Dephasing in which path measurements have been a topic of study in mesoscopic physics for quite some time, using nanoscale Aharonov-Bohm interferometers. Here is the first experimental measurement and there are many experimental and theoretical papers that followed (many originating from the same group, but not only).
Another field, where the interference of different paths has been studied for even longer, is the studies of weak localization. These are however more difficult for a newcomer due to the complexity of the underlying concepts and some rather advanced math. Weak localization is arguably a better representation of the two-slit/which-path concepts than the closed mesoscopic interferometers - the latter, despite their seeming resemblance to the hypothetical slits, exhibit a range of complex phenomena, such as phase rigidity, phase lapses due to Coulomb interactions, etc.
Then there are also the interferometry experiments using integer and fractional quantum Hall effect...
References:
Buks, R. Schuster, M. Heiblum, D. Mahalu & V. Umansky, Dephasing in electron interference by a ‘which-path’ detector, Nature volume 391, pages 871–874 (1998). (arXiv version)