## From Bits to Qubits

A digital computer both stores and processes information using bits, which can be either 0 or 1. Physically, a bit can be anything that has two distinct configurations: one represented by “0”, and the other represented by “1”. It could be a light bulb that is on or off, a coin that is heads or tails, or any other system with two distinct and distinguishable possibilities. In modern computing and communications, bits are represented by the absence or presence of an electrical signal, encoding “0” and “1” respectively.

A **quantum bit*** *is any bit made out of a quantum system, like an electron or photon. Just like classical bits, a quantum bit must have two distinct states: one representing “0” and one representing “1”. Unlike a classical bit, a quantum bit can also exist in superposition states, be subjected to incompatible measurements, and even be entangled with other quantum bits. Having the ability to harness the powers of superposition, interference and entanglement makes qubits fundamentally different and much more powerful than classical bits.

To build quantum computers and other quantum information technologies we need quantum objects that will act as qubits. Scientists have learned to harness and control many physical systems to act as qubits. This allows us to match the demands of different quantum technologies to the advantages of each type of qubit.

## Meet the Qubits

There are many kinds of qubits, some occurring naturally and others that are engineered. Some of the most common types include: