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A horrific nightmare scenario at CERN, surfer wins SUSY bet, and meet the father of the Super Soaker

Surf's up: Garrett Lisi when he is not winning bets with Nobel laureates (Courtesy: CC BY-SA 3.0/Cjean42) — Surf’s up: Garrett Lisi when he is not winning bets with Nobel laureates. (CC BY-SA 3.0/Cjean42)

By Hamish Johnston

The “nightmare scenario” of particle physics has a new meaning thanks to a bizarre video that appears to have been made by some scientists at CERN. The video seems to have been filmed at night at CERN’s main campus in Geneva and depicts an occult ceremony in which a woman is stabbed. While the video appears to be a spoof and there is no indication that anyone was actually harmed in its making, CERN officials are rightly concerned that such violent scenes were filmed on their premises. “CERN does not condone this type of spoof, which can give rise to misunderstandings about the scientific nature of our work,” a spokesperson told Agence France-Presse.

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UK Atomic Energy Authority gets a new chief executive

The UK fusion scientist Ian Chapman has been named as the next chief executive of the UK Atomic Energy Authority (UKAEA). On 1 October Chapman will succeed Steve Cowley, who has been head of the authority since 2009 and will become president of Corpus Christi College at the University of Oxford.

As head of the UKAEA, Chapman will lead the UK’s magnetic confinement fusion research programme at the Culham Science Centre in Oxfordshire. He will oversee the upgrade of the Mega Amp Spherical Tokamak, which is set to be ready in 2017, as well as the operation of the Joint European Torus (JET) – one of the world’s largest nuclear fusion devices. He will also lead the UKAEA’s other activities at Culham, including the recently opened Materials Research Facility, the RACE robotics centre and the Oxford Advanced Skills apprentice training facility.

With an MSc in mathematics and physics from Durham University, Chapman began working at Culham in 2004 while completing a PhD with Imperial College London. In 2014 he was named head of tokamak science at Culham and then became fusion programme manager a year later. Aged just 34, Chapman will be one of the youngest chief executives of a major research facility. “While I am young, I am also experienced,” he says. “I hope my profile means that fusion, and its huge potential to give the world cleaner energy, will get noticed.”

Broad portfolio

Chapman comes into the job at a crucial time for UK research following the country’s vote to leave the EU, which will be tricky to manage for Culham. The European Consortium for the Development of Fusion Energy – jointly run by 26 European member states and Switzerland – funds JET’s experiments. Cash for this is secure until 2018, but what happens after then is unknown. But Chapman told Physics World that he is confident about Culham’s future. “Science is an international endeavour,” he says. “I am positive for the future as we have a broad portfolio of activities.”

Indeed, the experiments carried out at JET will be crucial to the success of the ITER fusion experiment currently being built in Cadarache, France, when it turns on in the coming decade. While Chapman calls ITER “the most important experiment mankind has ever done”, he admits it is a “big challenge, with a lot of difficulties”. Yet he hopes that his appointment will inspire the next generation of scientist and engineers to make a success of the device. “It is my personal ambition to deliver fusion,” he adds.

Chapman’s appointment is backed by Culham’s outgoing boss. “Ian has risen quickly for good reason: he is a world-class scientist, a thoughtful manager, and a strategic thinker of the first order – astonishing in one so young,” says Cowley. “Culham is a precious UK asset and I am pleased that it will be in such good hands.”

'Chemtrails' are a con, say experts

Vast conspiracy: contrails over Horfield Common in Bristol.

By Hamish Johnston

Is there a government-led conspiracy that uses aeroplanes to lace the atmosphere with chemicals? Of course there isn’t, and now there is a peer-reviewed study that says so.

Dubbed the “secret large-scale atmospheric programme” (SLAP), the conspiracy concerns condensation trails (contrails) that can often be seen high up in the sky. These are the lines of cloud that are formed when water condensates around particulate matter in the exhaust from jet engines. But are those contrails actually “chemtrails” that are spreading noxious substances far and wide?

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Quantum mechanics trumps nonlocal causality

Quantum mechanics wreaks even more havoc with conventional ideas of causality than some have suspected – according to a team of researchers based in Australia, with collaborators in Scotland and Germany. They have shown that even allowing causality to be nonlocal – so that an event in one place can have an influence on another, distant place – is not enough to explain how quantum objects behave.

Without cause and effect, science would be impossible. You could never use an observation to deduce anything about the underlying mechanism that caused it. But quantum mechanics challenges our commonsense picture of causality – for example by implying that some things happen at random, with no apparent cause, or that an action in one place can seem to have an effect elsewhere, even if the two locations cannot interact.

This kind of nonlocality has become widely accepted in quantum theory, thanks to experiments on so-called entangled states. Here two or more quantum entities, such as photons of light, acquire interdependent properties, revealed by correlations in the measured values of their properties. For example, pairs of polarized photons can be entangled so that, if one has horizontal polarization, the other has vertical polarization.

Action at a distance?

Because quantum properties have inherent randomness, these correlations are typically revealed in averages of many measurements. The twist is that quantum mechanics seems to insist that these properties are not fixed until they are measured. This seems to imply that a measurement on one entangled photon affects the other instantaneously across space.

Perhaps quantum mechanics is incomplete, though, and the properties were actually fixed within the particles all along. This “local realist” picture, in which quantum particles have intrinsic, localized properties even if we can’t see them directly, was assumed by Albert Einstein and colleagues in 1935 when they argued that such instant action at a distance creates a paradox for quantum mechanics.

But after Northern Irish physicist John Bell showed in 1964 how to distinguish between the predictions of local realism and those of quantum mechanics, numerous experiments have shown that the quantum picture seems to be correct. There’s no real instantaneous action at a distance, because we can’t think of the measurement on one particle as “causing” some “effect” on the other.

Painting a realist picture

It’s still possible, however, to explain Bell-type tests of quantum correlations in a “realist” picture (where quantum objects possess fixed properties before measurement) if other of his assumptions are rejected. If, say, causation itself were nonlocal, so that an intervention in one place is felt elsewhere, then a measurement on one photon might directly influence that on the other, creating the correlation between them.

The new experiments, says Martin Ringbauer of the University of Queensland, who led the Australian group, “consider this class of realist models, where Bell’s central assumption of local causality is relaxed.”

To test whether a realist but nonlocally causal model is able to explain quantum phenomena, the team devised Bell-type experiments where such a model makes different predictions from quantum mechanics. First they performed a modified version of one of the earliest such experiments on entangled photons in the 1970s, called a Clauser-Horne-Shimony-Holt (CHSH) test.

Causality, not correlation

To test for causal effects and not just correlation in this test, they did not simply make passive measurements of photon polarization but actively intervened to change the outcome. “Imagine you are watching someone flick a light switch and observe that the light goes on and off in perfect correlation”, says Ringbauer. “You can’t tell whether the switch causes the light to go on, or the light going on causes the person to flick the switch, or there is some hidden common cause that is responsible for both the light going on and the person flicking the switch.”

However, if you’re in control of the switch yourself, you can tell the difference. In their experiment, Ringbauer and colleagues fixed the outcome of measurement on one photon by inserting optical devices that affected its polarization before the measurement was made. They then looked for a concurrent change in the statistics of the other. Because they saw none, they concluded that there could be no nonlocal causality at play in which measurement outcomes on one photon could cause changes in those on the other.

The team then did a more complicated experiment involving three possible measurement settings as opposed to just two for the CHSH experiment. This allowed them to verify that their conclusions are independent of the specific apparatus used to do the tests. In other words, the results do not depend on any particular type of intervention.

Radical revisions

The only way now that one might rescue some kind of classical (realist) causal interpretation of quantum correlations involves more radical revisions of Bell’s assumptions, says Ringbauer – for example, backwards-in-time causation or a “many-worlds” interpretation of quantum mechanics with multiple parallel universes.

Caslav Brukner, a quantum theorist at the University of Vienna, told physicsworld.com: “I like the work since it excludes a large class on nonlocal causal theories.” Previous tests looked only at a very specific version of such theories, he adds.

The experiment “is not only important from the perspective of quantum foundations, but might also have implications in quantum cryptography,” says Ognyan Oreshkov of the Free University of Brussels in Belgium – for example in cases where one can’t guarantee that the measurements made by the sender and receiver are kept secret.

The research is described in Science Advances.

Physics World 2016 Focus on Vacuum Technology is out now

By Matin Durrani

I’m pleased to say that the latest focus issue of Physics World, which explores the many fascinating applications of vacuum science and technology, is now out.

Plasma processing is a strong theme this year, as we discover why tools and techniques developed as part of the boom in semiconductor fabrication are now benefiting biomaterials. Elsewhere, we reflect on the strengths of the vacuum community with outgoing IUVSTA president Mariano Anderle.

And, as always, this vacuum focus issue provides a great chance to catch up with major industry players, including Pfeiffer Vacuum, Agilent, Honeywell and Edwards, to examine the latest instrument upgrades and trends across the sector.

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Thinking big thoughts

Everybody loves coincidences, so here is one: a few months ago, I began writing a popular-science book about how to bridge the gap in our understanding of the microscopic (quantum) world and the macroscopic one. If we could do this, and thus explain large-scale phenomena (such as weather) using the underlying microdynamics of molecules, we could transform both science and technology (though we might, unfortunately, also eliminate the UK’s commonest conversation starter). But would it be spiritually uplifting? Could this coherent and phenomenally powerful picture of the universe fulfil us in the same way that believing in God has traditionally done?

Just as I was grappling with this topic in my book’s final chapter, I received a request to review a book by Sean Carroll that asks similar questions, albeit from a completely different perspective. The short synopsis of The Big Picture is that it explores the question of whether science can explain everything in the world, and analyses the emerging picture of reality that such an explanation entails.

Coincidence? Well, yes and no. Yes, because Physics World did not know I was writing a book on a broadly similar topic. But also no, because in many ways the time is now ripe for this kind of discussion to happen. First, scientists are engaging more and more in interdisciplinary research, which is all about bridging gaps between different disciplines; behavioural economics, for example, applies psychology to the way we do financial transactions. Second, many parts of the world, Europe in particular, are becoming more and more secular. As a result, many people feel there is a void that used to be filled by religion, but which science is incapable of replacing.

Or is it? Carroll, in the best tradition of his California Institute of Technology predecessor Richard Feynman, argues that science can indeed provide a spiritually fulfilling picture of the universe. He calls this picture “poetic naturalism”. The naturalism part is self-explanatory. What you see is what you get: there is no supernatural spoon bending or talking to the dead (or rather, you can talk to the dead, but they don’t talk back), and Carroll presents convincing arguments (based on quantum field theory, our most accurate scientific explanation of the micro world) as to why such phenomena cannot be real.

Naturalism thus stated might sound boring. Not so, Carroll argues skilfully: the fact that there is no magic, doesn’t mean that there is no “magic”. That’s where the “poetic” part comes in. Like Feynman before him, Carroll firmly believes that having a scientific understanding of nature only adds to the beauty of what we see around us, and in some sense makes the whole coherent scaffolding of our understanding even more remarkable and awe-inspiring. The stories we’ve constructed through science about the universe, our origins and fate are, Carroll argues, just as magical as anything we see in religion, art and philosophy – if not more so.

As its name suggests, The Big Picture is broad. The range of subjects is breathtaking, with some pure science, some philosophy and even some passages that read almost like extracts from a self-help book. I enjoyed Carroll’s discussions of the difference between notions of complexity (loosely, something that has many interwoven parts highly mutually dependent) and entropy (a measure of disorder, which is frequently confused with complexity). I appreciated his explanation of how complex phenomena such as consciousness might emerge naturally even though they are not seen in microscopic neurological behaviour (which does not make consciousness any less real). And I learnt many historical facts, for instance about the contributions of Princess Elisabeth of Bohemia to the philosophy of René Descartes (Elisabeth, like Carroll, argued against the Cartesian dualism that manifested itself in the separation between the body and the soul).

Although an exciting read, the book is, of course, far from perfect. I have some minor technical quibbles about a few aspects. One is that Carroll avoids getting into a proper discussion of how one might attempt to reconcile the “many worlds” picture of the universe he promotes (I also subscribe to it – that’s not my issue) with the fact that the universe’s entropy was, in the past, very low. The subsequent increase in entropy is something we can understand only statistically and is hard to argue in a closed system. These are problems that go back to Ludwig Boltzmann’s clashes with his contemporaries in the late 19th century, and the low entropy of the past remains a profound mystery to us, but it does not come across as such here.

Another problem is that Carroll is not a natural writer. He occasionally misjudges the level of detail he needs to go into, and so some parts feel quite “textbookish”. I particularly felt this in his discussion of Bayes’ treatment of probabilistic inference, although it does contain a good explanation of coincidences, such as thinking of someone when the phone rings and it’s them (or indeed being asked to review a book when you’re writing one on the same subject). He tells many stories in-between the more detailed passages, to keep us entertained, but I think he is a much better science communicator than storyteller. Some stories feel unnaturally added on to break the monotony, and the transitions are not done as smoothly as, for instance, in the tremendously successful Freakonomics (a reference for science popularizers).

Despite these minor imperfections, this is no doubt a great book. I like its honest and direct style. It’s passionately written by a physicist who has clearly thought deeply not only about his own research interests, but also about how they fit into the bigger picture. And not only that: Carroll also shows us that science and spirituality do not necessarily come into conflict, something that most scientists feel is true (that’s why almost all of us physicists would choose the same profession if we were born again) but refrain from discussing openly, perhaps for fear of being called “irrational” and “mystical”. Carroll’s “big picture”, beautifully exposed and illustrated, is the closest I’ve seen to a scientific explanation of the meaning of it all. It’s science as magic at its best.

2016 Dutton Books £20.00/$28.00hb 480pp

Proton radius mystery deepens as deuterium measurement comes up short

The “proton radius puzzle” has been reinforced by a precise measurement of an atomic transition in muonic deuterium, which suggests the radius of the deuterium nucleus is much smaller than expected. This latest result tallies with a similar experiment on muonic hydrogen, which found that the radius of the proton is also smaller than expected. The discrepancy could mean that theory describing how muons and electrons interact with the proton is incorrect, or that there is an error in how the radius is calculated. Another possibility is that the Rydberg constant – which defines the energy scale for atomic transitions in hydrogen – requires a slight correction.

In the decades after the proton was discovered in 1917, physicists began to realize that it has a finite size, unlike the electron, which is essentially a point particle. The internationally recognized proton radius is about 0.8751(61) fm, where the figure in brackets is the uncertainty. This has been measured using two methods that give similar results: electron scattering and atomic spectroscopy.

In 2010, however, an international team led by Randolf Pohl at the Max Planck Institute for Quantum Optics in Garching, Germany, carried out spectroscopic measurements of muonic hydrogen. This comprises a proton bound to a negative muon, which is a much heavier cousin of the electron. These studies suggested that the radius of the proton is only about 0.84087(39) fm – about 4% less than the currently accepted value and with a much smaller uncertainty.

Lamb shift

Spectroscopic measurements of proton radius come courtesy of the Lamb shift in hydrogen’s atomic-energy levels. This is a result of the electron (or muon) interacting with the quarks inside a proton as described by quantum electrodynamics (QED). These interactions are slightly different for electrons in the 2S and 2P energy levels, with the resulting energy shift depending partly on the radius of the proton. Measurements made on muonic hydrogen give a much more precise value for the proton radius because the muon, which is much heavier than an electron, spends more time very near to – and often within – the proton than does an electron.

In this latest experiment, Pohl and colleagues looked at the Lamb shift in muonic deuterium, which has a nucleus consisting of not just a proton, but a neutron too. Instead of giving the radius of the proton, this measurement provides a measure of the “deuteron charge radius”, which is a measure of the size of the deuterium nucleus.

The measurements were done at the Paul Scherrer Institute in Switzerland by firing a muon beam at deuterium gas, which makes some of the deuterium molecules break apart to create atoms of muonic hydrogen. About 1% of the time the muon finds itself in the 2S state, where it can be excited to the 2P state by absorbing a photon from a laser pulse. The 2P state then decays by emitting an X-ray. Counting the number of such X-rays, while scanning the frequency of the laser pulse, gives a very precise measurement of the photon energy required to drive the 2S–2P transition. A complicated QED calculation is then done to obtain the deuteron charge radius.

Still smaller

The team found the deuteron charge radius to be about 2.12562(78) fm, which is smaller than the currently accepted value of 2.1424(21) fm. They could also use the deuteron charge radius to calculate the proton radius. This was found to be about 0.8356(20) fm – much closer to the muonic hydrogen value than to the currently accepted radius.

One striking aspect of the proton radius puzzle is that measurements made using electrons – both via scattering and from spectroscopy – give one set of values for the proton radius and for the deuteron charge radius, while measurements made using muons give different answers.

According to Pohl and colleagues, these discrepancies are not easy to reconcile within the Standard Model of particle physics. One possible explanation is that the Rydberg constant that is used to calculate the radii is incorrect. There could also be an error in how QED is used to calculate the radii. Beyond the Standard Model, the team points out that the discrepancy could be caused by a new force between muons and protons. While this seems far-fetched, it could also explain why the measured value of the muon’s dipole magnetic moment differs from the value predicted by the Standard Model.

The research is described in Science.

Cracking water drops caught on camera

(Courtesy: E Ghabache *et al./Phys. Rev. Lett.*)

By Tushna Commissariat

Drops of water normally tend to splash when they strike a surface. But what happens if they hit something very cold? It turns out they first freeze and then crack, forming intricate fracture patterns, one of which you can see in the image above.

It was taken using a high-speed camera by Christophe Josserand, Thomas Séon and colleagues at the Jean Le Rond d’Alembert Institute in France. They watched water solidifying as it dripped onto a stainless-steel surface cooled to various temperatures between 0 and −60 °C (Phys. Rev. Lett. 117 074501). Due to the contact between the drop and the surface, the water’s ability to freeze is limited and mechanical stress makes it fracture in a few milliseconds.

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China launches world’s first quantum science satellite

China has launched the world’s first satellite dedicated to testing the fundamentals of quantum communication in space. The $100m Quantum Experiments at Space Scale (QUESS) mission was launched today from the Jiuquan Satellite Launch Center in northern China at 01:40 local time. For the next two years, the craft – also named “Micius” after the ancient Chinese philosopher – will demonstrate the feasibility of quantum communication between Earth and space, and test quantum entanglement over unprecedented distances.

Work on QUESS – a collaborative endeavour between the Chinese Academy of Sciences and the Austrian Academy of Sciences – began in 2011 and the assembly was completed earlier this year. The 600 kg satellite will now be put into Earth orbit around 500 km above ground. The craft’s main instrument is a “Sagnac” interferometer that is used to generate two entangled infrared photons by shining an ultraviolet laser on a non-linear optical crystal.

Physicists have previously managed to separate entangled photons by distances up to 300 km on Earth. But because photons scatter when they travel down optical fibres or encounter atmospheric turbulence when sent between telescopes, it is hard to send entangled photons longer distances unless the experiments are performed in space.

Quantum encryption

The main goals of QUESS will be to demonstrate quantum key distribution (QKD) between the satellite and two stations on the ground – the Nanshan 25 m telescope at the Xinjiang Astronomical Observatory in western China and the Xinglong Observatory in Yanshan, around 200 km south of Beijing. A quantum key is a string of ones and zeros, representing the quantum states of particles. These can be used to encode and decode messages, which would be secure from eavesdroppers.

QUESS will perform a test of Bell’s inequality at a separation of over 1200 km – the greatest distance to date – to prove that entanglement can exist between particles separated by such a large distance. QUESS will also quantum teleport a photon state from the Ali observatory on the Tibetan Plateau to the satellite. “These goals will be performed solely by the Chinese team,” says Jianwei Pan from the University of the Science and Technology of China, who is QUESS’s chief scientist.

Pan adds that, once these targets have been met, the Chinese team will then collaborate with Anton Zeilinger and colleagues at the University of Vienna to create an “intercontinental” QKD channel between Beijing and Vienna, with the option of including stations in Italy and Germany. “QUESS will be the first test of quantum communication with a satellite,” says Zeilinger. “It can also be seen as a very significant step towards a future worldwide quantum internet.” Indeed, China is planning to launch a number of similar satellites to create a quantum communications network by 2030.

Challenges ahead

QUESS first faces a number of technical challenges in orbit, especially to make sure that the receiving telescopes on the ground can precisely track the satellite, which will be travelling at 8 km/s. “It’s very challenging to create a perfect quantum channel between the satellite and the ground station,” says Pan. “We have developed a high-frequency and high-accuracy acquiring, pointing and tracking technique to do that.”

Quantum physicist Alexander Ling, from the National University of Singapore, who is not part of the QUESS team, says he is looking forward to the data that will emerge from QUESS adding that there are now about a dozen groups worldwide working on space-based quantum experiments. Last January, his group launched and demonstrated a quantum entanglement source inside a cube-sat – a type of miniaturized satellite for space research weighing no more than 1.5 kg and with each side being around 10 cm long. “Since the access to space is becoming more easily available with the emergence of new satellite technologies such as nanosatellites, we should be able to see more quantum experiments in space,” he adds.

Thomas Jennewein at the University of Waterloo in Canada and colleagues are working on a quantum payload prototype that could fit onto a small satellite. They have already performed several feasibility experiments, such as sending quantum signals to a payload on a moving truck. Later this year, meanwhile, the European Space Agency is expected to carry out a detailed study into the possibility of using the International Space Station for quantum communication experiments.

QUESS is one of four missions belonging to the National Space Science Center’s strategic priority programme in space science. The others are the Dark Matter Particle Explorer, which took off in December 2015, Shijian-10, launched in April, and the Hard X-ray Modulation Telescope, which is set to take off in November.

What are the potential applications of topological insulators?

Topological insulators are a hot topic in condensed-matter physics on account of their special properties. Electrical insulators in the bulk, these materials have surface states that conduct electrons extremely well. In this video, Zahid Hasan of Princeton University in the US describes why topological insulators could lead to high-performance electronics and applications in quantum computing.

This video is part of our 100 Second Science series, in which researchers give concise presentations covering the spectrum of physics.

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A horrific nightmare scenario at CERN, surfer wins SUSY bet, and meet the father of the Super Soaker