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Category: quantum physics

Clean crystal surface lets single molecules hit ultimate quantum limit

Scientists at the Max Planck Institute for the Science of Light (MPL) have developed a technique for interrogating molecules on surfaces with spectroscopic precision, thereby reaching the ultimate quantum limit for the first time. With their findings, published in Science, the researchers open new opportunities for the study of molecule-surface interactions and molecular quantum technologies.

Many optical quantum technologies rely on nanoscale objects, such as atoms or molecules, that interact strongly with light. These quantum emitters are used for generating single photons, storing quantum information and entanglement distribution, processes that find application in quantum communication and computation.

To investigate these emitters individually, researchers need to keep them in one place for a long time. This is usually achieved by either trapping them in a vacuum or placing them inside a bulk material. Quantum emitters located on a surface would create new opportunities to manipulate their functionalities by “touching them,” for example, with an atomically sharp tip, as is used in scanning tunneling microscopy (STM) and atomic force microscopy (AFM).

Semiconductor quantum dots ‘reawaken’ predicted Rabi oscillations, boosting quantum control

Physicists at Paderborn University have, for the first time, experimentally demonstrated the so-called “return” of Rabi oscillations in semiconductor quantum dots. The phenomenon, which was first predicted theoretically in 2007, describes the decrease in the emission intensity of the quantum dots, which are initially damped by interactions with the lattice vibrations of a solid (phonons).

Only through sufficiently strong optical excitation can the original intensity be restored and the oscillation “reawakened”—an effect that previously existed only in idealized theoretical models and has now been proven.

The results, published in Physical Review Letters, mark a decisive step toward scalable quantum applications.

Trios of quantum particles form checkerboard layouts when particle density hits sweet spot

Trions form when three particles, like quarks or electrons, come together. This formation occurs in quantum particles in nuclear physics, semiconductors and magnets, and understanding its behavior can be challenging. Rice University’s Kaden Hazzard and his team recently developed a theory on how these formations occur and behave, which was published in Physical Review Letters.

“Our theory sheds light on how trions form and interact with each other,” said Hazzard, associate professor of physics and astronomy and corresponding author on the paper. “It predicts the strength of the interactions needed to form the trions, and that, after formation, they arrange themselves in a checkerboard pattern.”

If you imagine a space full of equal amounts of red, blue and yellow balls, a trion would form when a red, blue and yellow ball all stuck to each other, Hazzard explained. Once all the balls, or particles, are bound together, he was curious about how these trions would arrange themselves in space.

A thermodynamic approach to gravity could explain cosmic acceleration without dark energy

Gravity, the force that attracts objects toward each other, is currently framed by Albert Einstein’s theory of general relativity. This framework describes gravity as the curvature of spacetime, the invisible four-dimensional fabric of the universe.

While general relativity is now the central theory of gravity, it fails to explain some cosmological phenomena and mysteries, such as the so-called cosmological constant problem. This is the unexplained mismatch between the observed energy of empty space and the far greater values predicted by quantum theories.

In a recent paper published in Physical Review Letters, researchers at Imperial College London tried to frame gravity using thermodynamics, the framework that describes how energy and heat transform. Their study builds on a seminal paper by theoretical physicist Ted Jacobson, published more than three decades ago.

Quantum waves reveal one-sided motion marking elusive critical states

Sound waves, light waves and other types of waves, generally spread freely through space and over time. In 1958, physicist Philip W. Anderson first described a phenomenon via which irregularities or other sources of disorder in materials would prevent waves from propagating freely, which is now known as Anderson localization.

In quantum systems, one can observe quantum states that are spread throughout a system (i.e., extended), confined to a small region (i.e., localized) or somewhere between the two (i.e., critical). Critical quantum states have so far proved to be very difficult to identify and study using Anderson’s localization theory.

Researchers at the International Quantum Academy and Southern University of Science and Technology in China recently set out to further explore critical quantum states in a quantum processor based on superconducting qubits.

Copper thin films reveal ballistic electron transport that could reshape future chip wiring

A joint research team has experimentally observed ballistic transport in single-crystalline copper thin films, demonstrating that ballistic transport is achievable in an industry-standard metal at interconnect-relevant dimensions. The study, titled “Ballistic transport in nanodevices based on single-crystalline Cu thin films,” was published in Nature Communications.

Ballistic transport refers to a phenomenon in which electrons travel along straight trajectories without scattering. Until now, this behavior has mainly been observed in special quantum materials such as graphene or semiconductor nanostructures. In copper, where electron scattering is pronounced, realizing ballistic transport has been considered practically impossible.

In this study, the team led by Professor Gil-Ho Lee of the Department of Physics at POSTECH, Professor Emeritus Se-Young Jeong of the School of Transdisciplinary Engineering at Pusan National University and Professor Seong-Gon Kim of the Department of Physics and Astronomy at Mississippi State University, experimentally demonstrated that ballistic transport can occur in structures with a thickness of 80 nm and a linewidth of 150 nm, dimensions comparable to those used in semiconductor interconnects.

Scientists measure hidden quantum forces that could power a new generation of pharmaceutical drugs

It’s one thing to design a pharmaceutical drug. It’s another to know if and why it actually works; not on paper or in a computer model, but inside the chaotic world of living systems, where proteins twist into shape, atoms constantly pull and push each other apart, and molecular interactions are the difference between health and disease.

For decades, scientists have known that these interactions are driven by hidden quantum forces. The problem is that, like working blindfolded, they’ve never been able to measure them directly in biological systems.

Now, that era of blindfolded work may be ending.

The Topological Lower Bound of Boltzmann Entropy: Resolving the Pure Top Boundary Condition through Proton Phase-Locking (v.01)

We establish a fundamental, non-zero lower bound for thermodynamic entropy by mapping Ludwig Boltzmann’s classical relation onto the rigid topological boundaries of GLAB chronal dynamics. In standard statistical mechanics, the number of microstates is treated as an abstract mathematical variable capable of reducing to unity , which phenomenologically implies an absolute zero entropy state . We demonstrate that this boundary condition is physically unattainable because the minimal, topologically closed space-phase cell possesses an irreversible internal structure dictated by the free proton configuration. Characterizing the stable proton as an asymmetric quantum “pure top” subject to the Janibekov instability, we prove that it inherently occupies a degenerate phase space composed of 2 intrinsic spin projections and 3 spatial rotational axes. This yields a strict, immutable minimum statistical weight of. Consequently, the absolute minimum entropy of any isolated domain in our universe is bounded by the Proton Constant:. We mathematically demonstrate that if this lower bound were violated, the phase-locking mechanism governing stellar nucleosynthesis would collapse, rendering the existence of periodic nuclear cycles and stable matter impossible.

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