← quantum arcade

|LIGHTS QOUT⟩

lights out, where every light is a qubit

LEVEL1

MOVES0

PAR0

H LEFT0

Bring every qubit to |0⟩, with all arrows pointing up.

The gates

X
X press acts on the cell and its 4 neighbours. It swaps |0⟩ ↔ |1⟩ and leaves |+⟩ and |−⟩ alone, since X|±⟩ = ±|±⟩ is the same state up to a global phase.
Z
Z press acts on the same cross. It swaps |+⟩ ↔ |−⟩ and leaves |0⟩ and |1⟩ alone.
H
Hadamard acts on a single cell. It swaps |0⟩ ↔ |+⟩ and |1⟩ ↔ |−⟩, which moves the qubit between the X and Z puzzles. You only get as many as the level needs.

Reading the dials

|0⟩ points up. This is the goal.
|1⟩ points down: the light is on.
|+⟩ points right, on the equator.
|−⟩ points left, on the equator.

Each dial is a Bloch sphere seen from the side. Gates rotate the arrow the same way the real gate rotates the qubit.

Hints

X presses can't touch a |±⟩ cell, and Z presses can't touch |0⟩/|1⟩. That gives you two separate puzzles.
Each |±⟩ cell needs exactly one H to come home. Choose whether to fix its phase before the H or its bit after it.
🔒 locked cells can't be pressed, but presses on their neighbours still reach them.

Controls

click apply the selected gate · X Z H pick a gate
U undo · R reset · N/P next/previous level · M mute