Quantum Computing Series, Part 6: Quantum Teleportation

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Quantum teleportation
Source: New Atlas

Quantum teleportation is used to transmit information from one location to another. This quantum information, for example, can be the exact state of a particle such as an atom or a photon. The information transmits using the classical communication and previously shared quantum entanglement between the sending and receiving location. Because the transmission depends on classical communication, it cannot be used for faster-than-light transport or communication of classical bits. It has been proven possible to teleport one or more qubits of information between two (entangled) atoms; it has, however, not yet been achieved between molecules or anything larger.

It’s important to note that quantum information can be neither copied nor destroyed.

Teleportation can be applied not just to pure states but also to mixed states. The mixed states can be regarded as the state of a single subsystem of an entangled pair. Entanglement swapping is a simple example of quantum teleportation.

In a commonly used illustration, if Alice has a particle entangled with a particle owned by Bob, and Bob teleports it to Carol, then afterwards, Alice’s particle is entangled with Carol’s.

In other words, the state of Bob’s first particle can be teleported to Carol’s. Alice and Carol without even having any interaction with each other now have their particles entangled.

In quantum or classical information theory, it is best to work with the simplest possible unit of information, the two-state system. In classical information, this is a bit, represented using one or zero (or true or false). The quantum analog of a bit is a quantum bit, or qubit, a unit of quantum information. Qubits encode a type of information, called quantum information, which differs sharply from “classical” information. This difference is apparent, for example, in quantum information properties such as it being impossible to copy (the no-cloning theorem) and impossible to destroy (the no-deleting theorem).

Teleportation of Qubits

Quantum teleportation provides a mechanism to move a qubit from one location to another. And this is done without having to physically transport the underlying particle that a qubit is normally attached to. With the invention of the telegraph in 1830s, the information in the form of classical bits could be sent across great distances, even among the continents, at a high speed. Similarly, quantum teleportation holds the promise of one day moving the qubits likewise through open space.

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