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 Incoming links: Quantum circuit preparation of a three-qubit GHZ state

Past exam of the mathematics course of the University of Cambridge / 2025 / ii / Paper 4 / 10C / a / Solution Created 2026-09-24 Updated 2026-10-03

Apply a Hadamard gate to Alice's qubit, followed by a controlled-NOT gate from Alice to Bob and another from Alice to Charlie:

∣000 ⟩ ⟼ \frac{∣000 ⟩ + ∣100 ⟩}{2} ⟼ \frac{∣000 ⟩ + ∣110 ⟩}{2} ⟼ \frac{∣000 ⟩ + ∣111 ⟩}{2} .

Thus this circuit gives the required quantum circuit preparation of a three-qubit GHZ state.

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