kondensatets

Kondensatet refers to a state of matter in which a macroscopic number of bosons occupy the same quantum state, producing long-range phase coherence across the system. The phenomenon arises at very low temperatures when quantum statistical effects become dominant and the thermal de Broglie wavelengths of particles overlap. The concept was predicted by Albert Einstein in 1925 on the basis of Bose statistics and the energy spectrum of indistinguishable particles.

Bose-Einstein condensates (BECs) are the most widely studied form, realized first in 1995 with ultracold atoms such as rubidium-87 or sodium-23. In a BEC, the atoms act as a single quantum entity described by one macroscopic wavefunction. Other realizations include exciton-polariton condensates in semiconductor microcavities, where bound electron-hole pairs form a coherent state, and photon condensates in specially designed optical cavities. Fermionic condensates are formed by pairing fermions in a regime that connects BCS superconductivity to Bose condensation.

Key properties include macroscopic phase coherence, the ability to produce interference between independent condensates, and superfluid behavior with quantized vortices. Condensates are typically created by laser cooling and evaporative cooling in magnetic or optical traps, reaching nanokelvin temperatures.

The study of kondensatet provides insights into quantum many-body physics, quantum simulation, metrology, and the realization of atom lasers. Ongoing research explores interactions, dimensionality, and non-equilibrium dynamics in condensates, as well as applications in precision sensing and quantum information. Note: in Swedish, kondensatet means the condensate, and kondensatets is the possessive form meaning "the condensate's".