Quantum teleportation is a technique for transferring quantum information from a sender at one location to a receiver some distance away. Quantum teleportation only transfers quantum information. Moreover, the sender may not know the location of the recipient, and does not know which particular quantum state will be transferred.
One of the first scientific articles to investigate quantum teleportation is “Teleporting an Unknown Quantum State via Dual Classical and Einstein-Podolsky-Rosen Channels” published by C. H. Bennett, G. Brassard, C. Crépeau, R. Jozsa, A. Peres, and W. K.
Wootters in 1993, in which they used dual communication methods to send/receive quantum information. It was experimentally realized in 1997 by two research groups, led by Sandu Popescu and Anton Zeilinger, respectively.
Experimental determinations of quantum teleportation have been made in information content – including photons, atoms, electrons, and superconducting circuits – as well as distance with 1,400 km (870 mi) being the longest distance of successful teleportation by the group of Jian-Wei Pan using the Micius satellite for space-based quantum teleportation.
There has been a recent record set (as of September 2015) using superconducting nanowire detectors that reached the distance of 102 km (63 mi) over optical fiber. For material systems, the record distance is 21 metres (69 ft).
Challenges faced in quantum teleportation include the no-cloning theorem which sets the limitation that creating an exact copy of a quantum state is impossible, the no-deleting theorem that states that quantum information cannot be destroyed, the size of the information teleported, the amount of quantum information the sender or receiver has before teleportation, and noise that the teleportation system has within its circuitry.
In matters relating to quantum information theory, it is convenient to work with the two-state system of the qubit. The qubit functions as the quantum analog of the classic computational part, the bit, as it can have a measurement value of both a 0 and a 1, whereas the classical bit can only be measured as a 0 or a 1. The quantum two-state system seeks to transfer quantum information from one location to another location without losing the information and preserving the quality of this information.
This process involves moving the information between carriers and not movement of the actual carriers, similar to the traditional process of communications, as two parties remain stationary while the information (digital media, voice, text, etc.) is being transferred. The main components needed for teleportation include a sender, the information (a qubit), a traditional channel, a quantum channel, and a receiver.
An interesting fact is that the sender does not need to know the exact contents of the information that is being sent. The measurement postulate of quantum mechanics—when a measurement is made upon a quantum state, any subsequent measurements will “collapse” or that the observed state will be lost—creates an imposition within teleportation: if a sender makes a measurement on their information, the state could collapse when the receiver obtains the information since the state has changed from when the sender made the initial measurement.
For actual teleportation, it is required that an entangled quantum state or Bell state be created for the qubit to be transferred.