# Multifunctional quantum thermal device utilizing three qubits

## TL;DR

This paper proposes a three-qubit quantum thermal device capable of multiple functions such as heat current amplification, switching, stabilization, and rectification, based on steady-state dynamics with three heat baths.

## Contribution

It introduces a multifunctional quantum thermal device design that integrates several thermodynamic functions using three coupled qubits and heat baths.

## Key findings

- Can amplify heat currents as a transistor
- Functions as a thermal stabilizer and valve
- Controls unidirectional heat flow as a rectifier

## Abstract

Quantum thermal devices which can manage heat as their electronic analogues for the electronic currents have attracted increasing attention. Here a three-terminal quantum thermal device is designed by three coupling qubits interacting with three heat baths with different temperatures. Based on the steady-state behavior solved from the dynamics of this system, it is demonstrated that such a device integrates multiple interesting thermodynamic functions. It can serve as a heat current transistor to use the weak heat current at one terminal to effectively amplify the currents through the other two terminals, to continuously modulate them ranging in a large amplitude, and even to switch on/off the heat currents. It is also found that the three currents are not sensitive to the fluctuation of the temperature at the low temperature terminal, so it can behave as a thermal stabilizer. In addition, we can utilize one terminal temperature to ideally turn off the heat current at any one terminal and to allow the heat currents through the other two terminals, so it can be used as a thermal valve. Finally, we illustrate that this thermal device can control the heat currents to flow unidirectionally, so it has the function as a thermal rectifier.