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Category: particle physics – Page 173

A new article published in Opto-Electronic Science reviews the fundamentals and applications of optically trapped optical nanoparticles. Optical nanoparticles are one of the key elements of photonics. They not only allow optical imaging of a plethora of systems (from cells to microelectronics), but also behave as highly sensitive remote sensors.

The success of optical tweezers in isolating and manipulating individual optical nanoparticles has been recently demonstrated. This has opened the door to high-resolution, single-particle scanning and sensing.

The most relevant results in the quickly growing fields of optical trapping of individual optical nanoparticles are summarized by this article. According to different materials and their , the optical nanoparticles are classified into five families: , lanthanide-doped nanoparticles, polymeric nanoparticles, semiconductor nanoparticles, and nanodiamonds. For each case, the main advances and applications have been described.

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Scientists using the Telescope Array in Utah detected the second highest-energy cosmic ray ever. The singular subatomic particle was equivalent to dropping a brick on someone’s toe from waist height.

The Telescope Array comprises 507 surface detector stations arranged in a square grid located outside of Delta, Utah. It has been utilized to observe over 30 ultra-high-energy cosmic rays. These extreme cosmic rays have left scientists baffled about what produces them. The latest observation, as well as the highest-ever recorded event known as the Oh-My-God particle, appears to have originated from the Local Void, an empty area of space bordering the Milky Way galaxy.

“The particles are so high energy, they shouldn’t be affected by galactic and extra-galactic magnetic fields,” remarked John Matthews, Telescope Array co-spokesperson and co-author of the study. “You should be able to point to where they come from in the sky. But in the case of the Oh-My-God particle and this new particle, you trace its trajectory and there’s nothing high energy enough to have produced it. That’s the mystery — what the heck is going on?”

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In 1991, the University of Utah Fly’s Eye experiment detected the highest-energy cosmic ray ever observed. Later dubbed the Oh-My-God particle, the cosmic ray’s energy shocked astrophysicists. Nothing in our galaxy had the power to produce it, and the particle had more energy than was theoretically possible for cosmic rays traveling to Earth from other galaxies. Simply put, the particle should not exist.

The Telescope Array has since observed more than 30 ultra-high-energy , though none approaching the Oh-My-God-level energy. No observations have yet revealed their origin or how they are able to travel to Earth.

On May 27, 2021, the Telescope Array experiment detected the second-highest extreme-energy . At 2.4 × 1020eV, the energy of this single subatomic particle is equivalent to dropping a brick on your toe from waist height. Led by the University of Utah (the U) and the University of Tokyo, the experiment used the Telescope Array, which consists of 507 surface detector stations arranged in a square grid that covers 700 km2 (~270 miles2) outside of Delta, Utah, in the state’s West Desert.

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In recent years, physicists have been trying to better understand how quantum information spreads in systems of interacting particles—a phenomenon often referred to as “scrambling.” Scrambling in closed systems, physical systems that can only exchange energy with degrees of freedom within the system, is a characteristic feature of chaotic many-body quantum dynamics.

In open systems, which can exchange both energy and matter with their surroundings, scrambling is influenced by various additional factors, including noise and errors. While the effects of these additional influences are well-documented, leading for example to decoherence, how they affect scrambling remains poorly understood.

Two researchers from the University of California Berkeley (UC Berkeley) and Harvard University recently introduced a new framework, published in Physical Review Letters, that provides a universal picture for how information scrambling occurs in open quantum systems. Their framework offers a particularly simple viewpoint on how to understand and model the propagation of errors in an open quantum system and might already help to explain some previously puzzling observations gathered in magnetic resonance experiments.

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In 1960, DARPA funded three university-based Inderdisciplinary Laboratories (IDLs) that opened the way toward an enormous field of research and development known today as materials science and engineering. In this video, DARPA program managers, DARPA-funded researchers, and a Naval Research Laboratory scientist tell this field-building story as it unfolded over the past six decades, all the while delivering breakthroughs in the way materials are designed, processed, and deployed to push technologies forward. Intelligent processing of materials (IPM), accelerated insertion of materials (AIM), and integrated computational materials engineering (ICME) are among the specific programs detailed in the video. DARPA is currently developing technologies that enable the crafting of new materials with unprecedented properties by designing and controlling matter from atoms on up to human-scale systems.

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Experiments with an unconventional superconductor show that a change in the properties of the material’s electrons can, unexpectedly, cause the material to become dramatically less stiff.

Electrons flowing through a crystal lattice don’t usually get to call the shots: their behavior is generally set by the lattice structure. But certain materials exhibit an electron–lattice coupling that allows the conduction electrons to influence the lattice behavior. This electron version of “wagging the dog” is predicted to be quite weak, making it a surprise that experiments with an unconventional superconductor now uncover a large electron-driven softening of the material’s lattice [1]. The finding could provide new insights into the mechanisms underlying unconventional superconductivity.

The lattice in a crystalline material is a periodic framework of atoms held together by electrostatic bonds. That framework dictates the properties of electrons moving through the material. For example, if the lattice is altered by applying mechanical strain or by adding dopant atoms, the electron momenta will correspondingly change, which can affect the material’s electronic band structure.

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Three research groups have exploited the nuclear spins of ytterbium-171 to manipulate qubits before they are read out—an approach that could lead to efficient error-correction schemes for trapped-atom computing platforms.

Quantum computing on neutral-atom platforms has reached remarkable milestones in the past two decades. However, researchers have yet to overcome a key barrier to the realization of a neutral-atom-based quantum computer: the efficient correction of errors. In principle that barrier can be lowered with so-called midcircuit operations. These operations involve probing the quantum state of “ancilla” qubits without disturbing nearby “data” qubits used for computation. The ancilla qubit measurements can indicate whether the data qubits have undergone faulty operations, allowing for the data qubits to be corrected midcircuit—that is, during the execution of the computation rather than after its completion. Now three independent research groups have achieved midcircuit operation, or made progress toward this goal, with a novel choice of atom: ytterbium-171 (171 Yb) [1– 3].

A neutral-atom qubit platform consists of a two-dimensional (2D) array of atoms trapped by optical tweezers—tightly focused laser beams whose wavelengths are tuned far away from the atomic transitions. The size of the traps, limited by diffraction, is typically about 1 µm. Thanks to the large electric-dipole force from the focused laser and to a high vacuum, the atoms can stay trapped for as long as tens of seconds.

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Heisenberg’s uncertainty principle limits the precision with which two observables that do not commute with each other can be simultaneously measured. The Wigner-Araki-Yanase (WAY) theorem goes further. If observables A and B do not commute, and if observable A is conserved, observable B cannot be measured with arbitrary precision even if A is not measured at all. In its original 1960 formulation, the WAY theorem applied only to observables, such as spin, whose possible values are discrete and bounded. Now Yui Kuramochi of Kyushu University and Hiroyasu Tajima of the University of Electro-Communications—both in Japan—have proven that the WAY theorem also encompasses observables, such as position, that are continuous and unbounded [1]. Besides resolving the decades-long problem of how to deal with such observables, the extension will likely find practical applications in quantum optics.

The difficulty of extending the WAY theorem arose from how an unbounded observable L is represented: as an infinite-dimensional matrix with unbounded eigenvalues. To tame the problem, Kuramochi and Tajima avoided considering L directly. Instead, they looked at an exponential function of L, which forms a one-parameter unitary group. Although the exponential function is also unbounded, its spectrum of eigenvalues is contained within the complex plane’s unit circle. Thanks to that boundedness, Kuramochi and Tajima could go on to use off-the-shelf techniques from quantum information to complete their proof.

Because momentum is conserved, the extended WAY theorem implies that a particle’s position cannot be measured with arbitrary precision even if its momentum is not measured simultaneously. Similar pairs of observables crop up in quantum optics. Kuramochi and Tajima anticipate that their theorem could be useful in setting limits on the extent to which quantum versions of transmission protocols can outperform the classical ones.

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