Scientists observe Einstein's gravity in the quantum world
Recorded: Sept. 8, 2026, 6:11 a.m.
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Scientists observe Einstein’s gravity in the quantum world | Oxford University
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Explore the Oxford Excellence campaign You are here: Home News Scientists observe Einstein’s gravity in the quantum world 03 September 2026 Scientists observe Einstein’s gravity in the quantum world An international team including Nobel Prize-winning physicist Professor Sir Roger Penrose has observed a long-predicted effect of gravity on a falling quantum object for the first time. The result shows that a fundamental principle at the heart of Einstein’s theory of gravity remains consistent with the behaviour of matter in the quantum world. The study, led by Ben-Gurion University of the Negev, The University of Ulm and the University of Oxford, has been published in Science Advances. Tags: Computing and quantum Nature, climate and the physical universe Elements, cells, molecules and atoms Research Mathematical, Physical and Life Sciences A new study involving Oxford physicists provides an experimental connection between quantum physics and Einstein's theory of gravity. Image credit: sakkmesterke, Getty Images. For more than a century, physicists have relied on two extraordinarily successful descriptions of nature. Quantum mechanics explains the strange behaviour of atoms and other tiny objects. Einstein’s theory of gravity explains how objects fall and how gravity shapes the Universe. Yet physicists still do not fully understand how the two fit together.Now, an international team has performed an experiment that probes the point where they meet. In the study, the researchers observed a distinctive change in the quantum properties of atoms as they fell under gravity. Crucially, the effect they measured is the same one predicted when Einstein’s equivalence principle, a cornerstone of his theory of gravity, is applied to a quantum object. The equivalence principle states that for an observer in free fall, gravity should locally disappear. Someone falling freely in a lift, for example, would experience weightlessness. Whilst this theory has survived extraordinarily precise tests involving ordinary matter, it was unclear how this could be experimentally tested with quantum objects, which can behave as waves and effectively travel along more than one path.At the heart of the experiment is a new apparatus the researchers call the Quantum Galileo Interferometer in honour of Galileo’s work on gravity. It allowed them to do something unusual: effectively split the quantum wave associated with an atom into two paths, hold one in place while allowing the other to fall freely, and then reunite them to see how gravity had changed the falling wave. As this work required a new type of quantum interferometry, quantum theory specialist Professor Wolfgang Schleich from the University of Ulm developed the quantum understanding of the apparatus used. Putting an Einstein principle to a quantum test The experiment was carried out at Ben-Gurion University using clouds of rubidium atoms cooled to just above absolute zero and manipulated close to the surface of a specially designed atom chip. The 2D MOT apparatus which feeds the science chamber with cold atoms. Credit: Or Dobkowski. The experimental team, including PhD student Or Dobkowski, first used microwave pulses to put the ultracold atoms into a quantum superposition, effectively allowing each atom to travel along two different paths at once. They then used tiny electrical wires on the chip to generate precisely controlled magnetic fields. One part of the atomic wave responded to this magnetic field, allowing the researchers to apply an upward force that exactly counteracted the downward pull of gravity. In effect, this part was held stationary relative to the laboratory and the Earth.The other part was pushed upwards with a precisely controlled magnetic pulse, then switched into a state almost unaffected by the magnetic field so that it could fall freely under gravity – following a ballistic trajectory, similar to a ball thrown into the air. At the end of the fall, the researchers used another precisely controlled magnetic pulse to bring the two parts back together. When the two waves were reunited, they interfered with each other. That interference allowed the researchers to measure the tiny difference in quantum phase accumulated while one was falling and the other was held still.The phase measured in the new experiment is the same as the one predicted when Einstein's principle is applied to such a quantum wave. The result therefore provides an experimental connection between quantum physics and Einstein's theory of gravity.Although previous experiments have used quantum particles to measure gravity, the researchers say this is the first direct measurement of the predicted quantum phase of a freely falling object.Lead author Professor Ron Folman (Ben-Gurion University of the Negev) said: 'This is a unique paper, in the sense that it combines a hard experiment with a far-reaching theoretical interpretation, about one of the most fundamental questions in physics: How can gravity (described by Einstein’s theory of relativity) and quantum theory, be unified into one understanding of the universe? These two pillars of modern physics have so far eluded all attempts at a unified theoretical framework, but this complex experiment gives more hints as to how such a unification may be achieved.' — Study co-author Professor Vlatko Vedral, “We have no consistent theory telling us why quantum physics should fail. This experiment pushes quantum mechanics into one of its most intriguing frontiers, gravity, and shows that, once again, its predictions hold.” The atom chip used in the experiment (fabricated at Ben-Gurion University of the Negev). In the experiment the chip was upside-down and the atoms manipulated just under it. Credit: Ben-Gurion University of the Negev. The result does not unite quantum mechanics and gravity, nor does it show that gravity itself is quantum. Instead, it demonstrates that Einstein’s equivalence principle remains consistent with quantum mechanics in the regime tested.Also, the study does not overturn an argument made by study co-author Professor Sir Roger Penrose (University of Oxford) that quantum mechanics could break down for sufficiently massive objects held in quantum superpositions for long enough times. Whilst the present experiment did not reach the masses or timescales needed to test this idea, the research team hope the technique will be a step towards experiments with much heavier objects, including nanodiamonds, that could investigate this possibility. Such an experiment is now underway in the same group at Ben-Gurion University of the Negev.The international study included researchers from Ben-Gurion University of the Negev; the University of Oxford; the University of Southampton; German Aerospace Center, the Institute of Quantum Technologies, Ulm; Universität Ulm; and Texas A&M University.The study ‘Observation of the quantum phase of free fall and the consistency with the equivalence principle’ has been published in Science Advances.For more information about this story or republishing this content, please contact [email protected] Related content Last updated Professor Mark Harris: Towards the quantum humanities Human society and culture Global cultures and religion Computing and quantum Profile Last updated Reading time Oxford researchers contribute to major advance in the search for dark matter and gravitational waves Nature, climate and the physical universe Elements, cells, molecules and atoms Space, planets and the universe Mathematical, Physical and Life Sciences Research Last updated Reading time Strange winds reveal strongest hints yet of magnetic activity in exoplanets Mathematical, Physical and Life Sciences Nature, climate and the physical universe Space, planets and the universe Last updated Reading time Scientists unlock new route to extreme light intensities Mathematical, Physical and Life Sciences Nature, climate and the physical universe Space, planets and the universe Research Elements, cells, molecules and atoms Was this page helpful? 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An international research team, including Nobel Prize-winning physicist Professor Sir Roger Penrose, has conducted an experiment that reveals a connection between Einstein’s theory of gravity and the behavior of matter in the quantum world. The study demonstrated that a fundamental principle central to Einstein's theory of gravity remains consistent with how matter behaves at the quantum level. This investigation sought to probe the point where quantum mechanics and general relativity intersect, addressing the long-standing difficulty in unifying these two pillars of modern physics. The experimental setup utilized a novel apparatus called the Quantum Galileo Interferometer, which allowed researchers to observe a predicted effect of gravity on a falling quantum object for the first time. The core of the experiment involved manipulating clouds of rubidium atoms cooled near absolute zero using an atom chip. The methodology involved placing the ultracold atoms into a quantum superposition and splitting their associated quantum wave into two distinct paths. One portion was allowed to fall freely under gravity, while the other was held stationary relative to the laboratory. By reuniting these two paths, the researchers measured the difference in the quantum phase accumulated, which is directly influenced by the gravitational effect encountered during the fall. The measurement yielded a quantum phase result that precisely matched the prediction derived from applying Einstein's equivalence principle to a quantum object. This finding establishes an experimental link between quantum physics and Einstein's theory of gravity, showing consistency between the equivalence principle and quantum mechanics in the tested regime. While this experiment does not fully unify quantum mechanics and gravity, it strongly supports the idea that these theories are compatible within established physical laws. Furthermore, the results do not contradict arguments, such as those made by Professor Sir Roger Penrose, suggesting that quantum mechanics might not break down for sufficiently massive objects held in quantum superpositions for extended durations, although the current experiment did not reach those mass or timescale limits. The success of this work relied on new developments in quantum interferometry; Professor Wolfgang Schleich from the University of Ulm developed the necessary quantum understanding for the apparatus used. The research involved collaboration among institutions including Ben-Gurion University of the Negev, the University of Oxford, the University of Southampton, the German Aerospace Center, and Universität Ulm. Lead author Professor Ron Folman noted that this work combines a hard experiment with theoretical interpretation, offering further insights into how a unification of gravity and quantum theory might be achieved. The findings indicate that the predictions of both theories hold true when applied to systems involving quantum phenomena under gravitational influence. |