I dare say that if they were close to a practical capability, there is no way the Chinese government would allow them to publicise that fact.

Discussion (20 points, 3 days ago) https://news.ycombinator.com/item?id=41810563

Including an interesting breakdown by @adrian_b of how the article jumps to conclusions not published in the paper.

> Chinese scientists use quantum computers to crack military-grade encryption

So they don't use plain MITM like the NSA. /s