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Joao Medeiros: April 2009 Archives

By João Medeiros

One of the highlights of the “Science Beyond Fiction” conference in Prague was Lazlo Barabasi’s talk - “From Human Travel Patterns to Mobile Viruses”

Barabasi, author of the excellent book “Linked” , is one of the world experts on the topic of social networks.

In his talk, Barabasi presented novel insights about the science of human mobility patterns. The applications of such a study are incredibly wide-ranging, from understanding of how ideas and diseases spread, to the planning of traffic and urban spaces.

As one might guess, there is a huge element of randomness in the way we move.
Einstein, of course, was the first to theorize about random walk theory in the context of Brownian motion - the drunkard sailor paradigm (which constituted the first evidence for atoms).

The paradigm for how people move was first established by a series of studies by G.M.Vishwanathan on the mobility patterns of tagged birds and monkeys. What Vishwanathan found out was that animals do not follow the drunkard sailor pattern (ie, a Gaussian pattern) but instead follow a pattern compounded of lots of small steps with some big jumps, the so called Levy flight pattern, which is described as a power law distribution.

The first challenge in studying human mobility is how to get the data. Equipping millions of people with GPS track systems is prohibitively expensive (and probably ethically wrong).

But mobility data can be extracted from a variety of datasets which indirectly inform us of how we move.

For humans, this was first studied by Brockmann, who studied the motion of dollar bills (an explanation of their method can be found in their website What Brockmann found was that humans also obey the Levy flight pattern.
Barabasi also studied the mobility problem, using a mobile phone database composed of 7 million users, tracked between 2004 and 2009. His findings support the dollar bill findings.

Barabasi and collaborators (among whom is Cesar Hidalgo, who wrote a feature for PW last December) further discovered that the shape of human trajectories can be grouped into distinct categories according to typical ranges of motion, say one group for people who tend to move within a radius of 3 km, other for people who have radius of motion in the order of 100 km, etc.

What he found, was that within each category, the scaled patterns of motion are indistinguishable. This property - universality - means that all categories of human travelers can be described by one unified model.

This is important to understand many phenomena that derive from human mobility patterns. One such application is the understanding of mobile phone viruses.
Paradoxically, the first insight into the study of mobile phone viruses is to understand why mobile phone viruses are really not that relevant at the moment.

Experts estimate that there are approximately 600 varieties of mobile phone viruses. However, they exist only in smartphones, which, at the moment only detain 5% of the mobile phone marketshare.

These viruses spread in two ways. One, via Bluetooth, spreads in a manner similar to influenza, ie, related to physical proximity. The second mode of transmission is via MMS. These viruses spread in a manner akin to computer viruses and therefore have a capacity to spread non-locally.

In other words, the spread of Bluetooth virus depends on human mobility patterns, whilst MMS viruses depend on individual social networks. Understanding their modes of propagation leads us to understand their patterns of spreading. Simulations show that Bluetooth viruses may take days to reach everyone within a given region. MMS viruses, on the other hand, take only a matter of hours before reaching a maximum level of contagion. This saturation point is highly dependent on the level of market share of the smartphones.

MMS viruses are not dangerous below the level of 10% marketshare. Above that, however, we get a phase transition point and the virus can spread quickly everywhere within a matter of hours.

At the moment we are under that threshold, but when we reach that critical point, mobile phone viruses will become a serious threat to communications, especially since standard counter measures, such as anti-virus, are very difficult to install in smartphones due to the inherent memory capacity limitations on those phones.

Beyond the specific topic of mobile phone viruses, the work of Barabasi shows how mobile phones are quickly becoming a social experiment on itself, a gold mine of data in the study of social networks and human mobility patterns.

By João Medeiros

Just attended one of the best talks so far, here at the “Science beyond Fiction” conference in Prague — a really exciting, wacky and speculative talk by Artur Ekert, on quantum information science.

To Ekert, the questions that are used to “sell” quantum information science to “deciders” and funding bodies are usually of two kinds. A first argument, more scientifically motivated, sells the point that the true power of quantum computation is yet to be achieved, a computational capacity that will likely teach us much more about the fundamentals of nature. The second, more pragmatic approach, appeals to the exploration of the true fundamental limits in exploring quantum systems and what constraints they put on technology.

On the issue of framing the subject of quantum computation, Ekert says that it is really interesting how people from different cultural backgrounds react to the topic.

For instance when discussing the matter with computer scientists, Ekert uses a more philosophically inclined, logic based approach. According to him, computer scientists are naturally not really fond of atoms and messy quantum systems.

The question he asks his computer scientist collaborators is whether it is possible to construct a logic gate operating on a single bit, such that the same two consecutive operations produce a flip of the bit. Classically, of course, you cannot. But this is a possibility when using quantum systems.

Indeed, one of the fundamental differences between quantum and classical computational systems exists in the respective nature of the logical operations allowed by each system.

The bottomline realization is that information and computation are intimately linked to physics. Information is physical. This conclusion was to many computer scientists a shock and it marked the intellectual revolution that kickstarted quantum information science.

Physicists now realize that if you change the physics you change the nature of information. This has been a surprising revelation to many computer scientists, who since the work of Alan Turing have been playing with classical computer logic without a physical foundation, a logical framework which somehow worked.


Ekert also pointed out that quantum computation is one of the truly interdisciplinarity subjects.

Not only it has brought together mathematicians, computer scientists and physicists, but it has also brought people together within physics, scientists that beforehand would not talk to each other simply because they were using completely different jargon and codes. A common denominator was found in the language of quantum logic gates.

Ekert, who is based in Singapore, compared this situation with the way that sometimes Koreans and Chinese use to communicate: not by speaking, but via written characters.


Ekert also mentioned that recent advances in the study of the quantum aspects of life, such as the study of the role of quantum coherence in photosynthesis, opens the door to discover quantum computation already happening in natural systems. This is a most fascinating topic that will be featured in an upcoming feature by Paul Davies for PW.


The final aspect discussed by Ekert was the philosophical aspect of quantum computation, an side of science which has not been avoided by physicists. According to Ekert, quantum Information has elevated the questions about the nature of reality, randomness, complexity to the level of bona-fide scientific conundrums that should be addressed, rather than ignored.

Ekert himself is partial to question about the nature of randomness, the question of whether it is really possible to have events that have no underlying cause? What is so interesting about this question is that it essential goes against one’s understanding of science, which is intrinsically motivated by the notion of causality of phenomena in nature.


In the next issue of PW, Ekert authors a feature about Girolamo Cardano, the “gambling scholar”. Cardano was a Renaissance mathematician which by himself discovered the basic notions of probability and complex numbers, two of the fundamental pillars of quantum theory.

In the future, Ekert will write again for PW about quantum information science.

By João Medeiros

I’m in Prague attending the European Future Technologies Conference — “Science Beyond Fiction”. It has so far been prolific in ideas and science-fictionish future promises, despite a bumpy start.

Viviane Reding, the European Commissioner for Information Society and Media, and Mirek Topolanek, the Czech PM, were the high profile names planned to open the proceedings. They were, however, conspicuous by their absence.

Topolanek, understandably, is perhaps more concerned with his political future than with the future of science right now, after losing a no-confidence motion in Parliament last month. The Czechs also presently hold the EU presidency, so the overbooking of Topolanek’s diary is understandable. One can only hope that he can multitask.

Reding, on the other hand, used cutting-edge European technology to address the delegates via a prosaic video-stream. Given that she is the Commissioner for Information Society and Media, the symbolism is laudable.

Speaking on a blue background of distorted stars and clouds dangerously resembling a psychedelic motif, Reding proposed to boost Europe´s high-risk research into future technologies by doubling the current level of funding by 2015.

“Europe must be inventive and bold - especially in times of crisis. Research seeds innovation which is key for Europe’s long-term global competitiveness. Scientific and revolutionary breakthroughs constitute enormous opportunities and we must bring the best brains together to make the most of them,” said Reding. “Combining efforts of the 27 EU countries and stepping up cooperation with global partners is essential for Europe to take the lead in future information technologies that can yield radically new solutions for European citizens in domains such as health, climate change, the ageing population, sustainable development or security.”

In other words, Europe needs catch up with the US, China and Japan.

Unlimited computing power, computers mimicking the brain, mind controlled wheelchairs and friendly robotic companions are all part of this European sized mega super project. This initiative comes in the context of the Future and Emerging Technologies (FET) programme to promote long-term and high risk research in quantum computing and communications, nanoelectronics, neuro- and bio- information science, advanced robotics and complex systems.

Some of the research that resulted from FET sponsorship is in show here at an Exhibition.

On the “friendly robotic companions” category, I saw NAO, an extremely self-conscious robot that talked non-stop whilst pushing boxes around (or in the words of the researchers involved, “learning physics”). It did not really convince me, but kudos for looking so helpless and cute.

I was also the only volunteer to test drive a simulator type head-set - immersive journalism at its best — and had to control a joystick to run over black squares on a virtual road. I’m still trying to figure out why.

The issues of high-risk research and funding of basic science, of course, were already timely featured in PW’s May issue, on the excellent article by Mark Buchanan, “In search of black swans”
Glad to see that PW is driving the European science agenda.

Highlight of the day: Anton Zeilinger’s talk on Quantum Information (more on that later)