The theories of quantum mechanics and gravity are notorious for being incompatible, despite the efforts of scores of physicists over the past fifty years. However, recently an international team of researchers led by physicists from the University of Vienna, the Austrian Academy of Sciences as well as the University of Queensland (AUS) and the Stevens Institute of Technology (U.S.) have combined the key elements of the two theories describing the flow of time and discovered that temporal order between events can exhibit genuine quantum features.
Source:
https://phys.org/news/2019-08-quantum-gravity-tangled.html