Unlocking the Secrets of Quantum Information with Josephson Junctions

Insider Brief:

• Researchers from Aalto University, University of Helsinki, the University of Chicago, and others have made a groundbreaking discovery. They have found that Josephson junctions, crucial components of superconducting qubits, dissipate energy as photons, directly measured using a sensitive bolometer.

Energy radiates from Josephson junctions as photons, and for the first time, researchers have directly measured this radiation using a highly sensitive thermal detector known as a bolometer. This development sheds light on how superconducting qubits, the building blocks of quantum computers, lose energy—an issue that disrupts quantum information and compromises qubit performance.

Qubits and the Challenge of Decoherence

Superconducting qubits, used by quantum computing systems such as those from Google and IBM, operate at extremely low temperatures to maintain their quantum state. However, the stability of qubits can be compromised by heat dissipation, leading to decoherence when quantum states revert to classical behavior, erasing valuable quantum information.

Bolometer-Based Breakthrough in Measuring Energy Dissipation

To address this gap, the research team used a nano-bolometer to directly measure the weak radiation emitted from a Josephson junction. The bolometer converts radiation into heat, allowing researchers to analyze the energy dissipation in real-time. This approach identified several dissipation mechanisms, each dependent on the bias applied to the junction.

Looking Ahead: Counting Photons to Optimize Qubit Performance

This research offers a clearer picture of how qubits lose energy through photon emission, providing a direct method to measure coherence losses in superconducting quantum circuits. Future work for the group includes refining the bolometer to detect single-photon events, which could provide even more precise insights into energy dissipation and help optimize qubit technology for scalable quantum computing applications.

The authors who contributed to the study include Bayan Karimi, Gorm Ole Steffensen, Andrew P. Higginbotham, Charles M. Marcus, Alfredo Levy Yeyati, and Jukka P. Pekola.