Entanglement
Two qubits, one shared state — and results that match more often than any independent pair could.
Entanglement visualization
Measure one orb and watch the other. The beam between them is the entanglement.
State amplitudes
| Basis state | Probability |
|---|---|
| |00⟩ | 50.0% |
| |01⟩ | 0.0% |
| |10⟩ | 0.0% |
| |11⟩ | 50.0% |
Correlated, not connected
For the Bell state you only ever see 00 or 11. Yet look at P(A=1) on its own: it is 50%, a perfectly fair coin. Nothing about A alone reveals that B exists.
That is why entanglement cannot send a message: the correlation is only visible once the two result lists are brought together and compared.
Entropy measures how entangled
A single qubit pulled out of an entangled pair has no state of its own. Its Bloch vector shrinks to zero length and its entropy rises to 1 bit.
Drag θ on the partial preparation and watch the number sweep from 0 to 1 and back.
Why the product state is different
With H on A only, the two qubits are independent. Measuring A tells you nothing about B, the link goes dark, and the joint outcomes spread across all four possibilities instead of two. Compare the histograms.