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Category: quantum physics – Page 224

The universe is governed by four known fundamental forces: gravity, electromagnetism, the weak force, and the strong force. The strong force is responsible for dynamics on an extremely small scale, within and between the individual nucleons of atomic nuclei and between the constituents – quarks and gluons – that make up those nucleons. The strong force is described by a theory called Quantum Chromodynamics (QCD). One of the key details of this theory, known as “asymptotic freedom”, is responsible for both the subatomic scale of the strong force and the significant theoretical difficulties that the strong force has presented to physicists over the past 50 years.

Given the complexity of the strong force, experimental physicists have often led the research frontier and made discoveries that theorists are still trying to describe. This pattern is distinct from many other areas of physics, where experimentalists mostly search for and confirm, or exclude, theoretical predictions. One of the QCD areas where experimentalists have led progress is in the description of the collective behavior of systems with many bodies interacting via the strong force. An example of such a system is the quark-gluon plasma (QGP). A few microseconds after the Big Bang, the universe is supposed to have existed in such a state. The way the universe evolved in these brief moments and the structure that subsequently developed over billions of years is studied, in part, through experimental research on collective QCD effects. This briefing describes a recent exciting development in that research. To better understand the results, we begin with a series of analogies.

Imagine you are on a large university campus. You observe student movements in the middle of a busy exam period and find that the number of students entering the library in the morning is related to the number of students leaving in the evening. Perhaps this indicates some conserved quantity, like the number of students at the school. Each student in the library wants enough room to lay out their supplies and textbooks and get comfortable while studying. The library is nearly full and the students are evenly distributed across all the floors and halls of the library to ensure they have ample space. Recognizing and quantifying correlations like these can be useful for studying collective systems. By counting students “here” you can predict how many students are “there”, or by counting students “now” you can predict how many students you will get “later”. In this example, you may have insight into basic temporal and spatial correlations.

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We experimentally demonstrate optoacoustic cooling via stimulated Brillouin-Mandelstam scattering in a 50 cm long tapered photonic crystal fiber. For a 7.38 GHz acoustic mode, a cooling rate of 219 K from room temperature has been achieved. As anti-Stokes and Stokes Brillouin processes naturally break the symmetry of phonon cooling and heating, resolved sideband schemes are not necessary. The experiments pave the way to explore the classical to quantum transition for macroscopic objects and could enable new quantum technologies in terms of storage and repeater schemes.

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Color mixing is the process of combining two or more colors: red and green make yellow, blue and red make purple, red and green and blue make white. This process of mixing colors is the basis for the future of solid-state lighting. While currently white light is achieved by phosphor down-conversion, LED color mixing actually has a higher theoretical maximum efficiency, which is needed in order to achieve the 2035 DOE energy efficiency goals.

Despite the potential efficiency of color-mixed LED sources, there exists one significant challenge: green. The “green gap” is described as the lack of suitable green LEDs. Current green LEDs are made from state-of-the-art hexagonal III-nitride but only reach one third of the efficiency goals laid out in the 2035 DOE roadmap.

In a new study, researchers at the University of Illinois Urbana-Champaign have found a potential path to fill the green gap and report a green-emitting cubic III-nitride active layer with 32% internal quantum efficiency (IQE), which is more than 6 times higher efficiency than what is reported in the literature for conventional cubic active layers.

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An international team of researchers from Leibniz University Hannover (Germany) and the University of Strathclyde in Glasgow (United Kingdom) has disproved a previously held assumption about the impact of multiphoton components in interference effects of thermal fields (e.g., sunlight) and parametric single photons (generated in non-linear crystals). The journal Physical Review Letters has published the team’s research.

“We experimentally proved that the interference effect between thermal light and parametric single photons also leads to with the background field. For this reason, the background cannot simply be neglected and subtracted from calculations, as has been the case up to now,” says Prof. Dr. Michael Kues, Head of the Institute of Photonics and member of the Board of the PhoenixD Cluster of Excellence at Leibniz University Hannover.

The leading scientist was Ph.D. student Anahita Khodadad Kashi, who performs research on photonic quantum information processing at the Institute of Photonics. She investigated how the visibility of the so-called Hong-Ou-Mandel effect, a quantum , is affected by multiphoton contamination.

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Researchers at HZB have created an innovative technique to precisely measure minuscule temperature variations as small as 100 microkelvin in the thermal Hall effect, overcoming previous limitations caused by thermal noise. By applying this technique to terbium titanate, the team showcased its effectiveness in producing consistent and dependable outcomes. This advancement in measuring the thermal Hall effect sheds light on the behavior of coherent multi-particle states in quantum materials, particularly their interactions with lattice vibrations, known as phonons.

The laws of quantum physics apply to all materials. However, in so-called quantum materials, these laws give rise to particularly unusual properties. For example, magnetic fields or changes in temperature can cause excitations, collective states, or quasiparticles that are accompanied by phase transitions to exotic states. This can be utilised in a variety of ways, provided it can be understood, managed, and controlled: For example, in future information technologies that can store or process data with minimal energy requirements.

The thermal Hall effect (THE) plays a key role in identifying exotic states in condensed matter. The effect is based on tiny transverse temperature differences that occur when a thermal current is passed through a sample and a perpendicular magnetic field is applied (see Figure 2). In particular, the quantitative measurement of the thermal Hall effect allows us to separate the exotic excitations from conventional behavior.

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By Chuck Brooks

Computing paradigms as we know them will exponentially change when artificial intelligence is combined with classical, biological, chemical, and quantum computing. Artificial intelligence might guide and enhance quantum computing, run in a 5G or 6G environment, facilitate the Internet of Things, and stimulate materials science, biotech, genomics, and the metaverse.

Computers that can execute more than a quadrillion calculations per second should be available within the next ten years. We will also rely on clever computing software solutions to automate knowledge labor. Artificial intelligence technologies that improve cognitive performance across all envisioned industry verticals will support our future computing.

Advanced computing has a fascinating and mind-blowing future. It will include computers that can communicate via lightwave transmission, function as a human-machine interface, and self-assemble and teach themselves thanks to artificial intelligence. One day, computers might have sentience.

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PRESS RELEASE — It is hard to imagine our lives without networks such as the internet or mobile phone networks. In the future, similar networks are planned for quantum technologies that will enable the tap-proof transmission of messages using quantum cryptography and make it possible to connect quantum computers to each other.

Like their conventional counterparts, such quantum networks require memory elements in which information can be temporarily stored and routed as needed. A team of researchers at the University of Basel led by Professor Philipp Treutlein has now developed such a memory element, which can be micro-fabricated and is, therefore, suitable for mass production. Their results were recently published in the scientific journal Physical Review Letters.

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