Measurement turns an amplitude budget into an outcome and then updates the state used for later repeated measurements. The update is exact only for the stated basis, probabilities, and ideal result; real readout adds finite-shot scatter, detector assignment error, state-preparation error, decoherence, and leakage.
A measurement result updates the state used for repeat measurements. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Measurement uses the probability distribution
For many identically prepared systems, the exact expected counts out of 25 are 9 zero outcomes and 16 one outcomes. This is an expectation, not a random draw simulation.
Nzero=9,None=16
After a result, the state updates
After the zero result, a repeat measurement of the updated state gives zero with probability 1.
P(zero after zero)=1
Expected counts scale with trials
The probability distribution is fixed by the state. More identically prepared trials scale both expected counts in the same ratio.