In physics, a reference frame is an abstract coordinate system that specifies observations within that frame. Recently, it has been proposed to consider reference frames as physical objects that ultimately obey quantum mechanical laws. The transformations between such quantum reference frames can be seen as an extension of the transformations between classical reference frames. In my talk, I will show how the notion of quantum reference frames can help us formulate and test the weak and Einstein equivalence principles when a "free-falling laboratory" is in a quantum state (which can be spatiotemporally extended, for example), or when it falls into a superpositon of gravitational fields. This gives rise to the quantum Einstein equivalence principle, which could pave a fruitful way to the conceptual foundation of a future theory of quantum gravity.