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Can artificial intelligence predict future research directions in quantum science? Listen to this episode of the Physics World Weekly podcast to discover what is already possible.
My guests are Mario Krenn – who heads the Artificial Scientist Lab at Germany’s Max Planck Institute for the Science of Light – and Felix Frohnert, who is doing a PhD on the intersection of quantum physics and machine learning at Leiden University in the Netherlands.
Frohnert, Krenn and colleagues published a paper earlier this year called “Discovering emergent connections in quantum physics research via dynamic word embeddings” in which they analysed more than 66,000 abstracts from the quantum-research literature to see if they could predict future trends in the field. They were particularly interested in the emergence of connections between previously isolated subfields of quantum science.
We chat about what motivated the duo to use machine learning to study quantum science; how their prediction system works; and I ask them whether they have been able to predict current trends in quantum science using historical data.
Their paper appears in the journal Machine Learning Science and Technology. It is published by IOP Publishing – which also brings you Physics World. Krenn is on the editorial board of the journal and in the podcast he explains why it is important to have a platform to publish research at the intersection of physics and machine learning.
Errors in some of this year’s A-level physics exam papers could leave students without good enough grades to study physics at university. The mistakes have forced Tom Grinyer, chief executive of the Institute of Physics (IOP), to write to all heads of physics at UK universities, calling on them to “take these exceptional circumstances into account during the final admissions process”. The IOP is particularly concerned about students whose grades are lower than expected or are “a significant outlier” compared to other subjects.
The mistakes in question appeared in the physics (A) exam papers 1 and 2 set by the OCR exam board. Erratum notices had been issued to students at the start of the exam in June, but a further error in paper 2 was only spotted after the exam had taken place, causing some students to get stuck. Physics paper 2 from the rival AQA exam board was also seen to contain complex phrasing that hindered students’ ability to answer the question and led to time pressures.
A small survey of physics teachers carried out after the exam by the IOP, which publishes Physics World, reveals that 41% were dissatisfied with the OCR physics exam papers and more than half (58%) felt that students had a negative experience. Two-thirds of teachers, meanwhile, reported that students had a negative experience during the AQA exam. A-levels are mostly taken by 18 year olds in England, Wales and Northern Ireland, with the grades being used by universities to decide admission.
Grinyer says that the IOP is engaging in “regular, open dialogue with exam boards” to ensure that the assessment process supports and encourages students, while maintaining the rigour and integrity of the qualification. “Our immediate concern,” Grinyer warns, “is that the usual standardization processes and adjustments to grade boundaries – particularly for the OCR paper with errors – may fail to compensate fully for the negative effect on exam performance for some individuals.”
An OCR spokesperson told Physics World that the exam board is “sorry to the physics students and teachers affected by errors in A-level physics this year”. The board says that it “evaluated student performance across all physics papers, and took all necessary steps to mitigate the impact of these errors”. The OCR claims that the 13,000 students who sat OCR A-level physics A this year “can be confident” in their A-level physics results.
“We have taken immediate steps to review and strengthen our quality assurance processes to prevent such issues from occurring in the future,” the OCR adds. “We appreciated the opportunity to meet with the Institute of Physics to discuss these issues, and also to discuss our shared interest in encouraging the growth of this vital subject.”
Almost 23,500 students sat AQA A-level physics this year and an AQA spokesperson told Physics World that the exam board “listened to feedback and took steps to make A-level physics more accessible” to students and that there “is no need for universities to make an exception for AQA physics outcomes when it comes to admissions criteria”.
“These exam papers were error-free, as teachers and students would expect, and we know that students found the papers this year to be more accessible than last year,” they say. “We’ll continue to engage with any feedback that we receive, including feedback from the Institute of Physics, to explore how we can enhance our A-level physics assessments and give students the best possible experience when they sit exams.”
Students ‘in tears’
The IOP now wants A-level physics students to be given a “fair opportunity” when it comes to university admissions. “These issues are particularly concerning for students on widening participation pathways, many of whom already face structural barriers to high-stakes assessment,” the IOP letter states. “The added challenge of inaccessible or error-prone exam papers risks compounding disadvantage and may not reflect the true potential of these students.”
The IOP also contacted AQA last year over inaccessible contexts and language used in previous physics exams. But despite AQA’s assurances that the problems would be addressed, some of the same issues have now recurred. Helen Sinclair, head of physics at the all-girls Wimbledon High School, believes that the “variable quality” of recent A-level papers have had “far-reaching consequences” on young people thinking of going into physics at university.
“Our students have exceptionally high standards for themselves and the opaque nature of many questions affects them deeply, no matter what grades they ultimately achieve. This has even led some to choose to apply for other subjects at university,” she told Physics World. “This is not to say that papers should not be challenging; however, better scaffolding within some questions would help students anchor themselves in what is an already stressful environment, and would ultimately enable them to better demonstrate their full potential within an exam.”
Students come out of the exams feeling disheartened, and those students share their perceptions with younger students
Abbie Hope, Stokesley School
Those concerns are echoed by Abbie Hope, head of physics at Stokesley School in Stockton-on-Tees. She says the errors in this year’s exam papers are “not acceptable” and believes that OCR has “failed their students”. Hope says that AQA physics papers in recent years have been “very challenging” and have resulted in students feeling like they cannot do physics. She also says some have emerged from exam halls in tears.
“Students come out of the exams feeling disheartened and share their perceptions with younger students,” she says. “I would rather students sat a more accessible paper, with higher grade boundaries so they feel more successful when leaving the exam hall, rather than convinced they have underachieved and then getting a surprise on results day.” Hope fears the mistakes will undermine efforts to encourage uptake and participation in physics and that exam boards need to serve students and teachers better.
A ‘growing unease’
Rachael Houchin, head of physics at Royal Grammar School Newcastle, says this year’s errors have added to her “growing unease” about the state of physics education in the UK. “Such incidents – particularly when they are public and recurring – do little to improve the perception of the subject or encourage its uptake,” she says. “Everyone involved in physics education – at any level – has a duty to get it right. If we fail, we risk physics drifting into the category of subjects taught predominantly in selective or independent schools, and increasingly absent from the mainstream.”
Hari Rentala, associate director of education and workforce at the IOP, is concerned that the errors unfairly “perpetuate the myth” that physics is a difficult subject. “OCR appear to have managed the situation as best they can, but this is not much consolation for how students will have felt during the exam and over the ensuing weeks,” says Rentala. “Once again AQA set some questions that were overly challenging. We can only hope that the majority of students who had a negative experience as a result of these issues at least receive a fair grade – as grade boundaries have been adjusted down.”
Mixed news for pupils
Despite the problems with some specific papers, almost 45,000 students took A-level physics in the UK – a rise of 4.3% on last year – to reach the highest level for 25 years. Physics is now the sixth most popular subject at A-level, up from ninth last year, with girls representing a quarter of all candidates. Meanwhile, in Scotland the number of entries in both National 5 and Higher physics was 13,680 and 8560, respectively, up from 13,355 and 8065 last year.
“We are delighted so many young people, and increasing numbers of girls, are hearing the message that physics can open up a lifetime of opportunities,” says Grinyer. “If we can build on this momentum there is a real opportunity to finally close the gap between boys and girls in physics at A-level. To do that we need to continue to challenge the stereotypes that still put too many young people off physics and ensure every young person knows that physics – and a career in science and innovation – could be for them.”
However, there is less good news for younger pupils, with a new IOP report finding that more than half a million GCSE students are expected to start the new school year with no physics teacher. It reveals that a quarter of English state schools have no specialist physics teachers at all and fears that more than 12,000 students could miss out on taking A-level physics because of this. The IOP wants the UK government to invest £120m over the next 10 years to address the shortage by retaining, recruiting and retraining a new generation of physics teachers.
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Physicists at the Chinese Academy of Sciences (CAS) have used diamond-based quantum sensors to uncover what they say is the first unambiguous experimental evidence for the Meissner effect – a hallmark of superconductivity – in bilayer nickelate materials at high pressures. The discovery could spur the development of highly sensitive quantum detectors that can be operated under high-pressure conditions.
Superconductors are materials that conduct electricity without resistance when cooled to below a certain critical transition temperature Tc. Apart from a sharp drop in electrical resistance, another important sign that a material has crossed this threshold is the appearance of the Meissner effect, in which the material expels a magnetic field from its interior (diamagnetism). This expulsion creates such a strong repulsive force that a magnet placed atop the superconducting material will levitate above it.
In “conventional” superconductors such as solid mercury, the Tc is so low that the materials must be cooled with liquid helium to keep them in the superconducting state. In the late 1980s, however, physicists discovered a new class of superconductors that have a Tc above the boiling point of liquid nitrogen (77 K). These “unconventional” or high-temperature superconductors are derived not from metals but from insulators containing copper oxides (cuprates).
Since then, the search has been on for materials that superconduct at still higher temperatures, and perhaps even at room temperature. Discovering such materials would have massive implications for technologies ranging from magnetic resonance imaging machines to electricity transmission lines.
Enter nickel oxides
In 2019 researchers at Stanford University in the US identified nickel oxides (nickelates) as additional high-temperature superconductors. This created a flurry of interest in the superconductivity community because these materials appear to superconduct in a way that differs from their copper-oxide cousins.
Among the nickelates studied, La3Ni2O7-δ (where δ can range from 0 to 0.04) is considered particularly promising because in 2023, researchers led by Meng Wang of China’s Sun Yat-Sen University spotted certain signatures of superconductivity at a temperature of around 80 K. However, these signatures only appeared when crystals of the material were placed in a device called a diamond anvil cell (DAC). This device subjects samples of material to extreme pressures of more than 400 GPa (or 4 × 106 atmospheres) as it squeezes them between the flattened tips of two tiny, gem-grade diamond crystals.
The problem, explains Xiaohui Yu of the CAS’ Institute of Physics, is that it is not easy to spot the Meissner effect under such high pressures. This is because the structure of the DAC limits the available sample volume and hinders the use of highly sensitive magnetic measurement techniques such as SQUID. Another problem is that the sample used in the 2023 study contains several competing phases that could mix and degrade the signal of the La3Ni2O7-δ.
Nitrogen-vacancy centres embedded as in-situ quantum sensors
In the new work, Yu and colleagues used nitrogen-vacancy (NV) centres embedded in the DAC as in-situ quantum sensors to track and image the Meissner effect in pressurized bilayer La3Ni2O7-δ. This newly developed magnetic sensing technique boasts both high sensitivity and high spatial resolution, Yu says. What is more, it fits perfectly into the DAC high-pressure chamber.
Next, they applied a small external magnetic field of around 120 G. Under these conditions, they measured the optically detected magnetic resonance (ODMR) spectra of the NV centres point by point. They could then extract the local magnetic field from the resonance frequencies of these spectra. “We directly mapped the Meissner effect of the bilayer nickelate samples,” Yu says, noting that the team’s image of the magnetic field clearly shows both a diamagnetic region and a region where magnetic flux is concentrated.
Weak demagnetization signal
The researchers began their project in late 2023, shortly after receiving single-crystal samples of La3Ni2O7-δ from Wang. “However, after two months of collecting data, we still had no meaningful results,” Yu recalls. “From these experiments, we learnt that the demagnetization signal in La3Ni2O7-δ crystals was quite weak and that we needed to improve either the nickelate sample or the sensitivity of the quantum sensor.”
To overcome these problems, they switched to using polycrystalline samples, enhancing the quality of the nickelate samples by doping them with praseodymium to make La2PrNi2O7. This produced a sample with an almost pure bilayer structure and thus a much stronger demagnetization signal. They also used shallow NV centres implanted on the DAC cutlet (the smaller face of the two diamond tips).
“Unlike the NV centres in the original experiments, which were randomly distributed in the pressure-transmitting medium and have relatively large ODMR widths, leading to only moderate sensitivity in the measurements, these shallow centres are evenly distributed and well aligned, making it easier for us to perform magnetic imaging with increased sensitivity,” Yu explains.
These improvements enabled the team to obtain a demagnetization signal from the La2PrNi2O7 and La3Ni2O7-δ samples, he tells Physics World. “We found that the diamagnetic signal from the La2PrNi2O7 samples is about five times stronger than that from the La3Ni2O7-δ ones prepared under similar conditions – a result that is consistent with the fact that the Pr-doped samples are of a better quality.”
Physicist Jun Zhao of Fudan University, China, who was not involved in this work, says that Yu and colleagues’ measurement represents “an important step forward” in nickelate research. “Such measurements are technically very challenging, and their success demonstrates both experimental ingenuity and scientific significance,” he says. “More broadly, their result strengthens the case for pressurized nickelates as a new platform to study high-temperature superconductivity beyond the cuprates. It will certainly stimulate further efforts to unravel the microscopic pairing mechanism.”
As well as allowing for the precise sensing of magnetic fields, NV centres can also be used to accurately measure many other physical quantities that are difficult to measure under high pressure, such as strain and temperature distribution. Yu and colleagues say they are therefore looking to further expand the application of these structures for use as quantum sensors in high-pressure sensing.
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