MSGID: 1:317/3 6465a9de   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Curved spacetime in a quantum simulator    
      
     Date:   
         May 17, 2023   
     Source:   
         Vienna University of Technology   
     Summary:   
         The connection between quantum physics and the theory of relativity   
         is extremely hard to study. But now, scientists have set up a   
         model system, which can help: Quantum particles can be tuned in   
         such a way that the results can be translated into information   
         about other systems, which are much harder to observe. This kind of   
         'quantum simulator' works very well and can lead to new insights   
         about the nature of relativity and quantum physics.   
      
      
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   FULL STORY   
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   The theory of relativity works well when you want to explain cosmic-scale   
   phenomena -- such as the gravitational waves created when black holes   
   collide.   
      
   Quantum theory works well when describing particle-scale phenomena --   
   such as the behavior of individual electrons in an atom. But combining the   
   two in a completely satisfactory way has yet to be achieved. The search   
   for a "quantum theory of gravity" is considered one of the significant   
   unsolved tasks of science.   
      
   This is partly because the mathematics in this field is highly   
   complicated. At the same time, it is tough to perform suitable   
   experiments: One would have to create situations in which phenomena   
   of both the relativity theory play an important role, for example, a   
   spacetime curved by heavy masses, and at the same time, quantum effects   
   become visible, for example the dual particle and wave nature of light.   
      
   At the TU Wien in Vienna, Austria, a new approach has now been developed   
   for this purpose: A so-called "quantum simulator" is used to get to the   
   bottom of such questions: Instead of directly investigating the system of   
   interest (namely quantum particles in curved spacetime), one creates a   
   "model system" from which one can then learn something about the system   
   of actual interest by analogy. The researchers have now shown that this   
   quantum simulator works excellently. The findings of this international   
   collaboration involving physicists from the University of Crete,   
   Nanyang Technological University, and FU Berlin are now published in   
   the scientific journal Proceedings of the National Academy of Sciences   
   of the USA (PNAS).   
      
   Learning from one system about another The basic idea behind the quantum   
   simulator is simple: Many physical systems are similar. Even if they are   
   entirely different kinds of particles or physical systems on different   
   scales that, at first glance, have little to do with each other, these   
   systems may obey the same laws and equations at a deeper level.   
      
   This means one can learn something about a particular system by studying   
   another.   
      
   "We take a quantum system that we know we can control and adjust very well   
   in experiments," says Prof. Jo"rg Schmiedmayer of the Atomic Institute   
   at TU Wien.   
      
   "In our case, these are ultracold atomic clouds held and manipulated by   
   an atom chip with electromagnetic fields." Suppose you properly adjust   
   these atomic clouds so that their properties can be translated into   
   another quantum system.   
      
   In that case, you can learn something about the other system from the   
   measurement of the atomic cloud model system -- much like you can learn   
   something about the oscillation of a pendulum from the oscillation of a   
   mass attached to a metal spring: They are two different physical systems,   
   but one can be translated into the other.   
      
   The gravitational lensing effect "We have now been able to show that   
   we can produce effects in this way that can be used to resemble the   
   curvature of spacetime," says Mohammadamin Tajik of the Vienna Center   
   for Quantum Science and Technology (VCQ) -- TU Wien, first author of   
   the current paper. In the vacuum, light propagates along a so-called   
   "light cone." The speed of light is constant; at equal times, the light   
   travels the same distance in each direction. However, if the light is   
   influenced by heavy masses, such as the sun's gravitation, these light   
   cones are bent. The light's paths are no longer perfectly straight in   
   curved spacetimes. This is called "gravitational lens effect."  The same   
   can now be shown in atomic clouds. Instead of the speed of light, one   
   examines the speed of sound. "Now we have a system in which there is an   
   effect that corresponds to spacetime curvature or gravitational lensing,   
   but at the same time, it is a quantum system that you can describe with   
   quantum field theories," says Mohammadamin Tajik. "With this, we have   
   a completely new tool to study the connection between relativity and   
   quantum theory."  A model system for quantum gravity The experiments   
   show that the shape of light cones, lensing effects, reflections, and   
   other phenomena can be demonstrated in these atomic clouds precisely as   
   expected in relativistic cosmic systems. This is not only interesting for   
   generating new data for basic theoretical research -- solid- state physics   
   and the search for new materials also encounter questions that have a   
   similar structure and can therefore be answered by such experiments.   
      
   "We now want to control these atomic clouds better to determine even more   
   far- reaching data. For example, interactions between the particles can   
   still be changed in a very targeted way," explains Jo"rg Schmiedmayer. In   
   this way, the quantum simulator can recreate physical situations that are   
   so complicated that they cannot be calculated even with supercomputers.   
      
   The quantum simulator thus becomes a new, additional source of information   
   for quantum research -- in addition to theoretical calculations, computer   
   simulations, and direct experiments. When studying the atomic clouds,   
   the research team hopes to come across new phenomena that may have   
   been entirely unknown up to now, which also take place on a cosmic,   
   relativistic scale -- but without a look at tiny particles, they might   
   never have been discovered.   
      
       * RELATED_TOPICS   
             o Matter_&_Energy   
                   # Physics # Quantum_Physics # Albert_Einstein # Optics   
             o Computers_&_Math   
                   # Quantum_Computers # Computers_and_Internet #   
                   Spintronics_Research # Encryption   
       * RELATED_TERMS   
             o Quantum_entanglement o Quantum_mechanics o   
             Introduction_to_quantum_mechanics o Quantum_number o   
             Particle_physics o Wave-particle_duality o John_von_Neumann   
             o Albert_Einstein   
      
   ==========================================================================   
   Story Source: Materials provided by Vienna_University_of_Technology. Note:   
   Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Mohammadamin Tajik, Marek Gluza, Nicolas Sebe, Philipp   
      Schu"ttelkopf,   
         Federica Cataldini, Joa~o Sabino, Frederik Mo/ller, Si-Cong Ji,   
         Sebastian Erne, Giacomo Guarnieri, Spyros Sotiriadis, Jens Eisert,   
         Jo"rg Schmiedmayer. Experimental observation of curved light-cones   
         in a quantum field simulator. Proceedings of the National Academy   
         of Sciences, 2023; 120 (21) DOI: 10.1073/pnas.2301287120   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230517122129.htm   
      
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