Quantum Computing

From Wikipedia:

A classical computer has a memory made up of bits, where each bit is represented by either a one or a zero. A quantum computer, on the other hand, maintains a sequence of qubits, which can represent a one, a zero, or any quantum superposition of those two qubit states;^[8]:13–16 a pair of qubits can be in any quantum superposition of 4 states,^[8]:16 and three qubits in any superposition of 8 states. In general, a quantum computer with qubits can be in any superposition of up to different states.^[8]:17 (This compares to a normal computer that can only be in one of these states at any one time).

A quantum computer operates on its qubits using quantum gates and measurement (which also alters the observed state). An algorithm is composed of a fixed sequence of quantum logic gates and a problem is encoded by setting the initial values of the qubits, similar to how a classical computer works. The calculation usually ends with a measurement, collapsing the system of qubits into one of the {\displaystyle 2^{n}} eigenstates, where each qubit is zero or one, decomposing into a classical state. The outcome can, therefore, be at most {\displaystyle n} classical bits of information. If the algorithm did not end with a measurement, the result is an unobserved quantum state. (Such unobserved states may be sent to other computers as part of distributed quantum algorithms.)