Late introduction of `ControlledOnInt` operation

[remilvus]

Late introduction of `ControlledOnInt` operation

[tcNickolas]

Exercise 5 of the MultiQubitGates tutorial covers ControlledOnBitString function in quite a lot of detail, so we probably don't need an infinite number of tasks :-) BasicGates can be a good place for a task "Two-qubit gate - 4" (between the current tasks 2.3 and 2.4) introducing a zero-controlled NOT gate, as a simpler version of that exercise, and you can introduce both ControlledOn* functions in the hint/workbook for it. Maybe also point to that exercise for a more detailed version of the discussion.

[tcNickolas]

That's a good point, indeed Superposition task 1.12 uses it in the solution (as well as ControlledOnBitString) but doesn't offer a hint for it.

Do you want to open a pull request adding a hint to Superposition task 1.12 mentioning ControlledOnInt and ControlledOnBitString as useful library functions to use? A separate task wouldn't really work in the context of Superposition kata, since all the tasks there say "prepare this state" rather than "implement this unitary transformation".

[remilvus]

Yes, I would like to do that.

When mentioning adding this as a separate task, I was thinking it could be in one of the katas that come before Superposition. For example, Basic Gates Kata looks like a good candidate, as controlled gates are introduced there.
In my opinion, it's good to have both a hint and a task, especially if ControlledOnBitString operation is included. What do you think? Dividing new concepts into separate tasks seems like a good strategy, but at the same time it generates an infinite number of tasks in the limit.

[remilvus]

I'm starting to work on adding the task!