A quantum bit, otherwise known as a qubit, is one of the units used when dealing with quantum information. Another way to look at a qubit is that it is a state vector which is an object of math that can describe different quantum systems. In the case of the qubit, that quantum system is a two-level quantum-mechanical system. One of the biggest discussions when dealing with the qubit is its comparison to the traditional or classical bit when dealing with computer information.

Bit vs. Qubit

A bit is one of the most basic units for describing the process of a computer. It is understood to be either a "0" or a "1" which has led to the basic understanding of binary. A process can either be a 0 or a 1. This is easily compared to the process of turning on or off a light. When the light is off, it is a "0." When the light is on, it is a "1." This is the same thing that goes on in a computer. Most important, though, is the understanding that, no matter what, the process will always be either that 0 or 1.

A qubit, though, is vastly different. Whereas a bit must be either a 1 or a 0, a qubit doesn't have to be those. It can be 1 or 0, but also, it can be a superposition of them both. This provides more opportunity for efficiency when dealing with the qubit which is why there has been such a push for research in quantum computing.Qubit

Use of Qubit

A qubit doesn't have any more storage capability than a bit. Therefore, a quantum computer can hold only as much as the hard drive allows. What a qubit can do, though, is increase efficiency. Because the qubit can be either 1, 0 or a superposition of either, it allows for an increase in speed for processes to be accomplished.

Qubit Representation

Bra-ket notation – a technique of quantum state represtation – is used to describe the different vetors or basis states for qubits. Therefore, when dealing with the computation vectors, they are written as |0> and |1>. These are pronounced either "ket 0" or "ket 1" hence the name bra-ket notation.