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Category: particle physics – Page 116

To operate reliably a quantum computer needs to correct the errors introduced into the system by noise in its hardware. Error-correction approaches typically use “logical” qubits, which are qubits made up of as many as a few thousand “physical” qubits. Logical qubits are much less error prone than physical qubits, but the hardware overhead complicates the realization of fault-tolerant quantum computers based on this approach. Now a team led by Harry Levine and Oskar Painter of the Amazon Web Services Center for Quantum Computing in California has demonstrated a new qubit design with built-in error-detection ability [1]. Painter says this qubit could serve as an alternative building block for error-correcting schemes, substantially reducing complexity.

The demonstrated qubit is an “erasure” qubit, one in which the most likely error type involves the loss, or erasure, of the qubit’s state [2]. This error is easier to spot and correct for than other qubit errors, such as those that flip the qubit’s state. Researchers have previously demonstrated erasure qubits made from single atoms. The new study makes the leap to transmons, the superconducting qubit used in the quantum processors developed by Google and IBM.

The erasure qubit of Levine, Painter, and colleagues contains three transmons. Two of the transmons are coupled together and store a qubit’s worth of information in a single, shared microwave photon. The third transmon reveals the loss of the photon—the erasure—through a shift in its operating frequency. The researchers show that in this qubit erasure errors are the dominant error type and can be detected in real time. The researchers now plan to use their new qubit to build logic gates and error-correcting circuits.

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Astrophysicists have a cerium problem—models predict that certain stars should contain much less of this heavy element than astrophysical observations find. Recently performed experiments at CERN’s neutron time-of-flight (n_TOF) facility have widened the gap between theory and observations by 20% [1]. The researchers behind the work say that the results highlight the need for high-accuracy measurements of the nuclear properties of atoms, as well as for updated nucleosynthesis models of element formation. “Our experiment made the problem worse,” says Simone Amaducci of the INFN Laboratori Nationali del Sud, Italy. “That was unexpected, but it’s also interesting because it means there is something we don’t understand about how nucleosynthesis happens.”

Most of the Universe’s heavier elements form in stars via one of the so-called neutron-capture processes, in which an atomic nucleus absorbs one or more neutrons. In the slow neutron-capture process, or “s process,” the absorptions are spread out in time. As such, each absorption event results in either a stable nucleus with the same number of protons but one additional neutron or an unstable nucleus, which then radioactively decays to produce the nucleus of the next element in the periodic table—the one with one additional proton.

Using currently available models of the s process, researchers have correctly predicted the abundances of elements as heavy as barium (56 protons), lanthanum (57 protons), praseodymium (59 protons), and neodymium (60 protons) in stars that are known to be enriched via the s process. But the models appear to break down for cerium (58 protons), as the abundance predictions for this element in some low-mass, low-metallicity globular cluster stars have disagreed by up to 30% with observations. “This discrepancy is very strange, as the theory works for the neighboring elements,” says Sergio Cristallo, a team member who works on problems related to neutron capture at the National Institute of Astrophysics in Italy. “There is nothing in the models that should cause such a discrepancy just for one element.”

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Researchers have revolutionized quantum sensing with an algorithm that simplifies the assessment of Quantum Fisher Information, thereby enhancing the precision and utility of quantum sensors in capturing minute phenomena.

Quantum sensors help physicists understand the world better by measuring time passage, gravity fluctuations, and other effects at the tiniest scales. For example, one quantum sensor, the LIGO gravitational wave detector, uses quantum entanglement (or the interdependence of quantum states between particles) within a laser beam to detect distance changes in gravitational waves up to one thousand times smaller than the width of a proton!

LIGO isn’t the only quantum sensor harnessing the power of quantum entanglement. This is because entangled particles are generally more sensitive to specific parameters, giving more accurate measurements.

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Everyone loves a two-for-one deal—even physicists looking to tackle unanswered questions about the cosmos. Now, scientists at the Department of Energy’s SLAC National Accelerator Laboratory are getting just such a twofer: Particle detectors originally developed to look for dark matter are now in a position to be included aboard the Line Emission Mapper (LEM), a space-based X-ray probe mission proposed for the 2030s.

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Particles colliding in accelerators produce numerous cascades of secondary particles. The electronics processing the signals avalanching in from the detectors then have a fraction of a second in which to assess whether an event is of sufficient interest to save it for later analysis. In the near future, this demanding task may be carried out using algorithms based on AI, the development of which involves scientists from the Institute of Nuclear Physics of the PAS.

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Scientists from Massey University in New Zealand, the University of Mainz in Germany, Sorbonne University in France, and the Facility for Rare Isotope Beams (FRIB) discuss the limit of the periodic table and revising the concept of the “island of stability” with recent advances in superheavy element research. Their work first appeared in Nature Reviews Physics.

In addition to the Nature Reviews Physics, Physics Reports has published a review on the atomic electronic structure theory for superheavy elements.

What is the heaviest bound nucleus and the heaviest bound atom and what are their properties? The nuclei of chemical elements with more than 103 protons are labeled as “superheavy.” They are part of a vast unknown territory of these nuclei that scientists are trying to uncover. Exploring this uncharted territory provides prospects for discoveries that connect the broad areas of science.

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For the past hundred years, it has been widely recognized through X-ray and electron diffraction measurements that graphene interlayers can only accommodate a single layer of alkali metal. Each layer being fully filled by single layer alkali metal atoms is considered the theoretical charging limit.

However, there have been no reports of studies directly observing the atomic arrangement of interlayer alkali metals and verifying whether graphene layers can only accommodate a single layer of alkali metal atoms or whether other techniques can achieve higher density or multiple layers of alkali metals.

The research team developed a technique to insert dense alkali metals between graphene layers. Utilizing a high-performance low-voltage (60 kV) , they have successfully observed the arrangement structure of alkali metal atoms between the graphene layers. The alkali metals are found densely packed in a two-layer structure in both bilayer graphene and in the surface layer graphite due to the flexible extension ability of their interlayer spacing.

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Scientists have referred to black holes as cosmic objects that consume whatever comes into them but do not allow anything to escape from the inside. Stephen Hawking assumes that a black hole could be a portal to another universe. While addressing about 1,000 people at Harvard in 2015, Hawkings analyzed the groundbreaking theory with these words.

“Blackholes aren’t the eternal prisons they were once thought. Things can get out of a black hole, both from the outside and possibly through another universe. So, if you ever feel you’re in a black hole, don’t give up. There’s a way out.”

Scientists listening to the renowned astrophysicist were fascinated with his explanations. Keep in mind that Stephen Hawkings came up with Hawking’s radiation theory which revolutionized our understanding of black holes. According to this theory, Black holes thermally generate and emit subatomic particles until they lose their energy and proceed to evaporate. Based on this theory, Hawkings says that black holes are not entirely black and they don’t last for eternity.

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Whether in listening to music or pushing a swing in the playground, we are all familiar with resonances and how they amplify an effect—a sound or a movement, for example. However, in high-intensity circular particle accelerators, resonances can be an inconvenience, causing particles to fly off their course and resulting in beam loss. Predicting how resonances and non-linear phenomena affect particle beams requires some very complex dynamics to be disentangled.

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