... and when Becher was experimenting with phlogiston, no-one knew where that would lead.

Lol at comparing demonstrable advanced technology like quantum computing to phlogiston.

Anyway, experiments to prove/disprove phlogiston lead directly to our understanding of combustion and discovery of oxygen...

I think you rather miss the point, when electricity was postulated, no-one would know where it would lead, I point out that the same is true for phlogiston; one changed the world and the other went nowhere. My point is that just because something has so-far not been shown to be useful does not imply that it will eventually change the world.

Interesting that electricity has been useful in bringing about things Voltaire championed such as freedom of speech, and abolition of (slave) labor. However I think you meant Volta the inventor of the battery. Also QC seems to suffer from the opposite of lack of imagination about what it might be good for.

> Voltaire

I suspect you mean Volta[0], tho I did wonder if Voltaire[1] worked with electricity :)

[0] https://en.wikipedia.org/wiki/Alessandro_Volta

[1] https://en.wikipedia.org/wiki/Voltaire