With today's computers an electric bit (binary digit) can be either one (off) or zero (on). This means that with three bits today's computers can store only one of the eight possible combinations of 1 and 0: 1-1-1, 0-1-1, 1-0-1, 1-1-0, 0-0-0, 1-0-0, 0-1-0 and 0-0-1.
However, a quantum computer could store all eight combinations in three bits. Theoretically, a 3-qubit quantum computer could calculate eight times faster than a 3-bit PC. Following the maths, a 64-qubit quantum computer could therefore make calculations 2 to the power 64 times faster than a 64-bit PC - meaning 18 billion, billion times quicker.
Careful readers will see the writer made a mistake in his text. One isn't off but on, and zero means off in the binary world.