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Physicists Successfully Carry Out Controlled Transport of Stored Light

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著者: BeauHD
schwit1 shares a report from Phys.Org: A team of physicists led by Professor Patrick Windpassinger at Johannes Gutenberg University Mainz (JGU) has successfully transported light stored in a quantum memory over a distance of 1.2 millimeters. They have demonstrated that the controlled transport process and its dynamics has only little impact on the properties of the stored light. The researchers used ultra-cold rubidium-87 atoms as a storage medium for the light as to achieve a high level of storage efficiency and a long lifetime. The controlled manipulation and storage of quantum information as well as the ability to retrieve it are essential prerequisites for achieving advances in quantum communication and for performing corresponding computer operations in the quantum world. Optical quantum memories, which allow for the storage and on-demand retrieval of quantum information carried by light, are essential for scalable quantum communication networks. In their recent publication, Professor Patrick Windpassinger and his colleagues have described the actively controlled transport of such stored light over distances larger than the size of the storage medium. Some time ago, they developed a technique that allows ensembles of cold atoms to be transported on an 'optical conveyor belt' which is produced by two laser beams. The advantage of this method is that a relatively large number of atoms can be transported and positioned with a high degree of accuracy without significant loss of atoms and without the atoms being unintentionally heated. The physicists have now succeeded in using this method to transport atomic clouds that serve as a light memory. The stored information can then be retrieved elsewhere. Refining this concept, the development of novel quantum devices, such as a racetrack memory for light with separate reading and writing sections, could be possible in the future. The findings have been published in the journal Physical Review Letters.

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The First Room-Temperature Superconductor Has Finally Been Found

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著者: BeauHD
Joe2020 shares a report from Science News: Now, scientists have found the first superconductor that operates at room temperature -- at least given a fairly chilly room. The material is superconducting below temperatures of about 15 degrees Celsius (59 degrees Fahrenheit), physicist Ranga Dias of the University of Rochester in New York and colleagues report October 14 in Nature. The team's results "are nothing short of beautiful," says materials chemist Russell Hemley of the University of Illinois at Chicago, who was not involved with the research. However, the new material's superconducting superpowers appear only at extremely high pressures, limiting its practical usefulness. Dias and colleagues formed the superconductor by squeezing carbon, hydrogen and sulfur between the tips of two diamonds and hitting the material with laser light to induce chemical reactions. At a pressure about 2.6 million times that of Earth's atmosphere, and temperatures below about 15 degrees C, the electrical resistance vanished. That alone wasn't enough to convince Dias. "I didn't believe it the first time," he says. So the team studied additional samples of the material and investigated its magnetic properties. Superconductors and magnetic fields are known to clash -- strong magnetic fields inhibit superconductivity. Sure enough, when the material was placed in a magnetic field, lower temperatures were needed to make it superconducting. The team also applied an oscillating magnetic field to the material, and showed that, when the material became a superconductor, it expelled that magnetic field from its interior, another sign of superconductivity. The scientists were not able to determine the exact composition of the material or how its atoms are arranged, making it difficult to explain how it can be superconducting at such relatively high temperatures. Future work will focus on describing the material more completely, Dias says.

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