Quantum superposition

A quantum state can be a coherent combination of distinct states associated with different possible measurement outcomes. The combination can produce interference, and measurement generally yields one outcome.

Quantum state: A mathematical description of a quantum system used to predict measurement outcomes. Superposition is a property of quantum states, expressed through combinations of their possible components.
Hilbert space: A vector space with an inner product that provides the mathematical setting for quantum states. Quantum superpositions are vector sums within a system’s state space.
Stern–Gerlach experiment: An experiment that separates particles according to spin projections in an inhomogeneous magnetic field. It demonstrates spin measurements whose outcomes depend on the state’s preparation.
Quantum mixture: A statistical ensemble of quantum states represented by a density operator. Unlike a coherent superposition, a mixture lacks phase relations that generate interference.
Probability amplitude: A complex number whose squared magnitude gives the probability of a measurement outcome. Superposed components carry amplitudes that combine before probabilities are calculated.
Basis (linear algebra): A set of linearly independent vectors that can represent every vector in a vector space. A superposition is expressed as components relative to a chosen basis of states.
Double-slit experiment: An experiment in which particles passing through two openings produce an interference pattern under suitable conditions. Its interference pattern reveals contributions from alternatives combined in a quantum state.
Quantum entanglement: A relationship in which a composite quantum state cannot be factored into states of its parts. Entangled states can be superpositions of joint outcomes that do not reduce to independent parts.
Quantum interference: The enhancement or suppression of quantum outcome probabilities through the combination of probability amplitudes. Interference distinguishes a coherent superposition from a mere uncertainty about alternatives.
Linear combination: A sum of vectors multiplied by scalar coefficients. Superposition uses this mathematical structure, with quantum amplitudes as coefficients.

Linked from 33 pages