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Category: particle physics – Page 16

Shaking atoms to bring black-hole quantum chaos into the lab

Physicists have discovered a surprisingly simple way to reproduce one of the most fascinating models in modern physics—linked to black holes, quantum chaos and exotic electronic materials—using ultracold atoms trapped in light.

Instead of trying to build a highly complex system from scratch, the researchers show that gently “shaking” a standard optical lattice can transform it into an accurate simulator of the Sachdev–Ye–Kitaev (SYK) model, a theoretical model known for its extreme and unusual quantum behavior.

The findings are published in the journal Physical Review Letters.

Does dark energy really exist? Our work identifies cracks in the foundations of today’s cosmological model

According to our best understanding, the universe is expanding – and is doing so at an accelerating rate. This is believed to be caused by something called the “cosmological constant”, which was first proposed by Albert Einstein in his theory of general relativity. In recent decades, it has become better known as dark energy, which is believed to make up about 70% of the universe.

Crucial to this realisation were studies of Type Ia supernovae – exploding white dwarf stars. These are thought to emit a specific amount of light, which allows astronomers to determine their distances very accurately and thereby track the expansion of the universe. This work was awarded the 2011 Nobel prize in physics.

The accelerating expansion of the universe is thought to be due to negative pressure, an unusual property of dark energy that allows it to overcome the attractive force of gravity. Yet the exact nature of dark energy remains a puzzle. It cannot be explained by our best theory for the fundamental building blocks of the universe – known as the standard model of particle physics.

The Surprising Evidence our Universe is INSIDE a Black Hole

What if everything we know — every galaxy, every star, every atom — is actually inside a black hole? In this video, we explore the fascinating possibility that our entire universe could exist within a black hole embedded in a larger “parent” universe. This idea isn’t science fiction; it arises from real solutions to Einstein’s equations in general relativity and from modern efforts to connect gravity with quantum mechanics. We examine what physics predicts happens inside a black hole, how space and time behave at an event horizon, and why the Big Bang might resemble the birth of a black hole from the outside.

We also explore the deeper implications of this theory: whether a collapsing star in another universe could create a new expanding universe on the inside, how spin and entropy might relate to cosmic expansion, and what this could mean for the concept of a multiverse. Could every black hole be the seed of a new universe? And if so, what does that say about where we came from and the true structure of reality? This is one of the most mind-bending ideas in cosmology — and it challenges our very notion of what “inside” and “outside” even mean.

Why Flowing Spins Polarize Up or Down

One of the goals of spintronics is to flip the magnetization of ferromagnetic domains solely via an electrically controlled spin current flowing in a layer underneath. The antiferromagnet manganese germanide (Mn3Ge) is a prime candidate for providing that control thanks to the out-of-plane polarization of its spin currents. Now Mingxing Wu of the University of Tokyo and his colleagues have identified which of two mechanisms proposed by theorists is responsible for the polarization [1]. The answer is both.

The triangular lattice of Mn3Ge causes groups of three adjacent spins to orient themselves at 120° with respect to each other. That noncolinear arrangement engenders so-called Weyl points in the crystal’s band structure. Thanks to a quantum geometry property called Berry curvature, Weyl points act like internal magnetic fields that deflect electrons in a spin-dependent way.

Until the work of Wu and his colleagues, just how the deflection leads to out-of-plane polarization was unclear. It could conceivably arise either via a mechanism called spin swapping (SSW) or via the magnetic spin Hall effect (MSHE). To settle the question, the researchers subjected single-crystal strips of Mn3Ge topped with layers of permalloy (a nickel–iron alloy) to a technique called spin-torque ferromagnetic resonance (ST-FMR). The ST-FMR signal from MSHE depends on the orientation of the Mn3Ge lattice with respect to the spin current, whereas the signal from SSW does not. By creating differently oriented samples, Wu and his colleagues found that both mechanisms contribute to the out-of-plane spin polarization with comparable magnitudes. Now that the mystery has been solved, the next step is to harness both mechanisms for the magnetic-field-free switching of magnetization.

New multiplexing scheme accelerates long-distance quantum communication

Quantum networks, systems consisting of multiple connected nodes or devices that can transmit quantum information to one another, have the potential to advance future communications. These networks typically leverage entanglement, a quantum phenomenon that prompts two or more distant particles to become highly correlated, so that measuring one instantly affects the state of the other.

To ensure that distant particles have become entangled and can transmit quantum states, some quantum scientists try to realize so-called heralded entanglement. This entails confirmation, from a detectable signal, that entanglement between nodes has been established.

Researchers at Tsinghua University and Hefei National Laboratory recently introduced a promising strategy to accelerate the generation of heralded entanglement between multiple ions (i.e., atoms with an electrical charge). Their proposed approach, outlined in a paper published in Physical Review Letters, relies on a so-called multiplexing scheme, a technique to send multiple signals through the same communication channel.

Plasma design rules show how to preserve attosecond flashes for observing electrons

Researchers at Skoltech, together with a colleague from the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences, working within the joint SIOM–Skoltech laboratory, have determined how to select the thickness and density of a plasma target so that a pulse passing through it retains its attosecond duration and high intensity. The results will help improve the design of plasma-based sources of ultraviolet and X-ray radiation used to study ultrafast processes in matter.

The work is published in Applied Physics Letters.

An attosecond is 10⁻¹⁸ of a second. Pulses of this duration can be compared to an ultrafast camera flash: They make it possible to effectively “freeze” the motion of electrons and investigate processes that cannot be resolved using longer pulses. This is important for studying atoms, molecules, solids and new materials.

Detecting the body’s magnetic fields with a low-power Ramsey-based magnetometer

Our bodies generate extremely weak magnetic fields as electric currents flow through the heart, brain and other tissues. These signals are used in magnetocardiography and magnetoencephalography to assess heart function and brain activity, respectively. These fields can be detected at room temperature using diamond sensors containing nitrogen-vacancy (NV) centers, in which a carbon atom is replaced by a nitrogen atom adjacent to an empty lattice site.

However, conventional NV-center sensors typically require watt-level lasers to detect the extremely weak biomagnetic fields, which are usually below the picotesla level. These high-power lasers generate significant heat, limiting how close the sensor can be placed to biological tissue. Since biomagnetic fields rapidly weaken with distance, overcoming thermal and close-proximity challenges is essential for practical biomagnetic sensing.

A research team led by Professor Takayuki Iwasaki from the Department of Electrical and Electronic Engineering, School of Engineering, Institute of Science Tokyo, Japan, has developed a diamond quantum magnetometer using a low-power laser of just 210 mW, a light-trapping diamond waveguide and a compact microwave antenna. The new sensor limits its temperature rise to only 13 K while allowing it to be placed just 2 mm (0.08 inches) from the sample, enabling close-proximity biomagnetic measurements without compromising thermal safety.

The First Room-Temperature Quantum Material of Its Kind Is Spun From Atoms of Gold

Materials in a quantum state come with exotic properties that bend the laws of physics and offer huge potential to scientists – but they’re usually also incredibly delicate, and require ultra-low temperatures to exist and function.

That presents a problem when it comes to making the most of these materials and their characteristics: they need to move out of large lab refrigerators.

We’re now another step towards that being possible.

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