In quantum mechanics, superposition refers to the principle that a quantum system—like an electron or a photon—can exist in multiple states at the same time until it is measured or observed.
Unlike classical objects, which can only be in one definite state (like a coin being either heads or tails), a quantum particle can be in a combination of all possible states. For example, an electron in an atom can be in a blend of energy levels or a photon can take multiple paths simultaneously in an interference experiment.
This concept was famously illustrated by Schrödinger’s cat thought experiment, where a cat in a sealed box is considered both alive and dead at the same time, depending on the superposition of quantum events inside the box—until someone opens it and observes the result.
Superposition is at the heart of many quantum technologies. In quantum computing, for instance, quantum bits (qubits) can represent 0, 1, or both at once, allowing for vastly increased computational power compared to classical bits.