New study reveals quantum nature of gravity; to understand

In a paper recently published in the journal Physical Review X, researchers from the universities of Amsterdam and Ulm tackle a question that has until now been taboo for physicists: the true nature of gravity. Although it is the weakest force in nature and the most pervasive in all our lives, “it is also the cruelest,” according to research.

This is because gravity remains elusive when it comes to testing it, even though the curiosity to understand it has produced “many of the greatest achievements of human thought.” This means that science continues to not know whether this weak force is a classical field, a quantum field, or even an entity about which we have no idea.

Recognizing the difficulties theorists have so far encountered in testing their experimental proposals, the team led by mathematical physicist Ludovico Lami of the University of Amsterdam proposed a new approach to the question proposed by Richard Feynman in 1957: Can the gravitational field of a massive object enter quantum superposition?

How to do gravity-induced entanglement?

Lami explains that the issue of quantum superposition, proposed by the well-known American theoretical physicist, means that the object can be in more than one state at the same time. In this case, experimental testing will involve looking for entanglements caused by gravity.

This so-called experiment would bind two or more particles together through the force of gravity, as in traditional quantum entanglement accomplished by electromagnetism. “The existence of such entanglement would invalidate the hypothesis that the gravitational field is purely local and classical.”explains Lami.

The biggest hurdle will be correlating huge objects in the distance. a phenomenon called quantum delocalization, it is very difficult to reproduce. According to the authors, the largest mass of an object for which displacement has ever been observed was that of a large molecule, which was “significantly lighter than the smallest mass of an object ever gravitationally detected.”

Escaping the specter of quantum entanglement

The solution Lami and his colleagues came up with is frighteningly simple: overcome entanglement, that is, perform the experiment that will reveal the quantum nature of gravity without creating any entanglement.

In a statement, Lami explains how the experiment was done: “We designed and investigated a series of experiments involving large systems of ‘harmonic oscillators’, such as the torsion pendulums that Cavendish used in his famous experiment of 1797 to measure the intensity of the gravitational force”.

To ensure the validity of their model, the authors created a mathematical model that defines clear limits for signals of a quantum nature that cannot be explained by classical gravitational theory. They also evaluated what resources would be needed to implement their suggestions in real experiments. And they believe these solutions “will be within our reach really soon.”

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