Cryogenic sensor enabling broad-band and traceable power measurements.

Area of Science:

• Quantum Optics
• Cryogenic Engineering
• Metrology

Background:

• Recent advancements in ultrasensitive microwave detectors enable applications in circuit quantum electrodynamics.
• Existing cryogenic sensors are incompatible with broad-band, metrologically traceable power absorption measurements at ultralow powers.

Purpose of the Study:

• To demonstrate ultrasensitive, metrologically traceable power absorption measurements at ultralow powers.
• To overcome the limitations of current cryogenic sensors for broad-band power measurements.

Main Methods:

• Utilized an ultralow-noise nanobolometer with an added direct-current (dc) heater input.
• Employed dc-substitution techniques, comparing radio frequency (RF) and dc heating powers.
• Traced absorbed power to the Josephson voltage and quantum Hall resistance standards.

Main Results:

• Demonstrated two distinct dc-substitution methods for calibrating power delivered to a dilution refrigerator's base temperature stage.
• Successfully measured coaxial input line attenuation from 50 MHz to 7 GHz.
• Achieved measurement uncertainties as low as 0.1 dB at -114 dBm input power.

Conclusions:

• The nanobolometer provides a viable solution for metrologically traceable ultralow power measurements.
• This technique significantly expands the applicability of cryogenic sensors in precision measurements.
• Enables accurate characterization of microwave components and systems at ultralow power levels.