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Category: quantum physics – Page 375

Unlocking quantum potential: Harnessing high-dimensional quantum states with QDs and OAM

Quantum technology’s future rests on the exploitation of fascinating quantum mechanics concepts—such as high-dimensional quantum states. Think of these states as basic ingredients of quantum information science and quantum tech. To manipulate these states, scientists have turned to light, specifically a property called orbital angular momentum (OAM), which deals with how light twists and turns in space. Here’s a catch: making super bright single photons with OAM in a deterministic fashion has been a tough nut to crack.

Now, enter (QDs), tiny particles with big potential. A team of researchers from Sapienza University of Rome, Paris-Saclay University, and University of Naples Federico II combined the features of OAM with those of QDs to create a bridge between two cutting-edge technologies.

Their results are published in Advanced Photonics.

Aristotle’s Icebreaker: How Quantum Systems Defy Freezing Logic

Does hot water freeze faster than cold water? Aristotle may have been the first to tackle this question that later became known as the Mpemba effect.

This phenomenon originally referred to the non-monotonic initial temperature dependence of the freezing start time, but it has been observed in various systems — including colloids — and has also become known as a mysterious relaxation phenomenon that depends on initial conditions.

However, very few have previously investigated the effect in quantum systems.

Finite-depth scaling of infinite quantum circuits for quantum critical points

Year 2022 Infinite quantum computer :3.

The scaling of the entanglement entropy at a quantum critical point allows us to extract universal properties of the state, e.g., the central charge of a conformal field theory. With the rapid improvement of noisy intermediate-scale quantum (NISQ) devices, these quantum computers present themselves as a powerful tool to study critical many-body systems. We use finite-depth quantum circuits suitable for NISQ devices as a variational ansatz to represent ground states of critical, infinite systems. We find universal finite-depth scaling relations for these circuits and verify them numerically at two different critical points, i.e., the critical Ising model with an additional symmetry-preserving term and the critical XXZ model.

Researchers develop a protocol to extend the life of quantum coherence

For years, researchers have tried various ways to coax quantum bits—or qubits, the basic building blocks of quantum computers—to remain in their quantum state for ever-longer times, a key step in creating devices like quantum sensors, gyroscopes, and memories.

A team of physicists from MIT have taken an important step forward in that quest, and to do it, they borrowed a concept from an unlikely source—noise-cancelling headphones.

Led by Ju Li, the Battelle Energy Alliance Professor in Nuclear Engineering and professor of materials science and engineering, and Paola Cappellaro, the Ford Professor of Engineering in the Department of Nuclear Science and Engineering and Research Laboratory of Electronics, and a professor of physics, the team described a method to achieve a 20-fold increase in the coherence times for nuclear-spin qubits.

How artificial intelligence gave a paralyzed woman her voice back

Tiny dents on thin material produce photon-polarizing magnetic fields.

Researchers at Los Alamos National Laboratory have developed a technique that can produce polarized photons more easily and cheaply than existing methods. The technique.

Quantum communication uses photons to carry information, much as classical communication uses electrons. But while classical computers encode information by turning current… More.

Researchers at UC San Francisco and UC Berkeley have developed a brain-computer interface (BCI) that has enabled a woman with severe paralysis from a brainstem stroke to speak through a digital avatar.

It is the first time that either speech or facial expressions have been synthesized from brain signals. The system can also decode these signals into text at nearly 80 words per minute, a vast improvement over commercially available technology.

Continue reading “How artificial intelligence gave a paralyzed woman her voice back” | >

Why a blockbuster superconductivity claim met a wall of scepticism

Dias didn’t disappoint. He and his colleagues had created a material — lutetium mixed with nitrogen and hydrogen, or LuNH — that was a superconductor at room temperature, he announced.

That claim, which the scientists published in Nature the next day1, would have been historic — if true. Superconductors conduct electricity with zero resistance, meaning that no energy is lost as heat. But they usually work only at very low temperatures, well below −100 °C, so need expensive refrigeration. This limits their use to niche applications, such as magnetic resonance imaging scans and quantum computing. A superconducting material that needs no cooling could potentially transform electricity generation and transmission, transportation and a slew of other applications.

Dias’s claim was remarkable not only for the material’s balmy operating temperature of 21 °C (294 K), but also because it required comparatively modest pressures. Other teams working with hydrogen compounds, called hydrides, have observed superconductivity at high temperatures, but had to squeeze their samples to hundreds of gigapascals (GPa) — millions of times more than atmospheric pressure. Dias, by contrast, said that his hydride needed just 1 GPa (10,000 times atmospheric pressure): still impractical for real-world applications, but a striking advance. A patent application for LuNH, released in April, goes further, claiming superconductivity at room temperature and pressure.

Scientists demonstrate new, improved way to make infrared light, with quantum dots

Scientists with the University of Chicago have demonstrated a way to create infrared light using colloidal quantum dots. The researchers said the method demonstrates great promise; the dots are already as efficient as existing conventional methods, even though the experiments are still in early stages.

The dots could someday form the basis of infrared lasers as well as small and cost-effective sensors, such as those used in exhaust emissions tests or breathalyzers.

“Right now the performance for these dots is close to existing commercial sources, and we have reason to believe we could significantly improve that,” said Philippe Guyot-Sionnest, a professor of physics and chemistry at the University of Chicago, member of the James Frank Institute, and one of three authors on the paper published in Nature Photonics. “We’re very excited for the possibilities.”

Atomic-scale spin-optical laser: New horizon for optoelectronic devices

Researchers at the Technion—Israel Institute of Technology have developed a coherent and controllable spin-optical laser based on a single atomic layer. This discovery is enabled by coherent spin-dependent interactions between a single atomic layer and a laterally confined photonic spin lattice, the latter of which supports high-Q spin-valley states through the photonic Rashba-type spin splitting of a bound state in the continuum.

Published in Nature Materials and also featured in the journal’s Research Briefing, the achievement paves the way to study coherent spin-dependent phenomena in both classical and quantum regimes, opening new horizons in and optoelectronic devices exploiting both electron and photon spins.

Can we lift the spin degeneracy of light sources in the absence of magnetic fields at room temperature? According to Dr. Rong, “Spin-optical light sources combine photonic modes and electronic transitions and therefore provide a way to study the exchange of spin information between electrons and photons and to develop advanced optoelectronic devices.”