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Category: quantum physics

Twisted bilayer photonic crystals dynamically tune light’s handedness

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have created a chip-scale device that can dynamically control the “handedness” of light as it passes through—also known as its optical chirality—with a simple twist of two specially designed photonic crystals. The study is published in the journal Optica.

The work, led by graduate student Fan Du in the lab of Eric Mazur, the Balkanski Professor of Physics and Applied Physics, describes a reconfigurable twisted bilayer photonic crystal that can be tuned in real time using an integrated micro-electromechanical system (MEMS). The breakthrough opens new possibilities for advanced chiral sensing, optical communication, and quantum photonics.

“Chirality is very important in many fields of science—from pharma to chemistry, biology, and of course, physics and photonics,” Mazur said. “By integrating twisted photonic crystals with MEMS, we have a platform that is not only powerful from a physics standpoint, but also compatible with the way modern photonics are manufactured.”

Photonic ‘ski jumps’ efficiently beam light into free space

Photonic chips use light to process data instead of electricity, enabling faster communication speeds and greater bandwidth. Most of that light typically stays on the chip, trapped in optical wires, and is difficult to transmit to the outside world in an efficient manner.

If a lot of light could be rapidly and precisely beamed off the chip, free from the confines of the wiring, it could open the door to higher-resolution displays, smaller Lidar systems, more precise 3D printers, or larger-scale quantum computers.

Now, researchers from MIT and elsewhere have developed a new class of photonic devices that enable the precise broadcasting of light from the chip into free space in a scalable way.

Acoustic driving enables controlled condensation of light and matter on chip

An international research team led by Alexander Kuznetsov at the Paul Drude Institute for Solid State Electronics (PDI) in Berlin has demonstrated a fundamentally new way to control the condensation of hybrid light-matter particles. Using coherent acoustic driving to dynamically reshape the energy landscape of a semiconductor microcavity, the researchers achieved deterministic steering of a macroscopic quantum state into its lowest energy configuration.

The results, published in Nature Photonics, establish a strategy for engineering nonequilibrium quantum states and open prospects for ultrafast, tunable photonic technologies.

In collaboration with long-term partners from the National Scientific and Technical Research Council CONICET and the Bariloche Atomic Center and Balseiro Institute in Argentina, the team experimentally realized a universal scheme for selectively transferring populations within a multilevel quantum system using strong time periodic modulation.

Fiber setup compresses mid-infrared pulses to 187 femtoseconds using just 80 watts

Ultrashort mid-infrared (mid-IR) laser pulses are essential for applications such as molecular spectroscopy, nonlinear microscopy, and biomedical imaging, but their generation often relies on complex and power-intensive systems that are difficult to implement outside of specialized laboratories. These systems usually require high pump powers, elaborate optical setups, and precise alignment, which can limit their widespread adoption and practical use in everyday research and clinical settings.

In a paper published in the IEEE Journal of Quantum Electronics, a team of researchers from SASTRA Deemed University, Thanjavur, report a compact, fiber-based method for generating clean ultrashort mid-IR pulses at significantly reduced input power.

The study demonstrates that high-quality pulse compression can be achieved using a holmium-doped ZBLAN photonic crystal fiber integrated into a nonlinear optical loop mirror (NOLM), offering a simpler and more energy-efficient alternative to conventional systems.

Stacked quantum materials enable precise spin control without external magnetic fields

Spintronics—a technology that harnesses the electron’s magnetic quantum states to carry information—could pave the way for a new generation of ultra-energy-efficient electronics. Yet a major challenge has been the ability to control these delicate quantum properties with sufficient precision for practical applications. By combining different quantum materials, researchers at Chalmers University of Technology have now taken a decisive step forward, achieving unprecedented control over spin phenomena. The advance opens the door to next-generation low-power data processing and memory technologies.

Data centers, cloud services, AI and connected systems account for a rapidly growing share of global energy consumption. In the quest for new, more energy-efficient technological solutions, spin electronics, or spintronics, has proven to be a new and promising approach. Instead of relying solely on the movement of electric charge, spintronics use magnetic states to carry information. More specifically, it takes advantage of a quantum property of electrons known as spin, which makes electrons behave like tiny magnets.

“Just like a compass needle, an electron’s spin can point in one of two directions—up or down. These two directions can be used to represent digital information, in the same way today’s electronics use 0s and 1s,” explains Saroj Dash, Professor of Quantum Device Physics at Chalmers University of Technology.

This Spacetime Quasicrystal Could Solve Physicists’ Biggest Problem

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What is space, really? That’s one of the biggest questions in science. According to a pair of researchers from the Perimeter Institute, the answer to that is: a quasicrystal. What is a quasicrystal, and how is space a quasicrystal? Let’s take a look.

Paper: https://arxiv.org/abs/2601.

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What is space? That’s one of the biggest questions, not just in the foundations of physics, but in all of science. According to a new paper, the answer may be a quasicrystal, an idea from researchers working on quantum gravity. This video explores the implications of this idea, touching on concepts like String Theory and Loop Quantum Gravity, to understand what it might mean for theoretical physics.

Continue reading “This Spacetime Quasicrystal Could Solve Physicists’ Biggest Problem” | >

Watching quantum behavior in action: MagnetoARPES reveals time-reversal symmetry breaking in a kagome superconductor

Electron movement and structures described in quantum physics allow researchers to better understand how and why materials like superconductors behave as they do. Rice University researchers Jianwei Huang and Ming Yi have developed a new capability, magnetoARPES, building on angle-resolved photoemission spectroscopy (ARPES) that allows researchers to study quantum behaviors they have been unable to resolve using ARPES alone. The work has been published in Nature Physics.

MagnetoARPES adds a tunable magnetic field, external to the sample, to ARPES. This allows researchers to probe the full electronic response to a magnetic field, giving insights into why certain collective behaviors of electrons develop.

Magnetic fields have, historically, been excluded from ARPES experiments, but over the course of a few years of experimentation and simulations, Yi’s team found a viable way to incorporate this capability into the ARPES sample environment.

Quantum materials could enable the solar-powered production of hydrogen from water

Hydrogen fuel is a promising alternative to fossil fuels that only emits water vapor when used and could thus help to lower greenhouse gas emissions on Earth. In the future, it could potentially be used to fuel heavy-duty transport vehicles, such as trucks, trains, and ships, as well as industrial heating and decentralized power generation systems.

Unfortunately, most current methods to produce hydrogen rely on the burning of fossil fuels, which limits its environmental advantages. Given its potential, many energy engineers worldwide have been trying to devise more sustainable strategies to produce hydrogen on a large scale.

One proposed method for the clean production of hydrogen is known as photocatalytic water splitting. This approach entails splitting water molecules into hydrogen and oxygen, using photocatalysts (i.e., materials that respond to sunlight and prompt desired chemical reactions).

Ultrafast computing: Light-driven logic tops 10 terahertz in WS₂

The future for our computers will literally be at the speed of light. Extremely short light pulses can perform ultrafast logical operations: these are the findings of a study recently published in the journal Nature Photonics. The study represents an important step toward developing a new generation of information processing technologies, potentially hundreds of times faster than what we have at present.

Today’s computers rely on the movement of electrical charges inside transistors; however, these can only achieve a maximum frequency whose physical limits are hard to overcome. Unlike traditional electronics, based on the movement of electric charges, this innovative approach manipulates the state of electrons in matter by the use of oscillating light.

As Giulio Cerullo of the Politecnico di Milano explained, “We have shown that light can be used not only to transmit information, but also to process it. With the use of ultra-short laser pulses, we can control the quantum states of matter on time scales of a few millionths of a billionth of a second, i.e. at the same frequencies as light oscillations, speeds previously unknown in electronics.” These operations are performed at rates above 10 terahertz, over a hundred times faster than the best modern electronic devices.

Chemical shifts help track molecules breaking apart in real time

When molecules fall apart, their electric charge doesn’t stay put—it rearranges as bonds stretch and break. An international team of scientists has now tracked these ultrafast changes in the small molecule fluoromethane (CH₃F). It was the first time that the Small Quantum Systems (SQS) instrument at European XFEL could deliver detailed insights into transient states during chemical reactions. The research is published in the journal Physical Review X.

These intermediate states, that only exist temporarily while the reaction is ongoing, are often the key drivers of chemistry and therefore crucial to understand. Over the long term, that kind of insight can support progress in areas such as atmospheric science (where sunlight-driven reactions and fragmentation pathways shape air chemistry), as well as the study of complex molecular systems including biomolecules and proteins, where local excitation and charge transfer can trigger structural change.

In the experiment, the researchers first triggered the reaction with an optical laser pulse. Next, they used the X-ray laser pulses that the European XFEL produces, to eject an electron from the core of either the fluorine or the carbon atom in the molecule. They measured the electron’s kinetic energy, which reveals how strongly it was bound inside the atom. That binding energy is extremely sensitive to the local electrical environment, producing so-called “chemical shifts” that act like a fingerprint of the charge distribution surrounding the atom from which the electron has been ejected.

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