Quantum Thermal Machines and Pseudo-Hermiticity

• Grant number: 24/21707-0
• Support Opportunities: Research Grants - Visiting Researcher Grant - Brazil
• Start date: March 15, 2025
• End date: March 14, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - General Physics
• Principal Investigator: Miled Hassan Youssef Moussa
• Grantee: Miled Hassan Youssef Moussa
• Visiting researcher: Norton Gomes de Almeida
• Visiting researcher institution: Universidade Federal de Goiás (UFG). Instituto de Física, Brazil
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The goal of this project, for the visit of Prof. Norton Gomes de Almeida, from the Physics Institute of the Federal University of Goiás to the Physics Instituteof São Carlos (USP), focuses on the study of quantum heat engines under different circumstances, in particular when they are described by autonomous ornon-autonomous pseudo-Hermitian Hamiltonians. We must also consider that the working substances comprise many-body systems, such as dense or moderately dense atomic samples. Collective effects of superradiance and superabsorption emerge from these samples when in contact with thermal reservoirs, which should affect the figures of merit of the machines.We must also study the figure of merit of the engine when the hot reservoir is replaced by the Glauber amplifier, or multimodal pumping. This amplifier is generally used to promote the population inversion of the active medium inthe laser mechanism, and therefore constitutes an alternative way of supplying energy to the working substance.We must also analyze the possible limits of the eficiency of quantum heat engines. Although Carnot eficiency is a relevant theoretical limit, the associated zero power makes the machines useless from an experimental point of view. Recent works show that a higher eficiency power gain is possible, even theoretically close to Carnot eficiency, as long as work is performed on the system to compensate for friction losses. This technique, called adiabatic shortcut, allowsthe stages of the unitary evolutions of the machines to be performed in finite time, that is, with non-zero power. This method, however, requires fine control of the temporal evolution of the system, in addition to the work required forits implementation. Here, we intend to investigate the possibility of mimicking an adiabatic change by modulating the system frequency, in order to gain power without losing eficiency. The simulation of adiabatic changes withoutusing additional resources is a promising path that has already been explored in contexts other than quantum heat machines. (AU)