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Category: quantum physics

Quantum properties of multimode light observed despite extreme losses

Quantum properties of light are extremely delicate. When researchers attempt to measure them, even small losses on the way to a detector can make them invisible, limiting their use outside carefully controlled environments. A collaborative team of researchers involving scientists at the Max Planck Institute for the Science of Light (MPL) has shown a new way to measure several quantum channels of light at the same time and reveal their entanglement, even when almost all of the light is lost before reaching the detector. The results, recently published in Nature Communications, open new possibilities for scalable quantum technologies.

Anyone who has used an old radio or television is familiar with noise in the sound or picture. These are random fluctuations that distort the transmitted information. Light behaves in a similar way. It also exhibits noise, appearing as fluctuations of the electromagnetic field. Even perfect laser light has such fluctuations, known as shot noise.

Single ion maps 3D electromagnetic fields above chips with record sensitivity

Researchers at ETH Zurich have developed a method that uses a single ion to detect electromagnetic fields above a surface and to create a three-dimensional map of them. In the future, this approach can be used to improve chips for quantum computers and quantum sensors.

Single electrically charged atoms—ions—have been successfully used for some time as quantum bits in quantum computers and quantum sensors. Unlike the bulky ion traps of the early years, there are now miniaturized chips in which ions can be trapped and manipulated only a hair’s breadth above the surface of the chip. This has many advantages, but also one decisive drawback: Noisy electromagnetic fields coming from the chip itself can severely impair the sensitive quantum states of the ions and hence the performance of the computer or sensor.

A team of researchers led by Jonathan Home, a professor at the Institute for Quantum Electronics at ETH Zurich, has now developed a technique that allows them to create a very precise three-dimensional map of electric and magnetic fields very close to the surface of the chip. In the future, materials for chip production can be better optimized and tested for their suitability for use in quantum applications. The results of their research were recently published in Science Advances.

Orbitronics clears key hurdle with direct orbital currents, boosting signals 100-fold

Researchers at Johannes Gutenberg University Mainz (JGU) are the first to directly utilize orbital currents without the need for conversion of the orbital current into a spin current.

“We have thus realized the first purely orbitronic device approach,” said Dr. Christin Schmitt, a scientist in the research group of Professor Mathias Kläui at the JGU Institute of Physics.

Orbitronics is a promising technology for future memory devices, as it could enable the realization of large-scale storage media with extremely low energy consumption. It is based on orbital moments, which can be described in simplified terms as the quantum-mechanical “vortices” of electrons around atomic nuclei, as well as orbital currents, i.e., the movement of these circulations through an electrical conductor.

Spontaneous current loops in a kagome metal point to hidden quantum order

Quantum materials, materials exhibiting physical behavior governed by the laws of quantum mechanics, have proved promising for the development of numerous advanced technologies, including quantum technologies, memory devices and solar panels. In some of these materials, electrons can collectively arrange themselves in unusual patterns, giving rise to states that cannot be explained by classical physics theories.

For more than two decades, theoretical physicists have predicted the existence of a loop current order in some quantum materials. This is a state characterized by tiny electrical currents circulating around microscopic loops inside a crystal, which would produce no measurable electric current flowing through a material.

These current loops were predicted to emerge when electrons spontaneously organize themselves into a less symmetrical pattern than the crystal itself, even if atoms remain in similar positions. While this phenomenon was widely studied and described by theorists in the past, it has so far proved difficult to observe experimentally.

Quantum semiconductor design could expand search for dark matter

Dark matter accounts for 85% of the matter in the universe, but scientists still do not know what it is made of. A study, published in Physical Review Letters, by Rice University researchers proposes a detector design that could help search for axions, hypothetical particles that many physicists think could make up dark matter.

The proposed detector would rely on a class of semiconductor materials whose response changes when their orientation shifts within a magnetic field. This material response makes it easier to tune the detector, allowing researchers to probe a range of axion masses that have remained difficult to explore with existing technologies.

“We are proposing a well-studied material from condensed matter physics for a new application—axion detection,” said Jaanita Mehrani, a doctoral student in Rice’s Applied Physics Graduate Program who is the first author on the study. “What’s different about this material is that it doesn’t have to use complex mechanical tuning mechanisms, it simply tunes with the magnetic field.”

Quantum gravity tests may mistake ordinary spacetime for superposition

Everything around us, from atoms and molecules to planets and galaxies, is governed by two extraordinarily successful theories of physics: quantum mechanics and gravity. Quantum mechanics explains the behavior of the microscopic world, while Einstein’s theory of gravity describes the motion of stars, black holes and the expansion of the universe. Yet despite their successes, physicists are still searching for a theory of “quantum gravity” that would unite them into a single description of nature.

One of the most widely expected features of such a theory is that gravity should obey the laws of quantum mechanics. And this is where it gets difficult: Quantum mechanics predicts that any object can be delocalized over multiple places at once, which is routinely tested in experiments with atoms and even small clumps of metal. Gravity, according to Einstein’s theory, is space and time itself—it can be curved, flat or even have waves propagating through it, as confirmed by gravitational wave detectors. So many physicists believe that spacetime around a quantum object would also exist in multiple “states” simultaneously.

But what would such a situation actually look like?

Tiny magnetic waves could unlock quantum computers the size of a penny

A team of physicists has overcome a major obstacle in quantum computing by dramatically increasing the lifetime of magnons, tiny magnetic waves that can carry quantum information. The researchers extended their lifespan from just a few hundred nanoseconds to as long as 18 microseconds, nearly 100 times longer than previously achieved. The advance could eventually help make ultra-compact quantum computers, potentially as small as a 1-cent coin.

The international research team, led by Andrii Chumak of the University of Vienna, also uncovered an important insight. They found that the lifespan of magnons is not ultimately limited by the laws of physics, but by the quality of the material they travel through. Their findings were published in Science Advances.

Strange Things Are Happening in Quantum Computing

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Quantum computing is supposed to be one of the most exciting new technologies that humanity is working on, with companies promising it can be used in chemistry, material science, logistics, and finance. Over the years, those use cases have been slowly eroded, but investment in quantum tech has only increased. Why? Let’s take a look.

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(PDF) Holographic Entanglement-Weighted de Sitter Gravity

🌌 Holographic theory suggests a profound idea: the universe may store information on its boundary, while the spacetime we experience emerges from that information. In this view, gravity is not only a force between masses.

https://doi.org/10.13140/RG.2.2.17062.

It may also be a macroscopic effect of quantum information, especially entanglement, encoded on a cosmic horizon. 🧠✨

A simple way to express this is:

Horizon information → Entanglement → Spacetime geometry.

To describe how efficiently entanglement becomes geometry, we introduce an entanglement-weight field:

Here, W(x) represents the conversion efficiency from holographic entanglement to gravitational geometry.

This modifies the effective strength of gravity:

Continue reading “(PDF) Holographic Entanglement-Weighted de Sitter Gravity” | >
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