Measurement Strategies
Standard measurement asks each qubit "are you 0 or 1?" — the computational (Z) basis question. Placing an H immediately before measurement asks the X-basis question instead, and which question you choose decides which property of the state your counts can reveal.
What question does a measurement ask?
A measurement reads a qubit and returns one classical bit. But a measurement is not neutral — it asks a specific question, and different questions reveal different properties of the same state.
The standard question is "are you 0 or 1?", asked in the computational basis (also called the Z basis). A basis is simply the pair of reference states a measurement distinguishes between. Hardware and the Lab both measure only in this basis.
That sounds restrictive, but it isn't: to ask a different question, you rotate the state so that the question you want lines up with the readout you have. A gate placed immediately before measurement changes what is being asked.
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