Collapses the qubit from a probability cloud into a single definite answer — either |0⟩ or |1⟩ — chosen at random, weighted by the odds shown above. This is irreversible: all superposition is destroyed. This is the fundamental difference between quantum and classical.
What just happened
Try a gate to see it explained here
The glowing amber arrow is your qubit's state vector. North pole = |0⟩, south pole = |1⟩, equator = perfect superposition. Apply the H gate first to see superposition in action.
Operation history
|0⟩ north pole
|1⟩ south pole
state vector
projection
Bell state presets
Qubit A
Qubit B
not entangled
Apply gates
State amplitudes |αᵢⱼ|²
|00⟩
100%
φ = 0°
|01⟩
0%
φ = 0°
|10⟩
0%
φ = 0°
|11⟩
0%
φ = 0°
A = |0⟩
B = |0⟩
Two-qubit quantum states
A two-qubit system lives in a 4-dimensional Hilbert space spanned by |00⟩, |01⟩, |10⟩, |11⟩. Start by pressing Φ⁺ (a Bell state), then hit Measure — notice that no matter how many times you measure, A and B always agree. That's entanglement: measuring one qubit instantly determines the other, regardless of distance.
Operation history
Gates
H
X
Y
Z
S
T
CNOT
M
Q₀
Q₁
State amplitudes
Step: —
|00⟩
100%
|01⟩
0%
|10⟩
0%
|11⟩
0%
Build a circuit
Drag gates from the palette onto any slot in the Q₀ or Q₁ rows. CNOT placed on Q₀ controls Q₁ at the same step. Press Run to execute, or use Step → to advance one gate at a time and watch the state evolve.