  This talk presents: (a) A quantum-mechanically induced violation of the
principle of equivalence, and (b) Gravitationally-induced modification to the
wave particle duality. In this context I note that the agreement between the
predictions of general relativity and observations of the energy loss due to
gravitational waves emitted by binary pulsars is just as impressive as the
agreement between prediction of quantum electrodynamics and the measured value
of Lamb shift in atoms. However, general relativity has not yet yielded to a
successful quantised theory. There is a widespread belief that the two thories
are incompatible at some deep level. The question is: where? Here, I show that
the conceptual foundations of the theory of general relativity and quantum
mechanics are so rich that they suggest concrete modifications into each other
in the interface region. Specifically, I consider quantum states that have no
classical counterpart and show that such states must carry an inherent
violation of the principle of equivalence. On the other hand, I show that when
gravitational effects are incorporated into the quantum measurement process one
must induce a gravitationally induced modification to the de Broglie's
wave-particle duality. The reported changes into the foundations of the two
theories are far from in-principle modifications. These are endowed with
serious implications for the understanding of the early universe and, in
certain instances, can be explored in terrestrial laboratories.
