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August 2010 Archives

By Hamish Johnston

Over my summer holidays I read the spy-thriller Enigma by Robert Harris. It’s a rip-roaring novel about code breaking at Bletchley Park during the Second World War.

While reading, I couldn’t help wondering what the Bletchley boffins would have done if the Germans had used quantum cryptography to obscure their missives?

That’s why I was very interested to read a paper in Nature Photonics that offers a way to crack messages that are kept private using quantum key distribution (QKD).

QKD allows two parties (call them Alice and Bob) to exchange an encryption key, secure in the knowledge that the key hasn’t been read by an eavesdropper (called Eve).

This guarantee is possible because the key is transmitted in terms of quantum bits (qubits) of information. If intercepted and read by a third party, such qubits are changed irrevocably and this signals the presence of Eve to Alice and Bob.

One major problem facing the makers of any quantum information system is that no technology is “perfect” – and clever hackers could exploit differences between how a device actually operates and the performance assumed by system designers.

Many such “loopholes” have been identified and either fixed by changing the protocol – or have been shown to have a small chance of success.

But Vadim Makarov of the Norwegian University of Science and Technology and colleagues have discovered “how Eve can attack the systems with off-the-shelf components, obtaining a perfect copy of the raw key without leaving any trace of her presence”.

Chilling words…and how the “plug-and-play” system works seems like something out of science fiction.

As far as I can tell, a bright light is used to “blind” the highly-sensitive photon detectors used by Alice and Bob. This allows Eve to seize control of the dazzled correspondents’ QKD kit using a sequence of light pulses. Unaware that this is going on, Alice and Bob deliver the keys straight into Eve’s hands.

The systems in question are commercial QKD products made by ID Quantique and MagiQ Tecnologies. According to Marakov and colleagues, the MagiQ 5505 system has been discontinued and ID Quantique has implemented countermeasures.

Makarov works in the quantum hacking group at Trondheim – which I would like to think is a Nordic Bletchley Park!

You can read about the research at doi:10.1038/nphoton.2010.214.

By Hamish Johnston

“What actually goes on
when hunting a boson.”

If that’s the sort of rhyming couplet that tickles your fancy, you will love this music video from CERN.

It features the CERN choir performing “The particle physicists’ song”, a variation on the Flanders and Swann classic “The hippopotamus song”. The new words are by Danuta Orlowska, who is a clinical psychologist in London.

Other memorable lines include:

“They all thought of SUSY with love in their eyes”

and “Those physics professors were no idle guessers”.

And if you think you can do better than that, the choir suggests you e-mail your own verses to cern.song@hotmail.co.uk

If particle physics isn’t your bag and you’d prefer a song about nuclear power, then check out this reworking of “Yankee doodle dandy” from the American Nuclear Society. It’s from 2002 but a bit of a gem.

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The planeterrella in action. Courtesy: Guillaume Gronoff

By Margaret Harris

Earlier this month, lucky observers in the northern reaches of Europe and North America saw an unusually big burst of aurora activity after a large coronal mass ejection from the Sun collided with the Earth’s magnetic field, sparking a geomagnetic storm on 3–5 August. But the glowing plasma shown here does not come from the Sun; instead, it is produced by a tabletop device called a “planeterrella” – the round object in the middle of the photo.

Inspired by the early 20th century Norwegian physicist Kristian Birkeland, who used a similar device to explain the aurora borealis, or Northern Lights, the modern planeterrella is the brainchild of Jean Lilensten of the Laboratoire de Planetologie de Grenoble, France. You can read a bit more about how it’s constructed here.

In July, Lilensten won the first Europlanet Prize for Excellence in Public Engagement with Planetary Science for developing planeterrellas that can be used to demonstrate the workings of planetary aurorae for members of the public. You can see him and his prizewinning device a bit better in the photo below, which was taken by Cyril Simon.

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Courtesy: NASA/GSFC/LaRC/JPL, MISR team

By James Dacey

The flooding in Pakistan triggered by heavy monsoon rains at the end of July has killed more than 1200 people and affected more than 15 million others across the country, according to government estimates. The country’s president, Asif Ali Zardari, said yesterday that it will take up to three years to recover from the natural disaster, as quoted by the Associated Press.

This pair of images shows the extent of the floodwaters within the central and southern parts of Pakistan, where the image on the left is from 8 August 2009 and the one on the right is from 11 August 2010. They have been captured by the Nadir (vertical viewing) camera on the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA’s Terra spacecraft, which was launched in 1999.

The Indus River can be seen meandering across the image from upper right to lower left. But in the later view, flooding can be seen clearly in much of the surrounding region, particularly in the Larkana District to the west of the river. Each image is 300 × 425 km and false colours have been employed to enhance the contrast: water appearing in shades of blue and cyan; vegetation as red; clouds as white; and sediment as tan.

Since this image was captured, the floodwaters have spread further south into the Sindh province, which lies in the bottom half of this image. The United Nations warned yesterday of thousands more imminent evacuations, along with the threat of waterborne diseases, food shortages and lack of shelter.

NASA collaborates with Mary J Blige

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By James Dacey

In one of the less predictable pairings of the year, NASA has teamed up with Mary J Blige, the singer, actor, producer and all-round US megastar.

The pairing has come about in an attempt to encourage more young women in the US to pursue careers in science, technology, engineering and mathematics (STEM).

Blige co-founded the Foundation for the Advancement of Women Now (FFAWN) in 2008 to “inspire women from all walks of life to gain the confidence and skills they need to reach their individual potential”.

FFAWN has now joined forces with NASA’s Summer of Innovation (SoI) project, which started earlier this summer to help keep students engaged in STEM-related activities during the school break – part of Obama’s Educate to Innovate Campaign.

Blige is joined in this short video by NASA space shuttle astronaut Leland Melvin to explain the motivation behind the project.

Satellite image captures Russia ablaze

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Courtesy: EUMETSAT

By James Dacey

They are being described as the worst wildfires in modern Russian history and they show little sign of abating.

This image, captured by a EUMETSAT satellite, shows the thick grey smoke that has been sweeping towards Moscow from peat and forest wildfires in central and south Russia. They are a result of the country experiencing its hottest July since records began.

Today, the BBC has reported that Moscow’s daily death rate has now doubled as a result of the continuing heatwave and the wildfire smog. Meanwhile, there is also a state of emergency in the southern Urals as the fires approach Ozersk, a town that closed following Russia’s worst nuclear disaster in 1957.

This image was captured last Wednesday by the AVHRR instrument aboard the EUMETSAT’s Metop-A polar-orbiting satellite, launched in 1986. Moscow is marked by yellow writing towards the bottom left of the image.

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Shot putters throw furthest at an angle of 37–38°

By Nicola Guttridge

Wimbledon? The World Cup? The Open Championship? Sport isn’t a great interest of mine, but despite my general ineptitude at most athletic activities, a recent paper caught my eye today in which two researchers studied the optimum angle of release in shotput – a problem that has baffled scientists since the 1970s. It’s not 45°, as you might expect. Instead, it turns out that athletes can throw a shot furthest when launched at a lower angle of about 37–38°. So why this difference in angle?

Alexander Lenz at the Technical University of Dortmund and Florian Rappl of the University of Regensburg in Germany puzzled over this and now believe that they have an explanation. It seems that the limitations aren’t in the mechanics but are to do with the human body. What it boils down to is that we humans are much better at pushing outwards than upwards, and so throwing the shot at a slightly lower angle than the expected 45° makes it travel further. To read more about this study, try the arXiv blog post.

As they point out, the human body’s preference for low angles of release is also apparent in weightlifting where weight records for bench pressing are much higher than for when the athlete tries to lift when standing.

Perhaps I should not have been surprised by the non-45° angle for shotputting. Back in 2006 scientists at the University of Brunel calculated the best angle to launch a football at during a throw-in and found it to be 30° to the horizontal – again, disagreeing with the expected angle of 45°. Most of these mistaken predicted angles can be explained by the theoretical calculations treating humans like perfect machines, a little reminiscent of superman – something that I’m sure many footballers would appreciate!

Another post I stumbled upon while reading around the shotput study was one about a completely different type of putting – golf. Robert Grober, an expert on the physics of golf at Yale University, has come up with a model to describe the perfect putt. Apparently the secret to golfing success lies in the behaviour of a simple pendulum being driven at twice its resonant frequency – I’m not sure how practical it’d be to attempt to use Grober’s model on a golf course, but even so it’s quite an interesting read. But then what do I know? I don’t like sport.

About the author
Nicola Guttridge is an intern with physicsworld.com

2053 Suns

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By Michael Banks

In 2003 the photographer Michael White compiled a book, 100 Suns, containing photographs of nuclear explosions drawn from the archives of Los Alamos National Laboratory in New Mexico and the US National Archives in Maryland.

The 100 images were taken in an era of “visible” nuclear testing before such tests went underground in the 1960s.

The images are fascinating, sometimes beautiful, but a chilling reminder of the power of such weapons. Indeed, today marks 65 years since around 100,000 people were killed by the nuclear bomb that was dropped on Hiroshima by a US B-2 bomber in 1945.

This morning I came across a video made by the Japanese artist Isao Hashimoto plotting nuclear weapons tests on a map of the world. As the years tick by from 1965 to 1998 a flash of light shows when a test occurred, where and by who.

The video by Hashimoto covers 2053 nuclear explosions that happened in the time period from the detonations at Hiroshima and Nagasaki in 1945 to the tests by India and Pakistan in 1998 – the period around the Cold War is a particularly active one.

2053 bombs over a 53-year period give an average nuclear detonation once every 9.5 days – a harrowing statistic indeed.

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By Hamish Johnston

When the first transistor was unveiled in 1947 it was a lump of germanium with wires sticking out of it – and it would have been very difficult to convince folks that 60 years later the average person would be carrying millions of transistors around in their pockets.

Just a few years ago a typical quantum processor was a bench-top full of lasers and optics – or perhaps a vacuum chamber containing trapped ions. But now, several labs around the world have worked out how to integrate these components onto a single chip.

A few weeks ago I visited one such lab at the University of Bristol, which is just up the hill from physicsworld.com headquarters.

My host was the physicist Jeremy O’Brien, whose work we have covered in the past – and who has also helped us to make sense of recent developments in quantum computing.

One of Jeremy’s main projects is integrating optical components onto a chip and he showed me a controlled NOT (or CNOT) gate that had been built in his lab (pictured above with a pencil tip). The CNOT gate is a fundamental building block of a wide range of quantum information circuits and could find use in quantum computers, quantum metrology or quantum cryptography.

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It took O’Brien and his team five years to take the CNOT gate from a bench-top implementation to a chip. On the right is a photo of O’Brien (left) and colleague Xiao-Qi with a typical bench-top implementation (though not of a CNOT gate).

While the Bristol physicists have done well to fit all that kit onto a tiny chip, the job isn’t actually complete. That’s because the device doesn’t include the photon sources and detectors needed to perform a calculation – these are still bench-top components. Adding on these components will take another 5–10 years, according to O’Brien.

And then there’s the sticky issue of making a compatible quantum memory. Strictly speaking, a quantum memory is not needed in a quantum computer because the inputs and outputs could be classical bits of information.

However, a quantum memory would be handy in some cases – and to this end O’Brien and colleagues are looking at the use of quantum dots.

The lab tour was also my first real-life encounter with “blingtronics”, which among other things is focused on the use of diamonds to create quantum bits (or qubits). Diamonds are crystals of carbon that contain a few nitrogen atoms here and there. Each nitrogen atom is accompanying by a neighbouring vacancy (a lattice site with no atom) and resulting “N-V centre” includes an electron spin that is extremely well isolated from the outside world.

This means that the spin could operate as quantum bit of information (or qubit) at room temperature. This is unlike most stationary qubits, which must be cooled to near absolute zero to prevent them from being destroyed by noise.

However, this splendid isolation has its downside because it makes it difficult to use N-V centres in a quantum processor – some interaction is required for information to be exchanged

Now, Mikhail Lukin and colleagues at Harvard University have managed to entangle a single photon with an N-V centre, a process crucial to quantum processing. If you have access to Nature you can read the paper here.

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Alcohol-induced superconductivity (Courtesy: Keita Deguchi)

By Michael Banks

When I was doing my PhD in condensed-matter physics, I remember seeing my colleagues nearly shedding tears after unsuccessfully spending months trying to make a single, small sample of a high-temperature superconductor.

The problem is that once a new superconductor – a material that exhibits zero electrical resistance when cooled below a certain temperature – is discovered then it takes only a few months before every conceivable experiment is performed on it. Time, as well as the quality of the sample, is everything.

So this morning I couldn’t help but raise a smile while skimming through the arXiv preprint server when I found a paper by researchers in Japan who have studied the effect of growing a new type of superconductor in “hot commercial alcohol drinks” such as red and white wine, beer, Japanese sake, whisky and shochu.

By heating powders of iron, tellurium and tellurium sulfide together at 600 °C they produced samples of FeTe0.8S0.2. But instead of performing experiments on these samples, they decided to put them into 20 ml glass bottles containing different alcoholic beverages.

They found that when they put the sample in an ethanol-water mixture, only around 10% of the material was superconducting below 6 K. But when it was dunked into whisky, sake or wine the superconducting fraction of the sample jumped. Red wine was found to be the highest with 63% of the sample exhibiting superconductivity. The researchers also saw a small increase in the superconducting temperature, with the red wine sample giving a superconducting temperature of 7.8 K.

Why this happens is unclear, but the researchers speculate that oxygen provided by the alcoholic drinks somehow gets into the bulk of the material and acts as a catalyst for the superconducting behaviour. The bigger question, though, is how the Japanese scientists got into the research in the first place. I haven’t asked but my guess is it originated after a trip to the local izakaya.

So can we expect other researchers to start dipping other samples into their favourite tipple? Maybe so – after all, back in 2008 scientists in Mexico grew small diamonds from tequila.

Whatever next?

Size matters for male spiders

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Male spiders clamber towards females along silk bridges

By James Dacey

In the world of male spiders vying for the affection of their female counterparts, it seems that small is often better.

That’s according to a group of biologists who have come up with an interesting explanation of why male vegetation-inhabiting spiders with smaller bodies can find more opportunities to mate with females.

It is related to the agility of the male spiders. When they spy a potential mate, the males allow a strand of silk to fly on the wind towards a target close to the female. They then rush along this silky rope as fast as they can in a manoeuvre that would make Spider-Man proud.

A team led by Guadaloupe Corcobado, of the Spanish National Research Council’s Arid Zones Research Station in Almeria, has studied this “bridging” tactic in detail inside a wind tunnel. They find that the smaller, lighter males are significantly more adept at the procedure, which boosts their mating opportunities.

They describe their “gravity hypothesis” in a new paper in BMC Evolutionary Biology.