RF Diode Thermometry – Pushing the limits of cryogenic temperature sensing*

Addressing and operating the large number of qubits needed for fault-tolerant quantum computing requires the integration of classical circuitry close to or on the same chip as qubits operating at cryogenic temperatures. These classical circuits dissipate power which may affect qubit operation. Experimental tools to probe these static and dynamic effects are therefore of interest to the field and will lead to a better understanding of the recent temperature-dependence observed in semiconductor spin-qubit systems. Previously it has been shown that diode thermometry is the most sensitive cryogenic thermometry technique native to CMOS devices. In this work, we further increase the sensitivity of diode thermometry by using radiofrequency reflectometry (RF) techniques and demonstrate state-of-the-art cryogenic temperature sensing capabilities, maintaining sensitivity down to 20mK. The technique allows us to conduct pulsed heating experiments with a resolution of <1µs commensurate with that achieved in semiconductor qubit architectures. The ability to probe at high frequency provides insight into the dynamic temperature behavior of the chip as a result of both localized (on-chip) and global (PCB) level heating. This technique will allow future experimental studies of quantum thermodynamics in nanoelectronic systems as well as increase our understanding of dynamic power dissipation in cryoelectronic and quantum circuits.