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Description of quantum coherence in thermodynamic processes requires constraints beyond free energy (1405.2188v3)

Published 9 May 2014 in quant-ph

Abstract: Recent studies have developed fundamental limitations on nanoscale thermodynamics, in terms of a set of independent free energy relations. Here we show that free energy relations cannot properly describe quantum coherence in thermodynamic processes. By casting time-asymmetry as a quantifiable, fundamental resource of a quantum state we arrive at an additional, independent set of thermodynamic constraints that naturally extend the existing ones. These asymmetry relations reveal that the traditional Szilard engine argument does not extend automatically to quantum coherences, but instead only relational coherences in a multipartite scenario can contribute to thermodynamic work. We find that coherence transformations are always irreversible. Our results also reveal additional structural parallels between thermodynamics and the theory of entanglement.

Citations (594)

Summary

  • The paper demonstrates that free energy alone cannot capture quantum coherence, prompting the need for additional constraints.
  • It introduces time-asymmetry measures as a quantifiable resource to extend traditional thermodynamic models.
  • The study reveals that quantum coherence transformations incur inherent irreversibility, aligning with parallels found in entanglement theory.

Insights into Quantum Coherence and Thermodynamics

The paper "Description of quantum coherence in thermodynamic processes requires constraints beyond free energy" posits a critical examination of the conventional application of free-energy relations within the framework of quantum coherence in thermodynamic systems. Authored by Matteo Lostaglio, David Jennings, and Terry Rudolph, the work navigates deeply into reconciling the domains of quantum physics and thermodynamics, particularly when considering small-scale systems where quantum effects become predominant.

Summary of Key Findings

The research presented in the paper identifies that:

  1. Limitations of Free Energy in Quantum Contexts: Traditional thermodynamic systems use free energy relations to describe state transformations and work extraction. However, these become insufficient when addressing the nuances of quantum coherence—a fundamental quantum resource representing the capacity of a quantum state to exhibit superposition in energy bases.
  2. Introduction of Asymmetry Measures: The authors systematically introduce the concept of time-asymmetry as a quantifiable resource, offering a more comprehensive model that extends the traditional thermodynamic boundaries. This viewpoint leverages recent advancements in asymmetry theory to postulate additional constraints, essential for describing coherence transitions.
  3. Irreversibility in Coherence Transformations: The research demonstrates that while traditional irreversibility is often discussed in terms of entropy, at the quantum scale, coherence transformations naturally incur irreversible processes, independent of the traditional entropic account.
  4. Correlations with Entanglement Theory: Profound connections are drawn between thermodynamic inequalities and entanglement manipulation, as analogous structural parallels emerge, hinting at deeper rules governing resource theories in quantum mechanics.

Implications of the Research

Theoretical Implications: The necessity to account for coherence-specific constraints suggests reevaluating foundational principles of thermodynamics in the context of quantum mechanics. This may lead to new thermodynamic laws tailored for quantum information systems, offering a potential unified framework to address both macro and quantum scales.

Practical Implications: As quantum technologies mature, the exact characterization and utilization of quantum coherences—spanning communication, cryptography, and computation—require comprehensive models. This research emphasizes a paradigm where coherence is critical, influencing quantum stack layers from hardware to algorithmic architecture.

Future Developments

The paper suggests promising future avenues:

  • Refinement of Quantum Thermodynamic Theories: Developing constraints beyond the equilibrium assumptions is pivotal. Enhanced models may probe deeper into non-equilibrium quantum dynamics, paving the way for more robust predictions and control mechanisms in quantum systems.
  • Interdisciplinary Approaches: Linking quantum thermodynamics with other areas like quantum biology, cognitive computing, and material sciences could foster innovative technologies leveraging quantum coherences.
  • Extensive Empirical Exploration: Applications in quantum thermodynamics, including quantum heat machines and nanoscale engines, demand empirical validation. This research could guide parameterization and design of new experimental setups.

In conclusion, this paper provides a crucial step towards understanding and utilizing quantum coherence within thermodynamic processes. By extending the traditional free energy framework, the authors illustrate a necessary revision to thermodynamic laws in the quantum domain. Such insights are fundamental as the field progresses toward realizing fully operational quantum technologies.