Three qubits in less than three baths: Beyond two-body system-bath interactions in quantum refrigerators

TL;DR

This paper demonstrates a quantum refrigerator model using three qubits and two baths, where two qubits share a common bath, enabling steady-state and transient cooling effects beyond traditional two-body interactions.

Contribution

It introduces a novel three-qubit, two-bath quantum refrigerator model with common bath interactions, expanding the understanding of quantum cooling mechanisms.

Findings

Steady-state cooling achieved with three qubits and two baths.

Transient cooling observed in certain parameter regimes.

Cooling efficiency enhanced by increasing few-body interaction strength.

Abstract

We show that quantum absorption refrigerators, which have traditionally been studied as of three qubits, each of which is connected to a thermal reservoir, can also be constructed by using three qubits and two thermal baths, where two of the qubits, including the qubit to be locally cooled, are connected to a common bath. With a careful choice of the system, bath, and qubit-bath interaction parameters within the Born-Markov and rotating-wave approximations, one of the qubits attached to the common bath achieves a cooling in the steady state. We observe that the proposed refrigerator may also operate in a parameter regime where no or negligible steady-state cooling is achieved, but there is considerable transient cooling. The steady-state temperature can be lowered significantly by an increase in the strength of the few-body interaction terms existing due to the use of the common bath in the refrigerator setup. The proposed refrigerator built with three qubits and two baths is shown to provide steady-state cooling for both Markovian qubit-bath interactions between the qubits and canonical bosonic thermal reservoirs, and a simpler reset model for the qubit-bath interactions.