Quantum particles influenced by gravitational fields they never interact with
Andy
If you are superstitious, a black cat in your path is bad karma, even if you stay away. Similarly, in quantum physics, particles can feel the effect of a magnetic field without ever having direct contact with it. So far, scientists have shown that this mental quantum effect is not just for magnetic fields, but also for gravity—and it's no superstition. Usually, in order to feel the effect of a magnetic field, a particle must pass through it. In 1959, however, physicists Yakir Aharonov and David Bohm predicted that in a specific scenario, conventional wisdom would fail. The magnetic field at the cylindrical site can affect particles - such as electrons - that cannot enter the cylinder. In this scenario, the electrons do not have a clear location, but exist in "superpositions", quantum states characterized by the possibilities of the particle occurring in two different locations. Each broken particle simultaneously takes two different paths around the magnetic cylinder. Although the magnetic field never touches the electrons and thus exerts no force on them, the magnetic field changes the pattern in which the particles are at the end of this excursion, as confirmed by several experiments (SN: 3/ 1/86). In the new analysis, the same unusual physics is at play for the gravitational field, the physicists reported in January. 14 Science. "Every time I look at this analysis, I think, 'It's amazing that nature works this way,'" said physicist Mark Kasevich of Stanford University. Kasevich and colleagues released rubidium atoms in a 10-meter-high vacuum chamber, hit them with lasers to place them in quantum superpositions along two different trajectories, and watched the atoms fall. In particular, particles do not exist in a zone without a gravitational field. Instead, the analysis was designed to allow researchers to examine the effects of gravitational forces and show the impressive Aharonov-Bohm effect. The study not only shows a popular effect in physics in a new environment, but also shows the potential of studying the subtle effects of gravitational systems. For example, researchers tried to use this type of method to better measure Newton's gravitational constant G, which expresses the force of gravity, and is now known to be less accurate than other fundamental constants of nature (SN: 8/29/18 ). An important feature in this test is called interference. In quantum physics, atoms and other particles behave like waves that add and subtract, like two ripples in the ocean coming together to form a larger wave. At the end of the atoms' flight, scientists reconnect the two paths of the atoms so that their waves interfere and measure where the atoms end up. Arrival locations are particularly susceptible to adjustments that change where the crests and troughs of the waves hit, known as phase shifts. On top of the vacuum chamber, the scientists placed a piece of tungsten weighing 1.25 kilograms. To isolate the Aharonov-Bohm effect, the researchers performed the same analysis with and without this mass and for two different sets of ejected atoms, one flying close to the mass and the other further down. Each of these two sets of atoms is divided into superpositions, with one orbit closer to the mass than the other, separated by about 25 centimeters. https://zenodo.org/record/6891716 https://zenodo.org/record/6891957 https://zenodo.org/record/6891970 https://zenodo.org/record/6892510 https://zenodo.org/record/6892556 https://zenodo.org/record/6892623 https://zenodo.org/record/6892698 The group is surrounded by additional layers of atoms with superpositions separated by small distances. Comparing how the different sets of atoms interact, with and without the tungsten mass, induces a phase transition that is not due to gravity. Instead, this enhancement comes from time dilation, which is part of Einstein's theory of gravity, the general theory of relativity, which causes time to flow more slowly for a massive object. The two theories underlying this analysis, general relativity and quantum mechanics, do not work well together. Scientists don't know how to piece it together to describe reality. So for physicists, says Guglielmo Tino of the University of Florence, who was not involved in the new study, "to test gravity with a quantum sensor, I think that's one of the ... major challenges of today."
•Jul 24, 2022•0 citations