Minimal two-body quantum absorption refrigerator

We study the phenomenon of absorption refrigeration, where refrigeration is achieved by heating instead work, in two different setups: a minimal set up based on coupled qubits, and non-linearly resonators. Considering ZZ interaction between we outline basic ingredients required to achieve cooling. Using local as well global master equations, observe that inclusion XX type term qubit-qubit coupling detrimental compare cooling effect obtained qubit case with resonators (multi-level system) translates Kerr-type non-linearity. For small intermediate strengths non-linearity, multi-level quantum systems, for example qutrits, give better compared qubits. Keldysh non-equilibrium Green's function formalism, go beyond first order sequential tunneling processes higher refrigeration. find reduced equation calculations.