Development of a Cryogen-Free Dilution Refrigerator for Superconducting Quantum Computing

The superconducting quantum computer with strong data storage capability and fast execution speed has attracted a lot of attention in recent years and is finding practical applications in fields such as finance, military, biomedicine, and artificial intelligence. To suppress the thermal noise and to achieve high coherence, the quantum chips require millikelvin temperature, which poses a significant challenge for the suitable cryogenic system. The dilution refrigerator (DR) with ultra-low vibration and electromagnetic interference becomes an appropriate candidate for this purpose. To achieve the aimed millikelvin temperature, a cryogen-free DR composed of a Gifford-McMahon type pulse tube refrigerator (GM-type PTR), Joule-Thompson refrigerator (JTR), and dilution unit is investigated. This article presents the structural design of the DR and the coupling system with superconducting quantum chips. The cooling performance of the designed DR is estimated based on the developed cryogenic system. The minimum deduced temperature of 0.76 K in the still is achieved and the next steps to obtain the final temperature of 5 mK are underway.