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A: Fachverband Atomphysik

A 26: Atomic Clusters III

A 26.4: Hauptvortrag

Donnerstag, 5. März 2009, 15:30–16:00, VMP 6 HS-B

Resonant amplification of quantum fluctuations with a spinor gas — Carsten Klempt¹, Oliver Topic¹, Manuel Scherer¹, Thorsten Henniger¹, Garu Gebreyesus¹, Philipp Hyllus², Wolfgang Ertmer¹, Luis Santos², and •Jan Arlt¹ — ¹Institut für Quantenoptik — ²Institut für Theoretische Physik, Leibniz Universität Hannover, D-30167 Hannover

Bose-Einstein condensates of atoms with non-zero spin constitute not only an optimal scenario to investigate fundamental properties of magnetic superfluids, but also an ideal system to study amplification of quantum and classical fluctuations. This is strikingly manifested in a sample initially prepared in the m=0 state, where spin-changing collisions triggered by quantum fluctuations may lead to the creation of correlated pairs in m=± 1. We show that the pair creation efficiency is strongly influenced by the interplay between the external trapping potential and the Zeeman effect and reflects the confinement-induced magnetic-field dependence of elementary spin excitations of the trapped condensate. Remarkably, pair creation in our experiments is characterized by a multi-resonant dependence on the magnetic field. Pair creation at these resonances acts as strong parametric matter-wave amplifier. Depending on the resonance condition, this amplification can be extremely sensitive or insensitive to the presence of seed atoms. We show that pair creation at a resonance which is insensitive to the presence of seed atoms is triggered by quantum fluctuations and thus the system acts as a matter-wave amplifier for the vacuum state.