Lifeboat Foundation

Predicting the behavior of many interacting quantum particles is a complex task, but it’s essential for unlocking the potential of quantum computing in real-world applications. A team of researchers, led by EPFL, has developed a new method to compare quantum algorithms and identify the most challenging quantum problems to solve.

Quantum systems, from subatomic particles to complex molecules, hold the key to understanding the workings of the universe. However, modeling these systems quickly becomes overwhelming due to their immense complexity. It’s like trying to predict the behavior of a massive crowd where everyone constantly influences everyone else. When you replace the crowd with quantum particles, you encounter what’s known as the “quantum many-body problem.”

Quantum many-body problems involve predicting the behavior of numerous interacting quantum particles. Solving these problems could lead to major breakthroughs in fields like chemistry and materials science, and even accelerate the development of technologies like quantum computers.

For many years, scientists believed that fundamental particles like protons and neutrons that form an atomic nucleus, can’t be divided further into smaller units. However, in the following years, physicists discovered quarks and gluons.

While quarks are particles that combine to form protons and neutrons, gluons act like glue, binding the quarks together.

So far, scientists have been studying the atomic nucleus using two models. In the first model, at low energies like in most typical nuclear experiments, they describe the atomic nucleus in terms of protons and neutrons. This is the classic way of understanding the nucleus.

Electromagnetic radiation of extremely high energies is produced not only in the jets launched from active nuclei of distant galaxies, but also in jet-launching objects lying within the Milky Way, called microquasars. This latest finding by scientists from the international High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) radically changes the previous understanding of the mechanisms responsible for the formation of ultra-high-energy cosmic radiation and in practice marks a revolution in its further study.

Since the discovery of cosmic radiation by Victor Hess in 1912, astronomers have believed that the celestial bodies responsible in our galaxy for the acceleration of these particles up to the highest energies are the remains of gigantic supernova explosions, called supernova remnants.

However, a different picture comes from the latest data from the HAWC observatory: The sources of radiation of extremely high energies turn out to be microquasars. Astrophysicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow played a key role in the discovery.

While these findings, published in Physical Review Letters, did not lead to the observation of signals associated with these hypothetical dark matter particles, they established a new technique to search for axions using a tunable optical cavity.

A team of physicists from the universities of Amsterdam, Princeton and Oxford have shown that extremely light particles known as axions may occur in large clouds around neutron stars. These axions could form an explanation for the elusive dark matter that cosmologists search for—and moreover, they might not be too difficult to observe.

Axions—theorized particles that could account for dark matter—could accumulate around rapidly rotating neutron stars to the point that they become detectable.

From subatomic particles to complex molecules, quantum systems hold the key to understanding how the universe works. But there’s a catch: when you try to model these systems, that complexity quickly spirals out of control—just imagine trying to predict the behavior of a massive crowd of people where everyone is constantly influencing everyone else. Turn those people into quantum particles, and you are now facing a “quantum many-body problem.”

In their previous research, Mak and his colleagues engineered a highly tunable moiré Kondo lattice system based on MoTe₂/WSe₂ moiré bilayers. This material offers a unique opportunity to examine the Kondo destruction transition in a continuous manner, which has proved highly challenging in bulk heavy fermion materials.

“With this background, our Nature Physics paper studied the fate of the heavy fermions by continuously tuning the density of the itinerant carriers in the system, which tunes the effective Kondo coupling strength,” said Mak. “Near a critical density, we observed a destruction of the heavy fermions and the simultaneous emergence of a ferromagnetic Anderson insulator.”

As part of their new study, the researchers examined the Kondo lattice physics emerging in the moiré semiconductor: angle-aligned MoTe₂/WSe₂ heterobilayer presented in their previous paper. Their results highlight the promise of moiré Kondo lattices for studying the Kondo destruction transition using a tunable platform, as well as the possibility of realizing other exotic states of matter near such transition.

When driving though a bank of fog, car headlights are only of limited help as the light is scattered by the water particles suspended in the air. The situation is similar when you try to observe the inside of a drop of milk in water or the internal structure of an opal gem with the help of white light. In all these cases, multiple light scattering effects prevent examination of the interior.