In quantum computers, however, bits are expressed not only as 0 and 1 but also as superposition of 0 and 1. We can obtain probability variables between 0 and 1 from superposition of 0 and 1. A bit in classical computers corresponds to a qubit in quantum computers. This qubit in quantum computers has two basic states, states 0 and 1, which are equivalent to those in classical computers. Movements of electrons are most widely accepted in the study of quantum computers to physically express qubits.
Electrons have internal motions corresponding to spins in classical dynamics.
These have two eigen values, called an upward and downward spins. To express qubits, it is very convenient if the upward spin is deemed as state 0 and the downward one as state 1. A qubit has a state where it is not certain that the qubit is 0 or 1 until observed at an instance. This state is called a state of superposition. Electrons have such state where it is not certain until observed that their spins are upward or downward.