- Prepare a Bell pair
- Measure both in the same basis
- 00 or 11, ideally
background
Look at the pair
An entangled pair has a joint state that cannot be written as a separate pure state for each qubit. In an ideal Bell-pair example, measuring both qubits in the computational basis produces 00 or 11 with equal probabilities. Each local result is random, but the pair agrees.
Sources: IBM Quantum Learning
background
Where the analogy stops
Two sealed envelopes with matching cards can also produce matching results. That single measurement pattern alone does not prove entanglement. Quantum correlations across different measurement choices distinguish the full experiment. Entanglement does not provide controllable faster-than-light messaging.
Sources: IBM Quantum Learning
Check your understanding
Do matching outcomes by themselves prove entanglement?
Reveal the answer
No. Classically correlated systems can match too. You need an appropriate test with more than that one measurement setting.
Sources and review scope
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