Guided tour · Foundations · step 1 of 11
A qubit is not both 0 and 1
The usual explanation of superposition is misleading, and the Workbench can show you why in one circuit.
First, commit to an answer
A qubit in an equal superposition is measured 1000 times. Then the same circuit runs with a second H gate added before the measurement. What changes?
Decide before you follow the link. Nothing is recorded — the value is in having been wrong on purpose once.
Now go and look
Run this circuit, then delete one of the two h gates and run it again.
What you should see
Two H gates give 0 every time; one gives a 50/50 split. If a qubit were secretly 0 or 1 with equal chance, adding a second coin flip could not make the answer certain — so it was not a hidden coin.