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In quantum physics, a vacuum is not empty, but rather steeped in tiny fluctuations of the electromagnetic field. Until recently it was impossible to study those vacuum fluctuations directly. Researchers at ETH Zurich have developed a method that allows them to characterize the fluctuations in detail.

Emptiness is not really empty – not according to the laws of quantum physics, at any rate. The vacuum, in which classically there is supposed to be “nothing,” teems with so-called vacuum fluctuations according to quantum mechanics. Those are small excursions of an electromagnetic field, for instance, that average out to zero over time but can deviate from it for a brief moment. Jérôme Faist, professor at the Institute for Quantum Electronics at ETH in Zurich, and his collaborators have now succeeded in characterizing those vacuum fluctuations directly for the first time.

“The vacuum fluctuations of the electromagnetic field have clearly visible consequences, and among other things, are responsible for the fact that an atom can spontaneously emit light,” explains Ileana-Cristina Benea-Chelmus, a recently graduated Ph.D. student in Faists laboratory and first author of the study recently published in the scientific journal Nature. “To measure them directly, however, seems impossible at first sight. Traditional detectors for light such as photodiodes are based on the principle that light particles – and hence energy – are absorbed by the detector. However, from the vacuum, which represents the lowest energy state of a physical system, no further energy can be extracted.”

Continue reading “Fluc­tu­a­tions in the void” »

Ultra-secure online communications, completely indecipherable if intercepted, is one step closer with the help of a recently published discovery by University of Oregon physicist Ben Alemán.

Alemán, a member of the UO’s Center for Optical, Molecular, and Quantum Science, has made artificial atoms that work in ambient conditions. The research, published in the journal Nano Letters, could be a big step in efforts to develop secure quantum communication networks and all-optical quantum computing.

“The big breakthrough is that we’ve discovered a simple, scalable way to nanofabricate artificial atoms onto a microchip, and that the artificial atoms work in air and at room temperature,” said Alemán, also a member of the UO’s Materials Science Institute.

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In quantum mechanics, the Heisenberg uncertainty principle prevents an external observer from measuring both the position and speed (referred to as momentum) of a particle at the same time. They can only know with a high degree of certainty either one or the other—unlike what happens at large scales where both are known. To identify a given particle’s characteristics, physicists introduced the notion of quasi-distribution of position and momentum. This approach was an attempt to reconcile quantum-scale interpretation of what is happening in particles with the standard approach used to understand motion at normal scale, a field dubbed classical mechanics.

In a new study published in EPJ ST, Dr. J.S. Ben-Benjamin and colleagues from Texas A&M University, USA, reverse this approach; starting with quantum mechanical rules, they explore how to derive an infinite number of quasi-distributions, to emulate the classical mechanics approach. This approach is also applicable to a number of other variables found in quantum-scale particles, including particle spin.

For example, such quasi-distributions of position and momentum can be used to calculate the quantum version of the characteristics of a gas, referred to as the second virial coefficient, and extend it to derive an infinite number of these quasi-distributions, so as to check whether it matches the traditional expression of this physical entity as a joint distribution of position and momentum in classical mechanics.

Continue reading “Infinite number of quantum particles gives clues to big-picture behavior at large scale” »

While Wang’s team was the first in the world to unveil a detailed concept design for an LHC successor, there are three other competing proposals – one in Japan and two from CERN.

One team in Beijing is leading the charge to create the next generation of giant particle colliders to unlock the mysteries of the fundamental forces of the universe.

Tohoku University researchers have developed an algorithm that enhances the ability of a Canadian-designed quantum computer to more efficiently find the best solution for complicated problems, according to a study published in the journal Scientific Reports.

Quantum computing takes advantage of the ability of subatomic particles to exist in more than one state at the same time. It is expected to take modern-day computing to the next level by enabling the processing of more information in less time.

The D-Wave quantum annealer, developed by a Canadian company that claims it sells the world’s first commercially available quantum computers, employs the concepts of quantum physics to solve ‘combinatorial optimization problems.’ A typical example of this sort of problem asks the question: “Given a list of cities and the distances between each pair of cities, what is the shortest possible route that visits each city and returns to the original city?” Businesses and industries face a large range of similarly complex problems in which they want to find the optimal solution among many possible ones using the least amount of resources.

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In the 2018 movie Avengers: Infinity War, a scene featured Dr. Strange looking into 14 million possible futures to search for a single timeline in which the heroes would be victorious. Perhaps he would have had an easier time with help from a quantum computer. A team of researchers from Nanyang Technological University, Singapore (NTU Singapore) and Griffith University in Australia have constructed a prototype quantum device that can generate all possible futures in a simultaneous quantum superposition.

“When we think about the future, we are confronted by a vast array of possibilities,” explains Assistant Professor Mile Gu of NTU Singapore, who led development of the quantum algorithm that underpins the prototype “These possibilities grow exponentially as we go deeper into the future. For instance, even if we have only two possibilities to choose from each minute, in less than half an hour there are 14 million possible futures. In less than a day, the number exceeds the number of atoms in the universe.” What he and his research group realised, however, was that a quantum computer can examine all possible futures by placing them in a quantum superposition – similar to Schrödinger’s famous cat, which is simultaneously alive and dead.

To realise this scheme, they joined forces with the experimental group led by Professor Geoff Pryde at Griffith University. Together, the team implemented a specially devised photonic quantum information processor in which the potential future outcomes of a decision process are represented by the locations of photons – quantum particles of light. They then demonstrated that the state of the quantum device was a superposition of multiple potential futures, weighted by their probability of occurrence.

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Scientists from the U.S. Department of Energy’s Brookhaven National Laboratory, Stony Brook University, and DOE’s Energy Sciences Network (ESnet) are collaborating on an experiment that puts U.S. quantum networking research on the international map. Researchers have built a quantum network testbed that connects several buildings on the Brookhaven Lab campus using unique portable quantum entanglement sources and an existing DOE ESnet communications fiber network—a significant step in building a large-scale quantum network that can transmit information over long distances.

“In quantum mechanics, the physical properties of entangled particles remain associated, even when separated by vast distances. Thus, when measurements are performed on one side, it also affects the other,” said Kerstin Kleese van Dam, director of Brookhaven Lab’s Computational Science Initiative (CSI). “To date, this work has been successfully demonstrated with entangled photons separated by approximately 11 miles. This is one of the largest quantum entanglement distribution networks in the world, and the longest-distance entanglement experiment in the United States.”

This quantum networking testbed project includes staff from CSI and Brookhaven’s Instrumentation Division and Physics Department, as well as faculty and students from Stony Brook University. The project also is part of the Northeast Quantum Systems Center. One distinct aspect of the team’s work that sets it apart from other quantum networks being run in China and Europe—both long-committed to quantum information science pursuits—is that the entanglement sources are portable and can be easily mounted in standard data center computer server racks that are connected to regular fiber distribution panels.

Continue reading “Research team expands quantum network with successful long-distance entanglement experiment” »

Why does the observable universe contain virtually no antimatter? Particles of antimatter have the same mass but opposite electrical charge of their matter counterparts. Very small amounts of antimatter can be created in the laboratory. However, hardly any antimatter is observed elsewhere in the universe.

Physicists believe that there were equal amounts of matter and antimatter in the early history of the universe – so how did the antimatter vanish? A Michigan State University researcher is part of a team of researchers that examines these questions in an article recently published in Reviews of Modern Physics.

Jaideep Taggart Singh, MSU assistant professor of physics at the Facility for Rare Isotope Beams, or FRIB, studies atoms and molecules embedded in solids using lasers. Singh has a joint appointment in the MSU’s Department of Physics and Astronomy.

Continue reading “Time-reversal violation may explain abundance of matter over antimatter, physicist says” »

Stronger and more flexible than graphene, a single-atom layer of boron could revolutionize sensors, batteries, and catalytic chemistry.