Preview: What Makes Quantum Different
Three ideas separate quantum computing from everything in this module so far. You'll spend the rest of the track making each precise — here's the map.
- Superposition. A qubit isn't stuck at 0 or 1; it can be in a weighted combination of both at once, described by complex amplitudes. qubits carry amplitudes simultaneously.
- Interference. Because amplitudes can be negative or complex, contributions can cancel (destructive) or reinforce (constructive) — something probabilities can never do. Every quantum algorithm is, at heart, an arrangement for the wrong answers to interfere away.
- Entanglement. Two qubits can share a joint state that can't be described by looking at each one separately, producing correlations with no classical explanation.
None of these gives "try all answers in parallel for free" — measurement collapses the state to a single outcome. The art is using interference and entanglement so that the outcome you read is likely to be the one you want. Next module, we make the qubit itself concrete.
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