Quantum absorption refrigerator based on 3-body interaction resets qubit autonomously*

Absorption refrigerators are autonomous machines that utilize the natural flow of heat in available thermal gradients to cool objects. Here, we present the realization of a quantum absorption refrigerator based on a three-body interaction in superconducting circuits. We demonstrate its operation by cooling a transmon qubit autonomously below its residual thermal occupation. Time-domain control can modulate the refrigerators's continuous operation to reset the qubit for quantum information processing. The refrigerator is fueled by an engineered two-photon process between three qubits. Its thermal baths are realized with coupled waveguides populated with microwave photons whose spectral density is synthesized to be thermal. We find that, under optimal operating conditions, the excited-state population of a fully excited qubit reaches the steady-state value 0.05% ± 0.05% in about 1.6 μs, in agreement with theoretical simulations. Our proof-of-concept refrigerator demonstrates that quantum thermal machines can be harnessed to perform useful tasks on quantum processing units. It also initiates a path to experimental studies of quantum thermodynamics using superconducting quantum circuits coupled to propagating thermal microwave fields.