kvantesystem

A kvantesystem (quantum system) is a physical system whose behavior is described by quantum mechanics. The state of a kvantesystem is represented by a vector |ψ⟩ in a Hilbert space or, more generally, by a density operator ρ. Observables correspond to Hermitian operators, and measurement outcomes follow the Born rule. For a closed kvantesystem, time evolution is unitary and governed by the Schrödinger equation iħ d|ψ⟩/dt = H|ψ⟩, with the evolution operator U(t) = exp(-iHt/ħ). For mixed states, ρ(t) = U(t) ρ(0) U†(t).

In open kvantesystem, the system interacts with its environment, leading to non-unitary dynamics described by master equations, such as dρ/dt = -i/ħ [H, ρ] + L(ρ) (Lindblad form). Key phenomena include superposition, interference, and entanglement. Composite kvantesystems are described by tensor products of subsystems, and entanglement yields correlations that do not have classical analogs. Decoherence, the loss of quantum coherence due to environmental interactions, is central to the quantum-to-classical transition.

Examples of kvantesystems include atoms, electrons, photons, and superconducting qubits. Experimental platforms to realize kvantesystems span trapped ions, superconducting circuits, quantum dots, ultracold atoms in optical lattices, and photonic systems.

Kvantesystems form the foundation of quantum information science and underpin efforts in quantum computation, quantum communication, quantum sensing, and quantum simulation. Core concepts include the Hilbert space formalism, the Born rule, superposition, entanglement, and various representations such as the Schrödinger and Heisenberg pictures, as well as density-matrix formalisms for mixed states.