State
Routine with a good branch
A circuit that produces what you want on one branch and something useless on the others, with a flag telling the two apart. Almost every quantum subroutine hands back one of these, and what it costs to make the good branch likely is usually where the algorithm's cost sits.
A state is an object you can be holding, named once so that two routes reaching the same thing are drawn as reaching the same thing. It says nothing about how you got here or where you can go next — that is entirely in the processes below.
This is a kind of
This state is not recorded as a kind of anything else. It stands on its own in the vocabulary.
Narrower kinds of this
No state in the vocabulary is recorded as a narrower kind of this one.
Records that are this object
Nothing in the catalogue has been joined to this state. That is a gap in the join rather than a claim that no such object exists; the shelf on /repository lists what is joined and what is not, with the reason.
Work that arrives here
No recorded process returns this. Either it is where a reader starts — a problem, a matrix, a machine — or it is an object this graph names and no route yet reaches.
Work that starts here
- Amplify a success branch
Take a routine whose output lands in the wanted subspace only with probability , and raise that probability to near 1 using quadratically fewer repetitions than restarting the routine would need.