In contrast to what the article claims, it is also not a new idea. The original proposal was made 40 years ago, and it was immediately recognized that the required authenticated classical channel makes it useless in practice. Doesn't stop governments from spending vast amounts of money though.

Right, this is just an academic exercise and has no commercial use as far as I’ve heard

As far as I can tell, QKD is mainly useful to tell people to separate out the traffic that is really worth snooping onto a network that is hard to snoop on. It is much harder for someone to spy on your secrets when they don't pass through traditional network devices.

Of course, it also tells a dedicated adversary with L1 access exactly where to tap your cables.

At the repeaters?

How do QKD systems key and timecode repeaters?

Isn't it possible to measure a photon state without causing state collapse by measuring adjacent particles affected by the passing photon? Is it possible to have entanglement communications without such measurement capacity?

Thank you very much for saving me time!