Cryogenic bridging via propagating microwave quantum teleportation

In this study, we investigate the unconditional microwave quantum teleportation of Gaussian states and the feasibility of its realization with real microwave elements between two dilution refrigerators. Our approach involves employing the Braunstein–Kimble protocol for continuous variables, represented in the symplectic domain, with microwave components integrated into a teleportation circuit. This circuit is established between two dilution refrigerators, which are interconnected by a cryogenic link and incorporate a homodyne detector. The proposed framework offers controllability, suitable for implementation within a single refrigerator or between two separate refrigerators. It operates effectively across a temperature range spanning from milliKelvin to 4 K. This platform is useful for advancing superconducting quantum communication within and between refrigeration systems. Its potential extends to facilitating quantum local area networks and enabling distributed quantum computing protocols. Furthermore, we briefly discuss the complex realm of long-range open-air quantum microwave communication under realistic conditions. We also introduce a protocol designed to enhance entanglement distillation of two-mode squeezed states between two refrigerators. This enhancement targets the squeezing factor of the resource and improves the protocol efficiency.