kvanttitila
Kvanttitila is the quantum state of a system, a description that contains all information needed to determine the probabilities of outcomes for any measurement performed on the system. In quantum mechanics, kvanttitila can be represented in two main formalisms: as a pure state, given by a normalized vector |ψ⟩ in a Hilbert space (the wavefunction is a common representation in position space), or as a density operator ρ that describes statistical ensembles and mixed states.
In the density-operator formalism, ρ encodes both quantum superpositions and classical mixtures. The density operator satisfies Tr(ρ)
Time evolution of the kvanttitila is unitary for closed systems, described by iħ d|ψ⟩/dt = H|ψ⟩ or,
For composite systems, kvanttitila may be entangled; the state of subsystems is obtained by partial tracing