Controling EPR and Bell correlations in atomic Bose-Einstein condensates – CEBBEC

The CEBBEC project is undertaking several parallel investigations of entangled atoms and their possible use in quantum metrology. On the experimental front, both the LCF group in Palaiseau France and the LUH group in Hannover, Germany have succeeded in producing entangle atoms with spatial separations. They each used experimental protocols developed in their respective groups. The LCF group produced pairs of atoms which will be appropriate for a Bell inequality test, while the LUH group produced clouds of many atoms which will allow tests of entanglement with larger samples. This work was carried out with the collaboration of the BILBAO group. The TUW group has published a method of producing entangled samples using double well potentials on an atom chip an experimental work is proceeding to realise this idea. The LCF group also published an intermediate result concerning the observed statistics of their atom pair source. They show that the statistics are thermal and account very well for the observed contrast in their atomic Hong-Ou-Mandel experiment. The original experiment from 2015 was repeated recently to confirm the predicted contrast.

The consortium has been concentrating on experimental and theoretical methods to realize and exploit multipartite entanglement in atomic systems to improve atom interferometry protocols. Since the beginning of the project the experimental groups have successfully demonstrated two protocols for realizing entangled, and spatially separated atomic ensembles. Bell inequality and Einstein Rosen Podolsky tests are being planned and should be implemented by the end of the project. The theoretical groups have been working on advanced methods to take advantage of these quantum correlations, and the development of sophisticated techniques to characterize and quantify the entanglement. The consortium is collectively working towards using these ideas to improve the performance of atom interferometers.

On the experimental front, we have succeeded in producing entangled atoms with spatial separations. The LCF group produced pairs of atoms which will be appropriate for a Bell inequality test, while the LUH group produced clouds of many atoms which will allow tests of entanglement with larger samples. The TUW in Vienna group has published a method of producing entangled samples using double well potentials on an atom chip an experimental work is proceeding to realise this idea. The LCF group also published an intermediate result concerning the observed statistics of their atom pair source. They show that the statistics are thermal and account very well for the observed contrast in their atomic Hong-Ou-Mandel experiment.

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We bring together researchers on quantum information theory, Bose-Einstein condensates and atom interferometry to create and detect entanglement of large, spatially separated samples. Our purpose is both to gain a deeper understanding of of quantum information in many body systems as well as to develop practical approaches for manipulating and exploiting it. The ultimate goal is to enhance the performance of a separated path atom interferometer using entangled samples.
Atomic interactions in BEC's consititute a non-linearity highly analogous to four wave mixing or parametric down conversion in optics, and which can be exploited to create entanglement. Two separate lines of research have been pursued in the past; on the one hand one can use the spin degrees of freedom of an atom to produce atom pairs whose spins are entangled, and on the other one can entangle the motional degrees of freedom in a spirit close to that of the original EPR proposal. In the CEBBEC project, these two lines of research will be brought together in both the technological sense (using one kind of entanglement to make another) and conceptual one (studying complex situations in which both spin and motion are entangled) giving rise to new possibilites for applications and new theoretical challenges. The participating partners have developed sophisticated detection technologies which allow us to make new types of mesaurements. We intend to respond to the great need for theoretical work to understand and exploit them. Finally, we will address practical applications and explore their metrological validity.

The EU's Future and Emerging Technologies agenda aims to foster transformative research in quantum information science by coordinating efforts of different research communities. Our project aims to bring together two separate lines of research in which European groups have been leading players and to exploit the common ground that they share. We plan to combine the manipulation of atomic spins and of motional degrees of freedom. The present project will develop a unified approach in both the technological sense (using one kind of entanglement to make another) and conceptual one (studying complex situations in which both spin and motion are entangled) giving rise to new possibilities for applications and new theoretical challenges. We plan to optimize the extraction of relevant information from (entangled) physical systems as discussed in the Target Outcomes of the Call Announcement. In this context, we may go even farther and achieve new or radically enhanced functionalities with our research.