Continuous-variable quantum microwave state transfer between two dilution refrigerators

The tremendous success in scaling superconducting quantum information processors (SQIPs) has triggered the need for networking architectures between such devices. While, conceptually, microwave-to-optics-to-microwave approaches seem attractive, they, despite considerable efforts, still suffer from low conversion efficiencies in practice. On the other hand, SQIP systems naturally come with a millikelvin cryostat and microwave connectivity. As a viable alternative for quantum local area networks, we have set up a 6.6m long cryogenic link between one homemade and one Oxford Instruments Triton500 dilution refrigerator. This link also offers the possibility of routing signals between more than two refrigerators via an intermediate cold stage ("cold network node"). Here, we demonstrate the successful transfer of a continuous-variable quantum state over this cryogenic link with negligible losses. In the future, we plan to implement quantum microwave teleportation as a proof-of-principle communication protocol for all-microwave quantum local area networks.