Three myths about quantum computing — Part 3: Teleportation and superdense coding

13 Jul

Mamuta memuāri

This is the last post in the series on myths about quantum computing.

One of the most exciting things about quantum information is quantum teleportation—the ability to transmit quantum data by sending only classical bits. Superdense coding is another surprising protocol which lets you transmit two classical bits by sending only one qubit.

It is often mistakenly believed that these two features of quantum information do not have a classical equivalent. The goal of this post is to explain why this is not the case, and to clarify other related misconceptions.

Bell states

Let us first briefly discuss some simple facts that are useful for explaining how quantum teleportation works. Let $latex z, x \in \{0,1\}$. Then the following four two-qubit states are orthonormal and form a basis:

= \dfrac{|0,x\rangle + (-1)^z |1,\bar{x}\rangle}{\sqrt{2}}

This is known as Bell basis. One can prepare $latex |\beta_{zx}\rangle$…

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