Luschen, Henrik PBordia, PranjalHodgman, SeanSchreiber, MichaelSarkar, SaubhikDaley, Andrew JFischer, Mark HAltman, EhudBloch, ImmanuelSchneider, Ulrich2021-09-152021-09-152160-3308http://hdl.handle.net/1885/247912In the presence of disorder, an interacting closed quantum system can undergo many-body localization (MBL) and fail to thermalize. However, over long times, even weak couplings to any thermal environment will necessarily thermalize the system and erase all signatures of MBL. This presents a challenge for experimental investigations of MBL since no realistic system can ever be fully closed. In this work, we experimentally explore the thermalization dynamics of a localized system in the presence of controlled dissipation. Specifically, we find that photon scattering results in a stretched exponential decay of an initial density pattern with a rate that depends linearly on the scattering rate. We find that the resulting susceptibility increases significantly close to the phase transition point. In this regime, which is inaccessible to current numerical studies, we also find a strong dependence on interactions. Our work provides a basis for systematic studies of MBL in open systems and opens a route towards extrapolation of closed-system properties from experimentsWe acknowledge financial support by the European Commission (UQUAM, AQuS) and the Nanosystems Initiative Munich (NIM). Work at Strathclyde is supported by the EOARD via AFOSR Grant No. FA2386-14-1-5003. This research was supported in part by the National Science Foundation under Grant No. NSF PHY11-25915. M. H. F. acknowledges additional support from the Swiss Society of Friends of the Weizmann Institute of Science and S. S. H. acknowledges additional support from the Australian Research Council through Discovery Early Career Research Award No. DE150100315.application/pdfen-AUPublished by the American Physical Societyhttps://creativecommons.org/licenses/by/3.0/Atomic and Molecular PhysicsCondensed Matter Physics201710.1103/PhysRevX.7.0110342020-11-23Attribution 3.0 Unported (CC BY 3.0)