An international team that includes Nobel Prize-winning physicist Professor Sir Roger Penrose has directly observed a long-predicted gravitational effect in a falling quantum object for the first time. The finding shows that a central principle of Einstein's theory of gravity continues to agree with quantum behavior under the conditions tested. The research, led by Ben-Gurion University of the Negev, the University of Ulm and the University of Oxford, was published September 2 in Science Advances.
Modern physics rests on two remarkably successful frameworks. Quantum mechanics describes the unusual behavior of atoms and other extremely small objects, while Einstein's theory of gravity explains falling bodies and the large-scale structure of the Universe. Despite their individual success, physicists still do not have a complete theory that brings the two together.
The new experiment explores a region where these two descriptions overlap. Researchers measured a specific change in the quantum properties of atoms as they moved under the influence of gravity. The effect matched the prediction that follows when Einstein's equivalence principle, one of the foundations of his theory of gravity, is extended to a quantum object.
Testing Einstein's Equivalence Principle The equivalence principle says that gravity should effectively vanish locally for an observer in free fall. A person falling freely in a lift, for example, would experience weightlessness. The principle has been confirmed with extraordinary precision using ordinary matter, but testing it directly with quantum objects has been much more difficult because quantum objects can behave like waves and can effectively follow more than one path at the same time.
To make such a test possible, the team built an instrument called the Quantum Galileo Interferometer. The device allowed the researchers to split the quantum wave associated with an atom into two separate paths. One part could be kept in place while the other was allowed to fall freely.
The two were then brought back together so the researchers could determine how gravity had affected the falling wave. The experiment was carried out at Ben-Gurion University using clouds of rubidium atoms cooled to temperatures just above absolute zero. The atoms were manipulated near the surface of a specially designed atom chip.
Extract — continue reading at the source.
