Microwave teleportation through a warm link

Researchers at the Walther-Meißner-Institut (Bavarian Academy of Sciences) and TU Munich teleported microwave coherent states between two separate dilution refrigerators linked by a channel held at up to 4 K, far warmer than the millikelvin temperatures superconducting circuits need. Fidelity reached 72.3% at 1 K and 59.9% at 4 K, beating the no-cloning and classical thresholds respectively, as reported in Physical Review Letters.

Why it matters for teleportation

• Superconducting quantum computers work with microwaves, so this is a direct way to link them.
• Suggests network cables between fridges need not be cooled all the way down, which could make links cheaper.
• Limitation: fidelity drops sharply as the link warms, mainly because the hot connection heats the cold nodes; coherent states were teleported, not qubits.