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Category: particle physics – Page 276

If you’ve ever tried to carry on a conversation in a noisy room, you’ll be able to relate to the scientists and engineers trying to “hear” the signals from experimental quantum computing devices called qubits. These basic units of quantum computers are early in their development and remain temperamental, subject to all manner of interference. Stray “noise” can masquerade as a functioning qubit or even render it inoperable.

That’s why physicist Christian Boutan and his Pacific Northwest National Laboratory (PNNL) colleagues were in celebration mode recently as they showed off PNNL’s first functional superconducting qubit. It’s not much to look at. Its case—the size of a pack of chewing gum—is connected to wires that transmit signals to a nearby panel of custom radiofrequency receivers. But most important, it’s nestled within a shiny gold cocoon called a and shielded from stray . When the refrigerator is running, it is among the coldest places on Earth, so very close to absolute zero, less than 6 millikelvin (about −460 degrees F).

The extreme cold and isolation transform the sensitive superconducting device into a functional qubit and slow down the movement of atoms that would destroy the qubit state. Then, the researchers listen for a characteristic signal, a blip on their radiofrequency receivers. The blip is akin to radar signals that the military uses to detect the presence of aircraft. Just as traditional radar systems transmit and then listen for returning waves, the physicists at PNNL have used a low-temperature detection technique to “hear” the presence of a qubit by broadcasting carefully crafted signals and decoding the returning message.

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Breakthrough opens up new possibilities for the creation of next-generation materials.

A new way to self-assemble particles has been created by a team of physicists. This advance offers new promise for building complex and innovative materials at the microscopic level.

Self-assembly, introduced in the early 2000s, gives scientists a means to “pre-program” particles, which allows for the construction of materials without further human intervention. This is basically the microscopic equivalent of Ikea furniture that can assemble itself.

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Scientists managed to start the same chemical process that powers the Sun on August 8, 2021, by putting more electricity into a tiny gold capsule than the entire US electric system could handle.

It is extremely astonishing how the power of 192 laser beams sparked the same thermonuclear fire that fuels the Sun for a nanosecond.

The Sun produces energy by hurling hydrogen atoms together, generating helium in the process. We are now closer than ever to being able to harness chemical reactions with enough force to power the Sun. This is possible because fusion power technology has advanced.

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Circa 2019

Lodestone, a naturally-occurring iron oxide, was the first persistently magnetic material known to humans. The Han Chinese used it for divining boards 2,200 years ago; ancient Greeks puzzled over why iron was attracted to it; and, Arab merchants placed it in bowls of water to watch the magnet point the way to Mecca. In modern times, scientists have used magnets to read and record data on hard drives and form detailed images of bones, cells and even atoms.

Throughout this history, one thing has remained constant: Our magnets have been made from solid materials. But what if scientists could make magnetic devices out of liquids?

In a study published Thursday in Science, researchers managed to do exactly that.

Continue reading “This New Liquid Is Magnetic, and Mesmerizing” | >

Researchers have calculated the likelihood that a quantum state will decay when its evolution is inhibited by a dearth of final states.

Quantum systems are fragile, meaning a specific quantum state generally decays into other states over time. This decay process is formalized by Fermi’s golden rule (FGR), which in its traditional formalization applies when there exists an infinite continuum of states for the quantum system state to decay to—for example, when an excited atom emits a photon into a vacuum. Now Tobias Micklitz at the Brazilian Center for Research in Physics and colleagues have developed and solved a model showing how a quantum system evolves when its initial state is instead coupled to a finite set of states spread across discrete energy levels [1]. Micklitz says that their model could be the foundation for models of more complex, many-body quantum systems.

FGR-obeying systems occupy one end of a scale, where the coupling strength between the systems’ initial and final states is large relative to the energy gap between the various final states (zero for a continuum of states). At the other end of the scale, the coupling strength is much lower relative to this gap. A system that sits in this second regime remains in its initial state, as there are too few available final states for it to decay into.

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The concept of “symmetry” is essential to fundamental physics: a crucial element in everything from subatomic particles to macroscopic crystals. Accordingly, a lack of symmetry—or asymmetry—can drastically affect the properties of a given system.

Qubits, the quantum analog of computer bits for quantum computers, are extremely sensitive—the barest disturbance in a qubit system is enough for it to lose any it might have carried. Given this fragility, it seems intuitive that would be most stable in a symmetric environment. However, for a certain type of qubit—a molecular qubit—the opposite is true.

Researchers from the University of Chicago’s Pritzker School of Molecular Engineering (PME), the University of Glasgow, and the Massachusetts Institute of Technology have found that molecular qubits are much more stable in an asymmetric environment, expanding the possible applications of such qubits, especially as biological quantum sensors.

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Most mass in everyday matter around us resides in protons and neutrons inside the atomic nucleus. However, the lifetime of a free neutron—one not bounded to a nucleus—is unstable, decaying by a process called beta decay. For neutrons, beta decay involves the emission of a proton, an electron, and an anti-neutrino. Beta decay is a common process.

However, scientists have some significant uncertainties about the neutron lifetime and about the neutron decaying inside a nucleus that leads to a proton emission. This is called beta-delayed proton emission. There are only a few neutron-rich nuclei for which beta-delayed proton emission is energetically allowed. The radioactive nucleus beryllium-11 (11 Be), an isotope that consists of 4 and 7 , with its last neutron very weakly bound, is among those rare cases. Scientists recently observed a surprising large beta-delayed proton decay rate for 11 Be. Their work is published in Physical Review Letters.

The discovery of an exotic near-threshold that favors proton decay is a key for explaining the beta-delayed proton decay of 11 Be. The discovery is also a remarkable and not fully understood manifestation of quantum many-body physics. Many-body physics involves interacting . While scientists may know the physics that apply to each particle, the complete system can be too complex to understand.

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A team of physicists has created a new way to self-assemble particles—an advance that offers new promise for building complex and innovative materials at the microscopic level.

Self-assembly, introduced in the early 2000s, gives scientists a means to “pre-program” particles, allowing for the building of materials without further human intervention—the microscopic equivalent of Ikea furniture that can assemble itself.

The breakthrough, reported in the journal Nature, centers on emulsions—droplets of oil immersed in water—and their use in the self-assembly of foldamers, which are unique shapes that can be theoretically predicted from the sequence of droplet interactions.

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