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Category: quantum physics

The fundamental laws of physics are based on symmetries that determine the interactions between charged particles, among other things. Using ultracold atoms, researchers at Heidelberg University have experimentally constructed the symmetries of quantum electrodynamics. They hope to gain new insights for implementing future quantum technologies that can simulate complex physical phenomena. The results of the study were published in the journal Science.

The theory of quantum electrodynamics deals with the electromagnetic interaction between electrons and light particles. It is based on so-called U symmetry, which, for instance, specifies the movement of particles. With their experiments, the Heidelberg physicists, under the direction of Junior Professor Dr. Fred Jendrzejewski, seek to advance the efficient investigation of this complex physical theory. They recently experimentally realized one elementary building block. “We see the results of our research as a major step toward a platform built from a chain of properly connected for a large-scale implementation of quantum in ,” explains Prof. Jendrzejewski, who directs an Emmy Noether group at Heidelberg University’s Kirchhoff Institute for Physics.

According to the researchers, one possible application would be developing large-scale quantum devices to simulate complex physical phenomena that cannot be studied with particle accelerators. The elementary block developed for this study could also benefit the investigation of problems in materials research, such as in strongly interacting systems that are difficult to calculate.

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Data transmission that works by means of magnetic waves instead of electric currents: For many scientists, this is the basis of future technologies that will make transmission faster and individual components smaller and more energy-efficient. Magnons, the particles of magnetism, serve as moving information carriers. Almost 15 years ago, researchers at the University of Münster (Germany) succeeded for the first time in achieving a novel quantum state of magnons at room temperature—a Bose-Einstein condensate of magnetic particles, also known as a ‘superatome,’ i.e. an extreme state of matter that usually occurs only at very low temperatures.

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University researchers have discovered that quantum communications are possible with submerged objects in turbulent water. The revelation means it might someday be possible for the National Command Authority to use quantum communications to securely communicate with underwater submarines, particularly those that make up part of the nuclear triad.

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Using machine learning three groups, including researchers at IBM and DeepMind, have simulated atoms and small molecules more accurately than existing quantum chemistry methods. In separate papers on the arXiv preprint server the teams each use neural networks to represent wave functions of electrons that surround the molecules’ atoms. This wave function is the mathematical solution of the Schrödinger equation, which describes the probabilities of where electrons can be found around molecules. It offers the tantalising hope of ‘solving chemistry’ altogether, simulating reactions with complete accuracy. Normally that goal would require impractically large amounts of computing power. The new studies now offer a compromise of relatively high accuracy at a reasonable amount of processing power.

Each group only simulates simple systems, with ethene among the most complex, and they all emphasise that the approaches are at their very earliest stages. ‘If we’re able to understand how materials work at the most fundamental, atomic level, we could better design everything from photovoltaics to drug molecules,’ says James Spencer from DeepMind in London, UK. ‘While this work doesn’t achieve that quite yet, we think it’s a step in that direction.’

Two approaches appeared on arXiv just a few days apart in September 2019, both combining deep machine learning and Quantum Monte Carlo (QMC) methods. Researchers at DeepMind, part of the Alphabet group of companies that owns Google, and Imperial College London call theirs Fermi Net. They posted an updated preprint paper describing it in early March 2020.1 Frank Noé’s team at the Free University of Berlin, Germany, calls its approach, which directly incorporates physical knowledge about wave functions, PauliNet.2

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Underwater quantum links are possible across 30 meters (100 feet) of turbulent water, scientists have shown. Such findings could help to one day secure quantum communications for submarines.

Quantum cryptography exploits the quantum properties of particles such as photons to help encrypt and decrypt messages in a theoretically unhackable way. Scientists worldwide are now endeavoring to develop satellite-based quantum communications networks for a global real-time quantum Internet.

In addition to beaming quantum communications signals across the air, through a vacuum, and within fiber optic cables, researchers have investigated establishing quantum communications links through water. Such work could lead to secure quantum communications between submarines and surface vessels, and with other subs, aircraft, or even satellites.

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When people say quantum computing is “hot” right now they are most definitely talking metaphorically; today’s leading devices have to operate at close to absolute zero. Now two research groups have demonstrated technology that run s 15 times hotter, which could be a big step towards making the devices affordable and practical.

The reason quantum computers have to be run at such low temperatures is that the quantum states they rely on are incredibly fragile, and the slightest disturbance can cause the information encoded in them to be lost. To prevent this these devices are chilled to near absolute zero, where vibrations and thermal fluctuation are almost non existent.

But reaching these temperature requires incredibly powerful refrigeration technology, and it can easily cost millions of dollars to keep even today’s experimental devices at operating temperatures.

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Your phone’s GPS, the Wi-Fi in your house and communications on aircraft are all powered by radio-frequency, or RF, waves, which carry information from a transmitter at one point to a sensor at another. The sensors interpret this information in different ways. For example, a GPS sensor uses the angle at which it receives an RF wave to determine its own relative location. The more precisely it can measure the angle, the more accurately it can determine location.

In a new paper published in Physical Review Letters, University of Arizona engineering and optical sciences researchers, in collaboration with engineers from General Dynamics Mission Systems, demonstrate how a combination of two techniques—radio frequency photonics sensing and quantum metrology—can give sensor networks a previously unheard-of level of precision. The work involves transferring information from electrons to photons, then using to increase the photons’ sensing capabilities.

“This quantum sensing paradigm could create opportunities to improve GPS systems, astronomy laboratories and biomedical imaging capabilities,” said Zheshen Zhang, assistant professor of materials science and engineering and , and principal investigator of the university’s Quantum Information and Materials Group. “It could be used to improve the performance of any application that requires a of sensors.”

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O,.o circa 2007.

Theoretical physicists at the University of St. Andrews have created ‘incredible levitation effects’ by engineering the force of nature which normally causes objects to stick together by quantum force. By reversing this phenomenon, known as ‘Casimir force’, the scientists hope to solve the problem of tiny objects sticking together in existing novel nanomachines.

Professor Ulf Leonhardt and Dr Thomas Philbin of the University’s School of Physics & Astronomy believe that they can engineer the Casimir force of quantum physics to cause an object to repel rather than attract another in a vacuum.

Casimir force (discovered in 1948 and first measured in 1997) can be demonstrated in a gecko’s ability to stick to a surface with just one toe. However, it can cause practical problems in nanotechnology, and ways of preventing tiny objects from sticking to each other is the source of much interest.

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