A High-Powered Cryogenic System for Sub Kelvin Electronic Applications

Abstract We have developed a powerful table-top cryogenic platform for Quantum computing applications below 1 Kelvin. The system offers a cold plate optimized for the CMOS-spin qubits technology developed by CEA/LETI. The first step is to demonstrate a 100 qubits system. The cryogenic system is designed for 100 mW cooling power at 500 mK, required by this R&D activity. The solution chosen is a high-flow helium-3 Joule-Thomson cycle pre-cooled by a two-stage 4 Kelvin Pulse-Tube (PT420-RM). The table-top architecture is preferred in order to keep an easy access to the quantum processor and the control cryoelectronics components. The pulse-tube and the high flow Joule-Thomson recuperative heat exchangers are mounted into a separate coldbox. The remote cryostat offers three temperature stages: a 50 K stage, coupled to the pulse-tube first stage by a pressurized helium cooling loop; a 5 K stage, coupled to the second pulse-tube stage by a conductive copper link; and a 500 mK stage coupled to the Joule-Thomson cycle evaporator. The pumping speed required (~1000 L/s) is achieved by several dry compact turbopumps in order to reach the required helium-3 flow of 4 mmol/s at 10 Pa. We report the performances achieved with helium-4 and helium-3 on the prototype system.