Quantum Computing Explained

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APPLICATIONS OFENTANGLEMENT:TELEPORTATION ANDSUPERDENSE CODING

It is often said that entanglement is a resource in quantum computation and information. This is because we can use entanglement to accomplish communications and information processing tasks that would otherwise not be possible. In this chapter we will explore two areas where entanglement can be used to do some rather unusual tasks. The first of these, known as teleportation, is a procedure that allows one party (Alice) to send a quantum state to her friend (Bob) without that state being transmitted in the usual sense. By using entanglement, Alice and Bob can set up a quantum communications channel that links them together in a quantum way via the EPR paradox—allowing Alice to send her state to Bob in an almost magical fashion. As we will see, however, faster than light communication isn’t possible using teleportation because it is still necessary for Alice and Bob to maintain a classical communications link in order for teleportation to work.

In our second application of entanglement, we will look at superdense coding. This is a procedure that allows us to send two classical bits to a party using only a single qubit—demonstrating the power of quantum information processing.

TELEPORTATION

Anyone who has read science fiction or watched it on television is familiar with teleportation—a device or process by which people can jet around the galaxy. The basic idea is that you get scanned somehow, turned into energy, then ...