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Direct Detection of Down-Converted Photons Spontaneously Produced at a Single Josephson Junction
Dorian Fraudet1, Izak Snyman2, Denis M Basko3
1Institut Néel, Université Grenoble Alpes, CNRS, Grenoble INP, 38000 Grenoble, France.
Physical Review Letters
|February 6, 2025
Summary
Researchers observed spontaneous photon decay into multiple photons using a Josephson junction. This demonstrates photon triplet emission, a key signature of ultrastrong light-matter coupling in quantum optics.
Area of Science:
- Quantum Optics
- Condensed Matter Physics
- Superconducting Circuits
Background:
- Previous studies reported spectroscopic signatures of photon conversion in bosonic quantum impurity models.
- These signatures were evidenced as resonances in the many-body spectrum.
Purpose of the Study:
- To observe multimode fluorescence from a Josephson junction.
- To demonstrate spontaneous photon decay into multiple photons.
- To provide a direct signature of ultrastrong light-matter coupling.
Main Methods:
- Utilizing a small Josephson junction embedded in a high impedance superconducting transmission line.
- Employing state-of-the-art broadband parametric amplifiers for photon detection.
- Analyzing the emitted photon spectrum to identify triplet emission.
Main Results:
- Observed multimode fluorescence from the Josephson junction.
- Explicitly demonstrated photon triplet emission at a specific frequency.
- Identified this emission as the counterpart of inelastic photon decay at 3x the emission frequency.
Conclusions:
- The results provide direct evidence of spontaneous photon decay into multiple photons.
- This observation is a signature of ultrastrong light-matter coupling.
- Opens new avenues for research in many-body quantum optics.
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