Quantum circuits with SINIS structures

Area of Science:

• Cryogenic devices
• Superconducting electronics
• Microwave detection

Background:

• Superconductor-insulator-normal metal-insulator-superconductor (SINIS) tunnel junctions are fundamental components in advanced cryogenic applications.
• These devices are utilized in microwave detectors, electron coolers, primary thermometers, and Aharonov-Bohm interferometers.
• Fabrication and measurement of SINIS devices have been performed at temperatures as low as 100 mK.

Purpose of the Study:

• To optimize SINIS tunnel junction structures for enhanced sensitivity and responsivity in cryogenic devices.
• To develop and test SINIS arrays specifically for detecting 90 GHz radiation for radio astronomy.
• To evaluate the performance of SINIS receivers in a cryostat at low temperatures.

Main Methods:

• Manufacturing of SINIS structures using Dolan-type and Manhattan-type shadow evaporation, and magnetron sputtering.
• Suspension of the absorber above the substrate to improve ultimate sensitivity.
• Testing of SINIS arrays with a black body radiation source, band-pass filters, and an IMPATT diode radiation source.

Main Results:

• Achieved responsivity up to 30 electrons per photon at 350 GHz (72000 A/W) and voltage responsivity up to 3.9 × 10^9 V/W.
• Designed SINIS arrays demonstrated noise equivalent power below 10^-16 W·Hz^-1/2 for 90 GHz radiation detection.
• Successful mounting and testing of a SINIS receiver in a 3He cryostat at 260 mK at the Nasmyth focus of the BTA telescope.

Conclusions:

• Optimized SINIS tunnel junctions offer significant improvements in sensitivity and responsivity for cryogenic applications.
• The developed SINIS arrays are suitable for detecting faint microwave signals, particularly for radio astronomy at 90 GHz.
• The experimental setup and testing at the BTA telescope confirm the potential of SINIS devices for astronomical observations.