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Quantum Teleportation Protocol
Computation desk
Quantum teleportation moves an unknown quantum state from one place to another. It does so without sending the qubit itself. The Computation desk treats it as a small, exact circuit with a classical side channel.
- Shared entangled pair
- Bell-basis measurement of input and half-pair
- Two classical bits
- Conditional correction
- State recovered at receiver
What the protocol does
Two parties, usually called Alice and Bob, share a pair of qubits in an entangled state. Alice holds an unknown qubit she wishes to send. She holds one half of the pair. Bob holds the other.
Alice performs a joint measurement on her two qubits. The result is two classical bits. She sends them to Bob by ordinary means. Bob applies a Pauli correction chosen by those bits. His qubit then holds the original state. Alice's copy is gone, which is consistent with the no-cloning theorem. Nothing travels faster than light, because the bits must still be sent.
How the desk would arrange it
The protocol maps cleanly onto a three-qubit circuit. A Hadamard and a controlled-NOT make the shared pair. A second controlled-NOT and Hadamard rotate Alice's qubits into the measurement basis. The corrections are classically controlled gates on Bob's qubit. The desk reads this through the quantum circuit model, where each step is a named gate and the classical control is explicit.
At this size the circuit is easy to check. A state-vector simulation holds all eight amplitudes and can confirm that Bob's qubit matches the input for every measurement outcome. That is a statement about the ideal circuit. It is not a statement about hardware.
Limits and what to watch
Real devices are imperfect. Entangled pairs decohere, gates err, and measurement is noisy. Each of these lowers the fidelity of the recovered state. The desk would frame that question under noise and error, and would estimate fidelity from repeated runs, as set out in measurement and sampling. No such estimate is offered in this note.
The classical channel matters as much as the quantum one. Correction depends on bits arriving in time, which makes latency a design constraint on any system that runs the protocol across devices. That is a question for hybrid execution, where quantum steps and classical control share one schedule. The wider portfolio is at the portfolio index.
Finding from this desk
The protocol is a short sequence: share an entangled pair, entangle the input with one half, measure, send two classical bits, and apply a correction. The desk records no run of its own here, so no measured fidelity is claimed.