This episode of the Physics World Weekly podcast features a conversation with Colm O’Dwyer, who is professor of chemical energy at University College Cork in Ireland and president of the Electrochemical Society.

He talks about the role that electrochemistry plays in the development of modern technologies including batteries, semiconductor chips and pharmaceuticals. O’Dwyer chats about the role that the Electrochemical Society plays in advancing the theory and practice of electrochemistry and solid-state science and technology. He also explains how electrochemists collaborate with scientists and engineers in other fields including physics – and he looks forward to the future of electrochemistry.

The post Why electrochemistry lies at the heart of modern technology appeared first on Physics World.

Heart failure is a serious condition that occurs when a damaged heart loses its ability to pump blood around the body. It affects as many as 100 million people worldwide and it is a progressive disease such that five years after a diagnosis, 50% of patients with heart failure will be dead.

The UK-based company Ceryx Medical has created a new bioelectronic device called Cysoni, which is designed to adjust the pace of the heart as a patient breathes in and out. This mimics a normal physiological process called respiratory sinus arrhythmia, which can be absent in people with heart failure. The company has just began the first trial of Cysoni on human subjects.

This podcast features the biomedical engineer Stuart Plant and the physicist Ashok Chauhan, who are Ceryx Medical’s CEO and senior scientist respectively. In a wide-ranging conversation with Physics World’s Margaret Harris, they talk about how bioelectronics could be used treat heart failure and some other diseases. Chauhan and Plant also chat about challenges and rewards of developing medical technologies within a small company.

The post Ceryx Medical: company uses bioelectronics to coordinate the heart and lungs appeared first on Physics World.

What exactly is ice cream? For most of us, it’s a tasty frozen dessert, but to food scientists like Douglas Goff, it’s also a marvel of physics and chemistry. Ice cream is a complex multiphase material, containing emulsion, foam, crystals, solutes and solvent. Whether made in a domestic kitchen or on a commercial scale, ice cream requires a finely tuned ratio of ingredients and precision control during mixing, churning and freezing.

Goff is a researcher in food science at the University of Guelph in Canada and an expert in the science of ice cream. In addition to his research studying, among other things, structure and ingredient functionality in ice cream, Goff is also the instructor on the University of Guelph’s annual ice-cream course, which, having been taught since 1914, is the longest-running at the university.

In a conversation with Physics World’s Hamish Johnston, Goff explains the science of ice cream, why it’s so hard to make vegan ice cream and how his team performs electron microscopy experiments without their samples melting.

How would you describe the material properties of ice cream to a physicist?

Ice cream is an incredibly complex multi-phase system. It starts as an emulsion, where fat droplets are dispersed in a sugary water-based solution. Then we whip the emulsion to incorporate an air phase into it – this is called foaming (see “Phases in ice cream”). In a frozen tub of ice cream, about half of the volume is air. That air is present in the form of tiny bubbles that are distributed throughout the product.

Then we partially freeze the aqueous phase, turning at least half of the water into microscopically small ice crystals. The remaining unfrozen phase is what makes the ice cream soft, scoopable and chewable. It remains unfrozen because of all the sugar that’s dissolved in it, which depresses the freezing point.

So you end up with fat droplets in the form of an emulsion, air bubbles in the form of a foam, a partially crystalline solvent in the form of ice crystals, and a concentrated sugar solution.

What are the length scales of the different phases in the ice cream?

We’ve done a lot of electron microscopy research studying this in my lab. In fact, our research was some of the very first that utilized electron microscopy techniques for the structure of ice cream. The fat droplets are about one micron in diameter and the air bubbles, depending on the equipment that’s used, would be about 20 to 30 microns in diameter. The ice crystals are in the 10 to 20 micron size range.

It really is a beautiful thing to look at under an electron microscope, depending on the technique that you use (see image).

What are the big differences between ice cream that’s made in a commercial setting versus a domestic kitchen?

The freezing and whipping happen at the same time whether it’s an ice cream maker in the kitchen or a commercial operation. The biggest difference between what you do in the kitchen and what they’re going to do in the factory is the structure of the ice cream. Homemade ice cream is fine for maybe a day or two, but it starts to get icy pretty quickly, whereas we want a shelf life of months to a year when ice cream is made commercially.

This is because of the way the ice phase evolves over time – a process called recrystallization. If ice cream warms up it starts to melt. When the temperature is lowered again, water is frozen back into the ice phase, but it doesn’t create new ice crystals, it just grows onto the existing ice crystals.

This means that if ice cream is subject to lots of temperature fluctuation during storage, it’s going to degrade and become icy much quicker than if it was stored at a constant temperature. The warmer the temperature, the faster the rate of recrystallization. Commercial freezing equipment will give you much smaller ice crystal size than homemade ice cream machines. Low and constant temperature storage is what everybody strives for, and so the lower the temperature and the more constant it is, and the smaller the ice crystals are to begin with, the longer your shelf life before changes start occurring.

There’s also another structural element that is important for the long-term storage of ice cream. When that unfrozen sugary solvent phase gets concentrated enough, it can undergo a glass transition (see “Phases in ice cream”). Glass is an amorphous solid, so if this happens, there will be no movement of water or solute within the system and it can remain unchanged for years. For ice cream, the glass transition temperature is around –28 to –32° C so if you want long-term storage, you have to get down below that that glass transition temperature.

The third thing is the addition of stabilisers. Those are things like locust bean gum, guar gum or cellulose gum and there are some novel ones as well. What those do is increase the viscosity in the unfrozen phase. This slows down the rate of ice recrystallization because it slows down the diffusion of water and the growth of ice.

There are also some other novel agents that can prevent ice from recrystallizing into large crystals. One of these is called propylene glycol monostearate, it absorbs onto the surface of an ice crystal and prevents it from growing as the temperature fluctuates. This is also something we see in nature. Some insect, fish and plant species that live in cold environments have proteins that control the growth of ice in their blood and tissues. A lot of fish, for example, swim around with minute ice crystals in their in their body, but the proteins prevent the crystals from getting big enough to cause harm.

How does adding flavourings to ice cream change the manufacturing process?

When you think about ice cream around the world, there are hundreds of different flavours. The important question is whether the flavouring will impact the solution or emulsion.

For example, a chocolate chip will be inert, it’s not going to interact at all with the rest of the matrix. Strawberries on the other hand, really impact the system because of the high sugar content in the fruit preparation. We need to add sugar to the fruit to make sure it is softer than the ice cream itself – you don’t want to bite into ice cream and find a hard, frozen berry. The problem is that some of that sugar will diffuse into the unfrozen phase and lower its freezing point. This means that if you don’t do anything to the formulation, strawberry ice cream will be softer than something like vanilla because of the added sugar.

Another example would be alcohol-based flavours, anything from rum to Baileys Irish Cream or Frangelico, or even wine and beer. They’re very popular but the alcohol depresses the freezing point, so if you add enough to give you the flavour intensity that you want, your product won’t freeze. In that case, you might need to add less of the alcohol and a little bit more of a de-alcoholized flavouring.

You can try to make ice cream with just about any flavour, but you certainly have to look at what that flavouring is going to do to the structure and things like shelf life and so on.

Nowadays one can also buy vegan ice creams. How do the preparation and ingredients differ compared to dairy products?

A lot of it will be similar. We’re going to have an emulsified fat source, typically something like coconut oil or palm kernel oil, and then there’s the sugar, stabilisers and so on that you would have in a dairy ice cream.

The difference is the protein. Milk protein is both a very good foaming agent and a very good emulsifying agent. [Emulsifying and foaming agents are molecules that stabilize foams and emulsions. The molecules attach to the surface of the liquid droplets or air bubbles and stop them from coalescing with each other.] Plant proteins aren’t very good at either. If you look at cashew, almond or soy-based products, you’ll find additional ingredients to deliver the functionality that we would otherwise get from the milk protein.

What techniques do you use to study ice cream? And how do you stop the ice cream from melting during an experiment?

The workhorses of instrumentation for research are particle size analysis, electron microscopy and rheology (see “Experimental techniques”).

So first there’s laser light scattering which tells us everything we need to know about the fat globules and fat structure (see “Experimental techniques”). Then we use a lot of optical microscopy. You either need to put the microscope in a freezer or cold box or have a cold stage where you have the ice cream on a slide inside a chamber that’s cooled with liquid nitrogen. On the electron microscopy side (see “Experimental techniques”), we’ve done a lot of cryo-scanning electron microscopy (SEM), with a low-temperature unit.

We’ve also done a lot of transmission electron microscopy (TEM), which generally uses a different approach. Instead of performing the experiment in cold conditions, we use a chemical that “fixes” the structure in place and then we dry it, typically using a technique called “critical point drying” (see “Experimental techniques”). It’s then sliced into thin samples and studied with the TEM.

After decades of studying ice cream, do you still get excited about it?

Oh, absolutely. I’ve been fortunate enough to have travelled to many, many interesting countries and I always see what the ice cream market looks like when I’m there. It’s not just a professional thing. I also like to know what’s going on around the world so I can share that with people. But of course, how can you go wrong with ice cream? It’s such a fun product to be associated with.

• Listen to the full interview with Douglas Goff on the Physics World Weekly podcast.

The post A physicist’s guide to ice cream: the complex science behind one of the world’s most popular desserts appeared first on Physics World.

This episode of the Physics World Weekly podcast explores how the concept of humanitarian engineering can be used to provide high quality cancer care to people in low- and middle-income countries (LMICs). This is an important challenge because today only 5% of global radiotherapy resources are located in LMICs, which are home to the majority of the world’s population.

Our guests are two medical physicists at the University of Washington in the US who have contributed to the ebook Humanitarian Engineering for Global Oncology. They are Eric Ford, who edited the ebook and Afua Yorke, who along with Ford wrote the chapter “Cost-effective radiation treatment delivery systems for low- and middle-income countries”.

They are in conversation with Physics World’s Tami Freeman.

The post Humanitarian engineering can improve cancer treatment in low- and middle-income countries appeared first on Physics World.

As proclaimed by the United Nations, 2025 is the International Year of Quantum Science and Technology, or IYQ for short. This year was chosen because it marks the 100th anniversary of Werner Heisenberg’s development of matrix mechanics – the first consistent mathematical description of quantum physics.

Our guest in this episode of the Physics World Weekly podcast is the Turkish quantum physicist Mete Atatüre, who heads up the Cavendish Laboratory at the UK’s University of Cambridge.

In a conversation with Physics World’s Katherine Skipper, Atatüre talks about hosting Quantour, the quantum light source that is IYQ’s version of the Olympic torch. He also talks about his group’s research on quantum sensors and quantum networks.

• There is much more about Heisenberg’s mathematical breakthrough in quantum physics here: “Return to Helgoland: celebrating 100 years of quantum mechanics”.

The post International Year of Quantum Science and Technology: our celebrations begin with a look at quantum networks and sensors appeared first on Physics World.

This year marked the 70th anniversary of the European Council for Nuclear Research, which is known universally as CERN. To celebrate, we have published a bumper crop of articles on particle and nuclear physics in 2024. Many focus on people and my favourite articles have definitely skewed in that direction. So let’s start with the remarkable life of accelerator pioneer Bruno Touschek.

Bruno Touschek: the physicist who escaped the Nazi Holocaust to build particle colliders

Born in Vienna in 1921 to a Jewish mother, Bruno Touschek’s life changed when Nazi Germany annexed Austria in 1938. After suffering antisemitism in his hometown and then in Rome, he inexplicably turned down an offer to study in the UK and settled in Germany. There he worked on a “death ray” for the military but was eventually imprisoned by the German secret police. He was then left for dead during a forced march to a concentration camp in 1945. When the war ended a few weeks later, Touschek’s expertise came to the attention of the British, who occupied north-western Germany. He went on to become a leading accelerator physicist and you can read much more about the extraordinary life of Touschek in this article by the physicist and biographer Giulia Pancheri.

Nuclear clock ticks ever closer

Today, the best atomic clocks would only be off by about 10 ms after running for the current age of the universe. But, could these timekeepers soon be upstaged by clocks that use a nuclear, rather than an atomic transition? Such nuclear clocks could rival their atomic cousins when it comes to precision and accuracy. They also promise to be fully solid-state, which means that they could be used in a wide range of commercial applications. This year saw physicists make new measurements and develop new technologies that could soon make nuclear clocks a reality. Click on the headline above to discover how physicists in the US have fabricated all of the components needed to create a nuclear clock made from thorium-229. Also, earlier this year physicists in Germany and Austria showed that they can put nuclei of the isotope into a low-lying metastable state that could be used in a nuclear clock. You can find out more here: “Excitation of thorium-229 brings a working nuclear clock closer”.

Physics World Live: the future of particle physics

In 2024 we launched our Physics World Live series of panel discussions. In September, we explored the future of particle physics with Tara Shears of the UK’s University of Liverpool, Phil Burrows at the University of Oxford in the UK and Tulika Bose at the University of Wisconsin–Madison in the US. Moderated by Physics World’s Michael Banks, the discussion focussed on next-generation particle colliders and how they could unravel the mysteries of the Higgs boson and probe beyond the Standard Model of particle physics. You can watch a video of the event by clicking on the above headline (free registration) or read an article based on the discussion here: “How a next-generation particle collider could unravel the mysteries of the Higgs boson”.

‘Sometimes nature will surprise us.’ Juan Pedro Ochoa-Ricoux on eureka moments and the future of neutrino physics

Neutrinos do not fit in nicely with the Standard Model of particle physics because of their non-zero masses. As a result some physicists believe that they offer a unique opportunity to do experiments that could reveal new physics. In a wide-ranging interview, the particle physicist Juan Pedro Ochoa-Ricoux explains why he has devoted much of his career to the study of these elusive subatomic particles. He also looks forward to two big future experiments – JUNO and DUNE – which could change our understanding of the universe.

Using Minecraft to get young people interested in particle physics: Çiğdem İşsever on the importance of science in the early years

“Children decide quite early in their life, as early as primary school, if science is for them or not,” explains Çiğdem İşsever – who is leads the particle physics group at DESY in Hamburg, and the experimental high-energy physics group at the Humboldt University of Berlin. İşsever has joined forces with physicists Steven Worm and Becky Parker to create ATLAScraft, which creates a virtual version of CERN’s ATLAS detector in the hugely popular computer game Minecraft. In this profile, the science writer Rob Lea talks to İşsever about her passion for outreach and how she dispels gender stereotypes in science by talking to school children as young as five about her career in physics. İşsever also looks forward to the future of particle physics and what could eventually replace the Large Hadron collider as the world’s premier particle-physics experiment.

CERN celebrates 70 years at the helm of particle physics in lavish ceremony

This year marked the 70th anniversary of the world’s most famous physics laboratory, so the last two items in my list celebrate that iconic facility nestled between the Alps and the Jura mountains. Formed in the aftermath of the Second World War, which devastated much of Europe, CERN came into being on 29 September 1954. That year also saw the start of construction of the Geneva-based lab’s proton synchrotron, which fired-up in 1959 with an energy of 24 GeV, becoming the world’s highest-energy particle accelerator. The original CERN had 12 member states and that has since doubled to 24, with an additional 10 associate members. The lab has been associated with a number of Nobel laureates and is a shining example of how science can bring nations together after a the trauma of war. Read more about the anniversary here.

CERN at 70: how the Higgs hunt elevated particle physics to Hollywood status

When former physicist James Gillies sat down for dinner in 2009 with actors Tom Hanks and Ayelet Zurer, joined by legendary director Ron Howard, he could scarcely believe the turn of events. Gillies was the head of communications at CERN, and the Hollywood trio were in town for the launch of Angels & Demons. The  blockbuster film is partly set at CERN with antimatter central to its plot, and is based on the Dan Brown novel. In this Physics World Stories podcast, Gillies looks back on those heady days. Gillies has also written a feature article for us about his Hollywood experience: “Angels & Demons, Tom Hanks and Peter Higgs: how CERN sold its story to the world”.

The post Particle and nuclear physics highlights in 2024: celebrating the past and looking to the future appeared first on Physics World.

December might be dark and chilly here in the northern hemisphere, but it’s summer south of the equator – and for many people that means eating ice cream.

It turns out that the physics of ice cream is rather remarkable – as I discovered when I travelled to Canada’s University of Guelph to interview the food scientist Douglas Goff. He is a leading expert on the science of frozen desserts and in this podcast he talks about the unique material properties of ice cream, the analytical tools he uses to study it, and why ice cream goes off when it is left in the freezer for too long.

 

The post The physics of ice cream: food scientist Douglas Goff talks about this remarkable material appeared first on Physics World.

The Physics World 2024 Breakthrough of the Year goes to Mikhail Lukin, Dolev Bluvstein and colleagues at Harvard University, the Massachusetts Institute of Technology and QuEra Computing, and independently to Hartmut Neven and colleagues at Google Quantum AI and their collaborators, for demonstrating quantum error correction on an atomic processor with 48 logical qubits, and for implementing quantum error correction below the surface code threshold in a superconducting chip, respectively.

Errors caused by interactions with the environment – noise – are the Achilles heel of every quantum computer, and correcting them has been called a “defining challenge” for the technology. These two teams, working with very different quantum systems, took significant steps towards overcoming this challenge. In doing so, they made it far more likely that quantum computers will become practical problem-solving machines, not just noisy, intermediate-scale tools for scientific research.

Quantum error correction works by distributing one quantum bit of information – called a logical qubit – across several different physical qubits such as superconducting circuits or trapped atoms. While each physical qubit is noisy, they work together to preserve the quantum state of the logical qubit – at least for long enough to do a computation.

Formidable task

Error correction should become more effective as the number of physical qubits in a logical qubit increases. However, integrating large numbers of physical qubits to create a processor with multiple logical qubits is a formidable task. Furthermore, adding more physical qubits to a logical qubit also adds more noise – and it is not clear whether making logical qubits bigger would make them significantly better. This year’s winners of our Breakthrough of the Year have made significant progress in addressing these issues.

The team led by Lukin and Bluvstein created a quantum processor with 48 logical qubits that can execute algorithms while correcting errors in real time. At the heart of their processor are arrays of neutral atoms. These are grids of ultracold rubidium atoms trapped by optical tweezers. These atoms can be put into highly excited Rydberg states, which enables the atoms to act as physical qubits that can exchange quantum information.

What is more, the atoms can be moved about within an array to entangle them with other atoms. According to Bluvstein, moving groups of atoms around the processor was critical for their success at addressing a major challenge in using logical qubits: how to get logical qubits to interact with each other to perform quantum operations. He describes the system as a “living organism that changes during a computation”.

Their processor used about 300 physical qubits to create up to 48 logical qubits, which were used to perform logical operations. In contrast, similar attempts using superconducting or trapped-ion qubits have only managed to perform logical operations using 1–3 logical qubits.

Willow quantum processor

Meanwhile, the team led by Hartmut Neven made a significant advance in how physical qubits can be combined to create a logical qubit. Using Google’s new Willow quantum processor – which offers up to 105 superconducting physical qubits – they showed that the noise in their logical qubit remained below a maximum threshold as they increased the number of qubits.  This means that the logical error rate is suppressed exponentially as the number of physical qubits per logical qubit is increased.

Neven told Physics World that the Google system is “the most convincing prototype of a logical qubit built today”. He said that that Google is on track to develop a quantum processor with 100 or even 1000 logical qubits by 2030. He says that a 1000 logical qubit device could do useful calculations for the development of new drugs or new materials for batteries.

Bluvstein, Lukin and colleagues are already exploring how their processor could be used to study an effect called quantum scrambling. This could shed light on properties of black holes and even provide important clues about the nature of quantum gravity.

You can listen to Neven talk about his team’s research in this podcast. Bluvstein and Lukin talk about their group’s work in this podcast.

The Breakthrough of the Year was chosen by the Physics World editorial team. We looked back at all the scientific discoveries we have reported on since 1 January and picked the most important. In addition to being reported in Physics World in 2024, the breakthrough must meet the following criteria:

• Significant advance in knowledge or understanding

• Importance of work for scientific progress and/or development of real-world applications

• Of general interest to Physics World readers

Before we picked our winners, we released the Physics World Top 10 Breakthroughs for 2024, which served as our shortlist. The other nine breakthroughs are listed below in no particular order.

Light-absorbing dye turns skin of live mouse transparent

To a team of researchers at Stanford University in the US for developing a method to make the skin of live mice temporarily transparent. One of the challenges of imaging biological tissue using optical techniques is that tissue scatters light, which makes it opaque. The team, led by Zihao Ou (now at The University of Texas at Dallas), Mark Brongersma and Guosong Hong, found that the common yellow food dye tartrazine strongly absorbs near-ultraviolet and blue light and can help make biological tissue transparent. Applying the dye onto the abdomen, scalp and hindlimbs of live mice enabled the researchers to see internal organs, such as the liver, small intestine and bladder, through the skin without requiring any surgery. They could also visualize blood flow in the rodents’ brains and the fine structure of muscle sarcomere fibres in their hind limbs. The effect can be reversed by simply rinsing off the dye. This “optical clearing” technique has so far only been conducted on animals. But if extended to humans, it could help make some types of invasive biopsies a thing of the past.

Laser cooling positronium 

To the AEgIS collaboration at CERN, and Kosuke Yoshioka and colleagues at the University of Tokyo, for independently demonstrating laser cooling of positronium. Positronium, an atom-like bound state of an electron and a positron, is created in the lab to allow physicists to study antimatter. Currently, it is created in “warm” clouds in which the atoms have a large distribution of velocities, making precision spectroscopy difficult. Cooling positronium to low temperatures could open up novel ways to study the properties of antimatter. It also enables researchers to produce one to two orders of magnitude more antihydrogen – an antiatom comprising a positron and an antiproton that’s of great interest to physicists. The research also paves the way to use positronium to test current aspects of the Standard Model of particle physics, such as quantum electrodynamics, which predicts specific spectral lines, and to probe the effects of gravity on antimatter.

Modelling lung cells to personalize radiotherapy

To Roman Bauer at the University of Surrey, UK, Marco Durante from the GSI Helmholtz Centre for Heavy Ion Research, Germany, and Nicolò Cogno from GSI and Massachusetts General Hospital/Harvard Medical School, US, for creating a computational model that could improve radiotherapy outcomes for patients with lung cancer. Radiotherapy is an effective treatment for lung cancer but can harm healthy tissue. To minimize radiation damage and help personalize treatment, the team combined a model of lung tissue with a Monte Carlo simulator to simulate irradiation of alveoli (the tiny air sacs within the lungs) at microscopic and nanoscopic scales. Based on the radiation dose delivered to each cell and its distribution, the model predicts whether each cell will live or die, and determines the severity of radiation damage hours, days, months or even years after treatment. Importantly, the researchers found that their model delivered results that matched experimental observations from various labs and hospitals, suggesting that it could, in principle, be used within a clinical setting.

A semiconductor and a novel switch made from graphene

To Walter de Heer, Lei Ma and colleagues at Tianjin University and the Georgia Institute of Technology, and independently to Marcelo Lozada-Hidalgo of the University of Manchester and a multinational team of colleagues, for creating a functional semiconductor made from graphene, and for using graphene to make a switch that supports both memory and logic functions, respectively. The Manchester-led team’s achievement was to harness graphene’s ability to conduct both protons and electrons in a device that performs logic operations with a proton current while simultaneously encoding a bit of memory with an electron current. These functions are normally performed by separate circuit elements, which increases data transfer times and power consumption. Conversely, de Heer, Ma and colleagues engineered a form of graphene that does not conduct as easily. Their new “epigraphene” has a bandgap that, like silicon, could allow it to be made into a transistor, but with favourable properties that silicon lacks, such as high thermal conductivity.

Detecting the decay of individual nuclei

To David Moore, Jiaxiang Wang and colleagues at Yale University, US, for detecting the nuclear decay of individual helium nuclei by embedding radioactive lead-212 atoms in a micron-sized silica sphere and measuring the sphere’s recoil as nuclei escape from it. Their technique relies on the conservation of momentum, and it can gauge forces as small as 10^-20 N and accelerations as tiny as 10^-7 g, where g is the local acceleration due to the Earth’s gravitational pull. The researchers hope that a similar technique may one day be used to detect neutrinos, which are much less massive than helium nuclei but are likewise emitted as decay products in certain nuclear reactions.

Two distinct descriptions of nuclei unified for the first time

To Andrew Denniston at the Massachusetts Institute of Technology in the US, Tomáš Ježo at Germany’s University of Münster and an international team for being the first to unify two distinct descriptions of atomic nuclei. They have combined the particle physics perspective – where nuclei comprise quarks and gluons – with the traditional nuclear physics view that treats nuclei as collections of interacting nucleons (protons and neutrons). The team has provided fresh insights into short-range correlated nucleon pairs – which are fleeting interactions where two nucleons come exceptionally close and engage in strong interactions for mere femtoseconds. The model was tested and refined using experimental data from scattering experiments involving 19 different nuclei with very different masses (from helium-3 to lead-208). The work represents a major step forward in our understanding of nuclear structure and strong interactions. 

New titanium:sapphire laser is tiny, low-cost and tuneable

To Jelena Vučković, Joshua Yang, Kasper Van Gasse, Daniil Lukin, and colleagues at Stanford University in the US for developing a compact, integrated titanium:sapphire laser that needs only a simple green LED as a pump source. They have reduced the cost and footprint of a titanium:sapphire laser by three orders of magnitude and the power consumption by two. Traditional titanium:sapphire lasers have to be pumped with high-powered lasers – and therefore cost in excess of $100,000. In contrast, the team was able to pump its device using a $37 green laser diode. The researchers also achieved two things that had not been possible before with a titanium:sapphire laser. They were able to adjust the wavelength of the laser light and they were able to create a titanium:sapphire laser amplifier. Their device represents a key step towards the democratization of a laser type that plays important roles in scientific research and industry.

Entangled photons conceal and enhance images

To two related teams for their clever use of entangled photons in imaging. Both groups include Chloé Vernière and Hugo Defienne of Sorbonne University in France, who as duo used quantum entanglement to encode an image into a beam of light. The impressive thing is that the image is only visible to an observer using a single-photon sensitive camera – otherwise the image is hidden from view. The technique could be used to create optical systems with reduced sensitivity to scattering. This could be useful for imaging biological tissues and long-range optical communications. In separate work, Vernière and Defienne teamed up with Patrick Cameron at the UK’s University of Glasgow and others to use entangled photons to enhance adaptive optical imaging. The team showed that the technique can be used to produce higher-resolution images than conventional bright-field microscopy. Looking to the future, this adaptive optics technique could play a major role in the development of quantum microscopes.

First samples returned from the Moon’s far side

To the China National Space Administration for the first-ever retrieval of material from the Moon’s far side, confirming China as one of the world’s leading space nations. Landing on the lunar far side – which always faces away from Earth – is difficult due to its distance and terrain of giant craters with few flat surfaces. At the same time, scientists are interested in the unexplored far side and why it looks so different from the near side. The Chang’e-6 mission was launched on 3 May consisting of four parts: an ascender, lander, returner and orbiter. The ascender and lander successfully touched down on 1 June in the Apollo basin, which lies in the north-eastern side of the South Pole-Aitken Basin. The lander used its robotic scoop and drill to obtain about 1.9 kg of materials within 48 h. The ascender then lifted off from the top of the lander and docked with the returner-orbiter before the returner headed back to Earth, landing in Inner Mongolia on 25 June. In November, scientists released the first results from the mission finding that fragments of basalt – a type of volcanic rock – date back to 2.8 billion years ago, indicating that the lunar far side was volcanically active at that time. Further scientific discoveries can be expected in the coming months and years ahead as scientists analyze more fragments.

The post Two advances in quantum error correction share the <em>Physics World</em> 2024 Breakthrough of the Year appeared first on Physics World.

One half of the Physics World 2024 Breakthrough of the Year has been awarded to Mikhail Lukin, Dolev Bluvstein and colleagues at Harvard University, the Massachusetts Institute of Technology and QuEra Computing for demonstrating quantum error correction on an atomic processor with 48 logical qubits.

In this episode of the Physics World Weekly podcast, Bluvstein and Lukin explain the crucial role that error correction is playing in the development of practical quantum computers. They also describe how atoms are moved around their quantum processor and why this coordinated motion allowed them to create logical qubits and use those qubits to perform quantum computations.

The Physics World 2024 Breakthrough of the Year also cites Hartmut Neven and colleagues at Google Quantum AI and their collaborators for implementing quantum error correction below the surface code threshold in a superconducting chip. Neven talks about his team’s accomplishments in this podcast.

The post Mikhail Lukin and Dolev Bluvstein explain how they used trapped atoms to create 48 logical qubits appeared first on Physics World.

One half of the Physics World 2024 Breakthrough of the Year has been awarded to Hartmut Neven and colleagues at Google Quantum AI and their collaborators for implementing quantum error correction below the surface code threshold in a superconducting chip.

In this episode of the Physics World Weekly podcast, Neven talks about Google’s new Willow quantum processor, which integrates 105 superconducting physical qubits. He also explains how his team used these qubits to create logical qubits with error rates that dropped exponentially with the number of physical qubits used. He also outlines Googles ambitious plan to create a processor with 100, or even 1000, logical qubits by 2030.

The Physics World 2024 Breakthrough of the Year also cites Mikhail Lukin, Dolev Bluvstein and colleagues at Harvard University, the Massachusetts Institute of Technology and QuEra Computing for demonstrating quantum error correction on an atomic processor with 48 logical qubits. Lukin and Bluvstein explain how they did it in this podcast.

The post Hartmut Neven talks about Google Quantum AI’s breakthrough in quantum error correction appeared first on Physics World.

Physics World is delighted to announce its Top 10 Breakthroughs of the Year for 2024, which includes research in nuclear and medical physics, quantum computing, lasers, antimatter and more. The Top Ten is the shortlist for the Physics World Breakthrough of the Year, which will be revealed on Thursday 19 December.

Our editorial team has looked back at all the scientific discoveries we have reported on since 1 January and has picked 10 that we think are the most important. In addition to being reported in Physics World in 2024, the breakthroughs must meet the following criteria: 

• Significant advance in knowledge or understanding 

• Importance of work for scientific progress and/or development of real-world applications 

• Of general interest to Physics World readers 

Here, then, are the Physics World Top 10 Breakthroughs for 2024, listed in no particular order. You can listen to Physics World editors make the case for each of our nominees in the Physics World Weekly podcast. And, come back next week to discover who has bagged the 2024 Breakthrough of the Year. 

Light-absorbing dye turns skin of live mouse transparent

To a team of researchers at Stanford University in the US for developing a method to make the skin of live mice temporarily transparent. One of the challenges of imaging biological tissue using optical techniques is that tissue scatters light, which makes it opaque. The team, led by Zihao Ou (now at The University of Texas at Dallas), Mark Brongersma and Guosong Hong, found that the common yellow food dye tartrazine strongly absorbs near-ultraviolet and blue light and can help make biological tissue transparent. Applying the dye onto the abdomen, scalp and hindlimbs of live mice enabled the researchers to see internal organs, such as the liver, small intestine and bladder, through the skin without requiring any surgery. They could also visualize blood flow in the rodents’ brains and the fine structure of muscle sarcomere fibres in their hind limbs. The effect can be reversed by simply rinsing off the dye. This “optical clearing” technique has so far only been conducted on animals. But if extended to humans, it could help make some types of invasive biopsies a thing of the past. 

Laser cooling positronium 

To the AEgIS collaboration at CERN, and Kosuke Yoshioka and colleagues at the University of Tokyo, for independently demonstrating laser cooling of positronium. Positronium, an atom-like bound state of an electron and a positron, is created in the lab to allow physicists to study antimatter. Currently, it is created in “warm” clouds in which the atoms have a large distribution of velocities, making precision spectroscopy difficult. Cooling positronium to low temperatures could open up novel ways to study the properties of antimatter. It also enables researchers to produce one to two orders of magnitude more antihydrogen – an antiatom comprising a positron and an antiproton that’s of great interest to physicists. The research also paves the way to use positronium to test current aspects of the Standard Model of particle physics, such as quantum electrodynamics, which predicts specific spectral lines, and to probe the effects of gravity on antimatter. 

Modelling lung cells to personalize radiotherapy

To Roman Bauer at the University of Surrey, UK, Marco Durante from the GSI Helmholtz Centre for Heavy Ion Research, Germany, and Nicolò Cogno from GSI and Massachusetts General Hospital/Harvard Medical School, US, for creating a computational model that could improve radiotherapy outcomes for patients with lung cancer. Radiotherapy is an effective treatment for lung cancer but can harm healthy tissue. To minimize radiation damage and help personalize treatment, the team combined a model of lung tissue with a Monte Carlo simulator to simulate irradiation of alveoli (the tiny air sacs within the lungs) at microscopic and nanoscopic scales. Based on the radiation dose delivered to each cell and its distribution, the model predicts whether each cell will live or die, and determines the severity of radiation damage hours, days, months or even years after treatment. Importantly, the researchers found that their model delivered results that matched experimental observations from various labs and hospitals, suggesting that it could, in principle, be used within a clinical setting. 

A semiconductor and a novel switch made from graphene 

To Walter de Heer, Lei Ma and colleagues at Tianjin University and the Georgia Institute of Technology, and independently to Marcelo Lozada-Hidalgo of the University of Manchester and a multinational team of colleagues, for creating a functional semiconductor made from graphene, and for using graphene to make a switch that supports both memory and logic functions, respectively. The Manchester-led team’s achievement was to harness graphene’s ability to conduct both protons and electrons in a device that performs logic operations with a proton current while simultaneously encoding a bit of memory with an electron current. These functions are normally performed by separate circuit elements, which increases data transfer times and power consumption. Conversely, de Heer, Ma and colleagues engineered a form of graphene that does not conduct as easily. Their new “epigraphene” has a bandgap that, like silicon, could allow it to be made into a transistor, but with favourable properties that silicon lacks, such as high thermal conductivity. 

Detecting the decay of individual nuclei 

To David Moore, Jiaxiang Wang and colleagues at Yale University, US, for detecting the nuclear decay of individual helium nuclei by embedding radioactive lead-212 atoms in a micron-sized silica sphere and measuring the sphere’s recoil as nuclei escape from it. Their technique relies on the conservation of momentum, and it can gauge forces as small as 10^-20 N and accelerations as tiny as 10^-7 g, where g is the local acceleration due to the Earth’s gravitational pull. The researchers hope that a similar technique may one day be used to detect neutrinos, which are much less massive than helium nuclei but are likewise emitted as decay products in certain nuclear reactions. 

Two distinct descriptions of nuclei unified for the first time 

To Andrew Denniston at the Massachusetts Institute of Technology in the US, Tomáš Ježo at Germany’s University of Münster and an international team for being the first to unify two distinct descriptions of atomic nuclei. They have combined the particle physics perspective – where nuclei comprise quarks and gluons – with the traditional nuclear physics view that treats nuclei as collections of interacting nucleons (protons and neutrons). The team has provided fresh insights into short-range correlated nucleon pairs – which are fleeting interactions where two nucleons come exceptionally close and engage in strong interactions for mere femtoseconds. The model was tested and refined using experimental data from scattering experiments involving 19 different nuclei with very different masses (from helium-3 to lead-208). The work represents a major step forward in our understanding of nuclear structure and strong interactions.  

New titanium:sapphire laser is tiny, low-cost and tuneable 

To Jelena Vučković, Joshua Yang, Kasper Van Gasse, Daniil Lukin, and colleagues at Stanford University in the US for developing a compact, integrated titanium:sapphire laser that needs only a simple green LED as a pump source. They have reduced the cost and footprint of a titanium:sapphire laser by three orders of magnitude and the power consumption by two. Traditional titanium:sapphire lasers have to be pumped with high-powered lasers – and therefore cost in excess of $100,000. In contrast, the team was able to pump its device using a $37 green laser diode. The researchers also achieved two things that had not been possible before with a titanium:sapphire laser. They were able to adjust the wavelength of the laser light and they were able to create a titanium:sapphire laser amplifier. Their device represents a key step towards the democratization of a laser type that plays important roles in scientific research and industry. 

Quantum error correction with 48 logical qubits; and independently, below the surface code threshold   

To Mikhail Lukin, Dolev Bluvstein and colleagues at Harvard University, the Massachusetts Institute of Technology and QuEra Computing, and independently to Hartmut Neven and colleagues at Google Quantum AI and their collaborators, for demonstrating quantum error correction on an atomic processor with 48 logical qubits, and for implementing quantum error correction below the surface code threshold in a superconducting chip, respectively. Errors caused by interactions with the environment – noise – are the Achilles heel of every quantum computer, and correcting them has been called a “defining challenge” for the technology. These two teams, working with very different quantum systems, took significant steps towards overcoming this challenge. In doing so, they made it far more likely that quantum computers will become practical problem-solving machines, not just noisy, intermediate-scale tools for scientific research. 

Entangled photons conceal and enhance images 

To two related teams for their clever use of entangled photons in imaging. Both groups include Chloé Vernière and Hugo Defienne of Sorbonne University in France, who as duo used quantum entanglement to encode an image into a beam of light. The impressive thing is that the image is only visible to an observer using a single-photon sensitive camera – otherwise the image is hidden from view. The technique could be used to create optical systems with reduced sensitivity to scattering. This could be useful for imaging biological tissues and long-range optical communications. In separate work, Vernière and Defienne teamed up with Patrick Cameron at the UK’s University of Glasgow and others to use entangled photons to enhance adaptive optical imaging. The team showed that the technique can be used to produce higher-resolution images than conventional bright-field microscopy. Looking to the future, this adaptive optics technique could play a major role in the development of quantum microscopes. 

First samples returned from the Moon’s far side  

To the China National Space Administration for the first-ever retrieval of material from the Moon’s far side, confirming China as one of the world’s leading space nations. Landing on the lunar far side – which always faces away from Earth – is difficult due to its distance and terrain of giant craters with few flat surfaces. At the same time, scientists are interested in the unexplored far side and why it looks so different from the near side. The Chang’e-6 mission was launched on 3 May consisting of four parts: an ascender, lander, returner and orbiter. The ascender and lander successfully touched down on 1 June in the Apollo basin, which lies in the north-eastern side of the South Pole-Aitken Basin. The lander used its robotic scoop and drill to obtain about 1.9 kg of materials within 48 h. The ascender then lifted off from the top of the lander and docked with the returner-orbiter before the returner headed back to Earth, landing in Inner Mongolia on 25 June. In November, scientists released the first results from the mission finding that fragments of basalt – a type of volcanic rock – date back to 2.8 billion years ago, indicating that the lunar far side was volcanically active at that time. Further scientific discoveries can be expected in the coming months and years ahead as scientists analyze more fragments. 

The post Top 10 Breakthroughs of the Year in physics for 2024 revealed appeared first on Physics World.

This episode of the Physics World Weekly podcast features a lively discussion about our Top 10 Breakthroughs of 2024, which include important research in nuclear physics, quantum computing, medical physics, lasers and more. Physics World editors explain why we have made our selections and look at the broader implications of this impressive body of research.

The top 10 serves as the shortlist for the Physics World Breakthrough of the Year award, the winner of which will be announced on 19 December.

Links to all the nominees, more about their research and the selection criteria can be found here.

The post Exploring this year’s best physics research in our Top 10 Breakthroughs of 2024 appeared first on Physics World.

This episode of the Physics World Weekly podcast explores the science and commercial applications of metamaterials with Claire Dancer of the University of Warwick and Alastair Hibbins of the University of Exeter.

They lead the UK Metamaterials Network, which brings together people in academia, industry and governmental agencies to support and expand metamaterial R&D; nurture talent and skills; promote the adoption of metamaterials in the wider economy; and much more.

According to the network, “A metamaterial is a 3D structure with a response or function due to the collective effect of meta-atom elements that is not possible to achieve conventionally with any individual constituent material”.

In a wide-ranging conversation with Physics World’s Matin Durrani, Hibbins and Dancer talk about exciting commercial applications of metamaterials including soundproof materials and lenses for mobile phones – and how they look forward to welcoming the thousandth member of the network sometime in 2025.

The post How the UK Metamaterials Network supports scientific and commercial innovation appeared first on Physics World.