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Category: quantum physics – Page 11

Pairs of atoms observed existing in two places at once for the first time

Quantum physicists at ANU have observed atoms entangled in motion. “It’s really weird for us to think that this is how the universe works,” says Dr. Sean Hodgman from the ANU Research School of Physics. “You can read about it in a textbook, but it’s really weird to think that a particle can be in two places at once.”

Their experiment using helium atoms represents a major advancement over similar experiments using photons, which are particles of light. Unlike photons, helium atoms have mass and experience gravity. The research is published in Nature Communications.

“Experimentally, it’s extremely hard to demonstrate this,” says lead author and Ph.D. researcher, Yogesh Sridhar. “Several people have tried in the past to show these effects, and they have always come short.”

Silicon quantum computer performs logical operations for the first time

Silicon is ubiquitous in modern electronics, and now it is becoming increasingly useful in quantum computing. In particular, silicon’s compatibility with existing chip technology and its long coherence times in silicon-based spin qubits make it a promising material for scalable quantum computing. A new study, published in Nature Nanotechnology, has demonstrated silicon’s use in a logical quantum processor, representing the first of its kind.

Quantum computers are highly sensitive to errors from environmental noise, creating hurdles for practical quantum computation. To help suppress these errors, information can be encoded in logical qubits using fault-tolerant quantum computation (FTQC). Prior to this study, silicon had not been used for logical operations in FTQC.

“In silicon-based quantum processors, frequency crowding and cross-talk further exacerbate the errors as the system scales. To address these errors, logical encoding stands as the only viable solution by redundantly storing quantum information across multiple physical qubits. While logical qubits and operations have been successfully demonstrated in platforms such as superconducting circuits, neutral atoms, nitrogen-vacancy centers and trapped ions, their implementation in silicon-based spin qubits poses notable technical challenges,” the study authors write.

Framework unifies the classical and quantum Mpemba effects

Physicists have developed a new theoretical framework which unifies a wide array of seemingly unrelated “Mpemba effects”: counterintuitive cases where systems driven further from equilibrium relax faster than those closer to it. Reporting their results in Physical Review X, researchers led by John Goold at Trinity College Dublin show that both classical and quantum versions of the effect can be understood using the same underlying logic—resolving a long-standing conceptual puzzle.

In 1963, 13-year-old Tanzanian student Erasto Mpemba noticed that when he placed an ice cream mixture in the freezer while it was still hot, it froze faster than the other, initially cooler mixtures in the freezer. His observation was later confirmed in 1969 through a study involving Mpemba, together with physicist Denis Osborne.

Since then, effects analogous to the Mpemba effect have been observed in transitions ranging from crystallizing polymers to transitions in magnetic materials. Yet despite close experimental scrutiny, the mechanisms underlying the effect remained elusive.

Next-generation optical sensor can read photon spin across UV-to-infrared wavelengths

A research team led by Professor Jiwoong Yang of the Department of Energy Science and Engineering at DGIST has developed next-generation optical sensor technology capable of precisely detecting not only the intensity and wavelength of light but also its rotational direction—the spin information of photons. The team successfully implemented a quantum-dot-based optical sensor that can detect circularly polarized light (CPL) across an ultra-wide spectral range—from ultraviolet to short-wave infrared—demonstrating photodetection performance comparable to that of commercial silicon optical sensors. The paper is published in Advanced Materials.

CPL refers to light in which the electric field rotates helically as it propagates. This is directly linked to the spin information of photons—the fundamental particles of light. This polarization information serves as a crucial signal in next-generation security and communication technologies, such as quantum communication, quantum cryptography, and photonic quantum information processing, which is why related optical sensor technologies are attracting significant worldwide attention.

Conventional circularly polarized light sensors typically require the light-absorbing material itself to possess a specific helical orientation, known as a chiral structure. This approach not only limits the range of usable materials but also confines detection to narrow spectral regions, such as ultraviolet or visible light. Extending this technology into the infrared region, which is essential for quantum communication and optical sensing, has previously posed a major technical challenge.

Stabilized laser components could shrink quantum computers from room- to chip-scale

Scientists in the Riccio College of Engineering at the University of Massachusetts Amherst and the University of California Santa Barbara have demonstrated key laser and ion trap components necessary to help drastically shrink the size of quantum computers, an achievement aligned with the shrinking of integrated microprocessors in the 1970s, 80s and 90s that allowed computers to move from room-sized behemoths to today’s ultrathin smartphones.

The current state-of-the-art technology for quantum computing is too large and complex to scale and too sensitive and bulky to be portable. The largest and most sensitive components of these quantum systems are the optics, which include multiple lasers and vibration-isolated, temperature-controlled vacuum chambers that contain ultrastable optical cavities. These cavities stabilize the lasers to extremely high precision in order to control trapped ions for quantum computing and optical clocks.

Quantum researchers engineer extremely precise phonon lasers

When lasers were invented in the 1960s, they opened new avenues for scientific discovery and everyday applications, from scanners at the grocery store to corrective eye surgery. Conventional lasers control photons—individual particles of light—but over the past 20 years, scientists have invented lasers that control other fundamental particles, including phonons—individual particles of vibration or sound. Controlling phonons could open even more possibilities with lasers, such as taking advantage of unique quantum properties like entanglement.

A new squeezed phonon laser developed by researchers at the University of Rochester and Rochester Institute of Technology provides precise control over phonons at the nanoscale level. This could give new insights into the nature of gravity, particle acceleration, and quantum physics.

In a paper in Nature Communications, the researchers describe how they coax these individual particles of mechanical motion to behave like a laser.

Finding the ‘quantum needle’ in a haystack: New filtering method can isolate photons

In quantum technologies, everything depends on the ability to detect the properties carried by a single photon. But in the real world, that photon of interest is often buried in a sea of unwanted light—a true “needle in a haystack” challenge that currently limits the deployment of many applications, including secure quantum communication, quantum sensors used in telescope networks, as well as the interconnection of quantum computers to accelerate the development of new drugs and materials.

At the Institut national de la recherche scientifique (INRS), the team of Professor José Azaña, in collaboration with Professor Roberto Morandotti’s group, has developed a surprisingly simple and energy-efficient way to overcome this obstacle. The work was carried out by Benjamin Crockett during his Ph.D. at the INRS Énergie Matériaux Télécommunications Research Centre. He recently completed his degree and is now a Banting postdoctoral fellow at the University of British Columbia (UBC).

Their method not only reduces noise but, more importantly, recovers essential quantum properties that would otherwise be lost in bright environments where current technologies fail.

Quadratic gravity theory reshapes quantum view of Big Bang

Waterloo scientists have developed a new way to understand how the universe began, and it could change what we know about the Big Bang and the earliest moments of cosmic history. Their work suggests that the universe’s rapid early expansion could have arisen naturally from a deeper, more complete theory of quantum gravity. The paper, “Ultraviolet completion of the Big Bang in quadratic gravity,” appears in Physical Review Letters.

Dr. Niayesh Afshordi, professor of physics and astronomy at the University of Waterloo and Perimeter Institute (PI), led the research team that explored a novel method of combining gravity with quantum physics, the rules that govern how the smallest particles in the universe behave. While general relativity has been successful for more than a century, it breaks down at the extreme conditions that existed at the birth of the universe. To address this problem, the team used Quadratic Quantum Gravity, which remains mathematically consistent even at extremely high energies—similar to the kind present during the Big Bang.

Most existing explanations for the Big Bang rely on Einstein’s theory of gravity, plus additional components added by hand. This new approach offers a more unified picture that connects the earliest moments of the universe to the well-tested cosmology scientists observe today.

A universal scheme can verify any quantum state

Quantum technologies, devices that can process, store, or detect information leveraging quantum mechanical effects, could outperform classical devices in some tasks or scenarios. Despite their potential, verifying that these devices work correctly and truly realize desired quantum states can be challenging, particularly when they cannot be fully examined or inspected.

One approach to verify quantum states or measurements is known as self-testing. This is a technique that allows quantum scientists to confirm the properties of a quantum system solely by analyzing its outputs, instead of examining how it operates internally.

Researchers at Université libre de Bruxelles (ULB), the University of Gdansk, and the Polish Academy of Sciences recently introduced a new universal scheme that could be used to self-test any quantum state or measurement. Their protocol, introduced in a paper published in Nature Physics, works by placing a device within a simple star-shaped quantum network and assessing the correlations between measurements obtained from different outputs that share entangled quantum states, to determine whether they are aligned with theoretical predictions.

Novel protocol reconstructs quantum states in large-scale experiments up to 96 qubits

Quantum computers, systems that process information leveraging quantum mechanical effects, could outperform classical computers on some computationally demanding tasks. Despite their potential, as the size of quantum computers increases, reliably describing and measuring the states driving their functioning becomes increasingly difficult.

One mathematical approach to simplify the description of quantum systems entails the use of matrix-product operators (MPOs). These are mathematical representations that allow researchers to break down very large systems into a long chain of connected smaller pieces.

Researchers at Université Grenoble Alpes, Technical University of Munich, Max Planck Institute of Quantum Optics, University of Innsbruck and University of Bologna recently developed a new protocol that could be used to learn the MPO representations of quantum states in real, large-scale quantum experiments. Their protocol, presented in a paper published in Physical Review Letters, has so far been found to reliably reconstruct states in quantum systems including up to 96 qubits.

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