State
The period, recovered
What the promise was hiding: a single integer period, a real number known to enough bits to be useful, or a basis for the lattice of periods. Not a number with an error bar — an exact integer where the group is finite, and elsewhere an approximation whose precision is itself part of the answer.
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Records that are this object
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Work that arrives here
- Recover the period of a periodic function
Given a function you can evaluate in superposition and a promise that it repeats, find what it repeats by. This is the engine underneath factoring, discrete logarithms and a row of classical number-theory problems that had no efficient algorithm at all — and the whole difficulty is that the period is read out of an interference pattern rather than looked up.
Work that starts here
No recorded process takes this as its input. Nothing in this graph leaves from here.