Dissipative cryogenic filters with zero dc resistance.

Area of Science:

• Physics
• Electrical Engineering
• Materials Science

Background:

• Cryogenic radio frequency (RF) filters are essential for reducing thermal noise in sensitive experiments.
• Traditional filters can introduce unwanted resistance or dissipation at low temperatures.
• Minimizing black body radiation is critical for achieving millikelvin temperatures.

Purpose of the Study:

• To design and test novel cryogenic RF filters with zero direct current (DC) resistance.
• To achieve significant attenuation of unwanted RF signals at cryogenic temperatures.
• To enable sensitive measurements by reducing thermal noise in dilution refrigerators.

Main Methods:

• Fabrication of filters using wires with a superconducting core and a resistive sheath.
• Implementation of twisted wire pairs shielded with copper tape.
• Integration of additional 10 nF capacitors per line.

Main Results:

• Filters exhibit zero DC resistance, allowing low-frequency currents with negligible dissipation.
• Above a cutoff frequency (approx. 1 GHz), attenuation increases exponentially with frequency due to skin depth effects.
• A single filter stage achieved at least 45 dB attenuation above 10 MHz with added capacitors.
• Effective attenuation of room temperature black body radiation to levels corresponding to 10 mK above 10 MHz.

Conclusions:

• The developed cryogenic RF filters are highly effective in suppressing thermal noise.
• These filters are suitable for use in dilution refrigerators, enabling sensitive measurements at millikelvin temperatures.
• The design offers a practical solution for mitigating RF interference in quantum computing and sensitive detection applications.