Matter-wave interferometry provides an excellent tool for probing the environment and studying its coupling to isolated atoms. We will present several interferometry experiments done with a BEC on an atom chip  and in which different effects of the environment have been investigated. First, we will discuss fluctuations in the nearby environment probed by an interference of atoms trapped in a magnetic lattice very close (5μm) to a room temperature surface [2,3]. Here an order-of-magnitude improvement has been obtained over previous atom-surface distances for which spatial interference has been observed. Next, we will present a new interferometry of self-interfering clocks and show, in a proof-of-principle experiment, how it could probe the interplay of QM and GR . We will also describe a rule for “clock complementarity”, which we deduce theoretically and verify experimentally . Finally, we will discuss Stern-Gerlach interferometry  and describe it in the context of time irreversibility . To the best of our knowledge, this is the first time spatial Stern-Gerlach interferometry has been realized, and we analyze our data in the context of previous theoretical work relating the difficulties in realizing Stern-Gerlach interferometry to time irreversibility.
 Mark Keil, Omer Amit, Shuyu Zhou, David Groswasser, Yonathan Japha, Ron Folman, “Fifteen years of cold matter on the atom chip: Promise, realizations and prospects”, Journal of Modern Optics 63, 1840 (2016).
 Shuyu Zhou, David Groswasser, Mark Keil, Yonathan Japha, Ron Folman, “Robust spatial coherence 5μm from a room temperature atom-chip”, Phys. Rev. A 93, 063615 (2016).
 Yonathan Japha, Shuyu Zhou, Mark Keil and Ron Folman, Carsten Henkel, Amichay Vardi, “Suppression and enhancement of decoherence in an atomic Josephson junction”, New J. Phys. 18, 055008 (2016).
 Yair Margalit, Zhifan Zhou, Shimon Machluf, Daniel Rohrlich, Yonathan Japha, Ron Folman, “A self-interfering clock as a ‘which path’ witness”, Science 349, 1205 (2015).
 Atom Chip group, “Clock complementarity in the context of general relativity”, in preparation.
 Shimon Machluf, Yonathan Japha and Ron Folman, “Coherent Stern-Gerlach momentum splitting on an atom chip”, Nature Communications 4, 2424 (2013).
 Atom Chip group, “Probing the emergence of the arrow of time with a high visibility Stern-Gerlach interferometer”, in preparation.