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Researchers build space-time in a laboratory to unravel the mystery of quantum gravity


Starting from the theory of the hologram universe, researchers are trying to create a space-time model and observe quantum gravity through quantum entanglement.


In his 1997 study, Argentine-American theoretical physicist Juan Martin Maldacena first described the theory of the AdS / CFT (anti-de Sitter / conformal field theory) relationship, which presents a non-existent world that combines quantum mechanics and general relativity. and shows how theoretically the gravity described by the theory of relativity could be reconciled with the quantum world.


While quantum mechanics explains events in the smallest particle size range, strong, weak, and electromagnetic interactions mediated by gluons, bosons, or even photons, on a larger scale, general relativity describes the world, including the phenomenon of gravity. The discovery of quantum gravity, that is, the observation of the appearance of the gravitational effect at the level of the smallest particles, has not been possible so far for physicists, so the development of the theory of the universe is yet to come.


In the world of AdS / CFT, a CFT with a certain number of dimensions and an AdS with one more dimension correspond to each other in the same way as a two-dimensional starting point with all the information about the image and the resulting three-dimensional image, ie the space-time counterpart. but Sitter space is realized according to the CFT information on its ‘surface’.


This interface creates the inner one-dimensional space by quantum entanglement,


therefore, the duality of quantum mechanical and gravitational theory is also realized in it.


However, the Maldacena model, which is popular and regularly used by physicists, is no longer used only to perform theoretical calculations, but in a Stanford experimental physicist laboratory to try to build a space-time analogy and understand the possible operation of quantum gravity in a very practical way . Monika Schleier-Smith and her colleagues began experiments in 2019 to map a specific version of the AdS / CFT space, a version based on so-called p-adic numbers developed by Steven S. Gubser, a professor at Princeton University . In 2016.


The p-adic numbers in 1897, German mathematician Kurt Hensel was described as an extension of the rational numbers: it is an alternative number system whose members differ from the 'normal' figures that their value is determined by the prime. A characteristic of p-adic numbers is that they can be plotted as a symmetrical shape with nodes and branches, and Gubser discovers that this corresponds exactly to a tree-like structure inside an AdS / CFT space when p-adic numbers are used on the surface (CFT). in the description.

In order for this particular tree shape to appear not only on paper but also specifically in the laboratory, the quantum entanglement was sought by researchers who, under Schleier-Smith’s leadership, tried to create the predicted structure in reality as well. In an optical cavity, physicists cooled rubidium-87 atoms arranged in a row in adjacent groups to a temperature close to absolute zero degrees and then brought them into a state of laser entanglement, but the strength of the entanglement was modified by changing the magnetic field of the chamber.


When the magnetic field was uniform throughout the entire length of the chamber, the entanglement also became uniform between the different groups however, the modification succeeded in achieving the interaction at the local level, and with this control they were able to create a network of inter-atomic connections that was independent of the specific location of the atoms. That is, while the atoms were still physically aligned, the bonds formed by the entanglement took on the desired tree shape, similar to the special AdS / CFT space described by Gubser.


The experiment is only the initial phase of research that expects physicists to get closer to studying models that exist only in theories by creating increasingly complex patterns, but Maldacena, who told Quanta magazine about the study, could still be a big step forward.


"Our topic has always been very theoretical, so this connection to the experiments will raise even more questions," the physicist predicted.


Participants in the study are confident that similar observations could bring closer the possibility of understanding quantum gravity, which would otherwise have little chance, as it could only be achieved by studying black holes. However, the creation of a peculiar holographic world on a very small scale in the laboratory, or, as Schleier-Smith put it, the construction of a game model of quantum gravity, can replace direct observation that promises to be impossible. Patrick Hayden, a physicist at Stanford’s quantum information theory, says such an experiment may seem like a crazy idea, but it still represents an easier choice on the road to solving the much-researched mystery.


"Instead of trying to understand the creation of spacetime in the universe, let's build game universes in the lab and study the evolution of spacetime here."


Hayden said.

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