A Modular Cryogenic Link for Microwave Quantum Communication Over Distances of Tens of Meters

TL;DR

This paper introduces a modular cryogenic microwave link connecting superconducting quantum circuits over tens of meters, enabling distributed quantum computing and communication at millikelvin temperatures.

Contribution

The work presents the first demonstration of a cryogenic, modular microwave link spanning up to 30 meters, connecting separate superconducting quantum systems.

Findings

Achieved stable operation at below 50 mK over 30 meters

Demonstrated quantum communication between spatially separated superconducting circuits

Enabled loophole-free Bell test for non-locality verification

Abstract

Quantum technologies promise a radically new way to solve classically intractable computing problems. Superconducting circuits as a platform are at the forefront of this field. The cryogenic operation temperatures of superconducting circuits however impose challenges for the further scaling to many connected quantum information processing units into a local area or global network. In this work, we present a hardware solution for connecting quantum devices operating at microwave frequencies into local area networks, which enable the exchange of quantum information between spatially separated parties. Specifically, we demonstrate a modular system spanning distances of 5, 10 and 30 meters operated at cryogenic temperatures and connecting two superconducting circuit systems, located in individual dilution refrigerators, through a quantum communication channel. We develop a thermal model to evaluate the heat transfer processes in the setup, optimize the design and select appropriate materials for its construction. The assembled 30-meter-long system achieves operating temperatures of below 50 mK after a cooldown time of about six and a half days. This link enables the execution of distributed quantum computing and communication algorithms. It also adds the resource of non-locality, certified by a loophole-free Bell test, to the field of quantum science and technology with superconducting circuits.