Past exam of the mathematics course of the University of Cambridge 2012 iii Paper 66 2 a Solution Created 2026-10-03 Updated 2026-10-07
Quantum teleportation transfers the quantum state of an unknown qubit from a sender's carrier to a receiver's carrier. It also transfers correlations with any external reference. It does not determine classical amplitudes or send the original particle.
The standard deterministic protocol consumes one shared maximally entangled Bell pair and two classical bits from Alice to Bob. Alice performs a local Bell-basis measurement on the input and her half of the pair; Bob applies the corresponding local Pauli gate. The classical message is essential: before receiving it, Bob has the outcome-averaged density operator and cannot recover or detect the unknown state. The original input is consumed by the measurement, so quantum teleportation is compatible with the no-cloning theorem.
Quantum cloning Created 2026-09-24 Updated 2026-09-24
A cloning operation for a family of pure states would mapfor every state in that family. A single physical operation cannot clone every unknown quantum state.