#### Alladi Ramakrishnan Hall

#### Two models of quantum heat engines

#### George Thomas

##### IMSc

*Quantum heat engines play a crucial role in understanding thermodynamic features of quantum systems. In this talk, I will discuss two models of heat engines. In the first model [1], we study a Stirling engine which extracts work using quantized energy levels. We show that the lack of information about the position of the particle inside the potential well can be converted into useful work without*

resorting to any measurement. We show that the Carnot efficiency can be achieved in the low-temperature limit. Further, in the low-temperature limit, we estimate the amount of work extractable from

distinguishable particles, fermions and bosons. In the second model [2], we show that non-Markovian effects of the reservoirs can be used as a resource to extract work from an Otto cycle. We consider a class of non-Markovian dynamics for which the equilibrium state is not an invariant state [3,4]. We show an apparent violation of the second law of thermodynamics unless the cost of non-Markovian effects is considered. We also discuss the cost of non-Markovianity in terms of extractable work. After subtracting the minimum cost for the non-Markovianity, the Otto cycle becomes equivalent to a Carnot cycle. We illustrate our ideas with a specific example of non-Markovian evolution.

[1] G. Thomas, D. Das and S. Ghosh, Quantum heat engine using energy

quantization and resources of ignorance, arXiv: 1802.07681[quant-ph](2018).

[2] G. Thomas, N. Siddharth S. Banerjee and S. Ghosh, Thermodynamics

of non-Markovian reservoirs and heat engines, arXiv:1801.00744 [quant-ph] (2018).

[3] D. Chruscinski, A. Kossakowski, and S. Pascazio, Phys. Rev. A 81, 032101 (2010).

[4] S. Marcantoni, S. Alipour, F. Benatti, R. Floreanini, and A. T. Rezakhani, Sci. Rep. 7, 12447 (2017).

Done