Few reminders about quantum teleportation

image credit: Nature

People have the notion that the process known as “quantum teleportation” allows us to send messages (information) instantly. Wrong!

I thought it would be a good idea to share few facts about quantum teleportation.

Here’s a short description of quantum teleportation from Nature:

“The technique uses a pair of photons that are entangled, which means that their properties are strongly correlated. One of the entangled photons (blue) is given to the receiver — in principle, in advance of the quantum-teleportation process. The sender then prepares a photon in an unknown quantum state (pink) and combines this photon with the second entangled photon (grey) in a device called a Bell-state analyser. This device performs a joint measurement of the quantum states of the two photons and sends the result to the receiver as a classical (non-quantum) signal. Finally, the receiver uses this information to transform their photon, recreating the quantum state of sender’s photon.”

Here’s a short summary from Wikipedia

“Although the name is inspired by the teleportation commonly used in fiction, quantum teleportation is limited to the transfer of information rather than matter itself. Quantum teleportation is not a form of transportation, but of communication: it provides a way of transporting a qubit from one location to another without having to move a physical particle along with it.”

“The term [quantum teleportation] was coined by physicist Charles Bennett. The seminal paper first expounding the idea of quantum teleportation was published by C. H. Bennett, G. Brassard, C. Crépeau, R. Jozsa, A. Peres, and W. K. Wootters in 1993. Quantum teleportation was first realized in single photons, later being demonstrated in various material systems such as atoms, ions, electrons and superconducting circuits. The latest reported record distance for quantum teleportation is 1,400 km (870 mi) by the group of Jian-Wei Pan using the Micius satellite for space-based quantum teleportation.”

Philip Ball’s article in Nature provides good commentary on quantum teleportation. Few quotes from that article:

“Whatever it’s called, the process transfers the quantum state of one particle onto another, identical particle, and at the same time erases the state in the original. “

“Quantum teleportation does not transmit any faster-than-light causal influence, because you also need the classical channel — limited to light speed at best — to complete the process.”

“It’s crucial that the teleported state is never actually copied. The fact that it is destroyed during the entanglement-enabled teleportation ensures that there is never a duplicate. The process thereby observes a fundamental principle in quantum mechanics, called no-cloning: it is impossible to make a copy of an arbitrary (unknown) quantum state.”

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