Resonant amplification of quantum fluctuations in a spinor gas |
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Authors: | O Topic M Scherer G Gebreyesus T Henninger P Hyllus C Klempt W Ertmer L Santos and J J Arlt |
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Institution: | 1.Institut für Quantenoptik,Leibniz Universit?t Hannover,Hannover,Germany;2.Institut für Theoretische Physik,Leibniz Universit?t Hannover,Hannover,Germany;3.BEC-INFM, Dipartimento di Fisica,Università di Trento,Povo,Italy;4.QUANTOP, Danish National Research Foundation Centre for Quantum Optics, Department of Physics and Astronomy,University of Arhus,Arhus C.,Denmark |
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Abstract: | Bose-Einstein condensates of atoms with non-zero spin are known to constitute an ideal system to investigate fundamental properties
of magnetic superfluids. More recently it was realized that they also provide the fascinating opportunity to investigate the
macroscopic amplification of quantum and classical fluctuations. This is strikingly manifested in a sample initially prepared
in the m
F
= 0 state, where spin-changing collisions triggered by quantum fluctuations may lead to the creation of correlated pairs
in m
F
= ±1. We show that the pair creation efficiency is strongly influenced by the interplay between the external trapping potential
and the Zeeman effect. It thus reflects the confinement-induced magnetic field dependence of elementary spin excitations of
the condensate. Remarkably, pair production in our experiments is therefore 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 purely by quantum fluctuations and thus the
system acts as a matter-wave amplifier for the vacuum state. |
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Keywords: | |
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