Improving energy conversion efficiency in power electronics is vital for a sustainable society, with wide-bandgap semiconductors like GaN and SiC power devices offering advantages due to their high-frequency capabilities. However, energy losses in passive components at high frequencies hinder efficiency and miniaturization. This underscores the need for advanced soft magnetic materials with lower energy losses.
In a study published in Communications Materials, a research team led by Professor Mutsuko Hatano from the School of Engineering, Institute of Science, Tokyo, Japan, has developed a novel method for analyzing such losses by simultaneously imaging the amplitude and phase of alternating current (AC) stray fields, which are key to understanding hysteresis losses.
Using a diamond quantum sensor with nitrogen-vacancy (NV) centers and developing two protocols—qubit frequency tracking (Qurack) for kHz and quantum heterodyne (Qdyne) imaging for MHz frequencies—they realized wide-range AC magnetic field imaging. This study was carried out in collaboration with Harvard University and Hitachi, Ltd.
The researchers conducted a proof-of-principle wide-frequency-range magnetic field imaging experiment by applying an AC current to a 50-turn coil and sweeping the frequency from 100 Hz to 200 kHz for Qurack and 237 kHz to 2.34 MHz for Qdyne. As expected, the uniform AC Ampere magnetic field’s amplitude and phase were imaged using NV centers with high spatial resolution (2–5 µm), validating both measurement protocols.
Using this innovative imaging system, the team could simultaneously map the amplitude and phase of stray magnetic fields from the CoFeB–SiO2 thin films, which have been developed for high-frequency inductors. Their findings revealed that these films exhibit near-zero phase delay of up to 2.3 MHz, indicating negligible energy losses along the hard axis. Moreover, they observed that energy loss depends on the material’s magnetic anisotropy—when magnetization is driven along the easy axis, phase delay increases with frequency, signifying higher energy dissipation.
Overall, the results showcase how quantum sensing can be used to analyze soft magnetic materials operating at higher frequencies, which is considered to be a major challenge in developing highly efficient electronic systems. Notably, the capacity to resolve domain wall motion, one of the magnetization mechanisms strongly related to energy losses, is a pivotal step, leading to important practical advances and optimizations in electronics.
Looking forward, the researchers hope to further improve the proposed techniques in various ways. “The Qurack and Qdyne techniques used in this study can be enhanced by engineering improvements,” says Hatano. “Qurack’s performance can be enhanced by adopting high-performance signal generators to extend its amplitude range, whereas optimizing spin coherence time and microwave control speed would broaden Qdyne’s frequency detection range.”
“Simultaneous imaging of the amplitude and phase of AC magnetic fields across a broad frequency range offers numerous potential applications in power electronics, electromagnets, non-volatile memory, and spintronics technologies,” remarks Hatano. “This success contributes to the acceleration of quantum technologies, particularly in sectors related to sustainable development goals and well-being.”
Hyperspectral imaging (HSI), or imaging spectroscopy, captures detailed information across the electromagnetic spectrum by acquiring a spectrum for each pixel in an image. This enables precise identification of materials through their spectral signatures.
HSI supports Earth remote sensing applications such as automated classification, abundance mapping, and estimation of physical and biological properties like soil moisture, sediment density, water quality, biomass, leaf area, and pigment content.
Although HSI offers detailed insight into a remote sensing scene, HSI data may not be readily available for an intended application. Recent studies have attempted to combine HSI with traditional red-green-blue (RGB) video acquisition to lower costs and improve performance. However, this fusion technology still faces technical challenges.
In a recent study published in the Journal of Applied Remote Sensing, researchers from the Chester F. Carlson Center for Imaging Science at the Rochester Institute of Technology developed a bimodal video platform that combines a 371-band hyperspectral imaging system, operable in a low-rate video mode, with a standard RGB video camera. Led by Chris H. Lee, the team designed this system to bridge the gap between high-cost hyperspectral imaging and widely available RGB video technology.
The team demonstrated their proof-of-concept by capturing video data of the Lake Ontario shoreline at Hamlin Beach State Park in Rochester, New York.
“We developed a workflow that links reflectance data from a line-scanning hyperspectral imaging spectrometer with RGB video frames to predict hyperspectral imagery,” Lee says. “We established a correlation between the two data streams during a specific time segment, then used it to predict hyperspectral frames both before and after that segment using only RGB video.”
Illustrative diagram showing how the line-scanned HSI and snapshot RGB data are acquired and matched in time and space to construct the correlative model between spectra and RGB values using time- and space-matched pixels. In this study, the gimbal housing the Headwall imaging spectrometer (top left) nods along the vertical axis to scan the scene with integration time for each line of 9 ms, rotating at a constant rate of 3.958 deg/s to a desired maximum tilt angle labeled here as θe. Figure 4 shows an enlarged example of 10 pairs of spectra and RGB values for reference. Credit: Journal of Applied Remote Sensing (2025). DOI: 10.1117/1.JRS.19.024507
They captured visible to near-infrared hyperspectral video using a Headwall Hyperspec micro-High Efficiency imaging spectrometer, operating in its low-rate video mode. RGB data came from a widely available, low-cost GoPro Hero 8 Black. Lee’s group pushed the systems to their operational limits, acquiring video data at rates on the order of milliseconds and correlating the RGB and HSI data in both time and space.
To assess the accuracy of their workflow, the researchers compared the predicted reflectance with measured reflectance, after correcting for sensor and atmospheric effects. The results varied by wavelength range. In the visible spectrum, the platform predicted 95% of the water scene within 2% absolute reflectance, or about 30% of the water signal level.
In contrast, the near-infrared range showed larger errors: for 95% of the scene, the normalized residual error reached up to 90%. The team attributed this increase to the limited spectral data in RGB video in the shallow water scene.
“Our platform shows that we can predict hyperspectral frames from RGB video with reasonable accuracy in the visible range,” Lee notes. “The drop in performance at longer wavelengths highlights the need for broader spectral coverage of fewer-band data for the prediction algorithm.”
Looking ahead, Lee sees opportunities to enhance the system, “Future improvements will focus on aligning and calibrating the spectrometer and camera fields of view more precisely, and on developing more advanced prediction models.”
By combining affordable RGB cameras with hyperspectral technology, this new platform opens the door to more accessible environmental video monitoring. With further refinement, it could support a broad range of applications, from water quality assessment to vegetation analysis and beyond.
Diamond is one of the most prized materials in advanced technologies due to its unmatched hardness, ability to conduct heat and capacity to host quantum-friendly defects. The same qualities that make diamond useful also make it difficult to process.
Engineers and researchers who work with diamond for quantum sensors, power electronics or thermal management technologies need it in ultrathin, ultrasmooth layers. But traditional techniques, like laser cutting and polishing, often damage the material or create surface defects.
Ion implantation and lift-off is a way to separate a thin layer of diamond from a larger crystal by bombarding a diamond substrate with high-energy carbon ions, which penetrate to a specific depth below the surface. The process creates a buried layer in the diamond substrate where the crystalline lattice has been disrupted. That damaged layer effectively acts like a seam: Through high-temperature annealing, it turns into smooth graphite, allowing for the diamond layer above it to be lifted off in one uniform, ultrathin wafer.
A team of researchers at Rice University has developed a simpler and more effective way to achieve lift-off: instead of high-temperature annealing, they discovered that growing an extra epilayer of diamond atop the substrate after ion implantation is enough to turn the damaged layer graphite-like.
According to a study published in Advanced Functional Materials, the refined technique can bypass the high-temperature annealing and generates higher-purity diamond films than the original substrates. Moreover, the substrate sustains minimal damage in the process and can be reused, making the whole process resource-efficient and scalable.
(a) Theoretical model of the diamond block used in the MD simulations, where vacancies are confined to the central region. (b) Normalized pair radial distribution function, g(r), for pristine diamond (black curve) and diamond with vacancy densities of 1.0 × 10²² vac/cm³ (green curve), 2.8 × 10²² vac/cm³ (red curve), and 9.0 × 10²² vac/cm³ (blue curve). (c), (d), and (e) show MD snapshots of the final simulation frame for vacancy densities of 1.0 × 10²² vac/cm³, 2.8 × 10²² vac/cm³, and 9.0 × 10²² vac/cm³, respectively. Credit: Advanced Functional Materials (2025). DOI: 10.1002/adfm.202423174 “We found that diamond overgrowth converts the buried damage layer into a thin graphitic sheet, removing the need for energy‑heavy annealing,” said Xiang Zhang, assistant research professor of materials science and nanoengineering at Rice and a corresponding author on the study. “The resulting diamond film is purer and higher-quality than the original diamond, matching the electronic-grade quality.”
According to Zhang, these ultrapure diamond films “could revolutionize electronics, enabling faster, more efficient devices, or serve as the foundation for quantum computers that solve problems beyond today’s reach.”
To grow a new layer of diamond on the substrate, the researchers used microwave plasma chemical vapor deposition, a method that deposits new diamond material onto the surface in perfect alignment with the underlying crystal. The researchers hypothesized that the conditions of the growth process itself were enough to drive the conversion of the buried damage layer into graphite, without the need for additional heating.
To confirm this theory, the team examined how the interfaces between the diamond substrate, the buried damage layer and the overgrown film evolved during diamond overgrowth using a combination of transmission electron microscopy, electron energy loss spectroscopy, Raman spectroscopy and photoluminescence mapping.
“By correlating atomic‑level imaging with spectroscopic signatures, we demonstrate that diamond overgrowth is sufficient to form a clean graphitic release layer, preserve substrate smoothness and yield electronic‑grade diamond films, which is crucial for quantum technologies,” Zhang said.
By simplifying production and boosting sustainability, the new method could enable the development of transformative diamond-based technologies.
Blue phosphorescent OLEDs can now last as long as the green phosphorescent OLEDs already in devices, University of Michigan researchers have demonstrated, paving the way for further improving the energy efficiency of OLED screens.
“This moves the blues into the domain of green lifetimes,” said Stephen Forrest, the Peter A. Franken Distinguished University Professor of Electrical Engineering and corresponding author of the study in Nature Photonics.
“I can’t say the problem is completely solved—of course it’s not solved until it enters your display—but I think we’ve shown the path to a real solution that has been evading the community for two decades.”
OLED screens are standard in flagship smartphones and high-end televisions, providing high contrast and energy efficiency as variations in brightness are achieved by the light emitters rather than a liquid crystal layer over the top. However, not all OLEDs are equally energy efficient.
In current displays, red and green OLEDs produce light through the highly efficient phosphorescent route, whereas blue OLEDs still use fluorescence. This means while red and green OLEDs have a theoretical maximum of one photon for every electron running through the device, blue OLEDs cap out at a far lower efficiency.
Claire Arneson, PhD student in Forrest’s lab, demonstrates the glowing blue PHOLED. Its structure shows a pathway for efficient blue OLEDs that can last as long as the efficient green and red OLEDs already in high end televisions and flagship smartphone displays. Credit: Jero Lopera, Electrical and Computer Engineering, University of Michigan. The trouble is that blue light is the highest energy that an RGB device must produce: The molecules in blue phosphorescent OLEDs (PHOLEDs) need to handle higher energies than their red and green counterparts. Most of the energy leaves in the form of blue light, but when it is trapped, it can instead break down the color-producing molecules.
Previously, Forrest’s team discovered that there was a way to get that trapped energy out faster by including a coating on the negative electrode that helps the energy convert into blue light. Haonan Zhao, a recent Ph.D. graduate in physics, said it was like creating a fast lane.
“On a road that doesn’t have enough lanes, impatient drivers can crash into one another, cutting off all traffic—just like two excitons bumping into one another create a lot of hot energy that destroys the molecule,” said Zhao, first author of that study as well as the new one. “The plasmon exciton polariton is our optical design for an exciton fast lane.”
The details are based in quantum mechanics. When an electron comes in through the negative electrode, it creates what’s called an excited state in one of the molecules that produces blue light. That state is a negatively charged electron that jumps into a higher energy level and a positively charged “hole” that the electron leaves behind—together, they make an exciton.
Ideally, the electron would quickly jump back to its original state and fire off a blue photon, but excitons that use the phosphorescent route tend to hang around. Simply relaxing into their original state would violate a law of quantum mechanics. However, excitons very near the electrode produce photons faster because the shiny surface supports another quantum quasiparticle—surface plasmons. These are like ripples in the pond of electrons on the surface of the metal.
The new PHOLED, developed in the lab of Steve Forrest at the University of Michigan, shows a pathway for efficient blue OLEDs that can last as long as the efficient green and red OLEDs already in high end televisions and flagship smartphone displays. Credit: Marcin Szczepanski/Michigan Engineering If the exciton in the light-emitting material is close enough to the electrode, it gets a little help with the conversion to blue light because it can dump its energy into a surface plasmon—a phenomenon known as the Purcell effect. It does this because the exciton oscillates a little like a broadcast antenna, which creates waves in the electrons in the electrode.
This isn’t automatically helpful, though, as not all surface plasmons produce photons. To get the photon, the exciton must attach itself to the surface plasmon, producing a plasmon exciton polariton.
Forrest’s team encouraged this route by adding a thin layer of a carbon-based semiconductor onto the shiny electrode that encourages the exciton to transfer its energy and resonate in the right way. It also extends the effect deeper into the light-emitting material, so excitons further from the electrode can benefit.
The team reported on this last year, and they have since been putting this effect together with other approaches to finally produce a blue PHOLED that can last as long and burn as bright as a green one. These are the highlights of the design:
Two light-emitting layers (a tandem OLED): This cuts the light-emitting burden of each layer in half, reducing the odds that two excitons merge. Adding a layer that helps the excitons resonate with surface plasmons near both electrodes, so that both emitting layers have access to the fast lane The whole structure is an optical cavity, in which blue light resonates between the two mirror-like electrodes. This pushes the color of the photons deeper into the blue range.
When exposed to periodic driving, which is the time-dependent manipulation of a system’s parameters, quantum systems can exhibit interesting new phases of matter that are not present in time-independent (i.e., static) conditions. Among other things, periodic driving can be useful for the engineering of synthetic gauge fields, artificial constructs that mimic the behavior of electromagnetic fields and can be leveraged to study topological many-body physics using neutral atom quantum simulators.
Researchers at Ludwig-Maximilians-Universität, Max Planck Institute for Quantum Optics and Munich Center for Quantum Science and Technology (MCQST) recently realized a strongly interacting phase of matter in large-scale bosonic flux ladders, known as the Mott-Meissner phase, using a neutral atom quantum simulator. Their paper, published in Nature Physics, could open new exciting possibilities for the in-depth study of topological quantum matter.
“Our work was inspired by a long-standing effort across the field of neutral atom quantum simulation to study strongly interacting phases of matter in the presence of magnetic fields,” Alexander Impertro, first author of the paper, told Phys.org. “The interplay of these two ingredients can create a variety of quantum many-body phases with exotic properties.
“While their microscopic mechanisms are typically well understood, the emergent many-body properties are elusive and hard to probe in conventional solids, with a notable example being the (fractional) quantum Hall effect. Unfortunately, it turned out that the Floquet engineering technique, which is one of the primary methods for obtaining an effective magnetic field for neutral atoms, generally causes strong heating in interacting quantum systems.”
The heating processes prompted by Floquet engineering techniques are known to rapidly destroy fragile quantum states. As a result, most previous experiments probing exotic quantum many-body phases only focused on non-interacting or weakly interacting systems, while strongly-correlated ones remained limited to only two particles.
The first objective of the recent study by Impertro and his colleagues was to leverage the capabilities of a new experimental quantum simulation platform they developed to realize quantum many-body states with artificial magnetic fields and strong interactions producing little heating. In addition, they hoped to simulate larger systems that reached well beyond the two-particle systems realized in previous experiments.
In their experiments, the researchers utilized optical superlattices, a short-spacing vertical lattice and a so-called Feshbach resonance that provides an important tuning knob. In addition, they employed a recently developed technique for the precise measurement of particle currents.
“Using the optical superlattices, we partitioned a two-dimensional optical lattice into an independent array of ladder systems, in which we realize the experimental studies,” explained Impertro. “Additionally, the double-wells that form the rungs of the ladders are also the basis for the Floquet engineering technique that we use to create an artificial magnetic field.
“Intuitively, the technique modifies the motion of particles in the lattice using additional laser beams, which in turn imprint the effect of a magnetic field onto the atoms to mimic a Lorentz force or Hall deflection.”
Experimentally measured phase diagram (data points and solid line), which shows a significant difference to a comparable system without interactions (dashed lines). Credit: Alexander Impertro (LMU / MPQ Garching)
Finally, Impertro and his colleagues leveraged the Feshbach resonance in cesium. This property of cesium allowed them to tune the interaction strength between atoms over a wide range, which is important both for preparing the desired strongly interacting quantum states with low heating and to probe the response of the quantum states to a changing interaction strength.
“The central challenges we encountered when preparing the states were to find suitable parameter regimes where the heating rate due to the periodic modulation (Floquet engineering) is minimal, which is particularly challenging for large many-body systems, and to find preparation paths that allow us to adiabatically transform an easy-to-prepare initial state into the quantum state of interest, without creating excitations,” said Impertro.
“Lastly, a central quantity that characterizes the ground states of flux ladders, such as the Mott-Meissner phase, are persistent particle currents.”
Notably, quantum gas microscopes like the one employed by Impertro and his colleagues can typically only measure local densities and fail to measure currents. To enable the measurement of currents, the team employed a current detection technique that they developed as part of their earlier studies, adapting it for the purpose of their experiment.
“For the first time, we were able to prepare low-temperature states in Floquet engineered quantum systems with a large number of particles and microscopically study their properties,” said Impertro. “We also demonstrated the measurement of particle currents with full spatial resolution across large systems, which constitutes an entirely new way to probe these physics using quantum gas microscopy.
“This constitutes a key step towards studying fractional quantum Hall phases in synthetic quantum systems, which is a longstanding goal in various communities, ranging from superconducting qubits to photonics, neutral atoms and Rydberg atom arrays.”
Impertro and his colleagues hope that their recent efforts will inform future theoretical and experimental studies focusing on topological many-body physics. In the future, the methods they devised could help to realize other complex quantum phases that have so far proved difficult to engineer experimentally.
“On the one hand, we show that it is now indeed feasible to experimentally realize interacting systems with an artificial magnetic field and reach significant system sizes,” said Impertro. “This offers a new playground for quantum simulation of many-body systems in- and out-of-equilibrium in regimes that are extremely difficult to access with classical numerical techniques. On the other hand, a comparison with numerical simulations allowed us to extract an estimate of the effective temperature of the prepared states.”
The new methods introduced by Impertro and his colleagues could soon enable the validation of theoretical models of strongly interacting quantum many-body systems, while also potentially contributing to the future advancement of quantum technologies. In their next studies, the researchers plan to further explore the rich phase diagram of interacting flux ladders beyond the Mott-Meissner phase, for instance by probing vortex or symmetry-broken states.
“In these future studies, it will be central to reduce the experimentally accessible temperature scales further, as many of these phases are even more fragile,” added Impertro. “Additionally, a long-term goal is to extend the ladder geometry to full-2D systems, where exotic physics such as anyons in fractional quantum Hall states can be studied.”
Left: This scanning transmission electron microscope (STEM) image of a tantalum (Ta) film surface shows an amorphous oxide above the regularly arrayed atoms of crystalline Ta metal. Right: The STEM imaging combined with computational modeling revealed details of the interface between these layers, including the formation of the amorphous oxide (top layer) and a suboxide layer that retains crystalline features (second layer) above the regularly arrayed tantalum atoms. Credit: Brookhaven National Laboratory
Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and DOE’s Pacific Northwest National Laboratory (PNNL) have used a combination of scanning transmission electron microscopy (STEM) and computational modeling to get a closer look and deeper understanding of tantalum oxide. When this amorphous oxide layer forms on the surface of tantalum—a superconductor that shows great promise for making the “qubit” building blocks of a quantum computer—it can impede the material’s ability to retain quantum information.
Learning how the oxide forms may offer clues as to why this happens—and potentially point to ways to prevent quantum coherence loss. The research was recently published in the journal ACS Nano.
The paper builds on earlier research by a team at Brookhaven’s Center for Functional Nanomaterials (CFN), Brookhaven’s National Synchrotron Light Source II (NSLS-II), and Princeton University that was conducted as part of the Co-design Center for Quantum Advantage (C2QA), a Brookhaven-led national quantum information science research center in which Princeton is a key partner.
“In that work, we used X-ray photoemission spectroscopy at NSLS-II to infer details about the type of oxide that forms on the surface of tantalum when it is exposed to oxygen in the air,” said Mingzhao Liu, a CFN scientist and one of the lead authors on the study. “But we wanted to understand more about the chemistry of this very thin layer of oxide by making direct measurements,” he explained.
So, in the new study, the team partnered with scientists in Brookhaven’s Condensed Matter Physics & Materials Science (CMPMS) Department to use advanced STEM techniques that enabled them to study the ultrathin oxide layer directly. They also worked with theorists at PNNL who performed computational modeling that revealed the most likely arrangements and interactions of atoms in the material as they underwent oxidation.
Together, these methods helped the team build an atomic-level understanding of the ordered crystalline lattice of tantalum metal, the amorphous oxide that forms on its surface, and intriguing new details about the interface between these layers.
“The key is to understand the interface between the surface oxide layer and the tantalum film because this interface can profoundly impact qubit performance,” said study co-author Yimei Zhu, a physicist from CMPMS, echoing the wisdom of Nobel laureate Herbert Kroemer, who famously asserted, “The interface is the device.”
Emphasizing that “quantitatively probing a mere one-to-two-atomic-layer-thick interface poses a formidable challenge,” Zhu noted, “we were able to directly measure the atomic structures and bonding states of the oxide layer and tantalum film as well as identify those of the interface using the advanced electron microscopy techniques developed at Brookhaven.”
“The measurements reveal that the interface consists of a ‘suboxide’ layer nestled between the periodically ordered tantalum atoms and the fully disordered amorphous tantalum oxide. Within this suboxide layer, only a few oxygen atoms are integrated into the tantalum crystal lattice,” Zhu said.
The combined structural and chemical measurements offer a crucially detailed perspective on the material. Density functional theory calculations then helped the scientists validate and gain deeper insight into these observations.
“We simulated the effect of gradual surface oxidation by gradually increasing the number of oxygen species at the surface and in the subsurface region,” said Peter Sushko, one of the PNNL theorists.
By assessing the thermodynamic stability, structure, and electronic property changes of the tantalum films during oxidation, the scientists concluded that while the fully oxidized amorphous layer acts as an insulator, the suboxide layer retains features of a metal.
“We always thought if the tantalum is oxidized, it becomes completely amorphous, with no crystalline order at all,” said Liu. “But in the suboxide layer, the tantalum sites are still quite ordered.”
With the presence of both fully oxidized tantalum and a suboxide layer, the scientists wanted to understand which part is most responsible the loss of coherence in qubits made of this superconducting material.
“It’s likely the oxide has multiple roles,” Liu said.
First, he noted, the fully oxidized amorphous layer contains many lattice defects. That is, the locations of the atoms are not well defined. Some atoms can shift around to different configurations, each with a different energy level. Though these shifts are small, each one consumes a tiny bit of electrical energy, which contributes to loss of energy from the qubit.
“This so-called two-level system loss in an amorphous material brings parasitic and irreversible loss to the quantum coherence—the ability of the material to hold onto quantum information,” Liu said.
But because the suboxide layer is still crystalline, “it may not be as bad as people were thinking,” Liu said. Maybe the more fixed atomic arrangements in this layer will minimize two-level system loss.
Then again, he noted, because the suboxide layer has some metallic characteristics, it could cause other problems.
“When you put a normal metal next to a superconductor, that could contribute to breaking up the pairs of electrons that move through the material with no resistance,” he noted. “If the pair breaks into two electrons again, then you will have loss of superconductivity and coherence. And that is not what you want.”
Future studies may reveal more details and strategies for preventing loss of superconductivity and quantum coherence in tantalum.
More information: Junsik Mun et al, Probing Oxidation-Driven Amorphized Surfaces in a Ta(110) Film for Superconducting Qubit, ACS Nano (2023). DOI: 10.1021/acsnano.3c10740
While image denoising algorithms have undergone extensive research and advancements in the past decades, classical denoising techniques often necessitate numerous iterations for their inference, making them less suitable for real-time applications.
The advent of deep neural networks (DNNs) has ushered in a paradigm shift, enabling the development of non-iterative, feed-forward digital image denoising approaches.
These DNN-based methods exhibit remarkable efficacy, achieving real-time performance while maintaining high denoising accuracy. However, these deep learning-based digital denoisers incur a trade-off, demanding high-cost, resource- and power-intensive graphics processing units (GPUs) for operation.
In an article published in Light: Science & Applications, a team of researchers, led by Professors Aydogan Ozcan and Mona Jarrahi from University of California, Los Angeles (UCLA), U.S., and Professor Kaan Akşit from University College London (UCL), UK developed a physical image denoiser comprising spatially engineered diffractive layers to process noisy input images at the speed of light and synthesize denoised images at its output field-of-view without any digital computing.
Following a one-time training on a computer, the resulting visual processor with its passive diffractive layers is fabricated, forming a physical image denoiser that scatters out the optical modes associated with undesired noise or spatial artifacts of the input images.
Through its optimized design, this diffractive visual processor preserves the optical modes representing the desired spatial features of the input images with minimal distortions.
As a result, it instantly synthesizes denoised images within its output field-of-view without the need to digitize, store or transmit an image for a digital processor to act on it. The efficacy of this all-optical image denoising approach was validated by suppressing salt and pepper noise from both intensity- and phase-encoded input images.
Furthermore, this physical image denoising framework was experimentally demonstrated using terahertz radiation and a 3D-fabricated diffractive denoiser.
This all-optical image denoising framework offers several important advantages, such as low power consumption, ultra-high speed, and compact size.
The research team envisions that the success of these all-optical image denoisers can catalyze the development of all-optical visual processors tailored to address various inverse problems in imaging and sensing.
More information: Çağatay Işıl et al, All-optical image denoising using a diffractive visual processor, Light: Science & Applications (2024). DOI: 10.1038/s41377-024-01385-6
Putting hypersensitive quantum sensors in a living cell is a promising path for tracking cell growth and diagnosing diseases—even cancers—in their early stages.
Many of the best, most powerful quantum sensors can be created in small bits of diamond, but that leads to a separate issue: It’s hard to stick a diamond in a cell and get it to work.
“All kinds of those processes that you really need to probe on a molecular level, you cannot use something very big. You have to go inside the cell. For that, we need nanoparticles,” said University of Chicago Pritzker School of Molecular Engineering Ph.D. candidate Uri Zvi. “People have used diamond nanocrystals as biosensors before, but they discovered that they perform worse than what we would expect. Significantly worse.”
Zvi is the first author of a paper published in Proceedings of the National Academy of Sciences that tackles this issue. Together with researchers from UChicago PME and the University of Iowa, Zvi united insights from cellular biology, quantum computing, old-fashioned semiconductors and high-definition TVs to both create a revolutionary new quantum biosensor. In doing so, they shed light on a longstanding mystery in quantum materials.
By encasing a diamond nanoparticle with a specially engineered shell—a technique inspired by QLED televisions—the team created not only a quantum biosensor ideal for a living cell, but also uncovered new insights into how a material’s surface can be modified to enhance its quantum properties.
“It’s already one of the most sensitive things on Earth, and now they’ve figured out a way to enhance that further in a number of different environments,” said Zvi’s principal investigator, UChicago PME Prof. Aaron Esser-Kahn, a co-author of the paper.
A cell full of diamonds Qubits hosted in diamond nanocrystals maintain quantum coherence even when the particles are small enough to be “taken up” by a living cell—a good metaphor is the cell swallowing and chewing on them without spitting them out. But the smaller the diamond particles, the weaker the quantum signal.
“It excited people for a while that these quantum sensors can be brought into living cells and, in principle, be useful as a sensor,” said UChicago PME Asst. Prof. Peter Maurer, a co-author of the paper. “However, while these kind of quantum sensors inside of a big piece of bulk diamond have really good quantum properties, when they are in nano diamonds, the coherent properties, the quantum properties, are actually significantly reduced.”
Here, Zvi turned to an unlikely source for inspiration—quantum dot LED televisions. QLED TVs use vibrant fluorescent quantum dots to broadcast in rich, full colors. In the early days, the colors were bright but unstable, prone to suddenly blinking off.
“Researchers found that surrounding the quantum dots with carefully designed shells suppresses detrimental surface effects and increase their emission,” Zvi said. “And today you can use a previously unstable quantum dot as part of your TV.”
In a new paper, University of Chicago Pritzker School of Molecular Engineering researchers, including Asst. Prof. Peter Maurer (left) and first author and Ph.D. candidate Uri Zvi (right), and their collaborators created a revolutionary new quantum biosensor that sheds light on a longstanding question in quantum materials. Credit: Jason Smith Working with UChicago PME and Chemistry Department quantum dot expert Prof. Dmitri Talapin, a co-author of the paper, Zvi reasoned that since both sets of issues—the quantum dots’ fluorescence and the nanodiamond weakened signal—originated with the surface state, a similar approach might work.
But since the sensor is meant to go within a living body, not every shell would work. An immunoengineering expert, Esser-Kahn helped develop a silicon-oxygen (siloxane) shell that would both enhance the quantum properties and not tip off the immune system that something is awry.
“The surface properties of most of these materials are sticky and disordered in a way that the immune cells can tell it’s not supposed to be there. They look like a foreign object to an immune cell,” Esser-Kahn said. “Siloxane-coated things look like a big, smooth blob of water. And so the body is much more happy to engulf and then chew on a particle like that.”
Previous efforts to improve the quantum properties of diamond nanocrystals through surface engineering had shown limited success. As a result, the team expected only modest gains. Instead, they saw up to fourfold improvements in spin coherence.
That increase—as well as a 1.8-fold increase in fluorescence and separate significant increases to charge stability—was a riddle both baffling and enthralling.
Better and better “I would try to go to bed at night but stay up thinking ‘What’s happening there? The spin coherence is getting better—but why?” said University of Iowa Asst. Prof. Denis Candido, second author of the new paper. “I’d think ‘What if we do this experiment? What if we do this calculation?’ It was very, very exciting, and in the end, we found the underlying reason for the improvement of the coherence.”
The interdisciplinary team—bioengineer-turned-quantum-scientist Zvi, immunoengineer Esser-Kahn and quantum engineers Maurer and Talapin—brought Candido and University of Iowa Physics and Astronomy Prof. Michael Flatté in to provide some of the theoretical framework for the research.
“What I found really exciting about this is that some old ideas that were critical for semiconductor electronic technology turned out to be really important for these new quantum systems,” Flatté said.
They found that adding the silica shell didn’t just protect the diamond surface. It fundamentally altered the quantum behavior inside. The material interface was driving electron transfer from the diamond into the shell. Depleting electrons from the atoms and molecules that normally reduce the quantum coherence made a more sensitive and stable way to read signals from living cells.
This enabled the team to identify the specific surface sites that degrade coherence and make quantum devices less effective—solving a long-standing mystery in the quantum sensing field and opening new doors for both engineering innovation and fundamental research.
“The end impact is not just a better sensor, but a new, quantitative framework for engineering coherence and charge stability in quantum nanomaterials,” Zvi said.
A a view from inside the OMEGA target chamber during a direct-drive inertial fusion experiment at the University of Rochester’s Laboratory for Laser Energetics. Scientists fired 28 kilojoules of laser energy at small capsules filled with deuterium and tritium fuel, causing the capsules to implode and produce a plasma hot enough to initiate fusion reactions between the fuel nuclei. The temperatures achieved at the heart of these implosions are as high as 100 million degrees Celsius (180 million degrees Fahrenheit). The speed at which the implosion takes place is typically between 500 and 600 kilometers per second (1.1 to 1.35 million miles per hour). The pressures at the core are up to 80 billion times greater than atmospheric pressure. Credit: University of Rochester Laboratory for Laser Energetics photo / Eugene Kowaluk
Scientists from the University of Rochester’s Laboratory for Laser Energetics (LLE) led experiments to demonstrate an effective “spark plug” for direct-drive methods of inertial confinement fusion (ICF). In two studies published in Nature Physics, the authors discuss their results and outline how they can be applied at bigger scales with the hopes of eventually producing fusion at a future facility.
LLE is the largest university-based U.S. Department of Energy program and hosts the OMEGA laser system, which is largest academic laser in the world but still almost one hundredth the energy of the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California.
With OMEGA, Rochester scientists completed several successful attempts to fire 28 kilojoules of laser energy at small capsules filled with deuterium and tritium fuel, causing the capsules to implode and produce a plasma hot enough to initiate fusion reactions between the fuel nuclei. The experiments caused fusion reactions that produced more energy than the amount of energy in the central hot plasma.
The OMEGA experiments use direct laser illumination of the capsule and differ from the indirect drive approach used on the NIF. When using the indirect drive approach, the laser light is converted into X-rays that in turn drive the capsule implosion. The NIF used indirect drive to irradiate a capsule with X-rays using about 2,000 kilojoules of laser energy. This led to a 2022 breakthrough at NIF in achieving fusion ignition—a fusion reaction that creates a net gain of energy from the target.
“Generating more fusion energy than the internal energy content of where the fusion takes place is an important threshold,” says lead author of the first paper Connor Williams ’23 Ph.D. (physics and astronomy), now a staff scientist at Sandia National Labs in radiation and ICF target design. “That’s a necessary requirement for anything you want to accomplish later on, such as burning plasmas or achieving ignition.”
By showing they can achieve this level of implosion performance with just 28 kilojoules of laser energy, the Rochester team is excited by the prospect of applying direct-drive methods to lasers with more energy. Demonstrating a spark plug is an important step, however, OMEGA is too small to compress enough fuel to get to ignition.
“If you can eventually create the spark plug and compress fuel, direct drive has a lot of characteristics that are favorable for fusion energy compared to indirect drive,” says Varchas Gopalaswamy ’21 Ph.D. (mechanical engineering), the LLE scientist who led the second study that explores the implications of using the direct-drive approach on megajoule-class lasers, similar to the size of the NIF. “After scaling the OMEGA results to a few megajoules of laser energies, the fusion reactions are predicted to become self-sustaining, a condition called ‘burning plasmas.'”
Gopalaswamy says that direct-drive ICF is a promising approach for achieving thermonuclear ignition and net energy in laser fusion.
“A major factor contributing to the success of these recent experiments is the development of a novel implosion design method based on statistical predictions and validated by machine learning algorithms,” says Riccardo Betti, LLE’s chief scientist and the Robert L. McCrory Professor in the Department of Mechanical Engineering and in the Department of Physics and Astronomy. “These predictive models allow us to narrow the pool of promising candidate designs before carrying out valuable experiments.”
The Rochester experiments required a highly coordinated effort between large number of scientists, engineers, and technical staff to operate the complex laser facility. They collaborated with researchers from the MIT Plasma Science and Fusion Center and General Atomics to conduct the experiments.
More information: C. A. Williams et al, Demonstration of hot-spot fuel gain exceeding unity in direct-drive inertial confinement fusion implosions, Nature Physics (2024). DOI: 10.1038/s41567-023-02363-2
V. Gopalaswamy et al, Demonstration of a hydrodynamically equivalent burning plasma in direct-drive inertial confinement fusion, Nature Physics (2024). DOI: 10.1038/s41567-023-02361-4
Image shows the ion trap used to control the location of computational and refrigerant ions. The device was produced by Sandia National Laboratories. Credit: Sandia National Laboratories.
A new cooling technique that utilizes a single species of trapped ion for both computing and cooling could simplify the use of quantum charge-coupled devices (QCCDs), potentially moving quantum computing closer to practical applications.
Using a technique called rapid ion exchange cooling, scientists at the Georgia Tech Research Institute (GTRI) have shown that they could cool a calcium ion—which gains vibrational energy while doing quantum computations—by moving a cold ion of the same species into close proximity. After transferring energy from the hot ion to the cold one, the refrigerant ion is returned to a nearby reservoir to be cooled for further use.
Conventional ion cooling for QCCDs involves the use of two different ion species, with cooling ions coupled to lasers of a different wavelength that do not affect the ions used for quantum computing. Beyond the lasers needed to control the quantum computing operations, this sympathetic cooling technique requires additional lasers to trap and control the refrigerant ions, and that both increases complexity and slows quantum computing operations.
“We have shown a new method for cooling ions faster and more simply in this promising QCCD architecture,” said Spencer Fallek, a GTRI research scientist. “Rapid exchange cooling can be faster because transporting the cooling ions requires less time than laser cooling two different species. And it’s simpler because using two different species requires operating and controlling more lasers.”
https://www.youtube.com/embed/Uj9ITEhh3Pc?color=whiteVideo shows how a computational ion can be cooled by bringing it near a refrigerant ion of the same atomic species. Credit: Georgia Tech Research Institute
The ion movement takes place in a trap maintained by precisely controlling voltages that create an electrical potential between gold contacts. But moving a cold atom from one part of the trap is a bit like moving a bowl with a marble sitting in the bottom.
When the bowl stops moving, the marble must become stationary—not rolling around in the bowl, explained Kenton Brown, a GTRI principal research scientist who has worked on quantum computing issues for more than 15 years.
“That’s basically what we’re always trying to do with these ions when we’re moving the confining potential, which is like the bowl, from one place to another in the trap,” he said. “When we’re done moving the confining potential to the final location in the trap, we don’t want the ion moving around inside the potential.”
Once the hot ion and cold ion are close to each other, a simple energy swap takes place and the original cold ion—heated now by its interaction with a computing ion—can be split off and returned to a nearby reservoir of cooled ions.
The GTRI researchers have so far demonstrated a two-ion proof-of-concept system, but say their technique is applicable to the use of multiple computing and cooling ions, and other ion species.
A single energy exchange removed more than 96% of the heat—measured as 102(5) quanta—from the computing ion, which came as a pleasant surprise to Brown, who had expected multiple interactions might be necessary. The researchers tested the energy exchange by varying the starting temperature of the computational ions and found that the technique is effective regardless of the initial temperature. They have also demonstrated that the energy exchange operation can be done multiple times.
Heat—essentially vibrational energy—seeps into the trapped ion system through both computational activity and from anomalous heating, such as unavoidable radio-frequency noise in the ion trap itself. Because the computing ion is absorbing heat from these sources even as it is being cooled, removing more than 96% of the energy will require more improvements, Brown said.
The researchers envision that in an operating system, cooled atoms would be available in a reservoir off to the side of the QCCD operations and maintained at a steady temperature. The computing ions cannot be directly laser-cooled because doing so would erase the quantum data they hold.
Excessive heat in a QCCD system adversely affects the fidelity of the quantum gates, introducing errors in the system. The GTRI researchers have not yet built a QCCD that uses their cooling technique, though that is a future step in the research. Other work ahead includes accelerating the cooling process and studying its effectiveness at cooling motion along other spatial directions.
The experimental component of the rapid exchange cooling experiment was guided by simulations done to predict, among other factors, the pathways that the ions would take in their journey within the ion trap. “We definitely understood what we were looking for and how we should go about achieving it based on the theory and simulations we had,” Brown said.
The unique ion trap was fabricated by collaborators at Sandia National Laboratories. The GTRI researchers used computer-controlled voltage generation cards able to produce specific waveforms in the trap, which has a total of 154 electrodes, of which the experiment used 48. The experiments took place in a cryostat maintained at about 4 degrees Kelvin.
Researchers Spencer Fallek (left) and Kenton Brown are shown with equipment used to develop a new technique for cooling ions in quantum devices. Credit: Sean McNeil, GTRI
GTRI’s Quantum Systems Division (QSD) investigates quantum computing systems based on individual trapped atomic ions and novel quantum sensor devices based on atomic systems. GTRI researchers have designed, fabricated, and demonstrated a number of ion traps and state-of-the-art components to support integrated quantum information systems. Among the technologies developed is the ability to precisely transport ions to where they are needed.
“We have very fine control of how the ions move, the speed at which they can be brought together, the potential they’re in when they are near one another, and the timing that’s necessary to do experiments like this,” said Fallek.
Other GTRI researchers involved in the project included Craig Clark, Holly Tinkey, John Gray, Ryan McGill and Vikram Sandhu. The research was done in collaboration with Los Alamos National Laboratory.
