# Quantum thermal transistor based on the qubit-qutrit coupling

## TL;DR

This paper proposes a quantum thermal transistor using qubit-qutrit coupling, demonstrating its ability to control and amplify heat currents between three heat baths, with robustness to temperature fluctuations.

## Contribution

It introduces a novel quantum thermal transistor design based on qubit-qutrit coupling and analyzes its thermal behavior using both numerical and analytical methods.

## Key findings

- Enables switching and modulation of heat currents with weak control signals
- Achieves multiple-region heat current amplification
- Exhibits robustness to temperature fluctuations at the lower-temperature terminal

## Abstract

A quantum thermal transistor is designed by the strong coupling between one qubit and one qutrit which are in contact with three heat baths with different temperatures. The thermal behavior is analyzed based on the master equation by both the numerical and the approximately analytic methods. It is shown that the thermal transistor, as a three-terminal device, allows a weak modulation heat current (at the modulation terminal) to switch on/off and effectively modulate the heat current between the other two terminals. In particular, the weak modulation heat current can induce the strong heat current between the other two terminals with the multiple-region amplification of heat current. Furthermore, the heat currents are quite robust to the temperature (current) fluctuation at the lower-temperature terminal within certain range of temperature, so it can behave as a heat current stabilizer.