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Category: quantum physics

Researchers from the University of Nebraska-Lincoln and the University of California, Berkeley, have developed a new photonic device that could get scientists closer to the “holy grail” of finding the global minimum of mathematical formulations at room temperature. Finding that illusive mathematical value would be a major advancement in opening new options for simulations involving quantum materials.

Many scientific questions depend heavily on being able to find that mathematical value, said Wei Bao, Nebraska assistant professor of electrical and computer engineering. The search can be challenging even for modern computers, especially when the dimensions of the parameters—commonly used in quantum physics—are extremely large.

Until now, researchers could only do this with polariton optimization devices at extremely low temperatures, close to about minus 270 degrees Celsius. Bao said the Nebraska-UC Berkeley team “has found a way to combine the advantages of light and matter at suitable for this great optimization challenge.”

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Stanene is a topological insulator comprised of atoms typically arranged in a similar pattern to those inside graphene. Stanene films have been found to be promising for the realization of numerous intriguing physics phases, including the quantum spin Hall phase and intrinsic superconductivity.

Some also suggested that these films could host topological , a state that is particularly valuable for the development of quantum computing technology. So far, however, topological edge states in stanene had not been reliably and consistently observed in experimental settings.

Researchers at Shanghai Jiao Tong University, the University of Science and Technology of China, Henan University, Zhengzhou University, and other institutes in China have recently demonstrated the coexistence of topological edge states and superconductivity in one to five-layer stanene films placed on the Bi(111) . Their observations, outlined in a paper published in Physical Review Letters, could have important implications for the development of Stanene-based quantum devices.

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Researchers in the US have demonstrated the presence of quantum mechanical effects in acid–base interactions, challenging the Brønsted–Lowry theory. The resultant short hydrogen bond is stabilised by a delocalised proton, which rapidly shuttles between the acid and base molecules and is characterised by highly unusual spectral features.

The Brønsted–Lowry theory was proposed in 1923 and explains acid–base interactions in terms of proton transfer. This theory is one of the cornerstones of chemical understanding and is amongst the first principles taught to school students. But despite a growing appreciation for the limitations of traditional thinking, the surprising discovery of a quantum component to such fundamental reactivity was entirely serendipitous.

‘It was luck,’ admits Daniel Kuroda of Louisiana State University, one of the principal researchers involved in the study. ‘We were looking at the structure of liquids … and saw this paper [about an acid–base mixture] with close to the conductivity of sulfuric acid but no ionisation. We wanted to see what the structure was … so we started looking into the project and then realised that clearly we have something very different.’

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Using a newly developed technique, scientists at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg have measured the very small difference in the magnetic properties of two isotopes of highly charged neon in an ion trap with previously inaccessible accuracy. Comparison with equally extremely precise theoretical calculations of this difference allows a record-level test of quantum electrodynamics (QED). The agreement of the results is an impressive confirmation of the standard model of physics, allowing conclusions regarding the properties of nuclei and setting limits for new physics and dark matter.

Electrons are some of the most fundamental building blocks of the matter we know. They are characterized by some very distinctive properties, such as their negative charge and the existence of a very specific intrinsic angular momentum, also called spin. As a charged particle with spin, each electron has a magnetic moment that aligns itself in a magnetic field similar to a compass needle. The strength of this magnetic moment, given by the so-called g-factor, can be predicted with extraordinary accuracy by quantum electrodynamics. This calculation agrees with the experimentally measured g-factor to within 12 digits, one of the most precise matches of theory and experiment in physics to date. However, the magnetic moment of the electron changes as soon as it is no longer a “free” particle, i.e., unaffected by other influences, but instead is bound to an atomic nucleus, for example.

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Qubits are a basic building block for quantum computers, but they’re also notoriously fragile—tricky to observe without erasing their information in the process. Now, new research from the University of Colorado Boulder and the National Institute of Standards and Technology (NIST) could be a leap forward for handling qubits with a light touch.

In the study, a team of physicists demonstrated that it could read out the signals from a type of qubit called a superconducting qubit using , and without destroying the qubit at the same time.

The group’s results could be a major step toward building a , the researchers say. Such a network would link up dozens or even hundreds of quantum chips, allowing engineers to solve problems that are beyond the reach of even the fastest supercomputers around today. They could also, theoretically, use a similar set of tools to send unbreakable codes over long distances.

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Electrons and their behavior pose fascinating questions for quantum physicists, and recent innovations in sources, instruments and facilities allow researchers to potentially access even more of the information encoded in quantum materials.

However, these research innovations are producing unprecedented—and until now, indecipherable—volumes of data.

“The information content in a piece of material can quickly exceed the total information content in the Library of Congress, which is about 20 terabytes,” said Eun-Ah Kim, professor of physics in the College of Arts and Sciences, who is at the forefront of both research and harnessing the power of to analyze data from quantum material experiments.

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