A growing number of quantum engineers worldwide have been trying to realize large-scale quantum networks, which consist of several connected quantum computers or devices that share information with each other. The successful realization of these networks could potentially pave the way for the realization of new high-speed and secure communication systems, or even of a quantum version of the internet.

A key challenge when trying to realize large-scale quantum networks is ensuring that the quantum properties of microwave signals can be reliably transferred from one location to another. These signals are highly sensitive to random energy fluctuations associated with heat. Thus, systems introduced so far typically operate inside cooling machines known as dilution refrigerators.

Researchers at Walther-Meißner-Institute (WMI) and Technical University of Munich have introduced a new approach to successfully transfer quantum microwave states between two separate dilution refrigerators connected by a warmer superconducting cable, with temperatures of up to 4K.