Gravity is part of our everyday life. Still, the gravitational force remains mysterious: to this day we do not understand whether its ultimate nature is geometrical, as Einstein envisaged, or governed by the laws of quantum mechanics.
Until now, all experimental proposals to answer this question have relied on creating the quantum phenomenon of entanglement between heavy, macroscopic masses. But the heavier an object is, the more it tends to shed its quantum features and become "classical," making it incredibly challenging to make a heavy mass behave as a quantum particle
In a study published in Physical Review X this week, researchers from Amsterdam and Ulm propose an experiment that circumvents these issues.
Successfully combining quantum mechanics and gravitational physics is one of the main challenges of modern science. Generally speaking, progress in this area is hindered by the fact that we cannot yet perform experiments in regimes where both quantum and gravitational effects are relevant.
At a more fundamental level, as Nobel Prize laureate Roger Penrose once put it, we do not even know whether a combined theory of gravity and quantum mechanics will require a "quantization of gravity" or a "gravitization of quantum mechanics."
In other words: Is gravity fundamentally a quantum force, its properties being determined at the smallest possible scales, or is it a "classical" force for which a large-scale geometrical description suffices? Or is it something different yet?
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