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Category: particle physics – Page 6

A new twist on Heisenberg’s uncertainty principle can sharpen quantum sensors

For almost a century, Heisenberg’s uncertainty principle has stood as one of the defining ideas of quantum physics: a particle’s position and momentum cannot be known at the same time with absolute precision. The more you know about one, the less you know about the other.

In a new study published in Science Advances, our team demonstrates how to work around this restriction, not by breaking physics but by reshaping uncertainty itself.

The result is a breakthrough in the science of measurement that could power a new generation of ultra-precise quantum sensors operating at the scale of atoms.

Scientist Connected Light And Matter a Century Before Quantum Physics

The Irish mathematician and physicist William Rowan Hamilton, who was born 220 years ago last month, is famous for carving some mathematical graffiti into Dublin’s Broome Bridge in 1843.

But in his lifetime, Hamilton’s reputation rested on work done in the 1820s and early 1830s, when he was still in his twenties. He developed new mathematical tools for studying light rays (or “geometric optics”) and the motion of objects (“mechanics”).

Intriguingly, Hamilton developed his mechanics using an analogy between the path of a light ray and that of a material particle.

Scientist Connected Light And Matter Century Before Quantum Physics

The Irish mathematician and physicist William Rowan Hamilton, who was born 220 years ago last month, is famous for carving some mathematical graffiti into Dublin’s Broome Bridge in 1843.

But in his lifetime, Hamilton’s reputation rested on work done in the 1820s and early 1830s, when he was still in his twenties. He developed new mathematical tools for studying light rays (or “geometric optics”) and the motion of objects (“mechanics”).

Intriguingly, Hamilton developed his mechanics using an analogy between the path of a light ray and that of a material particle.

Physicists set record with 6,100-qubit array

Quantum computers will need large numbers of qubits to tackle challenging problems in physics, chemistry, and beyond. Unlike classical bits, qubits can exist in two states at once—a phenomenon called superposition. This quirk of quantum physics gives quantum computers the potential to perform certain complex calculations better than their classical counterparts, but it also means the qubits are fragile. To compensate, researchers are building quantum computers with extra, redundant qubits to correct any errors. That is why robust quantum computers will require hundreds of thousands of qubits.

Now, in a step toward this vision, Caltech physicists have created the largest array ever assembled: 6,100 neutral-atom qubits trapped in a grid by lasers. Previous arrays of this kind contained only hundreds of qubits.

This milestone comes amid a rapidly growing race to scale up quantum computers. There are several approaches in development, including those based on superconducting circuits, trapped ions, and neutral atoms, as used in the new study.

Spin may resolve century-old puzzle of light’s momentum in matter

When you shine a flashlight into a glass of water, the beam bends. That simple observation, familiar since ancient times, hides one of the oldest puzzles in physics: what really happens to the momentum of light when it enters a medium?

In , is not just a wave—it also behaves like a particle, carrying energy and . For more than a century, scientists have debated whether light’s momentum inside matter is larger or smaller than in empty space. The two competing answers are known as the Minkowski momentum, which is larger and seems to explain how light bends, and the Abraham momentum, which is smaller and matches the actual push or pull that light exerts on the medium.

The controversy never went away because experiments seemed to confirm both sides. Some setups measured the larger Minkowski value, others supported Abraham, leaving physicists with a paradox.

Information could be a fundamental part of the universe, and may explain dark energy and dark matter

For more than a century, physics has been built on two great theories. Einstein’s general relativity explains gravity as the bending of space and time.

Quantum mechanics governs the world of particles and fields. Both work brilliantly in their own domains. But put them together and contradictions appear—especially when it comes to black holes, dark matter, and the origins of the cosmos.

My colleagues and I have been exploring a new way to bridge that divide. The idea is to treat information—not matter, not energy, not even spacetime itself—as the most fundamental ingredient of reality. We call this framework the quantum memory matrix (QMM).

New tensor network-based approach could advance simulation of quantum many-body systems

The quantum many body problem has been at the heart of much of theoretical and experimental physics over the past few decades. Even though we have understood the fundamental laws that govern the behavior of elementary particles for almost a century, the issue is that many interesting phenomena are the result of the complex collective behavior of many interacting quantum particles. In the words of condensed matter theorist Philip W. Anderson: “More is different.”

Since simulating models with this many degrees of freedom exactly is entirely intractable computationally, approximations such as have been widely used to gain insight into their behavior. However, this approach requires that the theory is close to non-interacting, which renders it unusable in many cases of physical interest.

More recently, an approach based on insights from has shown great promise for tackling these non-perturbative regimes. It was understood that the low-energy quantum states of local models display relatively little entanglement compared to generic quantum states, a feature that is exploited in tensor network methods.

Ultrafast magnetization switching: Moving boundary challenges previous all-optical switching models

The field of ultrafast magnetism explores how flashes of light can manipulate a material’s magnetization in trillionths of a second. In the process called all-optical switching (AOS), a single laser pulse of several femtoseconds (≈10-15 seconds) duration flips tiny magnetic regions without the need for an externally applied magnetic field.

Enabling such an ultrafast control over magnetization, orders of magnitude faster than what can be achieved using a conventional magnet-based read/write head as in a magnetic hard drive, AOS is a promising candidate for novel spintronics devices that use magnetic spins with their associated as information carriers. Such devices typically consist of a stack of nanometer-thin materials, with the actual magnetic material being one of them.

Until now, the switching process was thought to happen uniformly in the magnetic material wherever the laser pulse deposits a sufficient amount of energy. In a study recently published in Nature Communications, researchers from the Max Born Institute together with collaborators from Berlin and Nancy revealed that this is not the case. Instead, there is an ultrafast propagation of a magnetization boundary into the depth of the material.

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