What are Quantum Computers?

A quantum computer is a computer that makes direct use of distinctively quantum mechanical phenomena to perform operations on data.

In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, the data is measured by qubits.

The Bloch sphere is a representation of a qubit, the fundamental building block of quantum computers.
Source: Wikipedia

The basic principle of quantum computation is that the quantum properties of particles can be used to represent and structure data, and that quantum mechanisms can be devised and built to perform operations with these data.

Why Quantum Computers?

Researchers have discovered that several classes of computational problems can be solved in ways that take advantage of quantum parallelism. WhipTech.com