Thermal spectrometer for superconducting circuits

Area of Science:

• Quantum Computing and Superconducting Circuits
• Microwave Physics and Spectroscopy
• Cryogenic Measurement Techniques

Background:

• Superconducting circuits are crucial for quantum phenomena research and quantum technologies.
• Traditional Radio Frequency (RF) measurement schemes are commonly used for circuit readout and characterization.
• Existing RF methods have limitations in frequency range and calibration requirements.

Purpose of the Study:

• To demonstrate a novel DC measurement technique for characterizing superconducting circuits.
• To investigate the properties of a coplanar waveguide resonator using a thermal spectrometer.
• To offer a simpler, wider-bandwidth, and potentially calibration-free alternative to RF spectrometers.

Main Methods:

• Utilized an on-chip bolometer to absorb a fraction of microwave photons from the resonator.
• Monitored the temperature rise of the bolometer via its DC signal.
• Correlated the DC thermometer signal with the resonator's absorption characteristics.

Main Results:

• Successfully determined the resonance frequency and lineshape (quality factor) of the coplanar waveguide resonator.
• The DC thermal measurement scheme demonstrated a wide frequency band potential up to 200 GHz.
• Achieved a frequency-independent reference level for the absorption signal and calibration-free operation in the low power regime.

Conclusions:

• A simple DC measurement using a thermal spectrometer is a viable method for analyzing superconducting circuits.
• This technique provides an effective alternative to conventional RF spectrometers, offering broader frequency coverage and simpler operation.
• The demonstrated method has significant potential for advancing quantum circuit characterization and quantum technology applications.