Summary

Transmitting qubit states from one place to another is vastly different from transmitting classical bits. For a qubit, the tiniest interaction with anything at all causes decoherence, which collapses the qubit’s state. So, the transmission of a qubit over a significant distance isn’t feasible.

But you can teleport a qubit’s state. With teleportation, a repeater stands halfway between a sender and a receiver. After creating an entangled pair, the repeater transmits one of the qubits to the sender and the other to the receiver. This cuts the qubit travel distance in half.

The state of the sender’s qubit doesn’t survive the teleportation process because the sender measures their qubit and sends the resulting bit to the receiver. And sending a classical bit over a considerable distance presents no difficulties. We’ve done so for several decades.

So far, in this book, we’ve described ways in which quantum computers manipulate...