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Category: quantum physics – Page 190

A new problem that only quantum computing can solve

As quantum computing develops, scientists are working to identify tasks for which quantum computers have a clear advantage over classical computers. So far, researchers have only pinpointed a handful of these problems, but in a new paper published in Physical Review Letters, scientists at Los Alamos National Laboratory have added one more problem to this very short list.

“One of the central questions that faces is what classes of problems they can most efficiently solve but cannot,” says Marco Cerezo, the Los Alamos team’s lead scientist. “At the moment, this is the Holy Grail of quantum computing, because you can count on two hands such problems. In this paper, we’ve just added another.”

Quantum computing harnesses the unique laws of quantum physics, such as superposition, entanglement and interference, which allow for information processing capabilities beyond those of classical devices. When fully realized, quantum computing promises to make advancements in cryptography, simulations of quantum systems and data analysis, among many other fields. But before this can happen, researchers still need to develop the foundational science of quantum computing.

Understanding quantum computing’s most troubling problem—the barren plateau

For the past six years, Los Alamos National Laboratory has led the world in trying to understand one of the most frustrating barriers that faces variational quantum computing: the barren plateau.

“Imagine a landscape of peaks and valleys,” said Marco Cerezo, the Los Alamos team’s lead scientist. “When optimizing a variational, or parameterized, , one needs to tune a series of knobs that control the solution quality and move you in the landscape. Here, a peak represents a bad solution and a valley represents a good solution. But when researchers develop algorithms, they sometimes find their model has stalled and can neither climb nor descend. It’s stuck in this space we call a barren .”

For these quantum computing methods, barren plateaus can be mathematical dead ends, preventing their implementation in large-scale realistic problems. Scientists have spent a lot of time and resources developing quantum algorithms only to find that they sometimes inexplicably stall. Understanding when and why barren plateaus arise has been a problem that has taken the community years to solve.

Harnessing magnons for quantum information processing

Researchers have determined how to use magnons—collective vibrations of the magnetic spins of atoms—for next-generation information technologies, including quantum technologies with magnetic systems.

From the computer hard drives that store our data to the motors and engines that drive power plants, magnetism is central to many transformative technologies. Magnetic materials are expected to play an even larger role in new technologies on the horizon: the transmission and processing of quantum information and the development of quantum computers.

New research led by scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory developed an approach to control the collective magnetic properties of atoms in real time and potentially deploy them for next-generation information technologies. This discovery could aid in developing future quantum computers, which can perform tasks that would be impossible using today’s computers, as well as “on chip” technologies—with magnetic systems embedded on semiconductor chips, or “on chip.”

Decades-old mystery of AlCl dipole moment resolved

In a study that closes a long-standing knowledge gap in fundamental science, researchers Boerge Hemmerling and Stephen Kane at the University of California, Riverside, have successfully measured the electric dipole moment of aluminum monochloride (AlCl), a simple yet scientifically crucial diatomic molecule.

Their results, published in Physical Review A, have implications for , astrophysics, and planetary science. The paper is titled “Measurement of the of AlCl by Stark-level spectroscopy.”

Until now, the dipole moment of AlCl was only estimated, with no experimental confirmation. The study’s precise measurement now replaces the theoretical predictions with solid experimental data.

No, Quantum Mechanics does Not Need Complex Numbers

No journal is perfect, and despite Nature being considered a high quality journal, I have recently come across a paper which is, to put it bluntly, is slop. It is a bit of slop easily debunkable by anyone who can do a tiny bit of linear algebra.

The paper is titled “Quantum theory based on real numbers can be experimentally falsified.” The entire paper is misleading because it presents a very specific representation of quantum mechanics based solely on real numbers, shows that it leads to different predictions than traditional quantum theory, and then concludes therefore complex numbers are a necessity for complex theory.

This is obviously false. A complex number is just two real numbers stitched together. Classical computers can’t operate on complex numbers and so they just break them apart into two real floating point numbers and do the equivalent calculations in that form, but then display it as a complex number, and they can reproduce anything you can reproduce using complex numbers. Indeed, my quantum computer simulator I had put together myself uses its own complex matrix library for linear algebra, and each element of the matrix is specified by two real numbers.

30 Space Phenomena That Are Still a Mystery

Dark matter constitutes about 27% of the universe, yet it remains one of the greatest mysteries in cosmology. Unlike normal matter, it does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects. Understanding dark matter is crucial for explaining galaxy formation and cosmic structure.

Accounting for approximately 68% of the universe, dark energy is a hypothetical form of energy proposed to explain the accelerated expansion of the universe. Its nature and properties remain unclear. Dark energy challenges our understanding of gravity and the ultimate fate of the cosmos.

Black holes are regions with a gravitational pull so strong that nothing, not even light, can escape. While we have theories describing their behavior, their interiors remain shrouded in mystery. The existence of black holes challenges the boundaries of our understanding of physics, including general relativity and quantum mechanics.

Oxford physicists recreate extreme quantum vacuum effects

Physicists at the University of Oxford have successfully simulated how light interacts with empty space – a phenomenon once thought to belong purely to the realm of science fiction. The simulations recreated a bizarre phenomenon predicted by quantum physics, where light appears to be generated from darkness. The findings pave the way for real-world laser facilities to experimentally confirm bizarre quantum phenomena. The results have been published in Communications Physics.

Using advanced computational modelling, a research team led by the University of Oxford, working in partnership with the Instituto Superior Técnico in the University of Lisbon, has achieved the first-ever real-time, three-dimensional simulations of how intense laser beams alter the ‘quantum vacuum’ – a state once assumed to be empty, but which quantum physics predicts is full of virtual electron-positron pairs.

Excitingly, these simulations recreate a bizarre phenomenon predicted by quantum physics, known as vacuum four-wave mixing. This states that the combined electromagnetic field of three focused laser pulses can polarise the virtual electron-positron pairs of a vacuum, causing photons to bounce off each other like billiard balls – generating a fourth laser beam in a ‘light from darkness’ process. These events could act as a probe of new physics at extremely high intensities.

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