Level 3

Interference

Interference happens when amplitudes meet and either reinforce or cancel.

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Visualize

01

H then H cancels the path to 1 and reinforces the path to 0.

Understand

A single H spreads the state; a second H can bring it back.

Why it matters

Quantum algorithms are mostly careful interference engineering.

Misconception

Interference is not noise; it is the signal-shaping mechanism.

Apply

Remove the second H and compare the result distribution.

Example DSL

# Interference: H then H returns to |0>
qubits 1
H 0
H 0
MEASURE 0
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Quick check

What should H followed by H usually measure from |0>?