Investigation and optimization of the continuous and discrete heat exchangers in the mK dilution refrigerator for cooling superconducting quantum chips

Abstract The recent decade has witnessed the rapid development of superconducting quantum computing in which its chips require to operate below 100 mK. The dilution refrigerator, which can operate continuously and stably and features the merits of low vibration and electromagnetic Interference, has become the enabling cooling technology for this purpose. There are two types of heat exchangers in the dilution refrigerator based on the effect of Kapitza resistance, namely the continuous and discrete heat exchangers. Their flow and heat transfer characteristics are crucial to the refrigerator’s performance. In this paper, a numerical model of the heat exchangers in the dilution refrigerator is established, based on which the effects of dimensions, the Kapitza thermal resistance, and viscous heating on the cooling performance are investigated. The optimal parameters are given, and the cooling capacity of the dilution unit can be improved from 19 μW to 25.2 μW at 20 mK theoretically, which would provide a better temperature environment for quantum computers requiring more qubits.