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In quantum physics, Fermi’s golden rule, also known as the golden rule of time-dependent perturbation theory, is a formula that can be used to calculate the rate at which an initial quantum state transitions into a final state, which is composed of a continuum of states (a so-called “bath”). This valuable equation has been applied to numerous physics problems, particularly those for which it is important to consider how systems respond to imposed perturbations and settle into stationary states over time.

Fermi’s golden rule specifically applies to instances in which an initial quantum state is weakly coupled to a continuum of other final states, which overlap its energy. Researchers at the Centro Brasileiro de Pesquisas Físicas, Princeton University, and Universität zu Köln have recently set out to investigate what happens when a quantum state is instead coupled to a set of discrete final states with a nonzero mean level spacing, as observed in recent many-body physics studies.

“The decay of a quantum state into some continuum of final states (i.e., a ‘bath’) is commonly associated with incoherent decay processes, as described by Fermi’s golden rule,” Tobias Micklitz, one of the researchers who carried out the study, told Phys.org. “A standard example for this is an excited atom emitting a photon into an infinite vacuum. Current date experimentations, on the other hand, routinely realize composite systems involving quantum states coupled to effectively finite size reservoirs that are composed of discrete sets of final states, rather than a continuum.”

Immunizing bees against pesticides.

‘We wanted to develop a strategy to detoxify managed pollinators and found we can do it by incorporating it into their food, senior author Minglin Ma, a biomaterials engineer at Cornell University told Chemistry World.

“Managed bee colonies are constantly in need of being replenished due to losses. This relieves the stress for beekeepers to meet the ever-increasing demand for pollination,” James Webb, also a co-author of the study, told Salon by email.

Continue reading “Antidote saved 100% of bees from lethal pesticide” »

Quantum physics is strange. At least, it is strange to us, because the rules of the quantum world, which govern the way the world works at the level of atoms and subatomic particles (the behavior of light and matter, as the renowned physicist Richard Feynman put it), are not the rules that we are familiar with — the rules of what we call “common sense.”

The quantum rules, which were mostly established by the end of the 1920s, seem to be telling us that a cat can be both alive and dead at the same time, while a particle can be in two places at once. But to the great distress of many physicists, let alone ordinary mortals, nobody (then or since) has been able to come up with a common-sense explanation of what is going on. More thoughtful physicists have sought solace in other ways, to be sure, namely coming up with a variety of more or less desperate remedies to “explain” what is going on in the quantum world.

These remedies, the quanta of solace, are called “interpretations.” At the level of the equations, none of these interpretations is better than any other, although the interpreters and their followers will each tell you that their own favored interpretation is the one true faith, and all those who follow other faiths are heretics. On the other hand, none of the interpretations is worse than any of the others, mathematically speaking. Most probably, this means that we are missing something. One day, a glorious new description of the world may be discovered that makes all the same predictions as present-day quantum theory, but also makes sense. Well, at least we can hope.

Quantum science has not only deepened human understanding of the structure of matter and its microscopic interactions, but also introduced a new paradigm of computing and information science—quantum computing and quantum simulation. Quantum informatics research has won the 2022 Nobel Prize in Physics.

Among many quantum computing and simulation platforms, Rydberg Atom Arrays is considered the most promising system to show quantum superiority among many programmable quantum simulator platforms in recent years due to its largest number of qubits and highest experimental accuracy.

Such optical lattices consist of individual neutral alkaline-earth atoms with significant dipole moments trapped in arrays of microscopic dipole traps, which can be optically moved at will to make desired lattice geometry. Each atom can be excited to its Rydberg state, and a pair of excited states interact through their dipole moments via a long-range interaction.

Quantum entanglement is the binding together of two particles or objects, even though they may be far apart – their respective properties are linked in a way that’s not possible under the rules of classical physics.

It’s a weird phenomenon that Einstein described as “spooky action at a distance”, but its weirdness is what makes it so fascinating to scientists. In a 2021 study, quantum entanglement was directly observed and recorded at the macroscopic scale – a scale much bigger than the subatomic particles normally associated with entanglement.

The dimensions involved are still very small from our perspective – the experiments involved two tiny aluminum drums one-fifth the width of a human hair – but in the realm of quantum physics they’re absolutely huge.

A team of researchers from the University of Warsaw in Poland, the Institute Pascal CNRS in France, the Military University of Technology in Poland and the British University of Southampton has shown that it is possible to control the so-called exceptional points. For the first time, physicists also observed the annihilation of exceptional points from different degeneracy points. You can read about the discovery that may contribute to the creation of modern optical devices in the latest Nature Communications.

The universe around us is made of elementary particles, most of which have their antiparticles. When a particle and an antiparticle, that is, matter and antimatter, meet each other, annihilation occurs. Physicists have long been able to produce quasiparticles and quasiantiparticles—elementary excitations: charge, vibration, energy—trapped in matter, most often in crystals or liquids.

“The world of quasiparticles can be very complicated, although paradoxically, the quasiparticles themselves help simplify the description of quantum phenomena,” explains Jacek Szczytko from the Faculty of Physics at the University of Warsaw.

Information variations in a chain-like system are associated to energy transactions with the environment, which can take place reversibly or irreversibly, with a lower theoretical energy limit^22,23. Fluctuations as a consequence of pure computations are on the order of the thermal level (i.e., similar to kT, being k the Boltzmann constant and T the absolute temperature), according to Landauer’s principle. Such energies are negligible at routine human scales but become significant when the size of the system is nanoscopic or smaller, because the work and heat it generates also compare with the thermal level. Small systems are based on nanostructures, including individual molecules and arrangements of atoms, such as biological and quantum systems.

Fluctuation theorems have appeared in recent years explaining quantitatively energy imbalances between forward and reverse pathways or between equilibrium and non-equilibrium processes^24,25. They have been tested experimentally^26,27,28, mostly in biomolecular systems analyzed on a one-by-one basis²⁹. Most of these theorems establish relations among thermodynamic potentials for general systems, often with no specific insight into information theory. This theory, in turn, deals with spatially-indexed, 1-dimensional arrangements of symbols, which may not be necessarily associated to a time order. Recent generalizations separate the role of information and feedback control^30,31, but still the interpretation of non-Markovianity, irreversibility and reversibility in terms of purely informational operations such as reading, writing and error correction^32,33 remains obscured.

Here, we analyze energy exchanges associated to the symbolic management of a sequence of characters, without reference to the physical construction of the chain. Just by considering reversibility at the single sequence level and conservation laws, we next present two pairs of fluctuations equalities in the creation of information sequences, which use depends on energy exchange constraints. Our analysis integrates key information concepts, namely, reading, writing, proof reading and editing in the thermodynamic description of a string of symbols with information.

Results from two leading dark matter experiments—XENONnT and PandaX-4T—rule out an enigmatic signal detected in 2020 and set new constraints on dark matter particle candidates consisting of light fermions, respectively.

Over the past decade, physicists have repeatedly scrutinized tanks containing tons of liquid xenon, hoping to spot the flashes of light that might indicate a collision between a dark matter particle and a xenon atom (see Viewpoint: Dark Matter Still at Large). Most of these studies were dedicated to detecting so-called weakly interacting massive particles (WIMPs), a leading dark matter candidate with a mass greater than 10 GeV. Now researchers have sifted through a new set of data for a much lighter prize: fermionic dark matter with a mass of a few tens of MeV [1]. Although the team found no signal beyond the expected background level, they have set the strongest constraints yet on models of sub-GeV fermionic dark matter.

The dataset is the first obtained by the PandaX-4T experiment at the China Jinping Underground Laboratory. The PandaX team searched this data for evidence of a beyond-the-standard-model interaction in which a fermionic dark matter particle is absorbed by the nucleus of a xenon atom. After the absorption, the xenon nucleus should recoil while emitting either a neutrino or an antineutrino. The interaction should also cause an energy deposition in the form of photons and electrons, which would register on photodetectors at the ends of the tank. Unlike the scattering of WIMPs, which is predicted to produce a broad-spectrum energy deposition, the absorption by nuclei of fermionic dark matter particles should deposit energy only in a narrow range.

The data collected so far represent the equivalent of exposing 0.6 tons of liquid xenon to hypothetical fermionic dark matter for one year. When PandaX-4T concludes in 2025, it will have achieved a cumulative exposure 10 times greater, generating even stronger constraints on theory.