Category: Physics

by Luke Auburn, University of Rochester

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

Provided by University of Rochester 

by John Toon, Georgia Institute of Technology

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.

The research is reported in the journal Nature Communications.

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.

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.

Kirigami is a traditional Japanese art form that entails cutting and folding paper to produce complex three-dimensional (3D) structures or objects. Over the past decades, this creative practice has also been applied in the context of physics, engineering, and materials science research to create new materials, devices and even robotic systems.

Researchers at Sichuan University and McGill University recently devised a new approach for the inverse engineering of kirigami, which does not rely on advanced computational tools and numerical algorithms. This new method, outlined in a paper published in Physical Review Letters, could simplify the design of intricate kirigami for a wide range of real-world applications.

“This work is a natural extension of our previous work on kirigami,” Damiano Pasini, senior corresponding author of the paper, told Phys.org.

“The first author, Chuan Qiao, is a former Ph.D. student of mine. During his Ph.D. under my supervision, Chuan worked on snapping interaction of thin shells and anisotropic morphing of kirigami. The study of the latter led to a paper published last year in Advanced Materials, where we adopted a unit cell approach to investigate the deformation of a kirigami made of rotating units with arbitrarily shaped triangles.”

In their previous studies, the researchers were able to better understand the role that the geometric parameters of slit patterns (e.g., internal angles and lengths) play in the anisotropic deployment of kirigami. To do this, they assessed changes in shape observed in the final deployment of kirigami by examining the length of the sides and internal angles of the triangular units.

“This triggered a set of interrelated questions, such as: how would a kirigami deform if we simply change the entire shape of the rotating unit in its entirety, as opposed to changing its geometric constituents individually, as we did in previous work? Is there a physical relation between the kirigami deformation and the shape of its rotating unit? And can this geometric relation establish an intuitive first-hand route for the inverse design of kirigami?” said Pasini.

“With these questions in mind, our goal then became twofold: to unveil the fundamental relation between the shape of the rotating units and the shape of the deployed kirigami and to leverage such a relation for the design of kirigami that foregoes the use of fairly sophisticated numerical methods currently used in the literature.”

In their new paper, Pasini and his colleagues showed that there is a simple relationship between the strain applied to a rotating unit (γ*max) and the shear deformation of a deployed triangle kirigami (γmax). Their proposed method to inversely design kirigami leverages this straightforward relationship.

The fundamental relationship between the strain applied to a rotating unit (γ*max) and the shear deformation of the deployed triangle kirigami (γmax). A shrink of the rotating units in their initial closed form corresponds to an expansion of the deployed kirigami. Credit: Qiao et al.
“The key notion is that the shear strain applied to the initial rotating units, which shrink horizontally when we move from the left to the middle sketch, is in the opposite direction of the shear strain of the deployed triangle kirigami, which, in contrast, expands horizontally (once it deploys),” said Pasini.

“This insight can be leveraged for the inverse design of kirigami. By a simple geometric tuning of the shape of the rotating units with shear strains, we can achieve on-target deployment. The only basic operation we need is to use an area-preserving map to apply the shear strain.”

The new approach for the engineering of kirigami introduced by this team of researchers requires three key ingredients. These are the contracted shape of the rotating units, the shape of a deployed kirigami, and an area-preserving map outlining the transition from the deployed kirigami to its non-deployed (i.e., contracted) form.

“With the ingredients above, the shear strain of the deployed triangle kirigami can be programmed by applying a shear strain to the shape of the rotating units in the opposite direction,” said Pasini. “Our method can now forego any numerical computations and program the shear deformation of a kirigami specimen at will in a swift, versatile manner.”

To demonstrate the potential of their inverse design method, Pasini and his colleagues used it to produce three different types of morphing targets, namely the contracted shape, the deployed shape, and the internal trajectories of rotating units in kirigami.

This recent study shows a fundamental relationship between the deformation of kirigami and the shape of their rotating units, which can be utilized to design these structures. The team’s geometric design method could soon be used to create a wide range of kirigami designs that could help to tackle complex engineering challenges.

“This work brings ground-rule insights into morphing matter with rotating units and offers an intuitive, firsthand geometric route for the swift design of complex kirigami,” added Pasini. “Similar observations can also be drawn by inspecting the morphing of quadrilateral kirigami, hence showing the promise of this work to describe other kirigami patterns.”

A research team has discovered how to make a promising energy-harvesting material much more efficient—without relying on rare or expensive elements. The material, called β-Zn4Sb3, is a tellurium-free thermoelectric compound that can convert waste heat into electricity.

In their study published in Advanced Science, scientists used advanced neutron scattering techniques to peek inside the crystal and found something surprising: tiny heat vibrations (called phonons) were being disrupted by “rattling” atoms inside the structure. This phenomenon, known as phonon avoided crossing, dramatically slowed down how heat travels through the material.

Thanks to this effect, the material’s thermal conductivity dropped to extremely low levels—great news for thermoelectric performance. Even better, the researchers found that the single-crystal version of this material also conducts electricity better than its polycrystalline counterpart, reaching a high power conversion efficiency of 1.4%.

These results show that smart phonon control can lead to high-performance, eco-friendly materials for converting heat into power.

In thermoelectric materials, avoided crossing refers to the interaction between propagating phonons and localized vibrational modes, where their energy dispersions repel each other rather than intersect. This phenomenon occurs under specific conditions, such as crystal symmetries or vibrational mode couplings.

However, when researchers developed the single-crystal β-Zn4Sb3, they observed an unexpected, avoided crossing, revealing unique phonon behavior that deviated from conventional thermoelectric materials.

The article explores the thermoelectric performance of single-crystalline β-Zn4Sb3, a tellurium-free material, by uncovering the microscopic mechanisms that lead to its ultralow lattice thermal conductivity (κL).

Using inelastic neutron scattering (INS), the researchers provide the first experimental observation of avoided crossing between longitudinal acoustic phonons and low-energy rattling modes. This interaction causes a significant reduction in phonon group velocity—from over 4000 m/s to about 591 m/s—and shortens phonon lifetimes to under 1 picosecond, both of which contribute to strongly suppressed heat transport.

The β-Zn4Sb3 single crystal achieves a κL of approximately 0.36 W/m·K in the 300–600 K range and a peak thermoelectric figure of merit (zT) of 1.0 at 623 K. Additionally, device-level testing shows a conversion efficiency (η) of 1.4% in a single-leg thermoelectric module—one of the highest reported for undoped Zn4Sb3.

Structural characterizations via TEM reveal a grain-boundary-free lattice with uniformly distributed moiré fringes, attributed to Zn concentration variations.

These nanoscale features further enhance phonon scattering without degrading electronic performance. Compared to polycrystalline samples, the single crystal exhibits significantly better electrical conductivity due to fewer defects and optimized carrier mobility.

“This discovery shows how heat flow can be engineered to design more efficient and sustainable energy technologies—without depending on scarce resources,” says Prof. Hsin-Jay Wu.

A team of physicists has embarked on a journey where few others have gone: into the glue that binds atomic nuclei. The resultant measurement, which was extracted from experimental data taken at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility, is the first of its kind and will help physicists image particles called gluons.

The paper revealing the results is published and featured as an editor’s suggestion in Physical Review Letters.

Gluons mediate the strong force that “glues” together quarks, another type of subatomic particle, to form the protons and neutrons situated at the center of atoms of ordinary matter. While previous measurements have allowed researchers to learn about the distribution of gluons in solitary protons or neutrons, they know less about how gluons behave inside protons or neutrons bound in nuclei.

“This result represents a big step forward in learning about where that gluon field is located in a proton,” said Axel Schmidt, an assistant professor of physics at George Washington University and a principal investigator of this work. “We see evidence that it might be changing when a proton or neutron is inside a nucleus.”

A charming guidepost particle

For more than four decades, the physics community has known that quarks, the building blocks of our visible universe, move slower when they make up a proton or neutron that’s inside an atomic nucleus compared to a solitary proton or neutron. But physicists haven’t been able to figure out why this phenomenon, known as the EMC effect, occurs.

To learn more about it, and the strong force in general, physicists need to probe gluons the way they probed quarks. However, measuring the distribution of gluons, which are neutral, is more challenging than measuring the distribution of electrically charged quarks.

“Studying these neutral particles that only interact by the strong force is much more difficult,” said Lucas Ehinger, a graduate student at the Massachusetts Institute of Technology who worked on the analysis that led to this measurement. “We know a whole lot less about them and their dynamics in nuclei, including whether there’s any kind of potential EMC effect with them.”

This work takes a step toward changing this. And it does so by measuring a different particle altogether: J/ψ (or J/psi).

The experiment was carried out at Jefferson Lab’s Continuous Electron Beam Accelerator Facility, a DOE user facility that supports the research of more than 1,650 nuclear physicists worldwide. CEBAF’s electron beams can be used to also produce beams of high-energy photons for experiments that explore atomic nuclei.

Shooting a beam of photons at protons and neutrons can produce J/ψ particles, which each promptly decays into an electron and positron. Detecting this pair shows how many J/ψ were produced during an experiment. J/ψ is made of charm quarks. Because charm quarks, one of the six flavors of quarks, are not part of the proton or neutron, physicists know J/ψ is born from the interaction between the photon and gluon, which can produce particles containing any flavor of quark.

The production of J/ψ is a well-known tool for studying gluon distributions. Previous experiments at Jefferson Lab used a photon beam to measure J/ψ production of a solitary proton in the GlueX detector. To produce J/ψ, which is a heavy particle, the energy of the photon beam had to be very high—at least 8.2 GeV.

In this work, the experimental team also used a photon beam to produce J/ψ. However, they were able to do so using photons below the 8.2 GeV energy threshold and measure the results in the GlueX detector.

This was possible because they were using different nuclei as targets: deuterium, helium and carbon. Unlike a solitary proton or neutron target, the protons and neutrons inside these nuclei are moving around. Their kinetic energy combines with the energy of the incoming below-threshold photon, and, together, they offer enough energy to create J/ψ.

As a result, the team was the first to measure J/ψ photoproduction below the photon energy threshold required for a stationary proton. Because this measurement was taken off nuclei, it images the glue holding together protons and neutrons bound inside the nucleus.

“We are in this frontier of nuclear glue. Essentially, nothing is known, so everything you measure is informative,” said Or Hen, professor of physics at MIT and a principal investigator of this work. “It’s super exciting and super difficult at the same time.”

Charting a map for future measurements

One reason this pathfinder measurement was difficult is because there weren’t previous measurements to guide it. Embarking on the analysis, the team wasn’t even sure it was possible. The experiment that collected this data wasn’t originally supposed to measure subthreshold J/ψ production; it was more of a hopeful add-on.

Thankfully, the researchers had Jackson Pybus on their team. Pybus led the bulk of the analysis while he was a graduate student at MIT. He called upon his training during a summer abroad in Germany. There, he had worked with a theoretician to learn about light-front dynamics.

This approach generally applies to quantum field theories, which describe relativistic particle behavior (particles moving close to the speed of light). In this research, it is most useful in describing particle systems like nuclei. Applying tricks from this theoretical method allowed Pybus and the team to extract this measurement.

“This work is both unique in terms of what physics it teaches us, but also in terms of the techniques that a graduate student implemented to get at that physics,” Hen said. “None of us, except for Jackson, would have been able to do this work. He deserves a lot of credit.”

When the experimentalists compared their sub-threshold measurement to theoretical predictions, they saw that more J/ψ were produced than theory predicted. This disparity hints that the nuclear glue behaves differently than the glue in solitary protons or neutrons, but more data are needed to determine exactly how. Fortunately, these results will serve as a map to guide similar future measurements.

“Now that we know that we can do this measurement, we would really like to optimize a longer experiment to measure this in detail and quantitatively pin down some of these potentially exotic effects, where we really only have a first look right now,” said Pybus, who is now a postdoctoral fellow at Los Alamos National Laboratory.

The data used in this work—made up of only dozens of J/ψ measurements– were collected during a relatively short six-week run in 2021. The team is proposing an experiment dedicated to studying the nuclear glue, again using CEBAF’s photon beam with the GlueX apparatus.

“Imagine what we could do if we had 100 days of dedicated accelerator time to really study this reaction,” Hen said. “We are now doing the very hard work of mapping out the frontier of the strong nuclear force with the hope that one day—maybe not in our lifetime—humanity’s improved knowledge will enable better technology and more sustainable power sources.”

These results could also steer gluon experiments at the forthcoming Electron-Ion Collider (EIC), which plans to further investigate gluons.

“We would like to learn about this problem and have a good handle of what’s going on and where to look prior to this machine turning on,” Schmidt said.

Tête de Moine, a semi-hard Swiss cheese that often finds its way onto charcuterie boards and salads, not only brings a rich, nutty and creamy flavor, but also adds a dramatic flare to the presentation. Instead of slicing, this cheese is shaved into delicate rosettes using a tool called a Girolle whose rotating blade gently scrapes thin layers of cheese into ruffled curls. These pretty cheese flowers are known to enhance the flavor and texture due to their high surface-to-volume ratio.

The unusual way Tête de Moine forms wrinkles when shaved, piqued the interest of a team of physicists who, in a study published in Physical Review Letters, set out to investigate the physical mechanisms behind these intricate shapes.

Similar morphogenetic patterns can be observed in the frilly edges of leaves, fungi, corals, or even torn plastic sheets, but the mechanisms that explain the similar shapes in these materials fail to account for the distinctive physical properties of cheese.

This study discovered that the frilly shapes arise as a result of variations in the cheese’s properties—such as firmness and elasticity—within a single Tête de Moine wheel, from the center to the edge. The distinctive flower shape is driven mainly by changes in friction caused by the cheese’s inhomogeneous texture and not by variations in mechanical properties like yield stress or fracture energy.

A typical Girolle has a wooden base, a central steel spike, and a removable rotating blade with a handle attached to it. Before serving, the cheese is skewered onto a steel rod until it reaches the wooden base, and then the rotating blade that sits on the cheese is mounted onto the rod. Rotating the blade’s handle scrapes off thin layers of the frilly cheese.

Schematic illustration of the experimental setup. Inset: depth of cut h0 as a function of vertical load per unit length of the blade Ft. Credit: Phys. Rev. Lett. (2025). DOI: https://doi.org/10.1103/PhysRevLett.134.208201
For this study, the researchers opted for cheese wheels from a single brand and age was used to maintain consistency. They also modified the Girolle to include: a motorized base of the Girolle to rotate the cheese at a steady speed of 1.14 rad/s, the blade at a fixed height and a tilt of −14.7° to ensure consistent slicing and adjustable weights to control the vertical cutting force precisely.

To understand the physical forces behind the cheese’s unique shape, the team measured key properties like depth of cut, mechanical properties such as Young’s modulus, yield stress, and fracture energy, as well as the friction coefficient at various positions on the cheese wheel.

They also integrated steady, real-time imaging into the setup, capturing side-view snapshots of the cutting process. This allowed them to visually confirm the cutting mechanism and observe how the cheese curls formed along the wheel’s edge.

a) Side view of instantaneous snapshots of the cheese layer formation on different radial positions x from the edge periphery, for Ft = 0.2 N/mm. b) Sketch illustrating the shear strain in a 2D plastic flow during cutting. Credit: Phys. Rev. Lett. (2025). DOI: https://doi.org/10.1103/PhysRevLett.134.208201
The experiments revealed that the cheese flowers form due to inhomogeneous plastic contraction during scraping, not from elastic deformation.

As the cheese wheel ages, it matures at different rates in different areas—the core remains softer while the edge becomes harder. This results in varying friction across the wheel, with much greater contraction in the inner core region of the cheese flower, leading to its characteristic buckling and frilly shape.

This was further confirmed by the observation that removing the low-friction outer layer produced flat and non-frilly cheese slices.

The researchers highlight that the shaping mechanism presented in this study could help develop new tools for the controlled processing of soft materials and enable the design of complex forms through a simple scraping technique.

by Sanjukta Mondal

A joint team of researchers led by scientists at King Abdullah University of Science and Technology (KAUST) and King Abdulaziz City for Science and Technology (KACST) has reported the fastest quantum random number generator (QRNG) to date based on international benchmarks. The QRNG, which passed the required randomness tests of the National Institute of Standards and Technology, could produce random numbers at a rate nearly a thousand times faster than other QRNG.

“This is a significant leap for any industry that depends on strong data security,” said KAUST Professor Boon Ooi, who led the study, which is published in Optics Express. KAUST Professor Osman Bakr also contributed to the study.

Random number generators are critical for industries that depend on security, such as health, finance, and defense. But the random number generators currently used are vulnerable because of an intrinsic flaw in their design.

“Most random number generators are ‘pseudorandom number generators.’ In other words, they seem random, but in reality, they are complicated algorithms that can be solved. QRNGs do not suffer from this concern,” explained Ooi.

The reason is that QRNG uses the principles of quantum mechanics to produce a truly unpredictable random number. The high random number generation rate reported in the new study was the result of innovations made by the scientists in the fabrication and the post-processing algorithms of the device.

The QRNG was constructed using micro-LEDs (light emitting diodes) less than a few micrometers in size, which reduces their energy demands and suggests the QRNG is portable, expanding the types of applications. In addition, the National Institute of Standards and Technology is recognized internationally for providing benchmarks to ascertain the quality of randomness.

Dr. Abdullah Almogbel, a contributor of the study who is also a researcher at the Microelectronics and Semiconductors Institute and director of the Center of Excellence for Solid-State Lighting at KACST, stated, “KACST, in its capacity as the national laboratory, is committed to advancing applied research that directly supports the objectives of Saudi Arabia’s Vision 2030—particularly in establishing global leadership across strategic sectors, including quantum-enabled innovations.

“Undertaking such research initiatives is expected to generate substantial value for a wide range of industries and further solidify their global standing.”

by King Abdullah University of Science and Technology

edited by Gaby Clark, reviewed by Robert Egan

 The precise measurement of states in atomic and molecular systems can help to validate fundamental physics theories and their predictions. Among the various platforms that can help to validate theoretical predictions are so-called diatomic molecular hydrogen ions (MHI), molecular ions that consist of two hydrogen nuclei (i.e., protons or their isotopes) and a single electron.

Compared to atomic ions, these molecular ions have a more complex internal structure, as they contain two nuclei instead of one. Even when they are in their lowest possible electronic energy level (i.e., the electron’s ground state), these two nuclei can still rotate and vibrate, producing a wide range of rovibrational states.

Researchers at the Max Planck Institute for Nuclear Physics recently introduced a new method to precisely control and non-destructively measure the rovibrational ground state of a single molecular hydrogen ion in a Penning trap (i.e., a device that confines charged particles using static electric and magnetic fields).

This method, outlined in a paper published in Physical Review Letters, could open new possibilities for the manipulation and measurement of rich quantum states in individual molecular ions.

“The work for the paper was inspired by the goal of the fundamental physics research community to compare H2+ and its antimatter counterpart H2- in the future,” Charlotte König, first author of the paper, told Phys.org. “An overview on this topic and measurement proposals can be found in a paper by Myers published in 2018.

Therefore, we have now developed and demonstrated nondestructive state detection and measurement techniques on a single molecular hydrogen ion (HD+) in a Penning trap; applicable to other molecular ions with an unpaired electron spin, i.e. to H2+ and H2-.”

The new method developed by König and her colleagues relies on an effect known as the continuous Stern Gerlach effect, first unveiled in the 1980s. This is a physical phenomenon that can be leveraged to measure the orientation of the magnetic moment (e.g., the electron spin) of single trapped particles, including ions, without destroying them.

“In our experiments, the orientation of the electron spin in the external magnetic field (B) of the Penning trap is mapped onto the ion motion in a magnetic bottle (B=B0+B2 x2), which is an established technique for atomic ions in Penning traps,” explained König.

“In the molecule, the energy splitting between electron spin up or down is unique to each rovibrational and hyperfine state. Therefore, resonantly driving an electron spin transition (detected by the continuous Stern Gerlach effect), gives us the information about which internal quantum state the ion is in.”

Using their newly proposed method, König and her colleagues demonstrated the confinement of an externally produced molecular hydrogen ion (HD+) for more than a month. In addition, they were able to detect the internal quantum state of this ion and control its hyperfine state.

“These are necessary requirements to enable future measurements of the antimatter molecular hydrogen ion H2- for tests of the fundamental charge-parity-time reversal symmetry,” said König. “The techniques could also be applied to other molecular ions, for which single particle control is envisioned.”

The recent research by this team of researchers and the new techniques it introduced could be used in future studies probing the states of both matter and antimatter molecular systems. Ultimately, it could help to unveil deviations from the Standard Model, shedding light on the limitations of current physical predictions.

“Our future research plans will include applying the demonstrated techniques to high-precision spectroscopy of single molecular hydrogen ions in our Penning trap apparatus,” added König. “This research will address either the hyperfine and Zeeman structure or the rovibrational level structure.”

by Ingrid Fadelli

You are the protagonist in a thriller. One morning, an unknown caller with a distorted voice says, “To save your city, solve the puzzle. Go to the coordinates. X marks the clue.” You rush to the spot and see an X on a distant billboard, too far to read. Your vision is sharp, but not that sharp. So, what do you do? A new laser emitter designed by a team of researchers from China could come to the rescue.

According to the study published in Physical Review Letters, the developed setup includes multiple laser emitters that enable super-resolution imaging of targets as small as millimeters in scale from a 1.36 kilometers (0.85 miles) distance in an outdoor urban environment. The device successfully images letter-shaped physical targets measuring 8×9 mm, with letter widths of 1.5 mm, placed at the far end of its imaging range.

Interferometry is a widely used imaging technique in astronomy which works by merging light from different sources to create an interference pattern. These interference patterns are formed when light waves interact to either reinforce or cancel each other depending on their phase differences. These patterns carry detailed information about the object or phenomenon being studied.

Intensity interferometry, on the other hand, does not rely on combining light amplitudes or maintaining phase information but on light from a single source being measured separately by two detectors or telescopes, and the variations in their recorded intensities are compared.

Studying intensity fluctuations, correlations and their changes with the distance between the detectors can help extract spatial details about the object being studied.

What makes intensity interferometry stand out? It can cut through atmospheric turbulence and ignore flaws in telescope optics—making it ideal for long-distance, high-resolution imaging. Yet, its applications have mostly been limited to observing bright stars or objects that can be lit up with nearby light sources.

Scientists have attempted to expand its scope to active imaging applications such as light detection and ranging or LiDAR, but the lack of suitable thermal light sources and robust image reconstruction algorithms make the process challenging.

To overcome these issues, the researchers created an intensity interferometer setup with pseudothermal illumination achieved by superimposing light from 8-phase-independent multiple laser emitters. This setup included two telescopes and an infrared laser system on a shared optical bench.

The laser system produced thermal illumination, and reconstructed sparse, noisy data being collected into a high-resolution image with the help of a computational algorithm.

To test the super-resolution capabilities of the device, the letters “USTC” were crafted out of hollowed-out blackened aluminum sheets which were then covered in retroreflective sheets and used as a complex imaging target positioned over a kilometer away.

Using the designed active intensity interferometer, the researchers successfully demonstrated super-resolution imaging of millimeter-scale targets at a distance of 1.36 km in an outdoor urban environment. The imaging system achieved a resolution of 3 mm, which is 14 times higher than the diffraction limit of a single telescope, typically around 42.5 mm.

Once scaled for use beyond the laboratory, this device could significantly accelerate advancements in long-range, high-resolution remote sensing, surveillance, and non-invasive imaging in challenging environments.

More information: Lu-Chuan Liu et al, Active Optical Intensity Interferometry, Physical Review Letters (2025). DOI: 10.1103/PhysRevLett.134.180201

Journal information: Physical Review Letters 

by Sadie Harley, reviewed by Robert Egan

Heat management at the nanoscale has long been a cornerstone of advanced technological applications, ranging from high-performance electronics to quantum computing. Addressing this critical challenge, we have been deeply intrigued by the emerging field of thermotronics, which focuses on manipulating heat flux in ways analogous to how electronics control electric energy. Among its most promising advancements are quantum thermal diodes, which enable directional heat control, and quantum thermal transistors, which regulate heat flow with precision.

Thermal diodes, much like their electrical counterparts, provide unidirectional heat transfer, allowing heat to flow in one direction while blocking it in the reverse. We find this capability revolutionary for heat management, as it has the potential to transform numerous fields.

For instance, thermal diodes can significantly improve the cooling of high-performance electronics, where heat dissipation is a major bottleneck. They could also enable more efficient energy harvesting by converting waste heat into usable energy, contributing to sustainability efforts.

Additionally, they offer applications such as dynamically managing building temperatures, enhancing the performance of thermoelectric generators, or even improving spacecraft thermal systems, where precisely controlled heat flow is critical.

In our research, we have noticed that most quantum thermal device models to date have relied on simple quantum systems with two stable energy levels, such as qubits. However, we see significant potential to go beyond these limitations.

At the Advanced Computing and Simulation Laboratory (AχL), Monash University, Australia, we have been exploring higher-dimensional quantum systems that expand the capabilities of these devices. By integrating qubit-qutrit architectures, we have demonstrated directional heat flow with improved efficiency and scalability.

This breakthrough, published in APL Quantum, lays the groundwork for practical, high-performance thermotronic systems that could address challenges ranging from overheating in modern technology to advancing sustainable energy solutions. These advancements represent a critical step forward, promising to redefine heat management and energy efficiency in the quantum era.

Harnessing quantum asymmetry to regulate unidirectional heat flow

The quantum thermal diode, based on the interaction between a qutrit (a quantum system with three stable energy levels) and a qubit (a system with two stable energy levels), introduces a novel approach to unidirectional heat transfer.

This system leverages the inherent properties of quantum mechanics to create an asymmetric energy landscape that naturally favors heat flow in one direction, depending on the temperature gradient. This directional behavior is analogous to the way an electronic diode facilitates unidirectional current flow based on the potential difference across its terminals.

The key to this thermal diode lies in how the energy levels of the qubit and qutrit align and interact. By carefully configuring the combined energy levels, we can facilitate heat transfer along the desired temperature gradient while effectively blocking it in the opposite direction. This directional control is achieved through precise quantum interactions, which utilize specific shared energy levels between the qubit and qutrit to establish the necessary conditions for asymmetry in heat flow.

What makes this system particularly groundbreaking is its ability to operate as a nearly perfect thermal diode across a broad temperature range. Unlike classical thermal systems, the quantum nature of this device allows for precise tuning of its properties, including the spacing of energy levels and the coupling strengths between the qubit and qutrit. This tunability enables unprecedented control over the heat transfer process, making the device highly adaptable to various applications.

Whether improving the heat management of nanoscale devices or developing next-generation thermotronic systems, we believe this architecture represents a major step forward in thermal management technologies. By combining a qutrit and a qubit into a single system, this design not only achieves directional heat flow but also enhances efficiency, offering a practical and scalable solution for advanced thermotronics.

Shaping future technologies: The transformative potential of quantum thermal diodes

The development of a quantum thermal diode is a transformative breakthrough with significant implications for quantum thermodynamics and nanoscale engineering. By enabling precise control of heat flow at the quantum level, this innovation addresses challenges that traditional cooling methods cannot solve, particularly in quantum circuits and advanced nanoscale devices.

For example, quantum thermal diodes can regulate heat dissipation in quantum processors, ensuring stable and optimal performance where even slight overheating could lead to disruptions. Additionally, they open up new opportunities for energy harvesting by capturing waste heat generated in quantum systems and converting it into usable energy. This capability has the potential to drive sustainable energy solutions across numerous applications.

Beyond energy efficiency, we believe quantum thermal diodes could pave the way for thermal logic devices—thermal analogs to electronic diodes—allowing computation to be performed using heat flow rather than electric current. Such a development would represent an entirely new paradigm in computation, with applications in fields requiring unique architectures for energy and heat management.

Furthermore, these devices hold significant promise in specialized areas, such as biomedical technologies, where precise thermal regulation is critical for maintaining the performance of sensitive quantum sensors. They could also prove vital in space exploration, where managing the temperature of delicate quantum instruments in extreme environments is essential.

By improving the efficiency of heat dissipation and enabling directional control, quantum thermal diodes not only enhance the functionality of nanoscale devices but also set the stage for the next generation of technologies.

With the potential to develop quantum thermal transistors and other advanced thermotronic devices, we believe this innovation has the power to redefine how we approach thermal management and energy utilization in a quantum-driven world. From nanoscale engineering to space exploration, the transformative potential of quantum thermal diodes promises to shape the technologies of tomorrow.

This story is part of Science X Dialog, where researchers can report findings from their published research articles. Visit this page for information about Science X Dialog and how to participate.

More information: Anuradhi Rajapaksha et al, Enhanced thermal rectification in coupled qutrit–qubit quantum thermal diode, APL Quantum (2024). DOI: 10.1063/5.0237842

Bios:
Anuradhi Rajapaksha earned her B.Sc. in electrical and electronic engineering (with first-class honors) from University of Peradeniya, Sri Lanka in 2021. Currently she is a PhD candidate and a member of the Advanced Computing and Simulations Laboratory at the Department of Electrical and Computer Systems Engineering, Monash University, Australia under the supervision of Prof. Malin Premaratne.

Sarath D. Gunapala received a Ph.D. degree in physics from the University of Pittsburgh, Pittsburgh, PA, USA, in 1986. In 1992, he joined NASA’s Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, where he is currently the Director of the Center for Infrared Photodetectors. He is also a Senior Research Scientist and a Principal Member of the Engineering Staff with the NASA Jet Propulsion Laboratory.

Malin Premaratne earned several degrees from the University of Melbourne, including a B.Sc. in mathematics, a B.E. in electrical and electronics engineering (with first-class honors), and a PhD in 1995, 1995, and 1998, respectively. Currently, he is a full professor at Monash University Clayton, Australia. His expertise centers on quantum device theory, simulation, and design, utilizing the principles of quantum electrodynamics.

Journal information: APL Quantum