4:00 PM (CET) 10 November 2020. Prof. Dr. RON FOLMAN (Ben-Gurion University of the Negev)
Matter-wave interferometers on the atom chip
Matter-wave interferometry provides an excellent tool for fundamental studies as well as technological applications. In our group, several interferometry experiments have been done with a BEC on an atom chip  examining different effects. For example, we studied fluctuations in the nearby environment by an interference of atoms trapped in a magnetic lattice very close (5μm) to a room temperature surface [2,3]. We realized a new interferometry scheme of self-interfering clocks and showed, in a proof-of-principle experiment, how this could probe the interplay of QM and GR . We also described a rule for “clock complementarity”, which we deduce theoretically and verify experimentally . In the clock interferometer, we have observed phase jumps due to the existence of a geometric phase . Furthermore, we realized Stern-Gerlach interferometry [7-10] despite several theoretical works which have shown over the years that fundamental barriers exist.
I will give a brief description of the advantages of the atom chip, and will then describe several of the interferometric schemes, and their connection to issues such as environmentally and gravitationally (red-shift) induced decoherence, as well as loss of coherence due to interferometer imprecision (the humpty-dumpty effect). I will conclude with an outlook concerning ideas for possible tests of exotic physics such as quantum gravity, and mention several speculations which we hope to examine in the future.
 M. Keil et al., “Fifteen years of cold matter on the atom chip: Promise, realizations and prospects”, Journal of Modern Optics 63, 1840 (2016).
 S. Zhou et al., “Robust spatial coherence 5m from a room temperature atom-chip”, Phys. Rev. A 93, 063615 (2016).
 Y. Japha et al., “Suppression and enhancement of decoherence in an atomic Josephson junction”, New J. Phys. 18, 055008 (2016).
 Y. Margalit et al., “A self-interfering clock as a ‘which path’ witness”, Science 349, 1205 (2015).
 Z. Zhou et al., “Clock complementarity in the context of general relativity”, Classical and Quantum Gravity 35, 185003 (2018).
 Zhifan Zhou, Yair Margalit, Samuel Moukouri, Yigal Meir, and Ron Folman “An experimental test of the geodesic rule proposition for the non-cyclic geometric phase”, Science Advances 6, eaay8345 (2020).
 S. Machluf et al., “Coherent Stern-Gerlach momentum splitting on an atom chip”, Nature Communications 4, 2424 (2013).
 Y. Margalit et al., “Analysis of a high-stability Stern-Gerlach spatial fringe interferometer”, New J. Phys. 21, 073040 (2019).
 O. Amit, Y. Margalit, O. Dobkowski, Z. Zhou, Y. Japha, M. Zimmermann, M. A. Efremov, F. A. Narducci, E. M. Rasel, W. P. Schleich, R. Folman. “T3 Stern-Gerlach matter-wave interferometer”, Phys. Rev. Lett. 123, 083601 (2019).
 Mark Keil, Shimon Machluf, Yair Margalit, Zhifan Zhou, Omer Amit, Or Dobkowski, Yonathan Japha, Samuel Moukouri, Daniel Rohrlich, Zina Binstock, Yaniv Bar-Haim, Menachem Givon, David Groswasser, Yigal Meir, Ron Folman, “Stern-Gerlach Interferometry with the Atom Chip”, Invited review paper, to appear in a book in honor of Otto Stern, https://arxiv.org/abs/2009.08112 (2020).