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The European nuclear research facility CERN announced on Tuesday that scientists using the upgraded Large Hadron Collider (LHC) had identified three previously unknown particles.

After a three-year suspension for improvements, the world’s biggest and most powerful particle collider resumed operation. The modernized LHC enables researchers to analyze twenty times more collisions than previously.

Using the improved collider, CERN researchers discovered a “pentaquark” and the first-ever pair of “tetraquarks.”

Over the last decade, improvements in optical atomic clocks have repeatedly led to devices that have broken records for their precision (see Viewpoint: A Boost in Precision for Optical Atomic Clocks). To achieve even better performance, physicists must find a way to cool the atoms in these clocks to lower temperatures, which would allow them to use shallower atom traps and reduce measurement uncertainty. Tackling this challenge, Xiaogang Zhang and colleagues at the National Institute of Standards and Technology, Colorado, have cooled a gas of ytterbium atoms to a record low temperature of a few tens of nanokelvin [1]. As well as enabling the next generation of optical atomic clocks, the researchers say that their technique could be used to cool atoms in neutral-atom quantum computers.

Divalent atoms such as ytterbium are especially suited to precision metrology, as their lack of net electronic spin makes them less sensitive than other species to environmental noise. These atoms can be cooled to the necessary sub-µK temperatures in several ways, but not all techniques are compatible with the requirements of high-precision clocks. For example, evaporative cooling, in which the most energetic atoms are removed, is time-consuming and depletes the atoms. Meanwhile, resolved sideband cooling chills the motion of the atoms only along the axis of the 1D optical trap, leaving their off-axis motion unaffected.

Zhang and colleagues cool their atoms using a laser tuned to ytterbium’s so-called clock transition, whose extremely narrow linewidth means that the atom can theoretically be cooled to below 10 nK. They demonstrate that the precision of a clock employing a shallow lattice trap enabled by such a temperature would not be limited by atoms tunneling between adjacent lattice sites, potentially allowing a measurement uncertainty below 10^-19.

The defining feature of a Bose-Einstein condensate is that its atoms behave very differently from what we normally expect. Instead of acting as independent particles, they all have the same (very low) energy and are coordinated with each other.

This is similar to the difference between photons (light particles) coming from the Sun, which may have many different wavelengths (energies) and oscillate independently, and those in laser beams, which all have the same wavelength and oscillate together.

In this new state of matter, the atoms act much more like a single, wave-like structure than a group of individual particles. Researchers have demonstrated wave-like interference patterns between two different Bose-Einstein condensates and even produce moving “BEC droplets.” The latter can be considered the atomic equivalent of a laser beam.

Scientists from the Faculty of Pure and Applied Sciences at The University of Tsukuba created scanning tunneling microscopy (STM) “snapshots” with a delay between frames much shorter than previously possible. By using ultrafast laser methods, they improved the time resolution from picoseconds to tens of femtoseconds, which may greatly enhance the ability of condensed matter scientists to study extremely rapid processes.

One picosecond, which is a mere trillionth of a second, is much shorter than the blink of an eye. For most applications, a movie camera that could record frames in a picosecond would be much faster than necessary. However, for scientists trying to understand the ultrafast dynamics of materials using STM, such as the rearrangement of atoms during a phase transition or the brief excitation of electrons, it can be painfully slow.

Now, a team of researchers at the University of Tsukuba designed an STM system based on a pump-probe method that can be used over a wide range of delay times as short as 30 femtoseconds (ACS Photonics, “Subcycle mid-infrared electric-field-driven scanning tunneling microscopy with a time resolution higher than 30 fs”).

Wolfgang “Wolfi” Mittig and Yassid Ayyad began their search for dark matter—also referred to as the missing mass of the universe—in the heart of an atom.

An atom is the smallest component of an element. It is made up of protons and neutrons within the nucleus, and electrons circling the nucleus.

Two-dimensional van der Waals materials have been the focus of work by numerous research groups for some time. Standing just a few atomic layers thick, these structures are produced in the laboratory by combining atom-thick layers of different materials (in a process referred to as “atomic Lego”).

Interactions between the stacked layers allow the heterostructures to exhibit properties that the individual constituents lack.

Continue reading “Coupling of electron-hole pairs” »

Physicists from Japan and the U.S. used atoms about 3 billion times colder than interstellar space to open a portal to an unexplored realm of quantum magnetism.

“Unless an alien civilization is doing experiments like these right now, anytime this experiment is running at Kyoto University it is making the coldest fermions in the universe,” said Rice University’s Kaden Hazzard, corresponding theory author of a study published on September 1, 2022, in the journal Nature Physics.

As the name implies, Nature Physics is a peer-reviewed, scientific journal covering physics and is published by Nature Research. It was first published in October 2005 and its monthly coverage includes articles, letters, reviews, research highlights, news and views, commentaries, book reviews, and correspondence.

❤️ Check out Weights & Biases and sign up for a free demo here: https://wandb.com/papers.

📝 The paper “A Fast Unsmoothed Aggregation Algebraic Multigrid Framework for the Large-Scale Simulation of Incompressible Flow” is available here:
http://computationalsciences.org/publications/shao-2022-multigrid.html.

Continue reading “A 1,000,000,000 Particle Simulation! 🌊” »

Circa 2018 face_with_colon_three Quantum storage.

A broadband-light storage technique using the Autler–Townes effect is demonstrated in a system of cold Rb atoms. It overcomes both inherent and technical limitations of the established schemes for high-speed and long-lived optical quantum memories.