Bolometric detection of Josephson radiation.

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Microwave Physics

Background:

• Large-scale quantum computation relies on Josephson junctions, but understanding single junctions remains challenging.
• Key issues include quantum phase transitions, environmental coupling, and superconducting qubit coherence.
• Existing detection methods for Josephson dynamics are limited.

Purpose of the Study:

• To design and build an engineered on-chip reservoir acting as a bolometer.
• To detect Josephson radiation from a Josephson junction under non-equilibrium conditions.
• To provide a sensitive, wide-band thermal detection scheme for microwave photons.

Main Methods:

• An engineered on-chip reservoir was connected to a Josephson junction.
• The reservoir functions as a bolometer, converting AC Josephson current to temperature rise.
• DC thermometry measured the temperature changes.
• A circuit model with realistic parameters was used for quantitative analysis.

Main Results:

• The bolometer efficiently detected Josephson radiation up to 100 GHz.
• The device converted microwave frequencies into measurable temperature rises.
• The circuit model accurately predicted current-voltage characteristics and measured power.
• Demonstrated an efficient, wide-band thermal detection scheme.

Conclusions:

• The engineered bolometer provides an efficient method for detecting microwave photons.
• This bolometer serves as a sensitive detector of Josephson dynamics.
• The findings offer a new tool for studying superconducting qubits and quantum computation.