Quantum teleportation is a protocol that transfers a quantum state from one location to another using a pre-shared entangled pair and two bits of classical communication. Despite its science-fiction name, teleportation does not transmit matter or information faster than light — the classical communication channel is required, limiting the overall transfer speed to classical communication speeds. What is remarkable is that the unknown quantum state is perfectly reconstructed at the destination without ever being measured (which would destroy it) or cloned (which is impossible by the no-cloning theorem).
The protocol works as follows: Alice and Bob share an entangled Bell pair. Alice performs a joint measurement on her half of the Bell pair and the qubit she wants to teleport, obtaining two classical bits of information. She sends these bits to Bob, who applies one of four possible correction operations to his half of the Bell pair based on Alice's message. The result is that Bob's qubit is now in the exact state Alice wanted to teleport, while Alice's original qubit has been destroyed by the measurement.
Quantum teleportation is not merely a theoretical curiosity — it is a fundamental primitive used throughout quantum computing and quantum networking. In fault-tolerant quantum computing, gate teleportation is used to implement non-Clifford gates (particularly the T gate) through magic state injection. In quantum networking, teleportation enables quantum state transfer between distant nodes connected by entanglement, forming the basis of quantum repeaters and the future quantum internet. Experimental demonstrations have teleported quantum states over distances exceeding 1,200 km via the Chinese Micius satellite.