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Category: quantum physics – Page 353

Sometimes to make big breakthroughs, you have to start very small.

One way that scientists can get the most out of certain is by fabricating that generate new properties at the material’s surfaces and edges. Cornell researchers used the relatively straightforward process of thermomechanical nanomolding to create single-crystalline nanowires that can enable metastable phases that would otherwise be difficult to achieve with conventional methods.

“We’re really interested in this synthesis method of nanomolding because it allows us to make many different kinds of materials into nanoscale quickly and easily, yet with some of the control that other nanomaterial synthesis methods lack, particularly control over the morphology and the size,” said Judy Cha, professor of materials science and engineering in Cornell Engineering, who led the project.

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A team of physicists has illuminated certain properties of quantum systems by observing how their fluctuations spread over time. The research offers an intricate understanding of a complex phenomenon that is foundational to quantum computing—a method that can perform certain calculations significantly more efficiently than conventional computing.

“In an era of it’s vital to generate a precise characterization of the systems we are building,” explains Dries Sels, an assistant professor in New York University’s Department of Physics and an author of the paper, which is published in the journal Nature Physics. “This work reconstructs the full state of a quantum liquid, consistent with the predictions of a quantum field theory—similar to those that describe the fundamental particles in our universe.”

Sels adds that the breakthrough offers promise for technological advancement.

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face_with_colon_three year 2012.

(Phys.org)—Both high-valued diamond and low-prized graphite consist of exactly the same carbon atoms. The subtle but nevertheless important difference between the two materials is the geometrical configuration of their building blocks, with large consequences for their properties. There is no way, any kind of matter could be diamond and graphite at the same time.

However, this limitation does not hold for quantum matter, as a team of the Quantum Many-Body Physics Division of Prof. Immanuel Bloch (Max-Planck-Institute of Quantum Optics and Ludwig-Maximilians-Universität München) was now able to demonstrate in experiments with ultracold quantum gases. Under the influence of laser beams single atoms would arrange to clear geometrical structures (Nature, November 1st, 2012). But in contrast to classical crystals all possible configurations would exist at the same time, similar to the situation of Schrödinger’s cat which is in a superposition state of both “dead” and “alive”. The observation was made after transferring the particles to a highly excited so-called Rydberg-state. “Our experiment demonstrates the potential of Rydberg gases to realise exotic states of matter, thereby laying the basis for quantum simulations of, for example, quantum magnets,” Professor Immanuel Bloch points out.

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We introduce quantum circuit learning (QCL) as an emerging regression algorithm for chemo-and materials-informatics. The supervised model, functioning on the rule of quantum mechanics, can process linear and smooth non-linear functions from small datasets (100 records). Compared with conventional algorithms, such as random forest, support vector machine, and linear regressions, the QCL can offer better predictions with some one-dimensional functions and experimental chemical databases. QCL will potentially help the virtual exploration of new molecules and materials more efficiently through its superior prediction performances.

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The “spooky action at a distance” that once unnerved Einstein may be on its way to being as pedestrian as the gyroscopes that currently measure acceleration in smartphones.

Quantum entanglement significantly improves the precision of sensors that can be used to navigate without GPS, according to a new study in Nature Photonics.

“By exploiting entanglement, we improve both measurement sensitivity and how quickly we can make the measurement,” said Zheshen Zhang, associate professor of electrical and computer engineering at the University of Michigan and co-corresponding author of the study. The experiments were done at the University of Arizona, where Zhang was working at the time.

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There are high expectations that quantum computers may deliver revolutionary new possibilities for simulating chemical processes. This could have a major impact on everything from the development of new pharmaceuticals to new materials. Researchers at Chalmers University have now, for the first time in Sweden, used a quantum computer to undertake calculations within a real-life case in chemistry.

“Quantum computers could in theory be used to handle cases where electrons and atomic nuclei move in more complicated ways. If we can learn to utilize their full potential, we should be able to advance the boundaries of what is possible to calculate and understand,” says Martin Rahm, Associate Professor in Theoretical Chemistry at the Department of Chemistry and Chemical Engineering, who has led the study.

Within the field of quantum chemistry, the laws of quantum mechanics are used to understand which are possible, which structures and materials can be developed, and what characteristics they have. Such studies are normally undertaken with the help of super computers, built with conventional logical circuits. There is however a limit for which calculations conventional computers can handle. Because the laws of quantum mechanics describe the behavior of nature on a subatomic level, many researchers believe that a quantum computer should be better equipped to perform molecular calculations than a conventional computer.

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Hydrogen, the most abundant element in the universe, is found everywhere from the dust filling most of outer space to the cores of stars to many substances here on Earth. This would be reason enough to study hydrogen, but its individual atoms are also the simplest of any element with just one proton and one electron. For David Ceperley, a professor of physics at the University of Illinois Urbana-Champaign, this makes hydrogen the natural starting point for formulating and testing theories of matter.

Ceperley, also a member of the Illinois Quantum Information Science and Technology Center, uses computer simulations to study how interact and combine to form different phases of matter like solids, liquids, and gases. However, a true understanding of these phenomena requires , and quantum mechanical simulations are costly. To simplify the task, Ceperley and his collaborators developed a machine learning technique that allows quantum mechanical simulations to be performed with an unprecedented number of atoms. They reported in Physical Review Letters that their method found a new kind of high-pressure solid hydrogen that past theory and experiments missed.

“Machine learning turned out to teach us a great deal,” Ceperley said. “We had been seeing signs of new behavior in our previous simulations, but we didn’t trust them because we could only accommodate small numbers of atoms. With our machine learning model, we could take full advantage of the most accurate methods and see what’s really going on.”

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