Quantum computing breaks a barrier of classical computing and manages to describe the collisions of particles that hold the secrets of the universe and matter like never before.

A team of researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) used quantum computing to successfully simulate an aspect of particle collisions that is normally ignored in high-energy physics experiments, such as those that occur in the Large Collider at CERN hadrons.

Particle collisions are fundamental because they serve to study the elements that make up the matter that the Universe is made of, including our bodies, and their interactions.

The quantum algorithm that the Berkeley researchers developed explains the complexity of radiation cascades, which are caused by explosions produced during particle collisions.

These explosions involve hadron production and decay processes, and classical algorithms model the radiation cascades that occur during these processes, dominated by the strong nuclear interaction characteristic of these subatomic particles.

However, in an article published in the journal Physical Review Letters, the authors of this research highlight that the classical algorithms that model radiation cascades overlook some of the quantum effects of these processes.

To fill this gap, the Berkeley researchers developed a quantum algorithm capable of interpreting the cascades of radiation that occur when hadrons collide.

__Quantum gibberish__

Hadrons are elementary particles made up of quarks (massive elementary fermions) that stay together due to strong nuclear interaction.

There are two types of hadrons, baryons (neutrons and protons) and mesons (such as pions, responsible for the existence of atomic nuclei).

They are all involved in particle collisions, which have revealed yet another complexity: protons and neutrons sometimes behave as if they were made up of "parts," which is why these apparent fractions are called partons, hypothetical subparticles of protons and neutrons bound to each other in a stable way.

What these researchers have achieved is to describe the shower of particles that occurs in all its complexity during collisions, taking into account even quantum effects that classical algorithms ignored.

To do this, they have used a quantum computer with enough resources to penetrate this mess of particles, collisions and radiation cascades, according to the main researcher, Christian Bauer, in a statement.

__Quantum computing to play__

To achieve this, this team has combined both quantum and classical computing: the quantum solution has only been applied to the part of particle collisions that cannot be addressed with classical computing. For the other interactions, he has used classical computation.

The result could be obtained with an additional strategy, known in physics as a toy model , which simplifies the complex to understand the essentials of the basic processes.

This simplified theory was skillfully executed on a quantum computer, where the implicit complexity can be analyzed in a completely new way that enables situations inaccessible to classical computing to be addressed.

What the quantum computer provides is a computation based on the quantum entanglement of the basic unit of information, the qubit, which instead of constituting a unit as in classical computation (bit), represents a quantum system with two simultaneous states that can be manipulated for computational purposes.

This technological capacity allows the generation of new algorithms that, in the case of this research, calculated all the possible results of the collisions, taking into account the state of the particles, the history of particle emissions, whether emissions were produced, and the amount of particles produced in the cascade of partons, including separate counts for bosons and fermions, the two basic types of elementary particles.

__Promising result__

The quantum computer "calculated these stories at the same time and summarized all the possible stories at each intermediate stage," Bauer explains.

This made it possible to integrate quantum effects that classical algorithms could not contemplate in the description of the collisions, thus achieving a significant result to deepen our understanding of particle collisions.

The result obtained in this research has its limitations: the researchers admit that it is likely that the "noise" of quantum computing has caused differences in the descriptions, so they consider that it will still be time before this technological feat can have an impact significant in high energy physics.

__Closer and closer__

They add that as hardware improves, it will be possible to account for more types of bosons and fermions in the quantum algorithm, improving its accuracy.

At that point, this development should have a much greater impact on high-energy physics and find application in experiments with heavy ion colliders, which are used in basic research.

Despite the limitations that this result may still show, it has been shown once again that quantum computing continues to rapidly approach the field of practical applications .

Reference:

Quantum Algorithm for High Energy Physics Simulations. Benjamin Nachman et al. Phys. Rev. Lett. 126, 062001. 10 February 2021. DOI: https: //doi.org/10.1103/PhysRevLett.126.062001

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