What is quantum teleportation, and how does it work?

Quantum teleportation is a method to transfer the quantum state of a particle (like a qubit) from one location to another, without physically moving the particle itself. It relies on quantum entanglement and classical communication. The process does not transmit matter or energy but enables the exact recreation of a qubit’s state at a remote location. Importantly, the original qubit’s state is destroyed during the process, adhering to the quantum no-cloning theorem, which prevents perfect duplication of an unknown quantum state.

The process involves three main steps. First, two entangled qubits (particles with correlated states) are created and shared between the sender (Alice) and receiver (Bob). For example, if Alice and Bob each hold one qubit from an entangled pair, their measurements will always correlate, even at a distance. Next, Alice performs a joint measurement on the qubit she wants to teleport and her half of the entangled pair. This measurement collapses both qubits into one of four possible states, which Alice communicates to Bob via a classical channel (e.g., email or radio). Finally, Bob uses this classical information to apply specific quantum operations (like Pauli-X or Z gates) to his entangled qubit, reconstructing the original qubit’s state. The teleportation is complete once Bob’s qubit matches the original state.

Quantum teleportation has practical applications in quantum computing and secure communication. For instance, in quantum networks, it could enable linking quantum processors over long distances, forming a distributed quantum computer. However, it requires pre-shared entanglement and classical communication, which limits its speed to the speed of light. Current implementations, such as those tested by IBM and others, are limited by error rates and decoherence, but advancements in error correction and stable qubits may address these challenges. Developers working on quantum protocols can leverage teleportation for tasks like quantum error correction or building modular quantum systems where qubits are shared across devices.