Advances in Engine Efficiency: Nanomaterials, Surface Engineering, and Quantum-Based Propulsion

Round 1

Reviewer 1 Report

This study deserves the highest praise, as it combines known data and, based on it, provides an assessment of new promising technologies, such as quantum engines and information-burning engines. I consider this article innovative, which will undoubtedly be cited many times in the future. I think the article can be published as presented.

Author Response

Dear Referee 1,

We deeply appreciate your thorough review of our manuscript and your encouraging comments regarding our work on quantum engines and information-burning engines. We are honored by your assessment of our study as innovative and are pleased to hear that you consider it a valuable contribution to the field. Your recognition of the potential impact of our research and your endorsement for publication as presented significantly motivate us.

Thank you once again for your positive feedback and support.

Sincerely,

Mario J. Pinheiro

Reviewer 2 Report

In this paper, the author presents an interesting discussion on exploiting nanomaterials and their potential applications in thermodynamic cycles.

I find the paper interesting. However, to be published, I ask the author to review the following points:

1- References are needed in the information engines section. Many quality papers deserve to be cited in the introduction. As an example:

* Park, J. J., Kim, K. H., Sagawa, T., & Kim, S. W. (2013). A heat engine is driven by purely quantum information. Physical review letters, 111(23), 230402.

*ÖZDEMİR, A. T., & MÜSTECAPLIOĞLU, Ö. E. (2020). Quantum thermodynamics and quantum coherence engines. Turkish Journal of Physics, 44(5), 404-436.

*Deffner, S., & Campbell, S. (2019). Quantum thermodynamics. Morgan & Claypool Publishers, 10, 2053-2571.

2- References are needed for the definition of entropy as an operator. I understand that the concept comes from the ensemble theory discussion where one shows that S= <-kB Ln \rho> as in the Greiner book. Please post some reference books.

3- The most critical point of the paper is related to the tremendous confusion generated between the Stirling and Otto cycles.

The Otto cycle does not have isothermal trajectories. It has isochoric processes connected to thermal reservoirs where the system undergoes a thermalization process that is not isothermal. 

The one with isothermal trajectories is the Stirling Cycle, and two adiabatic ones, as discussed in this paper. Please clarify this essential and critical point in the acceptance of this work.

Author Response

1. The additional references suggested by Referee 2 were introduced. Others additional references were included in the Introduction and the main text as well.
2. References to the groundbreaking works of Van Neuman, Granier and others were introduced in paragraphs 1-5 of Section Information burning engines and in the Introduction. 
3. In response to the valuable feedback from Referee 2, it is important to clarify a critical confusion identified in the manuscript regarding the Stirling and Otto cycles. Upon review, it is evident that the described quantum engine processes align more closely with the characteristics of the Stirling cycle, which includes isothermal expansion and compression phases, rather than the Otto cycle. The Otto cycle, by contrast, involves adiabatic (isentropic) processes and isochoric (constant volume) heat exchange, without isothermal trajectories. This mislabeling was inadvertent and is hereby corrected to accurately reflect the focus on quantum Stirling engines in this work. Quantum Stirling engines, which allow for isothermal heat exchange processes in addition to adiabatic phases, offer intriguing possibilities for efficiency and operation in quantum systems ([Quan et al., 2007]; [Gelbwaser-Klimovsky et al., 2015]). The potential of quantum Stirling engines to leverage quantum coherence and entanglement during isothermal processes presents a promising avenue for research, distinct from the quantum Otto engine which operates under different thermodynamic principles ([Quan et al., 2009]; [Rossnagel et al., 2014]). We regret any confusion caused by the initial misclassification and appreciate the opportunity to clarify this essential aspect of the study. Please, see correction in red color in the manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The corrections requested to the author have been taken into account.

The new version of the text seems to me to be correct and deserves to be published.