Cryogenic Microwave Probe Technology with High Thermal Insulation

Integration and low power consumption of cryogenic amplifiers, which are essential for reading out quantum qubits, are inevitable issues for scaling up quantum information processing systems. Although cryogenic probers play an important role in this development, measurement solutions using impedance tuners are not available due to the long high frequency wiring for thermal insulation. In this paper we propose a new probe head structure with high thermal insulation. We eliminate metal heat conduction by using electromagnetic coupling between planar resonant circuits. In addition to evaluating the transmission characteristics of the prototype probe head at room temperature, we experimentally assess its thermal stability under conditions with a significant thermal gradient. This technique enables shorter high-frequency lines in cryogenic probers by providing the probe head itself with thermal insulating properties.