analyzing a number of phenomena. This includes approaching Carnot efficiency (where we find that all machines do so essentially by becoming equivalent to the smallest thermal machines), entropy production in irreversible machines, and a way to view work in terms of negative temperature and population inversion. Moreover we introduce the idea of "genuine" thermal machines and are led to considering the concept of "strength" of work.
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For a bosonic bath with Ohmic spectrum, the local-validity inequalities are fulfilled as long as the inter-system coupling is much smaller than the oscillator frequency.
“For a bosonic bath with Ohmic spectrum, the last equations are fulfilled as long as W a g , which is usually the case for systems where the local approach is employed [38,44,46,51].”
From Markovian master equations for quantum thermal machines: Local versus global approach (2017) · cites this paper as [38]
Heat engines can only reach Carnot efficiency if they are effectively reduced to a single channel.
“The fact that heat engines can only reach Carnot efficiency if they are effectively reduced to a single channel is also discussed in [38].”
From Markovian master equations for quantum thermal machines: Local versus global approach (2017) · cites this paper as [38]
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References 42 · Cited by 215
Research works printed but not linked: 4
- Authors
- Brunner, N., Linden, N., Popescu, S., & Skrzypczyk, P.
- Affiliations
- University of Bristol (GB)
- University of Cambridge (GB)
- Venue
- Physical Review E
- Publisher
- American Physical Society (APS)
- Published
- 2012-05-14
- Volume
- 85
- Issue
- 5
- Pages
- 051117-051117
- ISSN
- 1539-3755 (ISSN-L)
- 1550-2376
- OpenAlex
- W1818332649
- Cited by
- 215
- References
- 42
- Citations by year
- 2026: 9 · 2025: 12 · 2024: 21 · 2023: 9 · 2022: 12 · 2021: 20 · 2020: 17 · 2019: 21 · 2018: 23 · 2017: 21 · 2016: 13 · 2015: 12 · 2014: 12 · 2013: 9 · 2012: 4
- FWCI
- 8.96
- Type
- journal article
- Language
- en
- Open access
- green
- arxiv.org
- Locations
- Physical Review E (publishedVersion)
- arXiv (Cornell University) (publishedVersion)
- PubMed (publishedVersion)
- Bristol Research (University of Bristol) (submittedVersion)
- arXiv (Cornell University)
- Funders
- Engineering and Physical Sciences Research Council
- Topics
- Physical Sciences › Physics and Astronomy › Statistical and Nonlinear Physics › Advanced Thermodynamics and Statistical Mechanics
- Physical Sciences › Engineering › Mechanical Engineering › Advanced Thermodynamic Systems and Engines
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Mechanics and Applications
- Keywords
- virtual temperature, negative temperature, thermal machines, heat bath, composite systems, Carnot efficiency, entropy production, work, population inversion, foundations of thermodynamics
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