Simultaneous cooling of qubits via a quantum absorption refrigerator and beyond

TL;DR

This paper presents a quantum thermal device capable of simultaneously cooling multiple qubits using engineered interactions with heat baths, exploring different master equations and network configurations to optimize cooling performance.

Contribution

It introduces a novel design for a quantum absorption refrigerator that can cool multiple qubits simultaneously and analyzes its operation under various conditions and configurations.

Findings

Simultaneous cooling of multiple qubits is achievable with the proposed device.

Local quantum master equations restrict the device to operate as a quantum absorption refrigerator.

Global quantum master equations suggest cooling beyond traditional absorption refrigerator regimes.

Abstract

We design a quantum thermal device that can simultaneously and dynamically cool multiple target qubits. Using a setup with three bosonic heat baths, we propose an engineering of interaction Hamiltonian using operators on different subspaces of the full Hilbert space of the system labelled by different magnetizations. We demonstrate, using the local as well as global quantum master equations, that a set of target qubits can be cooled simultaneously using these interaction Hamiltonians, while equal cooling of all target qubits is possible only when the local quantum master equation is used. However, the amount of cooling obtained from different magnetization subspaces, as quantified by a distance-based measure of qubit-local steady-state temperatures, may vary. We also investigate cooling of a set of target qubits when the interaction Hamiltonian has different magnetization components, and when the design of the quantum thermal device involves two heat baths instead of three. Further, we demonstrate, using local quantum master equation, that during providing cooling to the target qubits, the designed device operates only as a quantum absorption refrigerator. In contrast, use of the global quantum master equation indicates cooling of the target qubits even when the device works outside the operation regime of a quantum absorption refrigerator. We also extend the design to a star network of qubits interacting via Heisenberg interaction among each other, kept in contact with either three, or two heat baths, and discuss cooling of a set of target qubits using this device.