Proto quantum computer inspired by Victorians gets a speed boost

Quantum computers should theoretically outpace ordinary ones, but attempts to build a speedy quantum machine have so far come up short. Now an approach based on a Victorian counting device seems to be getting close.

This proto-quantum computer can only solve one problem. But that problem, called boson sampling, seems to be very difficult for an ordinary computer to solve, so physicists hope that such a device will conclusively demonstrate the promise of computing based on exotic physics. "The goal is to show quantum supremacy with the simplest approach," says Fabio Sciarrino of Sapienza University in Rome, Italy, who helped develop the new machine.

Boson samplers are based on a device created by the 19th-century polymath Francis Galton to study statistical distributions. It consists of a wooden board studded with offset rows of pegs. Balls are dropped one by one from the top of the board and ping their way down, bouncing left or right at each peg, before collecting in bins at the bottom. Since balls are more likely to end up in a central bin than one at the edges, you end up with a bell curve distribution across the width of the board. In the pre-computer age, it was one of the best ways to compute this distribution, which often crops up in statistics.

The quantum version swaps balls for photons, which travel along a network of intersecting channels in an optical chip. When two photons collide, their ensuing paths are determined by the laws of quantum mechanics, producing a unique distribution. With enough photons, calculating this distribution becomes very difficult on an ordinary computer, so doing it with real photons in a quantum device is the only practical option.

In 2012, four research groups, including Sciarrino's, demonstrated the first working boson samplers with three photons. But scaling to larger numbers was challenging as it is difficult to produce single photons on demand. The leading method, which involves shooting a laser at a crystal, spits out photons at random times, so you can't get enough in the boson sampler at once.

Scattershot approach

That's why Sciarrino has turned to a slightly different version of the problem, called scattershot boson sampling. This involves using a larger number of photon sources, so that their randomly generated photons have a higher chance of colliding. His team used six sources and were able to produce three photons at once. That means the new boson sampler is no more computationally powerful than the 2012 examples, but operates on average 4.5 times as fast.

"We only have shown a proof-of-principle improvement," says Sciarrino. Now his team is working to improve its sources even further, with the aim of challenging an ordinary computer – each additional photon roughly doubles the difficulty of the calculation. "If you want to start seeing a large improvement, you need something like 20 or 30 sources."

Scott Aaronson of the Massachusetts Institute of Technology, who helped come up with the idea of boson sampling, thinks the device is an important milestone, but not yet a breakthrough. "Hopefully they will have better scaling going forward," he says. "Twenty or 30 photons would be spectacular."

A boson sampler isn't inherently useful, although last year a group of researchers at Harvard University published a theoretical paper suggesting one might be able to calculate the vibrational properties of certain molecules. In any case, the skills and technology needed to get one working with more photons should help enable more general-purpose quantum computers in the future, says Aaronson.

Even if it can't factor large numbers or perform other quantum tricks, a device that unambiguously demonstrates quantum supremacy would be a major scientific breakthrough. Perhaps the first record-beating boson sampler will one day sit in a museum alongside Charles Babbage's difference engine, the mechanical precursor to modern computers. "I like that image," Aaronson says. "I'd go visit it in a museum."

Journal reference: Science Advances, DOI: 10.1126/sciadv.1400255

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Is super-diverse Amazon microbiome something to strive for?

The Yanomami people in the Venezuelan rainforest have the most diverse population of gut microbes ever seen, far more varied than Western guts. Does it matter?

Hunter-gathering in the rainforests and mountains of northern Brazil and southern Venezuela, the Yanomami eat a high-fibre diet based largely on cassava. For thousands of years, some groups have lived without contact with the rest of the world and are thought to be some of the few remaining communities never to have been exposed to antibiotics, which can wipe out the microbes in your gut.

So in some ways, the discovery, announced this week, that they carry the most diverse gut microbiomes ever documented is unsurprising. However, there is increasing evidence that our health is linked to the well-being of the microbes that call our gut home. So is the unspoilt, diverse ecosystem of the Yanomami something we should strive for?

Vaccination trip

Every year, the Venezuelan ministry of health visits newly identified communities to provide them with health services such as vaccinations, in part to protect them from diseases they could catch from gold miners that visit these regions. The decision to visit the particular Yanomami village that has now been studied was taken after it was spotted from the air in 2008.

Accompanied by interpreters who could explain the experiment in the Yanomami language, in 2009, scientists joined the medics and took mouth and forearm swabs and faecal samples from the villagers. The people they encountered had T-shirts and machetes and knew the Spanish word for "medicine", but said they had never encountered non-Yanomami people before.

Sequencing the genes in the faecal samples revealed that the Yanomami carried nearly double the diversity of microbial species in their intestines compared with people living in the US. They also had about 30 to 40 per cent more diversity than a less isolated group of Venezuelan hunter-gatherers that has largely maintained its traditional lifestyle but has occasionally used antibiotics and eaten processed foods.

The Western way

"Our results suggest that Westernisation leads to the reduction of diversity, to different microbiota compositions," Maria Dominguez-Bello of the New York University School of Medicine, who led the research, told a teleconference on Wednesday.

Her colleague Jose Clemente of the Icahn School of Medicine at Mount Sinai in New York, said the results suggest that even minimal exposure to modern lifestyle practices such as using antibacterial soaps and cleansers, taking antibiotics and having Caesarean sections, which mean babies don't pass through their mother's birth canal and pick up her microbes, can result in a dramatic loss of microbial biodiversity.

It can be difficult to disentangle which medical and lifestyle practices have the biggest impact on the microbiome says Jens Walter of the University of Alberta in Canada, who worked on both the Yanomami study and another one published this week that showed that the microbiomes of rural Papua New Guineans are also more diverse than those of US residents.

However, antibiotic use is high in Papua New Guinea, suggesting that it is other factors that are responsible for the relatively high microbiome diversity observed there.

Does it matter?

So does a more diverse microbiome make for a healthier person? Possibly. Healthier people do seem to host a more diverse array of microbes but it's hard to know whether one causes the other. There is some evidence that losing certain microbial species is linked to some cancers, plus giving mice antibiotics can make them gain weight, so perhaps a good mix of microbes in your gut can keep you from piling on the pounds.

"It is an interesting hypothesis that the rise of Western diseases might be caused by the depletion of the gut microbiota," says Walter. But it's difficult to draw any conclusions about the benefits of microbial diversity by comparing ourselves directly with the Yanomami or Papua New Guineans because overall health and life expectancy is greater in modern societies.

Walter doesn't recommend striving drastically to make the paltry Western gut look more Yanomamian. Poor sanitation is probably one factor contributing to the Papua New Guinean's high microbial diversity, but they have high levels of infectious diarrhoea as a result – not a situation that Western urbanised nations would want to return to.

And a quick-fix method, like receiving a faecal transplant from a Yanomami person, would not be safe, says Walter. But restricting antibiotics and Caesareans to medically necessary cases can't hurt, neither can eating more fibre, he suggests.

While visiting the village, the medics administered some antibiotics. Depending on the specific antibiotics given , one of the last remaining examples of a pre-antibiotic microbiome has probably already been sullied, says Björn Olsen of Uppsala University in Sweden. "It's becoming harder and harder to find people like these Amerindians in our extremely urbanised world," he says.

Journal references: Science Advances, DOI: 10.1126/sciadv.1500183 (Yanomami people); Cell Reports, DOI: 10.1016/j.celrep.2015.03.049 (Papua New Guineans)

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North pole of spinning dwarf planet Ceres glows in the sunlight

(Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

It's the sun-lit north pole of a dwarf planet, in more detail than we've ever seen before. These images of Ceres, the largest object in the asteroid belt between Mars and Jupiter, were snapped by NASA's Dawn spacecraft last Friday.

The spacecraft captured the photos from a distance of 33,000 kilometres as it passed over the dwarf planet's pole after more than a month on its dark side. It should soon gather views of other features, including a mysterious set of bright spots on the surface that could contain watery volcanoes.

Meanwhile, NASA's New Horizons probe is speeding its way towards Pluto and has sent back the first blurry colour photos of the dwarf planet and its largest moon, Charon. We'll get our best-ever view of Pluto when the spacecraft flies past it on 14 July.

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Feedback: Striving to name polyfailure

Feedback is our weekly column of bizarre stories, implausible advertising claims, confusing instructions and more

WHAT should we call the phenomenon exemplified by Feedback's perception that "anyone who suspects the probability of a set of independent failures occurring together to be vanishingly small should urgently make plans to cope with them all happening at once" (7 March)? So far, 21 readers have been keen to help.

Six of you suggested Murphy's law, also known as Sod's law: "Anything that can go wrong, will go wrong." Bill Sloman noted the "necessary corollary that whichever name you use for it won't be the one used by the person you are talking to". Bob Malcolm was reminded of a journalist asking a UK Met Office spokesperson, in the aftermath of some weather phenomenon, "Why can't you predict these freak events?"

Bob also likes the "Law of the Inevitability of Freak Events", ...

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Parasitic populations solve algorithm problems in half the time

PARASITES are nature's thieves, but we can harness this behaviour for our own gain.

We use algorithms to work out complicated problems like the best truck route or crew schedule, because finding a good solution means fiddling with the values of many parameters simultaneously.

One way they can do this is by using groups of virtual creatures that wander through "parameter space", looking for valleys that represent the lowest values. Mathematicians have taken inspiration from actual animals, from grey wolves to ants. One limitation, though, is that the animals sometimes fail to notice a deeper valley nearby. Adding parasites can stop this from happening, say Shi Cheng of the University of Nottingham Ningbo, in China, and his colleagues.

In their model, a swarm of animals searched for the lowest valleys, but was then joined by a second, parasitic population. This group searched for valleys, but also abducted the most successful animals and made them work for the parasite team.

The result of this struggle for life was a more varied collection of creatures that enabled the parasitic algorithm to solve a problem in half the time (Applied Soft Computing, doi.org/3j6).

This article appeared in print under the headline "Parasites make for efficient algorithms"

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Eye of the beholder: How colour vision made us human

(Image: Jimmy Turrel)

IT TOOK a rather unremarkable garment for people to begin to question their view of reality. On 26 February this year, a photo of a dress went viral – not for its stylishness, but because of its chameleonic colours. Some saw it as blue and black, while others thought it white and gold. Still others, to their enduring unease, saw first one combination, then the other.

The discussions that rippled across the web as a result illustrated a fundamental truth: colour is one of the most vivid and personal experiences we have. But while colour feels extremely real and present, we are still learning exactly how events in our evolutionary past combined to create our particular form of colour vision – and beyond the odd optical illusion, just how important it has been in making us who we are. "Humans wouldn't be here if we ...

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Dogs tap into human bonding system to get close to our hearts

Video: Eye-to-eye bonding

Ever felt hopelessly bonded to your pooch when it stares at you lovingly? It turns out that man's best friend may have hijacked a uniquely human bonding mechanism, ensuring that we love and care for it.

Knock-on chemical and behavioural effects occur when humans bond: eye contact leads to release of the "love hormone" oxytocin, which elicits caring behaviour, and this in turn causes the release of more oxytocin. This loop has been shown to be important for human bonding, for example between mothers and their children.

Oxytocin bonding occurs in other mammals, too, but humans were thought to be unique in using eye contact as part of this cycle. "Facing others is a threatening behaviour in other animals," says Miho Nagasawa at Azabu University in Japan.

But when she and her colleagues got a bunch of dog owners to gaze into their pets' eyes, they found that oxytocin levels rose not just in the humans – but in the pooches too.

In contrast, when Nagasawa's team tested hand-reared wolves, they found no such effect, and wolves spent little time gazing into their owners' eyes.

They then sprayed either oxytocin or a placebo into 27 dogs' noses, in a randomised experiment. Female dogs that received the hormone spent more time staring longingly at their owners, and oxytocin levels also rose in those people.

This means that the tendency to gaze into eyes must have evolved during the domestication of dogs, says Nagasawa. She adds that it's the first demonstrated case of convergent evolution in cognitive traits between a human and another species.

The only hitch was that although both male and female dogs – and their owners – received an oxytocin boost from eye contact, male dogs didn't spend more time looking at their owners' eyes when they were sprayed with the hormone.

Nagasawa suggests that this could be because among males oxytocin is known to increase hostility towards members of other groups, so the sprays might have made the male dogs more vigilant about strangers in the room during the experiment.

Close connection

Pat Shipman at Penn State University in University Park has argued that the co-evolution of dogs and humans – possibly starting as long as 36,000 years ago – gave humans the edge over Neanderthals.

"I had predicted that both domestic dogs and humans would show adaptations to enhanced non-verbal communication, but I had not thought of the oxytocin link," she says. "As the first species to be domesticated, dogs have a very ancient and very profound link to humans that affected both of us."

But not everyone is convinced this shows that dogs evolved to hijack our bonding mechanism through staring into our eyes.

Jessica Oliva at Monash University in Melbourne, Australia, agrees that oxytocin was key to the evolution of dogs from wolves, allowing them to bond with humans. But she thinks that the eye-gazing behaviour could be learned rather than having evolved over time. "It could be a conditioning thing," she suggests.

Clive Wynne of Arizona State University in Tempe agrees. He says that wolves he works with do make eye contact if they've been brought up in close contact with people. "I'm questioning the attempt to interpret these results as an evolutionary process," says Wynne.

Nagasawa agrees that wolves and other animals can learn to make eye contact, but says it comes easier to dogs. And to her, that suggests the behaviour has evolved.

She says this might just be the tip of the iceberg, too. Next, she wants to study whether dogs feel empathy with humans. "Most dog owners say when they feel sad, their dogs feel sad too. And when the owners feel happy, maybe the dogs feel happy too. So maybe the dogs are very sensitive to the owners' feelings," she says.

Journal reference: Science, DOI: 10.1126/science.1261022

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Plane creates vibrant landscape painting by firing laser pulses

(Image: Norbert Pfeifer/TU Wien)

What would Turner think of a landscape painting created by a plane? This artistic-looking map was captured in 3D by laser pulses fired from an aircraft as it flew over the conservation area of Ágotapuszta in Hungary. Each type of vegetation within the mosaic of salt meadows, grasslands and marshes is represented in a different colour.

The aerial system was developed by Norbert Pfeifer from the Vienna University of Technology in Austria and his colleagues to monitor Europe's nature reserves, which cover a fifth of the continent's surface. To retain their status, regular checks have to be carried out at least once every six years, which is far easier to do from the air than on land.

A plane scans a strip of land between 300 and 800 metres wide by directing half a million infrared laser pulses at the ground every second. By measuring the return travel time of each pulse, computer algorithms can work out the total distance of the round trip and build up the shape of a landscape.

Protruding features, such as trees, are revealed by pulses that have travelled a shorter distance. Even minute details like weeds and vehicle tracks come to life.

(Image: Norbert Pfeifer/TU Wien)

A ground-level view, shown above, can also be recreated by looking at a specific cross-section of the 3D map. From this detail, ecologists should be able to determine the leafiness and height of the trees as well as the species.

Journal reference: Canadian Journal of Remote Sensing, DOI: 10.5589/m13-013

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Paper microphone may help charge your cellphone

Screaming with rage at your dying cell phone battery doesn't help much, but that could be about to change. Researchers have developed a postage stamp-sized microphone that can harvest acoustic energy to top up your charge on the go.

Zhong Wang of the Georgia Institute of Technology in Atlanta and his colleagues created their microphone from a thin sheet of paper just a few centimetres across. They used a laser to zap a grid of microscopic holes in the paper, then coated one side in copper and laid it on top of a thin sheet of Teflon, joining the two sheets at one edge.

Sound waves vibrate the two sheets in different ways, causing them to come in and out of contact. This generates an electric charge, similar to the one made when your rub a balloon on your hair, which can charge a phone slowly.

The paper microphone could also be used as a way to recycle sound energy from the environment, getting free electricity from the "waste" sounds all around us. The charge can also be converted into a range of sound frequencies, allowing the initial sounds to be amplified.

The amount of power the microphone provides depends on its size, but it's around 121 milliwatts per square metre. "It can be made into any size you like," says Wang, though he admits a stamp-sized microphone fitted to your phone would only provide a small amount of power rather than fully charging your phone.

Journal reference: ACS Nano, DOI: 10.1021/acsnano.5b00618

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Fat FAQ: 9 answers to your burning questions

1. How quickly does eating too much cause new fat cells to form?

"Incredibly fast," says Matthew Rodeheffer, who studies obesity at Yale University, on the basis of recent research his team conducted on mice. After just five days on a high fat diet, new fat cells had appeared. In humans the process could be even faster, he says, potentially within a day. Once the cells are present, though, it takes them several weeks to actually fill up with fat.

But Giles Yeo at the University of Cambridge Metabolic Research Laboratories says having more fat cells isn't necessarily a bad thing. Being able to spread your fat over a larger number of cells means they are less likely to overfill, so you can store more fat while staying metabolically healthy. "Imagine each fat cell is like a balloon, but there is a safe limit to how much fat it ...

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