Quantum Microwave Router Cell Achieves Coherent 6GHz Photon Transfer at 10mK with Scalable Design

Quantum communication networks require precise control over individual photons, and researchers are now demonstrating a fundamental building block for such networks, a basic cell capable of routing microwave photons. Evgeniya Mutsenik, Aidar Sultanov, and Leonie Kaczmarek, along with colleagues at the Leibniz Institute of Photonic Technology, have experimentally realised this cell, achieving coherent control and exchange of photons between waveguides. This breakthrough establishes a versatile platform for exploring the behaviour of open quantum systems and represents a significant step towards building scalable quantum routers and network nodes, operating reliably even at the single-photon level. The team’s work demonstrates clear performance limits imposed by factors like temperature and photon number, paving the way for optimisation and future advancements in quantum communication technology.

This device, based on a transmon qubit coupled to two waveguides, operates reliably even at the single-photon level and allows for detailed characterization of photon interactions. By combining steady-state and time-domain measurements, the team reconstructed key system parameters, including relaxation, dephasing, and photon transfer efficiency, confirming predictions from a non-Hermitian Hamiltonian model.

The experimental results validate the device’s operation and demonstrate its potential as a building block for more complex quantum networks. Importantly, the researchers observed photon dressing effects in the high-photon regime, highlighting the device’s ability to probe strong light-matter interactions. Beyond its primary routing function, this basic cell provides a versatile platform for investigating fundamental quantum phenomena, such as coherence and photon-mediated interactions, opening avenues for further research in circuit quantum electrodynamics.

Superconducting Qubits and Quantum Circuit QED

This document represents a comprehensive collection of research papers focused on superconducting qubits and quantum circuit QED. It covers a broad range of topics essential for building and controlling quantum systems, with a focus on superconducting qubits, the fundamental building blocks of these quantum computers, and quantum circuit QED, the study of coupling these qubits to microwave resonators.

A significant portion of the research addresses the critical issue of noise and decoherence, major obstacles to building practical quantum computers, detailing various noise sources and techniques for mitigating their effects. The document also emphasizes the importance of spectroscopy and measurement techniques for characterizing qubit properties and performing quantum measurements, while exploring advanced theoretical concepts, such as non-Hermitian Hamiltonians and virtual transitions.

Furthermore, the collection highlights the importance of fabrication technologies for creating superconducting circuits, including wafer-scale fabrication and advanced materials. The inclusion of references to data analysis techniques, like Principal Component Analysis, demonstrates the use of sophisticated methods for extracting meaningful information from complex experimental data, and explores the connection between dissipative processes and qubit coherence.

Scalable Quantum Routing Cell Demonstrated Successfully

Researchers have successfully demonstrated a scalable basic cell for quantum routing, achieving coherent control and exchange of microwave photons between spatially separated waveguides. This device, based on a transmon qubit coupled to two waveguides, operates reliably even at the single-photon level and allows for detailed characterization of photon interactions. By combining steady-state and time-domain measurements, the team reconstructed key system parameters, including relaxation, dephasing, and photon transfer efficiency, confirming predictions from a non-Hermitian Hamiltonian model.

The experimental results validate the device’s operation and demonstrate its potential as a building block for more complex quantum networks. Importantly, the researchers observed photon dressing effects in the high-photon regime, highlighting the device’s ability to probe strong light-matter interactions. Beyond its primary routing function, this basic cell provides a versatile platform for investigating fundamental quantum phenomena, such as coherence and photon-mediated interactions, opening avenues for further research in circuit quantum electrodynamics.

The authors acknowledge that dephasing currently limits the system’s performance, with flux bias, temperature, and photon number all contributing factors. Future work will likely focus on mitigating these limitations to improve coherence and enhance the scalability of quantum routing architectures. The team intends to further explore the device’s capabilities for studying fundamental quantum interactions and developing advanced quantum technologies.