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Category: quantum physics – Page 47

Concept (the Dyson Scenario), proposed by Freeman Dyson in 1979, proposes a means by which an immortal society of intelligent beings in an open universe may escape the prospect of the heat death of the universe by extending subjective time to infinity even though expending only a finite amount of energy.

Bremermann’s limit can be invoked to deduce that the amount of time to perform a computation on 1 bit is inversely proportional to the change in energy in the system. As a result, the amount of computations that can be performed grows over time. The increase in energy available slows logarithmically, but never stops. Therefore, for any specific computation rate that requires a specific amount of energy, there will come a time when that energy is available to be used.

The intelligent beings would begin by storing a finite amount of energy. They then use half (or any fraction) of this energy to power their thought. When the energy gradient created by unleashing this fraction of the stored fuel was exhausted, the beings would enter a state of zero-energy-consumption until the universe cooled. Once the universe had cooled sufficiently, half of the remaining half (one quarter of the original energy) of the intelligent beings’ fuel reserves would once again be released, powering a brief period of thought once more. This would continue, with smaller and smaller amounts of energy being released. As the universe cooled, the thoughts would be slower and slower, but there would still be an infinite number of them. In 1998 it was discovered that the expansion of the universe appears to be accelerating rather than decelerating due to a positive cosmological constant, implying that any two regions of the universe will eventually become permanently separated from one another. Dyson noted that \.

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Neutron stars are some of the densest objects in the universe. They are the core of a collapsed megastar that went supernova, have a typical radius of 10 km—just slightly more than the altitude of Mt. Everest—and their density can be several times that of atomic nuclei.

Physicists love extreme objects like this because they require them to stretch their theories into new realms and see if they are confirmed or if they break, requiring new thinking and new science.

For the first time, researchers have used lattice quantum chromodynamics to study the interior of neutron stars, obtaining a new maximum bound for the speed of sound inside the star and a better understanding of how pressure, temperature and other properties there relate to one another.

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The quantum rules shaping molecular collisions are now coming into focus, offering fresh insights for chemistry and materials science. When molecules collide with surfaces, a complex exchange of energy takes place between the molecule and the atoms composing the surface. But beneath this dizzying complexity, quantum mechanics, which celebrates its 100th anniversary this year, governs the process.

Quantum interference, in particular, plays a key role. It occurs when different pathways that a molecule can take overlap, resulting in specific patterns of interaction: some pathways amplify each other, while others cancel out entirely. This “dance of waves” affects how molecules exchange energy and momentum with surfaces, and ultimately how efficiently they react.

But until now, observing in collisions with heavier molecules like methane (CH4) was nearly impossible because of the overwhelming number of pathways available for the system to take en route to the different collision outcomes. Many scientists have even wondered if all quantum effects would always “wash out” for these processes so that the simpler laws of classical physics, which apply to everyday, “macroscopic” objects, might be enough to describe them.

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Many next-generation quantum devices rely on single-photon emitters based on optically active defects in solids, known as color centers. Understanding their properties is fundamental to developing novel quantum technologies.

Now, in a study published in APL Materials, a multi-institutional research team led by Osaka University has sought to clarify the origin of the extremely bright color centers at the interface between (SiO2) and silicon carbide (SiC).

Previous research has demonstrated a range of factors that can play a role in the formation of these interface color centers, including the effect of annealing after oxidation. However, the energy level structure (i.e., the electronic transitions taking place) responsible for luminescence, a crucial factor for understanding the origin of color centers, was completely unknown.

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A new formula that connects a material’s magnetic permeability to spin dynamics has been derived and tested 84 years after the debut of its electric counterpart.

If antiferromagnets, altermagnets, and other emerging quantum materials are to be harnessed for spintronic devices, physicists will need to better understand the spin dynamics in these materials. One possible path forward is to exploit the duality between electric and magnetic dynamics expressed by Maxwell’s equations. From this duality, one could naively expect mirror-like similarities in the behavior of electric and magnetic dipoles. However, a profound difference between the quantized lattice electric excitations—such as phonons—and spin excitations—such as paramagnetic and antiferromagnetic spin resonances and magnons—has now been unveiled in terms of their corresponding contributions to the static electric susceptibility and magnetic permeability. Viktor Rindert of Lund University in Sweden and his collaborators have derived and verified a formula that relates a material’s magnetic permeability to the frequencies of magnetic spin resonances [1].

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Scientists have unlocked a new understanding of mesoporous silicon, a nanostructured version of the well-known semiconductor. Unlike standard silicon, its countless tiny pores give it unique electrical and thermal properties, opening up potential applications in biosensors, thermal insulation, photovoltaics, and even quantum computing.

Performing computation using quantum-mechanical phenomena such as superposition and entanglement.

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Quantum computers could be made with fewer overall components, thanks to technology inspired by Schrödinger’s cat. A team of researchers from Amazon Web Services has used “bosonic cat qubits,” to improve the ability of quantum computers to correct errors. The demonstration of quantum error correction requiring reduced hardware overheads is reported in a paper published in Nature.

The system uses so-called cat (qubits are the quantum equivalent to classical computing bits), which are designed to be resistant against certain types of noise and errors that might disrupt the output of quantum systems. This approach requires fewer overall components to achieve quantum error correction than other designs.

Quantum computers are prone to errors, which limits their potential to exceed the capabilities of classical computers at certain tasks. Quantum error correction is a method that helps reduce errors by spreading information over multiple qubits, allowing the identification and correction of errors without corrupting the computation. However, most approaches to quantum error correction typically rely on a large number of additional qubits to provide sufficient protection against errors, potentially leading to an overall decrease in efficiency.

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