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The gallium nitride purple surface-emitting laser with a power conversion efficiency of more than 20%. Credit: Tetsuya Takeuchi / Meijo University.

Gallium nitride (GaN) vertical-cavity surface-emitting lasers (VCSELs) are semiconductor laser diodes with promising applications in various fields, including adaptive headlights, retinal scanning displays, point-of-care testing systems, and high-speed visible light communication systems. Their high efficiency and low manufacturing costs make them especially appealing for these applications.

GaN-VCSELs are composed of two layers of special semiconductor mirrors, called distributed Bragg reflectors (DBRs), separated by active GaN-semiconductor layers, which form the optical resonant cavity, where laser light is generated. The length of this resonant cavity is crucial for controlling the target laser wavelength, called the resonance wavelength.

Ask anyone working in quantum computing and they may tell you they have been dealing with the frustratingly contrarian and intricately delicate state of entanglement since the beginning of time. However, a new study suggests this might be impossible. In fact, entanglement may have been absent in the earliest moments of the universe, researchers are reporting — a hypothesis that would — if validated — challenge our understanding of quantum mechanics and the nature of time itself.

The research, detailed in a paper by Jim Al-Khalili, of the University of Surrey and Eddy Keming Chen, University of California, San Diego and published on the pre-print server ArXiv, explores the so-called entanglement past hypothesis. In the study, the researchers explore why time only flows in one direction, a fundamental concept in both quantum physics and thermodynamics.

According to the researchers the concept of quantum entanglement, where two particles become so deeply linked that their properties seem to remain interconnected regardless of the distance between them, is central to modern quantum mechanics. It’s also a key ingredient for the potential of quantum computers to tackle massively complex calculations. It’s also why quantum computing is so vexing, because entanglement can be disrupted by external influences, leading to a process known as decoherence.

Swiss startup claims its Neuroplatform is a first for biocomputing.

Transistors are the basis for microchips and the whole electronic industry. The invention of transistors, by Bardeen and Brattain in 1947, awarded with a Nobel prize, is regarded as one of the most important discoveries of the 20th century.

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The rate at which the universe is currently expanding is known as the Hubble Rate. In recent years, different measurements have given different results for the Hubble rate, a discrepancy between theory and observation that’s been called the “Hubble tension”. Now, a team of astrophysicists claims the Hubble tension is gone and it’s the fault of supernovae data. Let’s have a look.

Continue reading “A Huge Cosmology Problem Might Just Have Disappeared” »

New research combining experimental and computational approaches provides deeper insights into proton spin contributions from gluons.

Nuclear physicists have been tirelessly exploring the origins of proton spin. A novel approach, merging experimental data with cutting-edge calculations, has now illuminated the spin contributions from gluons—the particles that bind protons. This advancement also sets the stage for three-dimensional imaging of the proton structure.

Joseph Karpie, a postdoctoral associate at the Center for Theoretical and Computational Physics (Theory Center) at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility, led this groundbreaking research.

Public cloud services employ special security technologies. Computer scientists at ETH Zurich have now discovered a gap in the latest security mechanisms used by AMD and Intel chips. This affects major cloud providers.

Over the past few years, hardware manufacturers have developed technologies that ought to make it possible for companies and governmental organizations to process sensitive data securely using shared cloud computing resources.

Known as confidential computing, this approach protects sensitive data while it is being processed by isolating it in an area that is impenetrable to other users and even to the cloud provider. But computer scientists at ETH Zurich have now proved that it is possible for hackers to gain access to these systems and to the data stored in them.

Advancements in qubit technology at the University of Basel show promise for scalable quantum computing, using electron and hole spins to achieve precise qubit control and interactions.

The pursuit of a practical quantum computer is in full swing, with researchers worldwide exploring a wide array of qubit technologies. Despite extensive efforts, there is still no consensus on which type of qubit best maximizes the potential of quantum information science.

Qubits are the foundation of a quantum computer. They’re responsible for processing, transferring, and storing data. Effective qubits must reliably store and rapidly process information. This demands stable, swift interactions among a large number of qubits that external systems can accurately control.

Researchers at the University of Hong Kong discovered Dirac spinons in the material YCu3-Br, providing evidence of a quantum spin liquid state and potentially advancing applications in quantum computing and high-temperature superconductivity.

Quasiparticles are fascinating entities that arise from collective behavior within materials and can be treated as a group of particles. Specifically, Dirac spinons are anticipated to exhibit unique characteristics similar to Dirac particles in high-energy physics and Dirac electrons in graphene and quantum moiré materials, such as a linear dispersion relation between energy and momentum. However, spin-½ charge-neutral quasiparticles had not been observed in quantum magnets until this work.

‘“To find Dirac spinons in quantum magnets has been the dream of generations of condensed matter physicists; now that we have seen the evidence of them, one can start to think about the countless potential applications of such highly entangled quantum material. Who knows, maybe one-day people will build quantum computers with it, just as people have been doing in the past half-century with silicon,’” said Professor Meng, HKU physicist and one of the corresponding authors of the paper.