What is quantum superposition ?

Quantum superposition is a fundamental principle of quantum mechanics that allows a quantum system, such as a qubit in quantum computing, to be in multiple states simultaneously. This principle is starkly different from the classical binary state in which a system can only be in one state at a time—either 0 or 1. In the context of a qubit, superposition means it can be in a state of 0, 1, or any quantum combination of these states. This is not just a theoretical curiosity; it's the working principle behind the massive parallel processing power of quantum computers.

When a qubit is in superposition, performing a computation on it is essentially performing the computation on both states (0 and 1) simultaneously. This capability allows quantum computers to process complex problems at speeds unattainable by classical computers. However, when a measurement is made, the qubit "chooses" one of its possible states, and the superposition collapses to either 0 or 1, which is observed as the outcome.

The ability to utilize superposition, along with quantum entanglement, enables quantum computers to perform certain calculations much more efficiently than classical computers. It is the reason why quantum computers hold such potential for revolutionizing fields that require the processing of large amounts of data and complex calculations, like cryptography, drug discovery, and materials science.