Few-qubit quantum refrigerator for cooling a multi-qubit system

TL;DR

This paper introduces a compact, few-qubit quantum refrigerator model using a spin-star system to cool multi-qubit systems, with potential applications in quantum computing and thermal management.

Contribution

It proposes a novel few-qubit spin-star refrigerator design that effectively cools multi-qubit systems and analyzes its efficiency and temperature bounds.

Findings

Central qubit becomes colder than environment under certain interactions

Refrigeration cycle controlled by number of ancilla qubits and interaction strength

Bounds on minimum achievable temperature established

Abstract

We propose to use a few-qubit system as a compact quantum refrigerator for cooling an interacting multi-qubit system. We specifically consider a central qubit coupled to $N$ ancilla qubits in a so-called spin-star model as our quantum refrigerator. We first show that if the interaction between the qubits is of the longitudinal and ferromagnetic Ising model form, the central qubit is colder than the environment. The colder central qubit is then proposed to be used as the refrigerant interface of the quantum refrigerator to cool down general quantum many-qubit systems. We discuss a simple refrigeration cycle, considering the operation cost and cooling efficiency, which can be controlled by $N$ and the qubit-qubit interaction strength. Besides, bounds on the achievable temperature are established. Such few-qubit compact quantum refrigerators can be significant to reduce dimensions of quantum technology applications, can be easy to integrate into all-qubit systems, and can increase the speed and power of quantum computing and thermal devices.