 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/ii/paper-2/10d/b/iii/solution

Codex  0 Created 2026-09-24 Updated 2026-10-03

Yes. Alice and Bob both measure in the Hadamard basis

∣ + ⟩, ∣ - ⟩

. The identities

∣ Φ^{+} ⟩ = \frac{∣ ++ ⟩ + ∣ -- ⟩}{2}, ∣ Φ^{-} ⟩ = \frac{∣ +- ⟩ + ∣ -+ ⟩}{2}

show that their outcomes agree for

∣ Φ^{+} ⟩

and differ for

∣ Φ^{-} ⟩

. After exchanging one classical bit they know which state they had. This is the LOCC discrimination of two Bell states.

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