Skip to main content

Reset your password

Please enter the e-mail address you used to register to reset your password

Note: The verification e-mail to change your password should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.

If you haven't received the e-mail in 24 hours, please contact customerservices@ioppublishing.org

Registration complete

Thank you for registering with Physics World
If you'd like to change your details at any time, please visit My account

Close
Home » Page 1335

Cloak-on-a-chip unveiled

 

An invisibility-cloak array made up of more than 25,000 individual minuscule cloaks has been built by a team of researchers in the US. The array is the first of its kind and operates in the visible frequency range. Individual cloaks could be used as biosensors, while the array could be used to test the performance of individual cloaks and as a way to study on-chip light manipulation.

The optical properties of materials are characterized by how they react to external electrical and magnetic fields. These properties are tailored in metamaterials – specially structured materials that possess unique optical properties that are not found naturally – so that light avoids a region of space to be cloaked. But a simpler way of achieving a similar effect is to use an “optical waveguide” – a structure, such as an optical fibre, that guides optical waves by total internal reflection.

Guiding the wave

This is what lead researcher Vera Smolyaninova and colleagues at Towson University and the University of Maryland did three years ago by placing a gold-coated lens on top of a gold-coated glass slide, where the area between the two surfaces acted as the waveguide. The double gold surfaces form a “good waveguide” explains Smolyaninova. The team found that light travelled around the space where the two surfaces touched.

These cloaks, the researchers realized, could be used to “trap” light – to slow it down, or even stop it, creating what is known as a “trapped rainbow”. The trapped rainbow is seen as different wavelengths of light – and so different colours – are stopped at slightly different radii within the lens. Now, the same team has made thousands of these cloaks – with each cloak being about 30 μm in diameter – that are then laid out together on a gold sheet. Each microlens bends light around itself, effectively hiding the area it contains. The cloak array was built using a commercially available microlens array that was coated with a gold film 30 nm thick. This was placed, gold-side down, onto a gold-coated glass slide and a laser beam was directed into the array to test the performance of the cloaks at different angles.

Shadows and reflections

One of the main aims of this study, according to Smolyaninova, was to see how multiple cloaks “interfere” with each other and how the proximity of each neighbouring cloak affects the path of light across the array. The researchers found that while the cloaks worked well when light was shone along the rows of microcloaks, light incident at varied angles or slightly flawed symmetry in the array design caused shadows and scattering to appear and imperfections to become clearly visible. “As there is such an increased matter–light interaction thanks to each rainbow,” explains Smolyaninova, “we can clearly see how light propagates across the array. So this could become a way of checking for cloak imperfections.”

Rainbow biosensors

An interesting application for this cloak array could be in the field of biosensors that identify materials using fluorescence spectroscopy – identification based on the amount of light absorbed and then emitted by the material. “In our array, light is stopped at the boundary of each of the cloaks, meaning we observe the trapped rainbow at the edge of each cloak. This means we could do ‘spectroscopy-on-a-chip’ and examine fluorescence at thousands of points all in one go,” says Smolyaninova.

Also, as slow light has a stronger interaction with molecules than light travelling at normal speeds, a more detailed analysis is possible. This means that it may, in theory, be possible to use this technology to build a biochip that has numerous sensors that perform tasks simultaneously. “For example, you could test for multiple genetic conditions in a person’s DNA in just one go,” says Smolyaninova. “You could possibly attach different dyes to different conditions and then look for them together.”

What are the chances of this being used to cloak large objects in everyday life? “While it is possible to just increase the radius of our lens, it is important to remember that this is a 2D cloak. So anything cloaked by it would be invisible only in that plane,” explains Smolyaninova. In the coming months the researchers will look into perfecting their method to manipulate light on a very small scale using a waveguide and then study the emerging properties of using, say, a fish-eye lens as the guide.

The research is published in New Journal of Physics.

Which ancient Greek made the most important contributions to natural philosophy?

By James Dacey

hands smll.jpg

Greece is rarely out of the news these days, but unfortunately that news is almost exclusively focused on the nation’s ongoing economic woes. It is a colossal understatement to say that the country is in a tricky situation right now: either remain in the Eurozone and accept a sustained period of deep austerity; or ditch the Euro and face a period of huge uncertainty while triggering financial shockwaves throughout the rest of Europe.

As the struggle to find a solution continues for the world’s leaders and top economists, I can’t help but wonder what the thinkers of ancient Greece would have made of the current situation. Would Plato or Aristotle have been able to take a break from considering the nature of reality to draw up a solution that benefits all? Or would this kind of affair be too rooted in the mundanities of the everyday world?

In this week’s Facebook poll we are looking back at the brains of ancient Greece by asking you the following question.

Which ancient Greek made the most important contributions to natural philosophy?

Archimedes
Aristotle
Democritus
Euclid
Plato
Pythagoras
Thales

Let us know by visiting our Facebook page. And please feel free to explain your response or suggest a different ancient Greek thinker by posting a comment on the Facebook poll.

In last week’s poll we asked “How significant would the discovery of the Higgs boson be?”. The majority of respondents (66%) chose the option that it would answer the most important question in particle physics. 26% of respondents chose the option that there are more important questions in particle physics. And the remaining 9% believe that it would answer the biggest outstanding question in physics.

Thank you for your participation and we look forward to hearing from you in this week’s poll.

How to make a material that shrinks when stretched

New metamaterials that shrink under tension and expand under compression might soon become a reality thanks to theoretical work done by scientists in the US. The researchers say the materials – which at first glance appear to violate the laws of physics – could be manufactured using currently available technology.

Metamaterials are synthetic materials that are often engineered to have properties not found in nature. Some of the most familiar have bizarre optical properties such as negative indices of refraction and have been used to create invisibility cloaks. More recently, research has also focused on metamaterials engineered to have exotic mechanical properties. These respond in unexpected ways to applied forces. For example, foams have been produced that get fatter rather than thinner when stretched.

Unstable equilibrium

Of particular interest is the possibility of manufacturing metamaterials that have a negative compressibility. That is they shrink under tension and expand under compression. Some materials already do this in response to a rapidly varying sinusoidal force – a result of time lag between the applied force and the resulting deformation. However, it had been assumed to be impossible to make a material that responded in this way to a constant force because such a material would have to exist in an unstable equilibrium.

If you take a rod of any normal material and apply tension, the material stretches slightly and exerts a restoring force that balances the tension. The result is a new state of equilibrium. Similarly, if you apply compression, it gets shorter, exerts a restoring force and reaches equilibrium. However, if you apply tension to a material with “negative compressibility”, the material responds by shrinking slightly, which increases the tension further, which causes it to shrink more. The logical consequence is that a slight applied tension would cause such a material to collapse and a slight applied pressure would cause it to explode. Such a material could clearly not exist.

But now Zachary Nicolaou and Adilson Motter at Northwestern University have found a little wiggle room in which such a material could exist. While they acknowledge the impossibility of a material having a continuous negative compressibility, they believe it should be possible to manufacture materials with negative compressibility at a particular point – allowing seatbelts to tighten up suddenly in the event of a car crash, for example. The trick is to design a material with two metastable structural configurations, one more compact than the other. The desired response would occur if the material could jump into the more compact state if the tension is increased beyond a particular value. Despite these bizarre requirements, the researchers have used molecular dynamics simulations to establish that such materials are indeed physically plausible.

Parallel with traffic

Motter is an expert on the physics of complex systems and networks, and draws a parallel with a famous paradox in traffic management – the removal of an intermediate road can actually reduce congestion by distributing traffic more evenly around the remaining roads, changing the traffic pattern from a “series” to a “parallel” one. “This is analogous to the system we are studying,” explains Motter, “to the extent that the constituents of the material are made up of four particles. When you apply tension, this causes the inner particles to decouple from each other – it’s like breaking a bond. That causes the outer particles to be more strongly attracted to each other – basically going from a series configuration to a parallel one. This causes the material to contract”.

That’s the theory, but Motter is also optimistic that such a metamaterial could actually be made. “The most straightforward approach would be to use elements that have spring-like behaviour, such as rubber,” he says. “Depending on how you assemble together little pieces of rubber, you could have a material that behaves in the way we are proposing here.”

“Interesting applications”

Nanoscientist Ping Sheng at Hong Kong University of Science and Technology, whose research group has developed materials that show negative compressibility in response to sinusoidal forces, says “The novel point about this work is that it proposes negative compressibility at zero frequency, i.e. with steady forcing. Such a system could still be stable because it would involve stored energy.”

He concludes, “I would be interested in seeing a physical realization of what has been proposed. That may indeed have some interesting applications.”

The research is published in Nature Materials.

When Creativity met Necessity

Necessity, they say, is the mother of invention. A metaphorical DNA test, however, suggests that its father is probably that old reprobate, Creativity. The simple fact is that for many inventors, a pressing need is not essential: scientists often create something new just because they can. Moreover, there is often a prolonged gestation period before Necessity actually gives birth, with a typical invention – be it a physical object, a protocol such as the World Wide Web or a theory – going through three stages as it passes from idea to prototype to product. In the case of Newtonian mechanics, for example, the three stages were the alleged apple, the impenetrable Principia and those neat equations we all know.

But whatever it is, an invention has to work both in principle and in practice. If it doesn’t, it is just a silly idea, and we all have plenty of those. Journalist Tyler Hamilton’s book Mad Like Tesla contains much that may turn out to be in the “silly idea” category. In it, he reports on the sincere but distinctly unconventional attempts of various maverick inventors – most of them Canadian, like Hamilton himself – to create new ways of harvesting sustainable energy. Maverick Canadians? Yes, they do exist.

Some of their efforts seem to fail at the idea stage: Thane Heins’s electric motor produces more power than it consumes, he says, but he is touchy about people testing it. Others falter as prototypes: Dick Weir and Carl Nelson’s supercapacitors should store energy more efficiently than batteries but, although the principle is sound, materials seem to be a problem and the demo date keeps receding. As for Cal Boerman and Gary Spirnak, their big idea is a giant solar collector in space, beaming microwave power to Earth. They cannot afford the luxury of a prototype – it is go for it or bust.

Only a few of the inventions in Hamilton’s book, such as Jay Harman’s energy-saving fans inspired by natural vortex motion, have made it to product stage, and all are viewed with suspicion by the energy business. However, as Hamilton keeps telling us, Nikola Tesla was also thought to be mad – yet that did not stop him from inventing the three-phase induction motor that powers much of modern industry.

Reading Hamilton’s book, you cannot help feeling that what powers some of these would-be Teslas is the X-Factor factor: the lust for fame. Yet fame, for most inventors, is an uncertain prize. In another book on odd inventions, How James Watt Invented the Copier, author René Schils focuses on the lesser-known activities of 25 famous scientists. These include the titular Watt, whose copier created duplicates by pressing letters written in slow-drying ink onto thin paper. This device was a minor commercial success, but most of us would not have heard of Watt had he not also revolutionized the design of steam engines.

The subtitle of Schils’s book, Forgotten Inventions of Our Great Scientists, is disingenuous, since only a few of his examples are true inventions. The rest are observations or calculations, though none the less fascinating for it. Astronomer Harlow Shapley, for instance, relocated the Sun to the suburbs of our galaxy, but sought relief from his day job (well, night job) by watching his observatory’s resident ants. He found that their speed depends on temperature, something entomologists had not noticed. Benjamin Franklin used his job as Britain’s deputy postmaster general (yes, really) to ask why mail boats took so long getting to America. Answer: the Gulf Stream, a phenomenon then unknown to the British navy. Thomas Young of double-slit fame helped to decipher hieroglyphs via the Rosetta Stone. And Rosalind Franklin – the only woman to appear in either of these two books – worked on carbon as well as DNA, paving the way for the discovery of buckyballs.

But the genuine inventions created by some of these big names can be interesting too. Exhibit A is Albert Einstein and Leó Szilárd’s absorption refrigerator, which worked on a principle still used in fridges for caravans. Inside their fridge you might find soda water, invented by pioneering chemist Joseph Priestley. And while sipping it, you could estimate how many years you have left to live by using life tables originally devised by Edmund Halley in moments spared from sorting out the regularly recurring comets.

There is plenty to think about in these two books. Why, for instance, is it so hard for inventors to break into established markets? In energy supply, obviously, companies cannot simply junk huge infrastructure investments in favour of something new, however good it might be. But what about Harman’s energy-saving vortex fan? Surely it cannot be that difficult to fit a different kind of fan to a computer? Maybe the fan is not all it is cracked up to be.

Overall, there is a strong whiff of boosterism around Hamilton’s book, and despite his hard-nosed journalistic training and frequent caveats, he has perhaps been charmed into accepting some of the wilder claims of these hippyish entrepreneurs. Still, at least all of them are trying to do something new. Some of the characters in Schils’s book, by contrast, have sidelines not a million miles away from the stuff they are famous for. Kelvin’s work on the transatlantic cable, for example, was simply another bit of mathematical pragmatism, of the same kind that led him to the absolute scale of temperature. And Darwin’s study of worms was, to him, not a sideline at all but central to his achievement and part of the famous peroration to On the Origin of Species.

Nonetheless, both books are worth a look for the sheer entertainment value of their subjects, be they kooky believers in bizarre phenomena or just scientists taking a break. Reading about such characters, you really cannot avoid the conclusion that Necessity may be the mother of invention, but its father is the compulsion to invent.

Between the lines: fiction special

Photo of the Large Electron-Positron Collider
Physics thrills: The star of Robert Harris’s new thriller is a physicist who once worked on CERN’s Large Electron–Positron collider. (Courtesy: CERN)

Colliders, quants and mayhem

Robert Harris is perhaps best known for his trio of historical novels about ancient Rome that began with his 2003 bestseller Pompeii. Now, the former TV journalist has turned his hand to something very different with The Fear Index – a thriller about an ex-CERN particle physicist called Alexander Hoffmann who sets up an enormously profitable hedge-fund firm that trades on the global financial markets. The Geneva-based business employs a string of PhD quants, and the secret of its success is a powerful computer that exploits algorithms that Hoffmann developed while working on CERN’s Large Electron–Positron collider. The company is about to secure $2bn in extra cash from a range of rich investors when trouble strikes. In a series of bizarre and grisly plot twists, Hoffmann is violently attacked in his home, dumps his wife, murders someone in a downtown brothel and watches a fellow company director fall to his death down an open lift shaft. It would be churlish to spoil the denouement, but it will come as no surprise to say that it is pretty preposterous. As a character, Hoffmann does physicists few favours, coming across as odd, unfeasibly intelligent, unsociable and generally rather weird. However, there are enough references to real physics to make the story almost believable, including a quant who was “recruited from the Rutherford Appleton Laboratory”, various discussions of a financial function called “a delta hedge” and a building security code of 1729, which – the author reminds us – is the smallest number expressible as the sum of two cubes in two different ways. Real CERN physicists will also enjoy the references to genuine Geneva locations. Interestingly, Harris thanks various members of the CERN press team, including media boss James Gillies, in the book’s acknowledgements. Overall, this is an entertaining if ultimately ridiculous story, not least for the supposedly geeky Hoffmann morphing into an action hero in the final few pages. File under “holiday reading”.

  • 2011 Arrow/Hutchinson £18.99/ $25.95hb £7.99/$13.83pb 336pp

Dark labyrinths

Those who like their holiday reading a bit more cerebral may prefer an intriguing new trilogy by Stuart Clark, an astronomy journalist who has recently turned to writing fiction. The first book in the series, The Sky’s Dark Labyrinth, is set in the early 1600s, when Kepler and Galileo were breathing new life into Copernicus’s notion of a Sun-centred cosmos. With the second book, The Sensorium of God, the scene shifts to Restoration England, where Newton, Hooke and Halley are on the cusp of a scientific revolution. (The third book, The Day Without Yesterday, has not been published yet, but it will focus on Einstein.) Clearly, there is plenty of good material here, and Clark uses it remarkably well. Although many events depicted in the books will be familiar to Physics World readers, Clark has nevertheless managed to weave the likes of Kepler’s conflict with the Danish observer Tycho Brahe, Galileo’s struggles with the Inquisition and Newton’s feuds with, well, pretty much everyone into a vivid and even suspenseful narrative, full of secret plots as well as astronomical discoveries. At times, one can practically smell the aroma of London’s fashionable coffeehouses in Sensorium, or feel the tension in Labyrinth as mercenaries stalk the streets outside Kepler’s home in Prague. One thing that comes across particularly well in both books is the violence and uncertainty of the world in which these great astronomers lived. Over the course of the narrative, nearly all of them lose family members to disease, and many – not just the Catholic Galileo, but also heterodox Protestants like Kepler and Newton – also fall foul of their countries’ religious establishments. At times, Clark over-eggs the science versus religion conflict slightly; in particular, two non-historical characters (a malevolent cardinal in Labyrinth and a fanatical Anglican spy in Sensorium) seem to have been invented solely to amp up the “religious leaders behaving badly” theme. But then again, this is fiction, and a little exaggeration is no bad thing.

  • 2011/2012 Polygon £8.99pb/£12.99hb 360pp/280pp

In the beginning

As opening lines go, the one in Alan Lightman’s novel Mr g takes some beating: “As I remember, I had just woken up from a nap when I decided to create the universe.” Simultaneously arresting and offhand, it perfectly encapsulates much of what follows in this curious little fable about a childlike god-figure (presumably the “Mr g” of the title) and the unexpected consequences of his decisions. Lightman is a theoretical physicist as well as a writer, and the early sections of this, his fifth novel, read like a fictional version of The First Three Minutes, Steven Weinberg’s classic account of the early universe Once Mr g has created time, he moves on to space, followed by dimensions, quantum physics and, eventually, matter. Not everything goes quite as planned. After Mr g formulates three “organizing principles” for his universe (which physicists will recognize as entropy, relative motion and the principle of cause and effect), he decides to arrange the comparative strengths of the universe’s fundamental forces into a pleasing ratio. What, he asks, could be more harmonious? But the result is a disaster: “almost immediately, the universe began writhing and straining…Evidently, the fourth law was not compatible with the first three.” And physics is not the only source of Mr g’s troubles. He must also deal with his squabbling Aunt Penelope and Uncle Deva, two other supernatural beings with whom he shares the formless Void, and the sinister Belhor – an entity that, like human suffering, is the unwished-for but possibly inevitable offshoot of Mr g’s creative efforts. The latter sections of the novel focus more on philosophy than physics, as Mr g experiments with creating conscious life directly, spars with Belhor over the consequences of free will, and keeps a close but largely non-interventionist watch over his creation. It is never clear what deep conclusions, if any, Lightman expects readers to draw from these antics, but to his credit the book retains much of its initial lightness until the very end – which, quite properly, comes not with a bang, but a whimper.

  • 2012 Corsair/Pantheon $24.95/£9.99hb 256pp/224pp

Shaken staples stick together

All experimental physicists know that some tasks can be tedious and painstaking, but Nick Gravish from the Georgia Institute of Technology has just taken this to a new level. In a series of experiments to find out more about the behaviour of U-shaped objects, Gravish and colleagues spent about 10 man-hours carefully trimming the arms of thousands of steel staples to see how their shape affects how the staples cling together.

To their surprise, the researchers found that there is an optimum arm length, above and below which the staples are less likely to stick together when shaken. As well as helping scientists to understand materials that are made of U-shaped components, the research could also provide insight into how biological systems as diverse as fire-ant rafts and eagle nests are formed.

Humble but complex

Physicists have a long history of studying the behaviour of granular materials, for example to find out why sand piles collapse or why grains jam when passing through an industrial “hopper”. Some granular materials – including some colloids – can even become entangled with each other and so behave very differently from particles with simple shapes, such as sand grains.

Humble staples are an ideal way of gaining a better understanding of how this entanglement occurs because they are a very simple example of an object that can mechanically grab hold of its neighbours. Carried out by Gravish, Dan Goldman and David Hu at Georgia Tech along with Scott Franklin at the Rochester Institute of Technology, each experiment began with a clump of staples all with the same arm length. The researchers placed the staples in a cylindrical mould that is on top of a vibrating plate. After vibrating the column of staples for about 20 s to ensure that it is in a tightly packed state, the team found that the density of the column was greatest for staples with no arms – essentially rods – and that the density dropped off for staples with longer arms.

The researchers then removed the cylinder before shaking the free-standing column again and monitoring it with a digital camera. As the column collapsed, they measured its height as a function of time, from which they derived the average energy required to disentangle one staple from another.

Long arms

As expected, this “energy barrier” rises as the arm length increases because a staple with a longer arm takes more energy to disentangle. What was surprising, however, was that the energy barrier did not keep on rising, but rather peaked in staples where the arms are about 40% of the width of the staple. For longer arms, the energy appeared to drop off.

When Gravish and colleagues carried out computer simulations of how the staples pack and collapse, they found that another factor was at work. It turns out that in the case of staples with arms longer than about 40% of their width, these objects do not pack as tightly as their shorter counterparts. The result is that there is less entanglement in the column to begin with and so it takes less energy to shake it apart.

While the team’s work should provide clues to the behaviour of materials made of entangled inanimate objects such as some colloids, Gravish and Goldman say that it cannot fully explain how living organisms such as fire ants hook themselves together into structures such as floating mats – which are made to save an entire ant colony in a flood. Instead, they believe that the work will allow biologists to differentiate between purely mechanical effects and behavioural effects that define how such structures are made.

The work is described in Physical Review Letters.

DIY Higgs discovery

viXra Higgs applet

Make your own Brazil band. (Courtesy: Phillip Gibbs)


By Hamish Johnston

The Large Hadron Collider is up and running at a collision energy of 8 TeV and – barring any disasters – it looks as if it may well give us a mass for the Higgs boson by the end of the year.

But why wait for the official pronouncement from CERN when you can aggregate all the latest measurements yourself using the handy “viXra unofficial Higgs combination Java applet”, which you can download here

The dashboard-style interface shows you the classic “Brazil band” plot and allows you to fiddle around with how data from different experiments are combined. The default setting is the “unofficial” combination used by viXra blogger Phillip Gibbs, but you can also use the “official” CERN settings, or even choose your own.

Now there’s no need to wait for the man with the beard to tell you when to break out the champagne – you can make that decision yourself.

Geoengineering balloon trial cancelled

A key part of a UK-led project to investigate the feasibility of injecting particles into the stratosphere with the aim of cooling the Earth has been cancelled. In what would have been one of the first trials of geoengineering, the Stratospheric Particle Injection for Climate Engineering (SPICE) project will now not undertake field tests. Instead, the project will be restricted to lab experiments and computer simulations.

SPICE is led by Matthew Watson from the University of Bristol and mainly funded by the UK’s Engineering and Physical Sciences Research Council (EPSRC). The trial would have involved pumping water to a height of 1 km through a suspended hose that is held aloft by a helium-filled balloon. This would have tested the technology behind potentially spraying particles such as sulphur into the stratosphere, which would mitigate global warming by reflecting a few per cent of incoming solar radiation.

Diagram showing how the SPICE collaboration planned send water 1000 m into the sky
Grounded

Last month, a statement by the SPICE team said it would not now progress with the trial stage of the project. This, it says, is because EPSRC had not given the go-ahead for a “stage gate” that would have opened the door for a public consultation about the technology before trials could begin. “It’s their money so we can’t spend it on something they’ve expressly told us not to do until we get the green light,” says SPICE member Hugh Hunt, a mechanical engineer at the University of Cambridge, UK. “They’ve taken a very long time and we’ve decided we’ve had enough of waiting.” Hunt adds that “when the moment is right” the researchers may try and perform a “test-bed” experiment but it will not be as thorough as the original SPICE trial.

Another reason why the trials have been cancelled is that a patent was submitted by Peter Davidson, who runs the UK consulting firm Davidson Technology, together with Hunt and his Cambridge colleague Chris Burgoyne. Filed before SPICE was proposed, the patent describes the apparatus and method that SPICE would use to deliver particles into the atmosphere. Although no-one has accused them of any wrongdoing, some members of the team think that the involvement of a patent might give opponents of the project ammunition to claim that people are gaining financial benefit from it.

“Given the emotive nature of geoengineering, research projects such as SPICE need to be squeaky clean – with no suggestion of vested interests,” says climate scientist Peter Cox from the University of Exeter, UK. The SPICE team will now concentrate on lab tests and computer simulations to determine what possible particles would work best in the stratosphere and to estimate the overall impact on the Earth’s climate.

Head of the US nuclear regulator resigns

The chairman of the US Nuclear Regulatory Commission (NRC), particle physicist Gregory Jaczko, has announced he is to resign. The announcement comes a year after congressional Republicans objected to his leadership in phasing out the proposed nuclear-waste repository in Yucca Mountain in Nevada. It is unclear when his resignation will become effective, with the Obama administration announcing its intention to nominate a new NRC chair soon, who must also receive Senate backing.

According to regulations, the NRC has five commissioners who regulate and license nuclear power, but the chairman has ultimate legal authority. Jaczko had spent seven years as a commissioner, including three as chairman, with his term set to expire in June 2013. “I have decided this is the appropriate time to continue my efforts to ensure public safety in a different forum,” he declared in an official statement. “This is the right time to pass along the public-safety torch to a new chairman who will keep a strong focus on carrying out the vital mission of the [NRC].”

“Serious damage”

Jaczko’s time as chairman had recently been hit by a number of accusations over the handling of the $10bn Yucca Mountain facility – a site that Congress had designated as the sole potential location for a national deep underground nuclear-waste dump before funding for the repository was terminated in 2011. After allegations by commission staff that Jaczko had “unilaterally and illegally” stopped a safety-evaluation report on the facility’s design, last June Hubert Bell, the NRC’s inspector general, accused Jaczko of “using forceful management techniques to accomplish his objectives” while noting that he had operated within the law.

In October Jaczko’s four fellow commissioners – George Apostolakis, William Magwood, William Ostendorff and Kristine Svinicki – then wrote a letter to the White House accusing Jaczko of “causing serious damage” to the commission that could affect safety at US nuclear plants. Indeed, Bell is known to be preparing a report that is expected to repeat some of the commissioners’ accusations.

Svinicki, the only female commissioner, told Congress last December that Jaczko had created a working environment in which women felt especially threatened. Jaczko has categorically denied that charge. Early this month the Obama administration nominated Svinicki, a former aide to Republican senators, for another term as an NRC commissioner.

Jaczko says that throughout his time at the NRC, the agency finalized new nuclear-safety regulations, completed the development and implementation of a safety-culture policy statement, as well as helping to make the NRC more open and transparent. “We stand as a stronger and more decisive regulator now because of these years of efforts,” he says. Jaczko also took a leading role in the NRC’s response to last year’s nuclear incident at Fukushima, Japan.

Vermont Senator Bernie Sanders, a socialist who supports Democratic policies, praised Jaczko for “his efforts to hold the nuclear industry accountable”. Republican Senate minority leader Mitch McConnell of Kentucky, however, said that “the only thing surprising about [Jaczko’s] resignation is the fact that the Obama administration has remained silent for more than a year after allegations of Jaczko’s offensive behaviour surfaced”.

Quantum teleportation record broken…again

By Hamish Johnston

Just yesterday we reported that physicists in China had shattered the record for quantum teleportation through free space by sending quantum states 97 km across a lake.

Anton Zeilinger

Now, a different team led by Anton Zeilinger (right) of the University of Vienna has extended this distance to 143 km by teleporting quantum states across the stretch of sea separating two of the Canary Islands. The team claims that its triumph takes the prospect of quantum teleportation to and from satellites one step closer.

Quantum teleportation involves sending a quantum state between two parties – from Alice to Bob – without actually sending a particle in that state. The process involves one quantum channel of communication between the two, along which one half of an entangled pair of photons is sent from Alice to Bob. Also required is a conventional communication channel, through which Alice can send Bob information about a measurement that she has made on a particle in the quantum state that she wants to teleport to Bob. Bob then uses this information to manipulate his entangled photon so that it is in the teleported state.

Zeilinger and co-workers teleported quantum states from La Palma to Tenerife, and to pull it off they had to develop several new technologies including a new source of entangled photon pairs and “ultra-low-noise” single-photon detectors. Timing also proved to be a challenge, because the 10 ns uncertainty in GPS timing signals was not good enough to achieve the teleportation. Instead, the team had to develop a new “entanglement-assisted clock synchronization” technique that relies on the detection of the entangled photons by Alice and Bob.

Beyond the technical challenges, the team say it had to contend with “exceptionally bad weather conditions” from May to July 2011 when the experiment was done, which included everything from sandstorms to snow.

The fact the team was able to overcome these technical and meteorological challenges bodes well for the ultimate goal of the research – the ability to teleport quantum states back and forth to satellites in low Earth orbits (LEOs). Although most LEO satellites are positioned about three times the distance between Tenerife and La Palma, the atmosphere is much thinner – and therefore much less disruptive – for most of that distance. As a result, teleportation to a satellite might actually be easier than sending photons across a stretch of sea.

This latest result is described in a preprint on the arXiv server.

Copyright © 2026 by IOP Publishing Ltd and individual contributors