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Particle collision in hadron collider, colorful swirling beams © vchalup.stock.adobe.com
Article in Nature

New Perspectives on the Complex World of Quantum Physics

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in
  • Particle Physics
  • Top News
  • Research
The picture shows a technical structure. In the foreground is the artistic visualization of the top quark entanglement. This is represented by two circular poles connected by an energetic beam of light. © Daniel Dominguez​/​CERN
The image shows the artistic visualization of top quark entanglement. The line between the particles emphasizes the inseparability of the top quark pair, which is produced by LHC collisions and recorded by ATLAS.
Quantum entanglement is a fascinating feature of quantum physics. If two particles are quantum-entangled, their state can only be described collectively, no matter how far apart the particles are. This phenomenon has already been applied in quantum cryptography and quantum computing, and in 2022 experiments with entangled photons were even awarded the Nobel Prize in Physics. The Atlas Collaboration at CERN in Switzerland has now succeeded in observing quantum entanglement between top quarks, the heaviest known fundamental particles, for the first time. The researchers have presented their findings in the prestigious journal Nature. One of the article’s co-authors is Dr. Andrea Knue, Associate Professor at the Department of Physics of TU Dortmund University.

To solve questions in physics so far unanswered, international scientists at the CERN research center in Geneva are investigating the properties and interactions of elementary particles, among other things. In the world’s most powerful particle accelerator, the Large Hadron Collider (LHC), protons are accelerated and made to collide. This generates billions of elementary particles, whose flow and decay are recorded by large detectors. One such detector is the ATLAS experiment, in which Professor Kevin Kröninger’s team is participating on the part of TU Dortmund University.

Until now, quantum entanglement at the high energies accessible at the LHC was largely unexplored. With its latest measurements, the ATLAS Collaboration is making an important contribution to a deeper understanding of the phenomenon: The researchers were able to observe quantum entanglement between a top quark and its antimatter counterpart for the first time. Top quarks pose challenges for scientists because they normally decay into other particles before they have time to combine with other quarks. That is why physicists observe these decay products to infer the top quark’s quantum properties. To observe entanglement between top quarks, the ATLAS team used data from proton-proton collisions that took place at an energy of 13 teraelectronvolts at the LHC between 2015 and 2018.

Also involved in this measurement was Dr. Andrea Knue from TU Dortmund University. She is a member of Professor Kevin Kröninger’s team and has additionally led the ATLAS experiment’s top quark research group for the last two years, in which around 300 scientists from throughout the world are collaborating. In her research, Dr. Knue studies the properties of top quarks, and her work has contributed to improving scientists’ understanding of “signal modeling”, which greatly influenced the precision of the measurement now presented in Nature. The latest findings on quantum entanglement of top quarks have since been corroborated by two further observations by scientists working on the CMS detector at CERN.

To the article in Nature

To the press release of CERN

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