An open-system model starts with a finite shot vector, so the state budget is a count ledger before any channel acts. The ledger is exact only for the stated counts and basis labels; real experiments add finite-shot noise, preparation error, detector assignment uncertainty, leakage, and calibration drift.
An open-system training model begins with a checked finite count ledger. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The state budget starts as a count vector
The open-system model starts with 100 zero shots and 0 one shots.
Nin=(100,0)
The finite ledger has a fixed total
The total is 100 plus 0, so the ledger carries 100 shots before any channel acts.