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A recipe for quantum chaos

The control of large, strongly coupled, multi-component quantum systems with complex dynamics is a challenging task.

It is, however, an essential prerequisite for the design of quantum computing platforms and for the benchmarking of quantum simulators.

A key concept here is that of quantum ergodicity. This is because quantum ergodic dynamics can be harnessed to generate highly entangled quantum states.

In classical statistical mechanics, an ergodic system evolving over time will explore all possible microstates states uniformly. Mathematically, this means that a sufficiently large collection of random samples from an ergodic process can represent the average statistical properties of the entire process.

Quantum ergodicity is simply the extension of this concept to the quantum realm.

Closely related to this is the idea of chaos. A chaotic system is one in which is very sensitive to its initial conditions. Small changes can be amplified over time, causing large changes in the future.

The ideas of chaos and ergodicity are intrinsically linked as chaotic dynamics often enable ergodicity.

Until now, it has been very challenging to predict which experimentally preparable initial states will trigger quantum chaos and ergodic dynamics over a reasonable time scale.

In a new paper published in Reports on Progress in Physics, a team of researchers have proposed an ingenious solution to this problem using the Bose–Hubbard Hamiltonian.

They took as an example ultracold atoms in an optical lattice (a typical choice for experiments in this field) to benchmark their method.

The results show that there are certain tangible threshold values which must be crossed in order to ensure the onset of quantum chaos.

These results will be invaluable for experimentalists working across a wide range of quantum sciences.

Read the full article

How to seed ergodic dynamics of interacting bosons under conditions of many-body quantum chaos – IOPscience

Pausch et al. 2025 Rep. Prog. Phys. 88 057602

Neural simulation-based inference techniques at the LHC

Precision measurements of theoretical parameters are a core element of the scientific program of experiments at the Large Hadron Collider (LHC) as well as other particle colliders.

These are often performed using statistical techniques such as the method of maximum likelihood. However, given the size of datasets generated, reduction techniques, such as grouping data into bins, are often necessary.

These can lead to a loss of sensitivity, particularly in non-linear cases like off-shell Higgs boson production and effective field theory measurements. The non-linearity in these cases comes from quantum interference and traditional methods are unable to optimally distinguish the signal from background.

In this paper, the ATLAS collaboration pioneered the use of a neural network based technique called neural simulation-based inference (NSBI) to combat these issues.

A neural network is a machine learning model originally inspired by how the human brain works. It’s made up of layers of interconnected units called neurons, which process information and learn patterns from data. Each neuron receives input, performs a simple calculation, and passes the result to other neurons.

NSBI uses these neural networks to analyse each particle collision event individually, preserving more information and improving accuracy.

The framework developed here can handle many sources of uncertainty and includes tools to measure how confident scientists can be in their results.

The researchers benchmarked their method by using it to calculate the Higgs boson signal strength and compared it to previous methods with impressive results (see here for more details about this).

The greatly improved sensitivity gained from using this method will be invaluable in the search for physics beyond the Standard Model in future experiments at ATLAS and beyond.

Read the full article

An implementation of neural simulation-based inference for parameter estimation in ATLAS – IOPscience

The ATLAS Collaboration, 2025 Rep. Prog. Phys. 88 067801

Chip-integrated nanoantenna efficiently harvests light from diamond defects

When diamond defects emit light, how much of that light can be captured and used for quantum technology applications? According to researchers at the Hebrew University of Jerusalem, Israel and Humboldt Universität of Berlin, Germany, the answer is “nearly all of it”. Their technique, which relies on positioning a nanoscale diamond at an optimal location within a chip-integrated nanoantenna, could lead to improvements in quantum communication and quantum sensing.

Illustration showing photon emission from a nanodiamond being directed by a bullseye antenna. The bullseye antenna is shown flat, and seven parallel orange arrows representing photons emerge from different parts of the bullseye, like candles on a birthday cake. At the centre of the bullseye is a diamond — Guided light: Illustration showing photon emission from a nanodiamond and light directed by a bullseye antenna. (Courtesy: Boaz Lubotzky)

Nitrogen-vacancy (NV) centres are point defects that occur when one carbon atom in diamond’s lattice structure is replaced by a nitrogen atom next to an empty lattice site (a vacancy). Together, this nitrogen atom and its adjacent vacancy behave like a negatively charged entity with an intrinsic quantum spin.

When excited with laser light, an electron in an NV centre can be promoted into an excited state. As the electron decays back to the ground state, it emits light. The exact absorption-and-emission process is complicated by the fact that both the ground state and the excited state of the NV centre have three sublevels (spin triplet states). However, by exciting an individual NV centre repeatedly and collecting the photons it emits, it is possible to determine the spin state of the centre.

The problem, explains Boaz Lubotzky, who co-led this research effort together with his colleague Ronen Rapaport, is that NV centres radiate over a wide range of angles. Hence, without an efficient collection interface, much of the light they emit is lost.

Standard optics capture around 80% of the light

Lubotzky and colleagues say they have now solved this problem thanks to a hybrid nanostructure made from a PMMA dielectric layer above a silver grating. This grating is arranged in a precise bullseye pattern that accurately guides light in a well-defined direction thanks to constructive interference. Using a nanometre-accurate positioning technique, the researchers placed the nanodiamond containing the NV centres exactly at the optimal location for light collection: right at the centre of the bullseye.

For standard optics with a numerical aperture (NA) of about 0.5, the team found that the system captures around 80% of the light emitted from the NV centres. When NA >0.7, this value exceeds 90%, while for NA > 0.8, Lubotzky says it approaches unity.

“The device provides a chip-based, room-temperature interface that makes NV emission far more directional, so a larger fraction of photons can be captured by standard lenses or coupled into fibres and photonic chips,” he tells Physics World. “Collecting more photons translates into faster measurements, higher sensitivity and lower power, thereby turning NV centres into compact precision sensors and also into brighter, easier-to-use single-photon sources for secure quantum communication.”

Nanodiamond quantum thermometer measures the temperature of worms

The researchers say their next priority is to transition their prototype into a plug-and-play, room-temperature module – one that is fully packaged and directly coupled to fibres or photonic chips – with wafer-level deterministic placement for arrays. “In parallel, we will be leveraging the enhanced collection for NV-based magnetometry, aiming for faster, lower-power measurements with improved readout fidelity,” says Lubotzky. “This is important because it will allow us to avoid repeated averaging and enable fast, reliable operation in quantum sensors and processors.”

They detail their present work in APL Quantum.

Illuminating quantum worlds: a Diwali conversation with Rupamanjari Ghosh

Homes and cities around the world are this week celebrating Diwali or Deepavali – the Indian “festival of lights”. For Indian physicist Rupamanjari Ghosh, who is the former vice chancellor of Shiv Nadar University Delhi-NCR, this festival sheds light on the quantum world. Known for her work on nonlinear optics and entangled photons, Ghosh finds a deep resonance between the symbolism of Diwali and the ongoing revolution in quantum science.

“Diwali comes from Deepavali, meaning a ‘row of lights’. It marks the triumph of light over dark; good over evil; and knowledge over ignorance,” Ghosh explains. “In science too, every discovery is a Diwali – a victory of knowledge over ignorance.”

With 2025 being marked by the International Year of Quantum Science and Technology, a victory of knowledge over ignorance couldn’t ring truer. “It has taken us a hundred years since the birth of quantum mechanics to arrive at this point, where quantum technologies are poised to transform our lives,” says Ghosh.

Ghosh has another reason to celebrate, having been named as this year’s Institute of Physics (IOP) Homi Bhabha lecturer. The IOP and the Indian Physical Association (IPA) jointly host the Homi Bhabha and Cockcroft Walton bilateral exchange of lecturers. Running since 1998, these international programmes aim to promote dialogue on global challenges through physics and provide physicists with invaluable opportunities for global exposure and professional growth. Ghosh’s online lecture, entitled “Illuminating quantum frontiers: from photons to emerging technologies”, will be aired at 3 p.m. GMT on Wednesday 22 October.

From quantum twins to quantum networks

Ghosh’s career in physics took off in the mid-1980s, when she and American physicist Leonard Mandel – who is often referred to as one of the founding fathers of quantum optics – demonstrated a new quantum source of twin photons through spontaneous parametric down-conversion: a process where a high-energy photon splits into two lower-energy, correlated photons (Phys. Rev. Lett. 59, 1903).

“Before that,” she recalls, “no-one was looking for quantum effects in this nonlinear optical process. The correlations between the photons defied classical explanation. It was an elegant early verification of quantum nonlocality.”

Those entangled photon pairs are now the building blocks of quantum communication and computation. “We’re living through another Diwali of light,” she says, “where theoretical understanding and experimental innovation illuminate each other.”

Entangled light

During Diwali, lamps unite households in a shimmering network of connection, and so too does entanglement of photons. “Quantum entanglement reminds us that connection transcends locality,” Ghosh says. “In the same way, the lights of Diwali connect us across borders and cultures through shared histories.”

Her own research extends that metaphor further. Ghosh’s team has worked on mapping quantum states of light onto collective atomic excitations. These “slow-light” techniques – using electromagnetically induced transparency or Raman interactions – allow photons to be stored and retrieved, forming the backbone of long-distance quantum communication (Phys. Rev. A. 88 023852, EPL 105 44002)

“Symbolically,” she adds, “it’s like passing the flame from one diya (lamp) to another. We’re not just spreading light – we’re preserving, encoding and transmitting it. Success comes through connection and collaboration.”

Beyond the shadows: Ghosh calls for the bright light of inclusivity in science. (Courtesy: Rupamanjari Ghosh)

The dark side of light

Ghosh is quick to note that in quantum physics, “darkness” is far from empty. “In quantum optics, even the vacuum is rich – with fluctuations that are essential to our understanding of the universe.”

Her group studies the transition from quantum to classical systems, using techniques such as error correction, shielding and coherence-preserving materials. “Decoherence – the loss of quantum behaviour through environmental interaction – is a constant threat. To build reliable quantum technologies, we must engineer around this fragility,” Ghosh explains.

There are also human-engineered shadows: some weaknesses in quantum communication devices aren’t due to the science itself – they come from mistakes or flaws in how humans built them. Hackers can exploit these “side channels” to get around security. “Security,” she warns, “is only as strong as the weakest engineering link.”

Beyond the lab, Ghosh finds poetic meaning in these challenges. “Decoherence isn’t just a technical problem – it helps us understand the arrows of time, why the universe evolves irreversibly. The dark side has its own lessons.”

Lighting every corner

For Ghosh, Diwali’s illumination is also a call for inclusivity in science. “No corner should remain dark,” she says. “Science thrives on diversity. Diverse teams ask broader questions and imagine richer answers. It’s not just morally right – it’s good for science.”

She argues that equity is not sameness but recognition of uniqueness. “Innovation doesn’t come from conformity. Gender diversity, for example, brings varied cognitive and collaborative styles – essential in a field like quantum science, where intuition is constantly stretched.”

The shadows she worries most about are not in the lab, but in academia itself. “Unconscious biases in mentorship or gatekeeping in opportunity can accumulate to limit visibility. Institutions must name and dismantle these hidden shadows through structural and cultural change.”

Her vision of inclusion extends beyond gender. “We shouldn’t think of work and life as opposing realms to ‘balance’,” she says. “It’s about creating harmony among all dimensions of life – work, family, learning, rejuvenation. That’s where true brilliance comes from.”

As the rows of diyas are lit this Diwali, Ghosh’s reflections remind us that light – whether classical or quantum – is both a physical and moral force: it connects, illuminates and endures. “Each advance in quantum science,” she concludes, “is another step in the age-old journey from darkness to light.”

This article forms part of Physics World‘s contribution to the 2025 International Year of Quantum Science and Technology (IYQ), which aims to raise global awareness of quantum physics and its applications.

Stayed tuned to Physics World and our international partners throughout the year for more coverage of the IYQ.

Find out more on our quantum channel.

Influential theoretical physicist and Nobel laureate Chen-Ning Yang dies aged 103

The Chinese particle physicist Chen-Ning Yang died on 18 October at the age of 103. Yang shared half of the 1957 Nobel Prize for Physics with Tsung-Dao Lee for their theoretical work that overturned the notion that parity is conserved in the weak force – one of the four fundamental forces of nature.

Born on 22 September 1922 in Hefei, China, Yang competed a BSc at the National Southwest Associated University in Kunming in 1942. After finishing an MSc in statistical physics at Tsinghua University two years later, in 1945 he moved to the University of Chicago in the US as part of a government-sponsored programme. He received his PhD in physics in 1948 working under the guidance of Edward Teller.

In 1949 Yang moved to the Institute for Advanced Study in Princeton, where he made pioneering contributions to quantum field theory, working together with Robert Mills. In 1953 they proposed the Yang-Mills theory, which became a cornerstone of the Standard Model of particle physics.

The ‘Wu experiment’

It was also at Princeton where Yang began a fruitful collaboration with Lee, who died last year aged 97. Their work on parity – a property of elementary particles that expresses their behaviour upon reflection in a mirror – led to the duo winning the Nobel prize.

In the early 1950s, physicists had been puzzled by the decays of two subatomic particles, known as tau and theta, which are identical except that the tau decays into three pions with a net parity of -1, while a theta particle decays into two pions with a net parity of +1.

There were two possible explanations: either the tau and theta are different particles or that parity in the weak interaction is not conserved with Yang and Lee proposing various ways to test their ideas (Phys. Rev. 104 254).

This “parity violation” was later proved experimentally by, among others, Chien-Shiung Wu at Columbia University. She carried out an experiment based on the radioactive decay of unstable cobalt-60 nuclei into nickel-60 – what became known as the “Wu experiment”. For their work, Yang, who was 35 at the time, shared the 1957 Nobel Prize for Physics with Lee.

Influential physicist

In 1965 Yang moved to Stony Brook University, becoming the first director of the newly founded Institute for Theoretical Physics, which is now known as the C N Yang Institute for Theoretical Physics. During this time he also contributed to advancing science and education in China, setting up the Committee on Educational Exchange with China – a programme that has sponsored some 100 Chinese scholars to study in the US.

In 1997, Yang returned to Beijing where he became an honorary director of the Centre for Advanced Study at Tsinghua University. He then retired from Stony Brook in 1999, becoming a professor at Tsinghua University. During his time in the US, Yang obtained US citizenship, but renounced it in 2015.

More recently, Yang was involved in debates over whether China should build the Circular Electron Positron Collider (CEPC) – a huge 100 km circumference underground collider that would study the Higgs boson in unprecedented detail and be a successor to CERN’s Large Hadron Collider. Yang took a sceptical view calling it “inappropriate” for a developing country that is still struggling with “more acute issues like economic development and environment protection”.

Yang also expressed concern that the science performed on the CEPC is just “guess” work and without guaranteed results. “I am not against the future of high-energy physics, but the timing is really bad for China to build such a super collider,” he noted in 2016. “Even if they see something with the machine, it’s not going to benefit the life of Chinese people any sooner.”

Lasting legacy

As well as the Nobel prize, Yang won many other awards such as the US National Medal of Science in 1986, the Einstein Medal in 1995, which is presented by the Albert Einstein Society in Bern, and the American Physical Society’s Lars Onsager Prize in 1990.

“The world has lost one of the most influential physicists of the modern era,” noted Stony Brook president Andrea Goldsmith in a statement. “His legacy will continue through his transformational impact on the field of physics and through the many colleagues and students influenced by his teaching, scholarship and mentorship.”

‘Science needs all perspectives – male, female and everything in-between’: Brazilian astronomer Thaisa Storchi Bergmann

As a teenager in her native Rio Grande do Sul, a state in Southern Brazil, Thaisa Storchi Bergmann enjoyed experimenting in an improvised laboratory her parents built in their attic. They didn’t come from a science background – her father was an accountant, her mother a primary school teacher – but they encouraged her to do what she enjoyed. With a friend from school, Storchi Bergmann spent hours looking at insects with a microscope and running experiments from a chemistry toy kit. “We christened the lab Thasi-Cruz after a combination of our names,” she chuckles.

At the time, Storchi Bergmann could not have imagined that one day this path would lead to cosmic discoveries and international recognition at the frontiers of astrophysics. “I always had the curiosity inside me,” she recalls. “It was something I carried since adolescence.”

That curiosity almost got lost to another discipline. By the time Storchi Bergmann was about to enter university, she was swayed by a cousin living with her family who was passionate about architecture. By 1974 she began studying architecture at the Federal University of Rio Grande do Sul (UFRGS). “But I didn’t really like technical drawing. My favourite part of the course were physics classes,” she says. Within a semester, she switched to physics.

There she met Edemundo da Rocha Vieira, the first astrophysicist UFRGS ever hired – who later went on to structure the university’s astronomy department. He nurtured Storchi Bergmann’s growing fascination with the universe and introduced her to research.

In 1977, newly married after graduation, Storchi Bergmann followed her husband to Rio de Janeiro, where she did a master’s degree and worked with William Kunkel, an American astronomer who was in Rio to help establish Brazil’s National Astrophysics Laboratory. She began working on data from a photometric system to measure star radiation. “But Kunkel said galaxies were a lot more interesting to study, and that stuck in my head,” she says.

Three years after moving to Rio, she returned to Porto Alegre, in Rio Grande do Sul, to start her doctoral research and teach at UFRGS. Vital to her career was her decision to join the group of Miriani Pastoriza, one of the pioneers of extragalactic astrophysics in Latin America. “She came from Argentina, where [in the late 1970s and early 1980s] scientists were being strongly persecuted [by the country’s military dictatorship] at the time,” she recalls. Pastoriza studied galaxies with “peculiar nuclei” – objects later known to harbour supermassive black holes. Under Pastoriza’s guidance, she moved from stars to galaxies, laying the foundation for her career.

Between 1986 and 1987, Storchi Bergmann often travelled to Chile to make observations and gather data for her PhD, using some of the largest telescopes available at the time. Then came a transformative period – a postdoc fellowship in Maryland, US, just as the Hubble Space Telescope was launched in 1990. “Each Thursday, I would drive to Baltimore for informal bag-lunch talks at the Space Telescope Science Institute, absorbing new results on active galactic nuclei (AGN) and supermassive black holes,” Storchi Bergmann recalls.

Discoveries and insights

In 1991, during an observing campaign, she and a collaborator saw something extraordinary in the galaxy NGC 1097: gas moving at immense speeds, captured by the galaxy’s central black hole. The work, published in 1993, became one of the earliest documented cases of what are now called “tidal disruption events”, in which a star or cloud gets too close to a black hole and is torn apart.

Her research also contributed to one of the defining insights of the Hubble era: that every massive galaxy hosts a central black hole. “At first, we didn’t know if they were rare,” she explains. “But gradually it became clear: these objects are fundamental to galaxy evolution.”

Another collaboration brought her into contact with Daniela Calzetti, whose work on the effects of interstellar dust led to the formulation of the widely used “Calzetti law”. These and other contributions placed Storchi Bergmann among the most cited scientists worldwide, recognition of which came in 2015 when she received the L’Oréal-UNESCO Award for Women in Science.

Her scientific achievements, however, unfolded against personal and structural obstacles. As a young mother, she often brought her baby to observatories and conferences so she could breastfeed. This kind of juggling is no stranger to many women in science.

“It was never easy,” Storchi Bergmann reflects. “I was always running, trying to do 20 things at once.” The lack of childcare infrastructure in universities compounded the challenge. She recalls colleagues who succeeded by giving up on family life altogether. “That is not sustainable,” she insists. “Science needs all perspectives – male, female and everything in-between. Otherwise, we lose richness in our vision of the universe.”

When she attended conferences early in her career, she was often the only woman in the room. Today, she says, the situation has greatly improved, even if true equality remains distant.

Now a tenured professor at UFRGS and a member of the Brazilian Academy of Sciences, Storchi Bergmann continues to push at the cosmic frontier. Her current focus is the Legacy Survey of Space and Time (LSST), about to begin at the Vera Rubin Observatory in Chile.

Her group is part of the AGN science collaboration, developing methods to analyse the characteristic flickering of accreting black holes. With students, she is experimenting with automated pipelines and artificial intelligence to make sense of and manage the massive amounts of data.

Challenges ahead

Yet this frontier science is not guaranteed. Storchi Bergmann is frustrated by the recent collapse in research scholarships. Historically, her postgraduate programme enjoyed a strong balance of grants from both of Brazil’s federal research funding agencies, CNPq (from the Ministry of Science) and CAPES (from the Ministry of Education). But cuts at CNPq, she says, have left students without support, and CAPES has not filled the gap.

“The result is heartbreaking,” she says. “I have brilliant students ready to start, including one from Piauí (a state in north-eastern Brazil), but without a grant, they simply cannot continue. Others are forced to work elsewhere to support themselves, leaving no time for research.”

She is especially critical of the policy of redistributing scarce funds away from top-rated programmes to newer ones without expanding the overall budget. “You cannot build excellence by dismantling what already exists,” she argues.

For her, the consequences go beyond personal frustration. They risk undermining decades of investment that placed Brazil on the international astrophysics map. Despite these challenges, Storchi Bergmann remains driven and continues to mentor master’s and PhD students, determined to prepare them for the LSST era.

At the heart of her research is a question as grand as any in cosmology: which came first – the galaxy or its central black hole? The answer, she believes, will reshape our understanding of how the universe came to be. And it will carry with it the fingerprint of her work: the persistence of a Brazilian scientist who followed her curiosity from a home-made lab to the centres of galaxies, overcoming obstacles along the way.

Precision sensing experiment manipulates Heisenberg’s uncertainty principle

Physicists in Australia and the UK have found a new way to manipulate Heisenberg’s uncertainty principle in experiments on the vibrational mode of a trapped ion. Although still at the laboratory stage, the work, which uses tools developed for error correction in quantum computing, could lead to improvements in ultra-precise sensor technologies like those used in navigation, medicine and even astronomy.

“Heisenberg’s principle says that if two operators – for example, position x and momentum, p – do not commute, then one cannot simultaneously measure both of them to absolute precision,” explains team leader Ting Rei Tan of the University of Sydney’s Nano Institute. “Our result shows that one can instead construct new operators – namely ‘modular position’ x̂ and ‘modular momentum’ p̂. These operators can be made to commute, meaning that we can circumvent the usual limitation imposed by the uncertainty principle.”

The modular measurements, he says, give the true measurement of displacements in position and momentum of the particle if the distance is less than a specific length l, known as the modular length. In the new work, they measured x̂ = x mod l_x and p̂ = p mod l_p, where l_x and l_p are the modular length in position and momentum.

“Since the two modular operators x̂ and p̂ commute, this means that they are now bounded by an uncertainty principle where the product is larger or equal to 0 (instead of the usual ℏ/2),” adds team member Christophe Valahu. “This is how we can use them to sense position and momentum below the standard quantum limit. The catch, however, is that this scheme only works if the signal being measured is within the sensing range defined by the modular lengths.”

The researchers stress that Heisenberg’s uncertainty principle is in no way “broken” by this approach, but it does mean that when observables associated with these new operators are measured, the precision of these measurements is not limited by this principle. “What we did was to simply push the uncertainty to a sensing range that is relatively unimportant for our measurement to obtain a better precision at finer details,” Valahu tells Physics World.

This concept, Tan explains, is related to an older method known as quantum squeezing that also works by shifting uncertainties around. The difference is that in squeezing, one reshapes the probability, reducing the spread in position at the cost of enlarging the spread of momentum, or vice versa. “In our scheme, we instead redistribute the probability, reducing the uncertainties of position and momentum within a defined sensing range, at the cost of an increased uncertainty if the signal is not guaranteed to lie within this range,” Tan explains. “We effectively push the unavoidable quantum uncertainty to places we don’t care about (that is, big, coarse jumps in position and momentum) so the fine details we do care about can be measured more precisely.

“Thus, as long as we know the signal is small (which is almost always the case for precision measurements), modular measurements give us the correct answer.”

Repurposed ideas and techniques

The particle being measured in Tan and colleagues’ experiment was a ¹⁷¹Yb⁺ ion trapped in a so-called grid state, which is a subclass of error-correctable logical state for quantum bits, or qubits. The researchers then used a quantum phase estimation protocol to measure the signal they imprinted onto this state, which acts as a sensor.

This measurement scheme is similar to one that is commonly used to measure small errors in the logical qubit state of a quantum computer. “The difference is that in this case, the ‘error’ corresponds to a signal that we want to estimate, which displaces the ion in position and momentum,” says Tan. “This idea was first proposed in a theoretical study.”

Towards ultra-precise quantum sensors

The Sydney researchers hope their result will motivate the development of next-generation precision quantum sensors. Being able to detect extremely small changes is important for many applications of quantum sensing, including navigating environments where GPS isn’t effective (such as on submarines, underground or in space). It could also be useful for biological and medical imaging, materials analysis and gravitational systems.

Their immediate goal, however, is to further improve the sensitivity of their sensor, which is currently about 14 x10^-24N/Hz^1/2, and calculate its limit. “It would be interesting if we could push that to the 10^-27N level (which, admittedly, will not be easy) since this level of sensitivity could be relevant in areas like the search for dark matter,” Tan says.

Another direction for future research, he adds, is to extend the scheme to other pairs of observables. “Indeed, we have already taken some steps towards this: in the latter part of our present study, which is published in Science Advances, we constructed a modular number operator and a modular phase operator to demonstrate that the strategy can be extended beyond position and momentum.”

Eye implant restores vision to patients with incurable sight loss

A tiny wireless implant inserted under the retina can restore central vision to patients with sight loss due to age-related macular degeneration (AMD). In an international clinical trial, the PRIMA (photovoltaic retina implant microarray) system restored the ability to read in 27 of 32 participants followed up after a year.

AMD is the most common cause of incurable blindness in older adults. In its advanced stage, known as geographic atrophy, AMD can cause progressive, irreversible death of light-sensitive photoreceptors in the centre of the retina. This loss of photoreceptors means that light is not transduced into electrical signals, causing profound vision loss.

The PRIMA system works by replacing these lost photoreceptors. The two-part system includes the implant itself: a 2 × 2 mm array of 378 photovoltaic pixels, plus PRIMA glasses containing a video camera that captures images and, after processing, projects them onto the implant using near-infrared light. The pixels in the implant convert this light into electrical pulses, restoring the flow of visual information to the brain. Patients can use the glasses to focus and zoom the image that they see.

The clinical study, led by Frank Holz of the University of Bonn in Germany, enrolled 38 participants at 17 hospital sites in five European countries. All participants had geographic atrophy due to AMD in both eyes, as well as loss of central sight in the study eye over a region larger than the implant (more than 2.4 mm in diameter), leaving only limited peripheral vision.

Around one month after surgical insertion of the 30 μm-thick PRIMA array into one eye, the patients began using the glasses. All underwent training to learn to interpret the visual signals from the implant, with their vision improving over months of training.

Eye images before and after array implantation — **The PRIMA implant** Representative fundus and OCT images obtained before and after implantation of the array in a patient’s eye. (Courtesy: Science Corporation)

After one year, 27 of the 32 patients who completed the trial could read letters and words (with some able to read pages in a book) and 26 demonstrated clinically meaningful improvement in visual acuity (the ability to read at least two extra lines on a standard eye chart). On average, participants could read an extra five lines, with one person able to read an additional 12 lines.

Nineteen of the participants experienced side-effects from the surgical procedure, with 95% of adverse events resolving within two months. Importantly, their peripheral vision was not impacted by PRIMA implantation. The researchers note that the infrared light used by the implant is not visible to remaining photoreceptors outside the affected region, allowing patients to combine their natural peripheral vision with the prosthetic central vision.

“Before receiving the implant, it was like having two black discs in my eyes, with the outside distorted,” Sheila Irvine, a trial patient treated at Moorfields Eye Hospital in the UK, says in a press statement. “I was an avid bookworm, and I wanted that back. There was no pain during the operation, but you’re still aware of what’s happening. It’s a new way of looking through your eyes, and it was dead exciting when I began seeing a letter. It’s not simple, learning to read again, but the more hours I put in, the more I pick up. It’s made a big difference.”

The PRIMA system – originally designed by Daniel Palanker at Stanford University – is being developed and manufactured by Science Corporation. Based on these latest results, reported in the New England Journal of Medicine, the company has applied for clinical use authorization in Europe and the United States.

Single-phonon coupler brings different quantum technologies together

Researchers in the Netherlands have demonstrated the first chip-based device capable of splitting phonons, which are quanta of mechanical vibrations. Known as a single-phonon directional coupler, or more simply as a phonon splitter, the new device could make it easier for different types of quantum technologies to “talk” to each other. For example, it could be used to transfer quantum information from spins, which offer advantages for data storage, to superconducting circuits, which may be better for data processing.

“One of the main advantages of phonons over photons is they interact with a lot of different things,” explains team leader Simon Gröblacher of the Kavli Institute of Nanoscience at Delft University of Technology. “So it’s very easy to make them interface with systems.”

There are, however, a few elements still missing from the phononic circuitry developer’s toolkit. One such element is a reversible beam splitter that can either combine two phonon channels (which might be carrying quantum information transferred from different media) or split one channel into two, depending on its orientation.

While several research groups have already investigated designs for such phonon splitters, these works largely focused on surface acoustic waves. This approach has some advantages, as waves of this type have already been widely explored and exploited commercially. Mobile phones, for example, use surface acoustic waves as filters for microwave signals. The problem is that these unconfined mechanical excitations are prone to substantial losses as phonons leak into the rest of the chip.

Mimicking photonic beam splitters

Gröblacher and his collaborators chose instead to mimic the design of beam splitters used in photonic chips. They used a strip of thin silicon to fashion a waveguide for phonons that confined them in all dimensions but one, giving additional control and reducing loss. They then brought two waveguides into contact with each other so that one waveguide could “feel” the mechanical excitations in the other. This allowed phonon modes to be coupled between the waveguides – something the team demonstrated down to the single-phonon level. The researchers also showed they could tune the coupling between the two waveguides by altering the contact length.

Although this is the first demonstration of single-mode phonon coupling in this kind of waveguide, the finite element method simulations Gröblacher and his colleagues ran beforehand made him pretty confident it would work from the outset. “I’m not surprised that it worked. I’m always surprised how hard it is to get it to work,” he tells Physics World. “Making it to look and do exactly what you design it to do – that’s the really hard part.”

Prospects for integrated quantum phononics

According to A T Charlie Johnson, a physicist at the University of Pennsylvania, US whose research focuses on this area, that hard work paid off. “These very exciting new results further advance the prospects for phonon-based qubits in quantum technology,” says Johnson, who was not directly involved in the demonstration. “Integrated quantum phononics is one significant step closer.”

As well as switching between different quantum media, the new single-phonon coupler could also be useful for frequency shifting. For instance, microwave frequencies are close to the frequencies of ambient heat, which makes signals at these frequencies much more prone to thermal noise. Gröblacher already has a company working on transducers to transform quantum information from microwave to optical frequencies with this challenge in mind, and he says a single-phonon coupler could be handy.

One remaining challenge to overcome is dispersion, which occurs when phonon modes couple to other unwanted modes. This is usually due to imperfections in the nanofabricated device, which are hard to avoid. However, Gröblacher also has other aspirations. “I think the one component that’s missing for us to have the similar level of control over phonons as people have with photons is a phonon phase shifter,” he tells Physics World. This, he says, would allow on-chip interferometry to route phonons to different parts of a chip, and perform advanced quantum experiments with phonons.

The study is reported in Optica.

This jumping roundworm uses static electricity to attach to flying insects

Researchers in the US have discovered that a tiny jumping worm uses static electricity to increase the chances of attaching to its unsuspecting prey.

The parasitic roundworm Steinernema carpocapsae, which live in soil, are already known to leap some 25 times their body length into the air. They do this by curling into a loop and springing in the air, rotating hundreds of times a second.

If the nematode lands successfully, it releases bacteria that kills the insect within a couple of days upon which the worm feasts and lays its eggs. At the same time, if it fails to attach to a host then it faces death itself.

While static electricity plays a role in how some non-parasitic nematodes detach from large insects, little is known whether static helps their parasitic counterparts to attach to an insect.

To investigate, researchers are Emory University and the University of California, Berkeley, conducted a series of experiments, in which they used high-speed microscopy techniques to film the worms as they leapt onto a fruit fly.

They did this by tethering a fly with a copper wire that was connected to a high-voltage power supply.

They found that a charge of a few hundred volts – similar to that generated in the wild by an insect’s wings rubbing against ions in the air – fosters a negative charge on the worm, creating an attractive force with the positively charged fly.

Carrying out simulations of the worm jumps, they found that without any electrostatics, only 1 in 19 worm trajectories successfully reached their target. The greater the voltage, however, the greater the chance of landing. For 880 V, for example, the probability was 80%.

The team also carried out experiments using a wind tunnel, finding that the presence of wind helped the nematodes drift and this also increased their chances of attaching to the insect.

“Using physics, we learned something new and interesting about an adaptive strategy in an organism,” notes Emory physicist Ranjiangshang Ran. “We’re helping to pioneer the emerging field of electrostatic ecology.”

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