Lifeboat Foundation

Physicists at Harvard University in the US have created a novel strongly interacting quantum liquid known as a Laughlin state in a gas of ultracold atoms for the first time. The state, which is an example of a fractional quantum Hall (FQH) state, had previously been seen in condensed-matter systems and in photons, but observations in atoms had been elusive due to stringent experimental requirements. Because atomic systems are simpler than their condensed-matter counterparts, the result could lead to fresh insights into fundamental physics.

“Some of the most intriguing phenomena in condensed-matter physics emerge when you confine electrons in two dimensions and apply a strong magnetic field,” explains Julian Léonard, a postdoctoral researcher in the Rubidium Lab at Harvard and the lead author of a paper in Nature on the new work. “For example, the particles can behave collectively as if they have a charge that is only a fraction of the elementary charge – something that does not occur anywhere else in nature and is even ruled out by the Standard Model for all fundamental particles.”

The way in which such fractional charges arise is still not fully understood because it is difficult to study solid-state systems at an atomic scale. This is why it is so desirable to study the behaviour of FQHs in synthetic quantum systems such as cold atoms, which act as quantum simulators for more complex condensed-matter phenomena.

The future of electronics will be based on novel kinds of materials. Sometimes, however, the naturally occurring topology of atoms makes it difficult for new physical effects to be created. To tackle this problem, researchers at the University of Zurich have now successfully designed superconductors one atom at a time, creating new states of matter.

What will the computer of the future look like? How will it work? The search for answers to these questions is a major driver of basic physical research. There are several possible scenarios, ranging from the further development of classical electronics to neuromorphic computing and quantum computers.

The common element in all these approaches is that they are based on novel physical effects, some of which have so far only been predicted in theory. Researchers go to great lengths and use state-of-the-art equipment in their quest for new quantum materials that will enable them to create such effects. But what if there are no suitable materials that occur naturally?

Japanese scientists have discovered a compound, ethylammonium lead iodide, which can store and release ammonia safely and efficiently. This finding holds potential for ammonia’s role as a carbon-free hydrogen carrier, contributing to the transition towards a decarbonized society.

Researchers at the RIKEN Center for Emergent Matter Science (CEMS) in Japan have discovered a compound that uses a chemical reaction to store ammonia, potentially offering a safer and easier way to store this important chemical. This discovery, published in the Journal of the American Chemical Society on July 10, makes it possible not only to safely and conveniently store ammonia, but also the important hydrogen is carries. This finding should help lead the way to a decarbonized society with a practical hydrogen economy.

For society to make the switch from carbon-based to hydrogen-based energy, we need a safe way to store and transport hydrogen, which by itself is highly combustible. One way to do this is to store it as part of another molecule and extract it as needed. Ammonia, chemically written as NH₃, makes a good hydrogen carrier because three hydrogen atoms are packed into each molecule, with almost 20% of ammonia being hydrogen by weight.

The images shed light on how electrons form superconducting pairs that glide through materials without friction.

When your laptop or smartphone heats up, it’s due to energy that’s lost in translation. The same goes for power lines that transmit electricity between cities. In fact, around 10 percent of the generated energy is lost in the transmission of electricity. That’s because the electrons that carry electric charge do so as free agents, bumping and grazing against other electrons as they move collectively through power cords and transmission lines. All this jostling generates friction, and, ultimately, heat.

But when electrons pair up, they can rise above the fray and glide through a material without friction. This “superconducting” behavior occurs in a range of materials, though at ultracold temperatures. If these materials can be made to superconduct closer to room temperature, they could pave the way for zero-loss devices, such as heat-free laptops and phones, and ultra-efficient power lines. But first, scientists will have to understand how electrons pair up in the first place.

“A phonon represents the collective motion of an astronomical number of atoms,” Cleland says. “And they all have to work together in order to obey quantum mechanics. There was this question in the back of my mind, will this really work? We tried it, and it’s kind of amazing, but it really does work.”

Splitting a phonon

The team created single phonons as propagating wavepackets on the surface of a lithium niobate chip. The phonons were created and detected using two superconducting qubits, which were located on a separate chip, and coupled to the lithium niobate chip through the air. The two superconducting qubits were located either of the chip, with a two-millimetre-long channel between them hosting the travelling phonons.

The quantum nature of interactions between elementary particles allows drawing non-trivial conclusions even from processes as simple as elastic scattering. The ATLAS experiment at the LHC accelerator reports the measurement of fundamental properties of strong interactions between protons at ultra-high energies.

The physics of billiard ball collisions is taught from early school years. In a good approximation, these collisions are elastic, where both momentum and energy are conserved. The scattering angle depends on how central the collision was (this is often quantified by the impact parameter value—the distance between the centers of the balls in a plane perpendicular to the motion). In the case of a small impact parameter, which corresponds to a highly central collision, the scattering angles are large. As the impact parameter increases, the scattering angle decreases.

In particle physics, we also deal with elastic collisions, when two particles collide, maintaining their identities, and scatter a certain angle to their original direction of motion. Here, we also have a relationship between the collision parameter and the scattering angle. By measuring the scattering angles, we gain information about the spatial structure of the colliding particles and the properties of their interactions.

An international team of physicists has succeeded in measuring a property of the electron known as topological spin winding for the first time. The team obtained this result by studying the behaviour of electrons in so-called kagome metals, which are materials that have unique quantum properties related to their physical shape, or topology. The work could advance our understanding of the physics of superconductors and other systems that contain strongly correlated electrons.

Kagome metals are named after a traditional Japanese basket-weaving technique that produces a lattice of interlaced, symmetrical triangles with shared corners. When the atoms of a metal or other conductor are arranged in this kagome pattern, their electrons behave in unusual ways. For example, the wavefunctions of the electrons can interfere destructively, resulting in highly localized electronic states in which the particles interact strongly with each other. These strong interactions lead to a range of quantum phenomena, including magnetic ordering of unpaired electrons spins that can produce, for example, ferro-or antiferromagnetic phases, superconducting structures, quantum spin liquids and abnormal topological phases. All these phases have applications in advanced nanoelectronics and spintronics technologies.

In the new work, researchers led by Domenico Di Sante of the University of Bologna in Italy studied the spin and electronic structure of XV₆Sn₆, where X is a rare-earth element. These recently-discovered kagome metals contain a Dirac electronic band and a nearly flat electronic band. At the point at which these bands meet, an effect called spin-orbit coupling creates a narrow gap between the bands. This spin-orbit coupling also creates special type of electronic ground state at the material’s surface.

It seems quantum mechanics and thermodynamics cannot be true simultaneously. In a new publication, University of Twente researchers use photons in an optical chip to demonstrate how both theories can be true at the same time.

In quantum mechanics, time can be reversed and information is always preserved. That is, one can always find back the previous state of particles. It was long unknown how this could be true at the same time as thermodynamics. There, time has a direction and information can also be lost. “Just think of two photographs that you put in the sun for too long, after a while you can no longer distinguish them,” explains author Jelmer Renema.

There was already a theoretical solution to this quantum puzzle and even an experiment with atoms, but now the University of Twente (UT) researchers have also demonstrated it with photons. “Photons have the advantage that it is quite easy to reverse time with them,” explains Renema. In the experiment, the researchers used an optical chip with channels through which the photons could pass. At first, they could determine exactly how many photons there were in each channel, but after that, the photons shuffled positions.

Inside a lab, scientists marvel at a strange state that forms when they cool down atoms to nearly absolute zero. Meanwhile, just outside their window, trees are absorbing sunlight and converting it into new leaves. These two scenarios may seem entirely unrelated, but a recent study from the University of Chicago proposes that these processes are not as distinct as they might appear on the surface.

Published in the journal PRX Energy, the study established connections at the atomic level between the process of photosynthesis and exciton condensates, —a strange state of physics that allows energy to flow frictionlessly through a material. According to the authors, this discovery is not only fascinating from a scientific perspective, but it may also offer new perspectives for electronics design.