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'Spooky-action-at-a-distance' Observed at Highest Ever Energies at the Large Hadron Collider in Geneva

Writer's picture: Triple HelixTriple Helix

Figure 1:  Quantum Physics & Superposition (4)


Written by Vivian Kang ‘28

Edited by Josue Navarro ‘25


Quantum entanglement, or as Einstein once described it, 'spooky action at a distance' was recently observed by scientists at the Large Hadron Collider (LHC) in Geneva at record high energies in top and anti-top quarks (1).

 

The study of quantum entanglement is an elusive one by nature, and so, these results represent a major step forward in the field of quantum mechanics, opening up many new research areas. However, to understand what these results mean we must first break down the concepts of superposition and entanglement.

 

Superposition is essentially the ability for a quantum system to be in two states simultaneously (2), where a quantum system is any system that obeys the laws of quantum mechanics. Think of Schrodinger's cat, which as a quantum state is both dead and alive at the same time until it is observed. It is as if the cat has not decided whether or not it drank the poison, until someone opened the box to see. Essentially, a quantum system's state being set is dependent upon an observer and it relates to a system in a single location.

 

Quantum entanglement on the other hand, is superposition at two distinct locations. In the context of the recent experiment, the quantum system is the top quark and the anti-top quark. For these two particles to be entangled means for them to be intrinsically linked, independent of distance, where the actions of one instantaneously affect the other (3).

 

These are both classified as elementary particles, more specifically, they are quarks - the fundamental particles that make up protons and neutrons. These elementary particles can be understood as disturbances within their specific quantum field. Our world is a bunch of superimposed (not the type of superposition we just discussed) quantum fields (4). And so, when a field gets excited it produces these bumps or disturbances in the field which we know is the particle itself. Now we can also imagine the bump in the opposite direction to be the antiparticle.

 

These particles have a specific property that is very important for quantum entanglement: spin. Spin is the angular momentum (velocity of rotation) of a particle, and can only be either up or down (4).

 

The Large Hadron Collider essentially creates these disturbances in the field, which allows us to study these particles. The collider uses two super magnets to bend and focus beams of protons that, as the name suggests, collide and release bursts of energy, disturbing the field (1).

 

And so, even if one particle is light years away from the other, if they are both entangled by their spin, once one is observed to be in a spin state of either up or down, the other transitions from a quantum state of superposition to the opposite spin instantaneously. This seems to break one of the most fundamental laws of physics which is that nothing can travel faster than the speed of light, otherwise known as Einstein's principle of locality. This is because it does to some extent. The information about the quantum state of the particle travels faster than the speed of light (4).

 

The scientists at the LHC in Geneva were able to observe such a mind-boggling phenomenon, at the highest energy yet recorded, by studying data sets and experiment results from 2015 to 2018 (2). Because top quarks are the heaviest of the quarks, they often decay, or break down, into other particles fairly quickly. They transfer to these subproducts certain properties, one of which includes spin. And so by studying the angle between these two decay products, the scientists were able to observe not only the existence, but the degree of spin entanglement of both these particles (3).

 

With these new findings, researchers hope to continue probing the intricacies of the Standard Model, the currently accepted theory around the fundamental particles and forces of the universe. Furthermore, they can take a deeper dive into understanding entanglement itself, exploring how long entanglement lasts and what breaks the entanglement. This could help us further understand what happened to our universe after the Big Bang and the initial stage of rapid expansion, where it is believed to have been in an entangled state (1).

 

The implications of this breakthrough in the field of quantum physics are vast, and could revolutionize our understanding of the fundamental forces that govern the universe.


 

References

  1. Center N, Andreatta D. Rochester physicists find ‘spooky action at a distance’ at CERN [Internet]. News Center. 2024 [cited 2024 Sep 25]. Available from: https://www.rochester.edu/newscenter/what-is-quantum-entanglement-top-quarks-610202/

  2. Aad G, Abbott B, Abeling K, Abicht NJ, Abidi SH, Aboulhorma A, et al. Observation of quantum entanglement with top quarks at the ATLAS detector. Nature. 2024 Sep;633(8030):542–7.

  3. Andreatta D, Rochester U of. Physicists confirm quantum entanglement persists between top quarks, the heaviest known fundamental particles [Internet]. [cited 2024 Sep 25]. Available from: https://phys.org/news/2024-06-physicists-quantum-entanglement-persists-quarks.html

  4. What is quantum entanglement? | Space [Internet]. [cited 2024 Sep 25]. Available from: https://www.space.com/31933-quantum-entanglement-action-at-a-distance.html

  5. Wolchover N. Quanta Magazine. 2020 [cited 2024 Sep 25]. What Is a Particle? Available from: https://www.quantamagazine.org/what-is-a-particle-20201112/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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