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Logo: Institut für Quantenoptik/Leibniz Universität Hannover
Logo Leibniz Universität Hannover
Logo: Institut für Quantenoptik/Leibniz Universität Hannover
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Spin Dynamics as a Source of Entangled Atoms

At ultra low temperatures neutral atoms can form a Bose-Einstein Condensates (BEC) - the atomic analougue of the laser in optics. Such condensates offer a high degree of control and can be used to realize sensors with highest precision and to investigat fundamental effects. In a so-called dipole trap, which can be realized by a red detuned laser beam, atoms in all spin states can be captured. Thereby, the BEC gains an additional degree of freedom and a so-called spinor condensate can be created.

Within this project we were able to demonstrate that spin changing collisions in a spinor condensate can be employed for the creation of entanglement in close analogy to parametric down conversion in optics. We could demonstrate the first creation of continuous variable Einstein-Podolsky-Rosen entanglement and new interferometry concepts which overcome the classical precision limit of atomic sensors.

Image of a cold Rubidium cloud ín the magneto-optical trap.

Parametric Amplification of Matter Waves

Optical parametric amplification is a well-established method for the creation of entangled photons and squeezed states of light. In this project we demonstrated that spin changing collisions in a spinor condensate can act as a parametric amplifier for atoms.

In optical parametric down conversion a strong pump laser beam enters a non-linear crystal. This non-linearity leads to the conversion of a pump to photon to two photons at half the frequency. Thereby the so-called signal and idler beams build up, which exhibit entanglement and can be used to create squeezed states of light.


The parametric amplification of atoms starts with the preparation of a BEC in Zeeman level mF=0 which acts as the coherent pump. If a resonance condition is fulfilled, two atoms in this condensate can collide and thereby one atom is transferred to the level mF=-1 while the other atom is transferred to the level mF=+1 conserving the projection of the total spin. This pair creation process is intrinsically non-linear and leads to the creation of entangled states in the Zeeman level mF=-1 and mF=+1. These levels are the analogue of the signal and idler beam in optics.

Section Experiment

Within the procjet a number of new experimental techniques were implemented and investigated. More details on the experimental apparatus can befound within the section Experiment.

Experimental Investigations

Recent experimental investigations performed within the project:

Research on Spinor Gases

Research on Potassium-Rubidium Mixtures

Research on Experimental Techniques