The two pillars of modern physics are the theories of General Relativity (GR) and Quantum Mechanics (QM). After decades of theoretical attempts to unify these two pillars under one theoretical framework (often referred to as quantum-gravity), these pillars remain independent. To some this situation is so unnatural, that they claim it actually hints that at least one of the theories is wrong in some fundamental way. As technology in quantum-optics labs improves, new experiments – working at the interface of these two theories – can be realized. Such experiments will hopefully provide new insights that will eventually allow for the sought-after unification to be finally achieved.
In this talk, I will present three experiments conducted at this interface, two already realized and one planned. The experiments are based on Stern-Gerlach interferometry [1]. The first involves clock interferometry, in which a single clock in a spatial superposition experiences two different proper times due to gravitationally induced red shift [2-4]. The second involves the measurement of the quantum phase of a free-falling object and the observation of the consistency of the Einsteinian equivalence principle in the quantum domain [5]. While the first two were realized with atoms, the third involves massive objects, specifically, nano-diamonds [6-8]. Leaping by ten orders of magnitude in mass relative to the atomic experiments, the third experiment makes use of so-called active mass, where not only the gravitational field of Earth needs to be taken into account. Time permitting, I will also discuss new decoherence channels [9,10].