# Bolometric detection of Josephson radiation

**Authors:** Bayan Karimi, Gorm Ole Steffensen, Andrew P. Higginbotham, Charles M. Marcus, Alfredo Levy Yeyati, Jukka P. Pekola  
**arXiv:** [2402.09314](https://arxiv.org/abs/2402.09314)  
**Date:** 2024-02-14  
**Summary page:** https://www.summarizepaper.com/en/paper/2402.09314v1/

## Key points

- Josephson junctions (JJs) have been extensively studied since the 1960s in the field of quantum information processing
- Unresolved questions regarding a single junction include understanding quantum phase transitions, coupling to environment, and improving coherence of superconducting qubits
- Authors designed and built an engineered on-chip reservoir that acts as an efficient bolometer for detecting Josephson radiation under non-equilibrium conditions
- Bolometer converts AC Josephson current at microwave frequencies up to $100 GHz into measurable DC temperature rise
- Experiment demonstrates efficient and wide-band thermal detection scheme for microwave photons
- Sensitive detector for studying Josephson dynamics beyond standard conductance measurements
- Previous work by Devoret et al., Vion et al., Golubov et al. on macroscopic quantum tunneling, thermal activation, and current-phase relation in Josephson junctions respectively
- References to earlier works on Josephson effect in small tunnel contacts by Ivanchenko and Zil'berman, and Caldeira and Leggett's work on quantum tunneling in dissipative systems
- Mentions Tafuri's book on Josephson junctions for metrology applications
- Research presents innovative approach to detect Josephson radiation using an on-chip bolometer
- Findings contribute to understanding single junction behavior and potential implications for improving coherence of superconducting qubits and advancing quantum information processing technologies

## Summary

In the field of quantum information processing, Josephson junctions (JJs) have been extensively studied since the 1960s. Despite advancements in building quantum devices based on multiple JJs, there are still unresolved questions regarding a single junction. These include understanding quantum phase transitions, the coupling of JJs to their environment, and improving the coherence of superconducting qubits. To address these challenges, the authors of this study designed and built an engineered on-chip reservoir that acts as an efficient bolometer for detecting Josephson radiation under non-equilibrium (biased) conditions. The <kw>bolometer</kw> is capable of converting alternating current (ac) Josephson current at microwave frequencies up to about $100\,$GHz into a measurable direct current (dc) temperature rise. The experiment conducted by the researchers demonstrates an efficient and wide-band thermal detection scheme for <kw>microwave photons</kw>. It also provides a sensitive detector for studying Josephson dynamics beyond standard conductance measurements. By using a circuit model, they were able to quantitatively capture both the current-voltage characteristics and the measured power. This research builds upon previous work in the field. For example, Devoret et al. [4] conducted measurements of macroscopic quantum tunneling out of the zero-voltage state of a current-biased Josephson junction. Vion et al. [5] investigated thermal activation above a dissipation barrier in small Josephson junctions. Golubov et al. [6] studied the current-phase relation in Josephson junctions. The study also references earlier works on the <kw>Josephson effect</kw> in small tunnel contacts by Ivanchenko and Zil'berman [7], as well as Caldeira and Leggett's work on quantum tunneling in dissipative systems [8]. Additionally, it mentions a book edited by Tafuri [9], which explores Josephson junctions for metrology applications. Overall, this research presents an innovative approach to detect Josephson radiation using an on-chip bolometer. The findings contribute to the understanding of single junction behavior and have potential implications for improving the coherence of superconducting qubits and advancing <kw>quantum information processing</kw> technologies.