Cryogenic sensor enabling broad-band and traceable power measurements

TL;DR

This paper introduces a cryogenic nanobolometer with an added dc heater for broad-band, traceable power measurements at ultralow powers, enabling precise calibration of microwave signals.

Contribution

It presents a novel cryogenic sensor that combines rf and dc power measurement capabilities for traceable, broad-band power calibration at ultralow powers.

Findings

Achieved power measurement uncertainty as low as 0.1 dB at -114 dBm.

Demonstrated accurate attenuation measurement from 50 MHz to 7 GHz.

Extended the nanobolometer with a dc heater for enhanced calibration capabilities.

Abstract

Recently, great progress has been made in the field of ultrasensitive microwave detectors, reaching even the threshold for utilization in circuit quantum electrodynamics. However, cryogenic sensors lack the compatibility with broad-band metrologically traceable power absorption measurements at ultralow powers, which limits their scope of applications. Here, we demonstrate such measurements using an ultralow-noise nanobolometer which we extend by an additional direct-current (dc) heater input. The tracing of the absorbed power relies on comparing the response of the bolometer between radio frequency (rf) and dc-heating powers traced to the Josephson voltage and quantum Hall resistance. To illustrate this technique, we demonstrate methods to calibrate the power that is delivered to the base temperature stage of a dilution refrigerator using our in-situ power sensor. As an example, we demonstrate the ability to measure accurately the attenuation of a coaxial input line between the frequencies of 50 MHz and 7 GHz with an uncertainty down to 0.1 dB at typical input power of -114 dBm.