Quantum Bits

 

Let’s look at the classical bit and compare it to the quantum bit .

Imagine that the state of a classical bit is an arrow which points upwards when it is in the state 0 or downwards for the state 1.

 

Evidently, a classical bit can only be in one of the discrete states, i.e. 0 or 1.

On the other hand, the quantum bit or qubit can simultaneously be in state 0 and state 1, because of quantum mechanics!

In fact, if we think of a bit in state 0 as an arrow pointing to the north pole of a sphere and a bit in state 1 as an arrow pointing to the south pole of a sphere, a quantum bit can point to any point on the sphere.

Note

This way of depicting the state of a quantum bit is called the Bloch sphere representation. The state of the qubit is represented as an arrow pointing to a given point on the Bloch sphere.

This means that the dimensionality of the state of a qubit is higher than for the state of a classical bit, which means that it can do more in terms of computation.

Because qubits are quantum, let’s learn a few of their quantum properties in the next pages.