Switching the function of the quantum Otto cycle in non-Markovian dynamics: heat engine, heater and heat pump

TL;DR

This paper investigates how non-Markovian dynamics in a quantum Otto cycle can enable switching between heat engine, heater, and heat pump functions by controlling interaction times, revealing novel energy flow behaviors and potential quantum cooling applications.

Contribution

It introduces a framework for controlling quantum cycle functions via non-Markovian interaction times and analyzes the associated energy flow and system cooling effects.

Findings

Interaction energy between bath and qubit is non-negligible and varies with interaction time.

Non-Markovian effects enable switching the cycle's function among engine, heater, and heat pump.

Shortening interaction time can cool the qubit, useful for quantum computing.

Abstract

Quantum thermodynamics explores novel thermodynamic phenomena that emerge when interactions between macroscopic systems and microscopic quantum ones go into action. Among various issues, quantum heat engines, in particular, have attracted much attention as a critical step in theoretical formulation of quantum thermodynamics and investigation of efficient use of heat by means of quantum resources. In the present paper, we focus on heat absorption and emission processes as well as work extraction processes of a quantum Otto cycle. We describe the former as non-Markovian dynamics, and thereby find that the interaction energy between a macroscopic heat bath and a microscopic qubit is not negligible. Specifically, we reveal that the interaction energy is divided into the system and the bath in a region of the short interaction time and remains negative in the region of the long interaction time. In addition, a counterintuitive energy flow from the system and the interaction energy to the hot bath occurs in another region of the short interaction time. We quantify these effects by defining an index of non-Markovianity in terms of the interaction energy. With this behavior of the interaction energy, we show that a non-Markovian quantum Otto cycle can switch functions such as an engine as well as a heater or a heat pump by controlling the interaction time with the heat bath. In particular, the qubit itself loses its energy if we shorten the interaction time, and in this sense, the qubit is cooled through the cycle. This property has a possibility of being utilized for cooling the qubits in quantum computing. We also describe the work extraction from the microscopic system to a macroscopic system like us humans as an indirect measurement process by introducing a work storage as a new reservoir.