> produce at least a small nuclear explosion

The Manhattan Project scientists actually did this before anybody broke ground at Los Alamos. It was called the Chicago Pile. And if the control rods were removed and the SCRAM disabled, it absolutely would have created a "small nuclear explosion" in the middle of a major university campus.

Given the level of hype and how long it's been going on, I think it's totally reasonable for the wider world to ask the quantum crypto-breaking people to build a Chicago Pile first.

https://en.wikipedia.org/wiki/Chicago_Pile-1

TIL about the Chicago Pile! (I don't know enough about the physics to tell if it could have indeed exploded.)

> On 2 December 1942

https://en.wikipedia.org/wiki/Chicago_Pile-1

> on July 16, 1945

https://en.wikipedia.org/wiki/Trinity_(nuclear_test)

Two years and a half. This is still a good metaphor for "once you can make a small one, the large one is not far at all."

What? No. No matter what anybody did with the Chicago Pile, it would never have produced a small version of a nuclear detonation.