What happens when quantum mechanics and relativity meet?

A century ago, physicists proposed what free fall should entail for a quantum wave. Should their conclusion prove incorrect, quantum mechanics and Einstein's theory of gravity would unequivocally contradict each other. However, testing this theory has remained unattainable due to the lack of an interferometer capable of executing the required measurement.

Recently, a team spearheaded by Ron Folman, a physicist from Ben-Gurion University of the Negev, along with associates from Germany, the United Kingdom, and the United States, including Nobel laureate Roger Penrose, managed to accomplish this feat. They constructed a novel interferometer enabling a solitary atom to traverse two paths simultaneously: one involving free fall and the other remaining stationary.

These paths converge at the same destination simultaneously, allowing the researchers to quantify the impact of the fall on an atom's wave-like characteristic. This inquiry has been in the making since Galileo's time. Physicists have comprehended how to depict a falling entity - its location, velocity, and rate of acceleration. Quantum mechanics, conversely, posits that all objects embody wave-like properties.

Folman elucidates, "Every particle, regardless of whether it's a car or a spaceship or an atom, behaves as a wave. Everything that possesses a wave-like nature, akin to sea waves, sound waves, undergoes oscillations, and these oscillations are quantified through a measure known as phase. A phase simply indicates whether the entity is at the wave's zenith or nadir."