Complementarity-entanglement tradeoff in quantum gravity

The quantization of gravity remains one of the most important???yet extremely elusive???challenges at the heart of modern physics. Any attempt to resolve this long-standing problem seems to be doomed, as the route to any direct empirical evidence (i.e., detecting gravitons) that sheds light on the quantum aspect of gravity is far beyond the current capabilities. Recently, it was discovered that gravitationally induced entanglement, tailored in the interferometric frameworks, can be used to witness the quantum nature of gravity. Even though these schemes offer promising tools for investigating quantum gravity, many fundamental and empirical aspects of the schemes are yet to be discovered. Considering the fact that, besides quantum entanglement, the quantum uncertainty and complementarity principles are the two other foundational aspects of quantum physics, the quantum nature of gravity needs to manifest all of these features. Here, we lay out an interferometric platform for testing these nonclassical aspects of quantum mechanics in the quantum gravity setting, which connects gravity and quantum physics in a broader and deeper context. As we show in this work, all of these fundamental features of quantum gravity can be framed and thoroughly analyzed in an interferometric scheme.