QTurkey’s student branch Quantum Marmara will organize a seminar titled “Nonuniform level scaling in quantum heat engines” with Dr. Alhun Aydın on Wednesday, May 21st at 13:30 in person. Don’t forget to apply to attend!
The event will take place on Wednesday, May 21st at 13:30 in the Göztepe Campus, Faculty of Science, GZFC-114 lecture hall.
Abstract: Size-invariant shape transformation is a technique of changing the shape of a potential by preserving the Lebesgue measure. Such transformations to quantum systems cause the energy levels of the working substance to scale nonuniformly and alter the thermodynamic properties of few-level systems in a non-classical way. In quantum heat engines, the working substance is usually a few-level quantum system. For such systems, the nonuniform level scaling unleashes some unusual thermodynamic behaviors, e.g. spontaneous transitions into lower entropy states and cooling (heating) by effective compression (expansion), which are impossible in classical systems. Here, we investigate this new type of operation in quantum heat engines, which opens a new degree of freedom in controlling quantum thermal machines. We first explain the underlying physical reason for such behaviors by examining the effects of size-invariant modifications on the energy level structure of the quantum substance in detail. In particular, a geometry-induced eigenstate swapping occurs due to the shrinkage of the eigenstates leading to an excessive occupation of the ground-state, while the that of excited states decrease. This causes a competition between the ground state and thermal contributions to the thermodynamic properties. We also identify avoided crossing effects in the spectra that are important in determining the nature of the transitions. Furthermore, we discuss the quantum Stirling and Otto cycle variants under isoformal (size- and shape-preserving) process, along with the role of quantum coherence. The effect we discuss here is so general that it could be realized in any finite-level quantum system (even in a qubit) undergoing a size-preserving transformation.
