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Category: quantum physics – Page 558

New research by Surrey’s Nuclear Physics Group has shown that it’s possible to mimic excited quantum states with exotic nuclei, opening up a host of opportunities for next generation radioactive beam facilities, such as the Facility for Rare Isotope Beams (FRIB).

The results of the project – which was a collaboration between the University of Surrey and Michigan State University, USA – were published in Physical Review Letters in January 2021. The lead author was Surrey PhD student Samuel Hallam, who also studied for his undergraduate physics degree at Surrey.

One of the biggest challenges in nuclear physics is measuring reactions that occur on excited quantum states, such as are found in exploding stars due to extreme temperature and density. Until now, physicists have had to determine the rates at which nuclear reactions occur in these conditions through theoretical estimates.

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Ultrafast electron microscope in Argonne’s Center for Nanoscale Materials. Credit: Argonne National Laboratory.

Ultrafast electron microscope opens up new avenues for the development of sensors and quantum devices.

Everyone who has ever been to the Grand Canyon can relate to having strong feelings from being close to one of nature’s edges. Similarly, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have discovered that nanoparticles of gold act unusually when close to the edge of a one-atom.

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Researchers have created a scalable quantum computing platform that has been shrunk down to the size of a penny, which would serve as the basis for a quantum computer that can achieve quantum speeds while using far fewer devices than current designs.

The team hopes their research, published in Nature Communications, will help push quantum computing forward in the constant pursuit of use in real-world applications.

Over the past few years, quantum computing has gone from science fiction to a realistic technology that may see use in the next few decades. While quantum teleportation and even quantum computer chips have been demonstrated previously, the technology is still a long way off seeing real-world use.

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Complementarity relation of wave-particle duality is analyzed quantitatively with entangled photons as path detectors.

The twenty-first century has undoubtedly been the era of quantum science. Quantum mechanics was born in the early twentieth century and has been used to develop unprecedented technologies which include quantum information, quantum communication, quantum metrology, quantum imaging, and quantum sensing. However, in quantum science, there are still unresolved and even inapprehensible issues like wave-particle duality and complementarity, superposition of wave functions, wave function collapse after quantum measurement, wave function entanglement of the composite wave function, etc.

To test the fundamental principle of wave-particle duality and complementarity quantitatively, a quantum composite system that can be controlled by experimental parameters is needed. So far, there have been several theoretical proposals after Neils Bohr introduced the concept of “complementarity” in 1,928 but only a few ideas have been tested experimentally, with them detecting interference patterns with low visibility. Thus, the concept of complementarity and wave-particle duality still remains elusive and has not been fully confirmed experimentally yet.

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Maryland-based IonQ has unveiled a new kind of chip in its quest to scale up its type of quantum computer technology. Its computers calculate using the quantum states of ions electromagnetically trapped in the space near a chip. Previous traps were made using silicon chipmaking processes, but the company has now switched to an evaporated glass trap technology—a way of constructing micrometer-scale features in fused silica glass often used to make microfluidic chips. Its previous trap technology, the company says, could not have supported IonQ’s new quantum architecture, which is based on multiple chains of ion-based qubits. Ultimately, IonQ executives say, the glass chip’s reconfigurable chains of ions will allow for computers with qubits that number in the triple digits.

“The purpose of an ion trap is to move ions around with precision, hold them in the environment, and get out of the way of the quantum operation,” explains Jason Amini, who led the evaporated glass trap team at IonQ. The 3D glass and metal structure Amini’s team constructed does all three better than its previous chips could, Amini says. Stray electric fields from charge on the silicon-based chip could destabilize the ions’ delicate quantum states, reducing the fidelity of quantum computation. But the evaporated glass design “hides any material that could hold charge,” he says. The effect is a more stable trap that computes better.

Another advantage, Amini says, is that the trap could be shaped to “get out of the way” of quantum operations. In an ion trap computer the ions’ quantum states are manipulated by zapping them with lasers. “We have to bring a lot of laser beams over the surface,” says Amini. The glass chip is “shaped to allow lasers to come through and address the device.”

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“We are thinking about volumes in millions.”

“We are thinking about volumes in millions, not the thousands that people talk about with quantum computers based on superconducting,” said Marcus Doherty, chief science officer.

Quantum Brilliance delivered its first system to the Pawsey Supercomputing Centre in Australia earlier this year and is beginning to ship to other commercial customers.

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Physics World

An ultra-precise quantum sensor based on trapped beryllium ions is up to 20 times better at detecting weak electric fields than previous atomic devices. By introducing entanglement between the collective motion of the ions and their electronic spin, a collaboration led by the US National Institute of Standards and Technology (NIST) demonstrated that the ion displacement sensitivity in the presence of an electric field was an order of magnitude greater than for classical protocols with trapped ions. With further improvements, the technology could even be used in the search for dark matter.

Quantum sensors can detect and measure signals that are undetectable with their classical counterparts. They are thus a promising tool in many areas of fundamental science, including biological imaging as well as physics. Of the many different systems being pursued as quantum sensors, trapped ions could be particularly favourable due to experimenters’ precise control over their parameters and their ability to introduce entanglement into the system.

The Ion Storage Group at NIST, led by John Bollinger, decided to exploit these properties for measuring very weak electric fields. “We realized our ion crystal can be incredibly sensitive to electric fields,” explains Kevin Gilmore, a former graduate research assistant at NIST and the lead author of a paper describing the research. “We found a protocol that exploits our ability to produce quantum entangled states and is very sensitive to small displacements of the ions driven by weak electric fields. It’s a neat demonstration of how quantum effects can be used to gain an advantage over classical systems.”

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Water is the most abundant yet least understood liquid in nature. It exhibits many strange behaviors that scientists still struggle to explain. While most liquids get denser as they get colder, water is most dense at 39 degrees Fahrenheit, just above its freezing point. This is why ice floats to the top of a drinking glass and lakes freeze from the surface down, allowing marine life to survive cold winters. Water also has an unusually high surface tension, allowing insects to walk on its surface, and a large capacity to store heat, keeping ocean temperatures stable.

Now, a team that includes researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Stockholm University in Sweden have made the first direct observation of how in water tug and push neighboring water molecules when they are excited with laser light. Their results, published in Nature today, reveal effects that could underpin key aspects of the microscopic origin of water’s strange properties and could lead to a better understanding of how water helps proteins function in living organisms.

“Although this so-called nuclear quantum effect has been hypothesized to be at the heart of many of water’s strange properties, this experiment marks the first time it was ever observed directly,” said study collaborator Anders Nilsson, a professor of chemical physics at Stockholm University. “The question is if this quantum effect could be the missing link in theoretical models describing the anomalous properties of water.”

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