Improved powder filters for qubit measurements

Area of Science:

• Cryogenic Engineering
• Electrical Engineering
• Materials Science

Background:

• Sensitive measurements at cryogenic temperatures require effective noise suppression.
• Existing powder filters often have limitations in frequency response, size, or reproducibility.
• Hermetic feedthroughs are also crucial for maintaining low-temperature environments.

Purpose of the Study:

• To design and fabricate miniature low-pass metal powder filters for cryogenic applications.
• To improve upon the performance characteristics of existing powder filters.
• To create filters that are also suitable for use as hermetic feedthroughs.

Main Methods:

• Design and fabrication of miniature metal powder filters.
• Characterization of filter performance at cryogenic temperatures (4.2 K).
• Evaluation of transmission characteristics, including cutoff frequency and roll-off rate.

Main Results:

• The fabricated filters exhibit smooth transmission characteristics with no ripples.
• Filters demonstrate a steep decay above the cutoff frequency (-50 dB per decade).
• At 4.2 K, a single filter has a cutoff frequency of 1 MHz and identical, reproducible responses.

Conclusions:

• Miniature low-pass metal powder filters are suitable for noise-sensitive cryogenic measurements.
• The developed filters offer improved frequency response and significantly smaller dimensions compared to previous designs.
• These filters provide reliable performance and can function as hermetic feedthroughs at low temperatures.