Ultracold atoms

Ultracold atoms are atoms cooled to temperatures where quantum statistics and coherent matter waves dominate their behavior, enabling controlled studies of quantum many-body physics.

Laser cooling: A family of techniques that uses light to reduce the motion of atoms. Scattered photons slow atoms before they reach the lowest temperatures.
De Broglie wavelength: The wavelength associated with a particle's momentum in quantum mechanics. Cooling lengthens atomic matter waves until neighboring atoms can overlap.
Feshbach resonance: A scattering resonance that occurs when colliding atoms couple to a molecular state. Experiments use it to tune interactions between ultracold atoms.
Doppler cooling: Laser cooling based on the Doppler shift of light scattered by moving atoms. It provided a foundational route to cooling dilute atomic gases with light.
Liquid helium-4: A quantum liquid whose low-temperature behavior includes superfluidity and Bose condensation. It exhibits related quantum phenomena, but its dense, strongly interacting atoms are less individually controllable.
Magneto-optical trap: A trap that combines laser forces and magnetic fields to cool and confine neutral atoms. It commonly captures and cools atoms at the start of an ultracold-atom experiment.
Bose–Einstein statistics: The quantum statistics governing indistinguishable bosons, which may share the same state. Bosonic atoms can accumulate in one state as their matter waves overlap.
Bose–Hubbard model: A lattice model describing interacting bosons that can move between sites. Optical lattices of ultracold atoms realize its competition between tunneling and interaction.
Sisyphus cooling: Laser cooling in which atoms repeatedly climb potential hills and lose kinetic energy. It pushed laser cooling below the Doppler limit in landmark experiments.
Superconducting qubits: Qubits made from superconducting electrical circuits and operated as engineered quantum systems. They offer controllable quantum dynamics in circuits rather than mobile neutral atoms.

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