Level 3
Phase
Phase is hidden direction inside an amplitude that changes how paths combine later.
Visualize
Phase may not show up immediately in counts, but it can change later interference.
Understand
S and T gates adjust phase without acting like ordinary flips.
Why it matters
Phase is central to QFT, Shor-style period finding, and interference tricks.
Misconception
If counts do not change immediately, the circuit state may still have changed.
Apply
Place phase gates between two H gates and observe the final probability shift.
Example DSL
# Phase kick with S and T qubits 1 H 0 S 0 T 0 H 0 MEASURE 0
Quick check
Why can phase be hard to notice?