Randomness is a fascinating concept that attracts the interest of multiple thinkers, from philosophers, to mathematicians, physicists, computer scientists and engineers. From a fundamental perspective, the question of whether random processes exist is essential for our understanding of nature. From an applied perspective, randomness is a valuable resource for cryptography, algorithms and simulations. Standard methods for generating randomness, including the current quantum solutions, rely on strong assumptions on the devices that are difficult to meet in practice. However, quantum correlations violating a Bell inequality allow for completely new methods for generating certified randomness. These methods are known as device-independent because they don't require any modelling of the inner working of the devices. Moreover, they are intrinsically quantum, as no classical system can violate a Bell inequality. Device-independent quantum random-number generators protocols represent a change of paradigm for randomness that solve fundamental and practical drawbacks of standard schemes. The article reviews the efforts and the theoretical and experimental challenges to design device-independent randomness generation protocols. Generators with unprecedented standards of quality and security seem within reach using quantum technologies.
Every year, a committee of experts sits down with a tough job to do: from among all ICREA publications, they must find a handful that stand out from all the others. This is indeed a challenge. The debates are sometimes heated and always difficult but, in the end, a shortlist of 24 publications is produced. No prize is awarded, and the only additional acknowledge is the honour of being chosen and highlighted by ICREA. Each piece has something unique about it, whether it be a particularly elegant solution, the huge impact it has in the media or the sheer fascination it generates as a truly new idea. For whatever the reason, these are the best of the best and, as such, we are proud to share them here.
LIST OF SCIENTIFIC HIGHLIGHTS
Certified randomness in quantum physics (2016)
Acín Dal Maschio, Antonio (ICFO)view details
A “Molecular Selfie” reveals how a chemical bond breaks: Proton is seen escaping the molecule (2016)
Biegert, Jens (ICFO)view details
Imagine what it would be like to watch how the individual atoms of molecules rearrange during a chemical reaction to form a new substance, or to see the compounds of DNA move, rearrange and replicate. The simple idea of watching how molecules break, or transform, during chemical reactions has, until now, been unfathomable since it requires tracking all of the atoms, which constitute a molecule, with sub-atomic spatial and few-femtosecond temporal resolution. Hence, taking such “snapshots” with a combined spatio-temporal resolution to witness a molecular reaction was considered fodder for science fiction.
In their recent study, reported in Science, the team led by ICREA Prof. Dr. Jens Biegert head of the Attoscience and Ultrafast Optics Group at ICFO in collaboration with researchers from the USA, the Netherlands, Denmark and Germany, have reported the first real time and space imaging of molecular bond breakup in acetylene (C2H2) nine femtoseconds (1 femtosecond = 1 millionth of a billionth of a second) after its ionization. The team was able to track the individual atoms of one isolated acetylene molecule with a spatial resolution as small as 0.05 Ångström – less than the width of an individual atom – and with a temporal resolution of 0.6 femtoseconds. What’s more, they were able to trigger the breakup of only one of the bonds of the molecule and see how one proton leaves the molecule.
The team took a single electron, steered it along a specific path with the laser and scattered it off an isolated molecule to record its diffraction pattern. It is mind-boggling to imagine the length and time scales of the experiment. The fantastic cooperation between experimentalists and theorists, atomic physicists and quantum chemists from ICFO, Kansas State University, Max-Planck-Institut für Kernphysik, Physikalisch Technische Bundesanstalt, Center for Free Electron Laser Science/DESY/CUI, Aarhus University, Friedrich-Schiller University Jena, Leiden University, and Universität Kassel made it possible to achieve such feat.
Saving freshwater from salts: Global call to change the way we regulate salinity (2016)
Brucet, Sandra (UVIC)view details
Many human activities such as agriculture and mining are increasing water salinity in rivers and lakes and this has adverse effects on human health and ecosystem functioning. It can also have high economic costs due to loss of ecosystem services and direct costs related to water for human consumption. Our study also warns that in most cases preventive actions focus solely on human uses of water, ignoring the protection of aquatic biodiversity. Some countries have made progress in regulating salinity on the basis of ecological criteria. Even so, the degree of protection is insufficient. In most cases these are only recommendations based on the total quantity of salt, without taking into account the concentration of different ions that have different toxicity.
We call for global solutions and preventive policies based on the scientific consensus, taking into account social, economic and environmental issues in order to protect aquatic ecosystems from increasing salinity. We also predict that climate change will aggravate this situation because water evaporation will increase, diminishing the capacity of rivers and lakes to dilute salts, and sea level rise will cause intrusion in coastal freshwaters. We propose incentives for good practices and the use of technology that will reduce salt concentrations in freshwaters. We also recommend permits and controls for enterprises that discharge salt-rich effluents into freshwaters in order to control the concentration and timing depending on the dilution capacity of receiving waters.
Ecological disasters caused by increasing salinity, though few in number, have brought about large-scale loss of biodiversity and suffering for human inhabitants affected, as is the case of the fisheries collapse in the Aral Sea. We are still in time to prevent further disasters if appropriate prevention practices are put in place. Nonetheless, increasingly saline aquifers and arable land already make it impossible to cultivate certain crops (e.g. Ebro valley), rendering it harder to provide drinking water. The countries of southern Europe will suffer most from this situation and experience greatest difficulties in economic activities.
A big year for a small effect (2016)
Catalán Bernabé, Gustau (ICN2)view details
Flexoelectricity is a property of all insulating materials whereby they generate a voltage when they are bent. Flexoelectricity is however a tiny, almost inmeasurable, effect at the macroscale, hence it remains relatively unknown. This year, however, there have been a couple of notable advances may change the status of flexoelectricity. The first has been the demonstration that, at the nanoscale, electromechanical actuators can be made that bend in response to voltage1. The key to their big performance is that things are much easier to bend when they are nanoscopically thin. In addition to being competitive in terms of performance, flexoelectric actuators also have other advantages over competing piezoelectric technology: their architecture is simpler, their performance is more linear and less temperature-dependent, and the range of available flexoelectric materials is enormous. Last, but not least, our flexoelectric actuators are made on silicon substrates, meaning that they are compatible with the key material and fabrication processes already used by microelectronics industry, which should facilitate their industrial uptake.
In parallel with the effort to make devices that exploit the large magnitude of flexoelectricity at the nanoscale, there is also a very active search for ways to make it meaningful also at the macroscale. Here we have made a major breakthrough discovery: by bending semiconductors it is possible to achieve effective flexoelectric coefficients that are hundreds and even thousands of times larger than for insulators2. An important additional aspect of semiconductor flexoelectricity is that it grows with thickness. This means that, unlike insulators, semiconductor flexoelectrics remain as potent at the macroscale as they are at the nanoscale.
Cell therapy to regenerate retina (2016)
Cosma, Maria Pia (CRG)view details
Retinitis pigmentosa affects 1 in 3,500 individuals, who undergo progressive loss of vision, and for which currently there is no cure. Our approach aims to regenerate the photoreceptors, specific cell type in the retina, which respond to light.
We transplanted adult stem cells isolated from the bone marrow of mice and we observed fusion of these cells with Müller glia, a type of retinal glial cells which has a variety of functions. The Wnt signaling pathway is activated in the bone marrow cells before they are transplanted. We observed enhanced survival and proliferation of the hybrids as well as their reprogramming into intermediate photoreceptor precursors, which finally differentiate into photoreceptors. We demonstrated that this type of cell transplantation can rescue the retinal degeneration phenotype in retinitis pigmentosa mice.
Although the mammalian nervous system is unable to replace neuron lost due to degeneration, our findings suggest that photoreceptors can be generated by the reprogramming of Müller glia. In the future, this approach may have the potential to be used as a strategy for reversing retinal degeneration and cure blindness.
Linking Polycomb with Elongins (2016)
Di Croce, Luciano (CRG)view details
Multipotency is the property of different cell types to self-renew and to generate specialized progeny through multistep differentiation processes.The best proxy for this is embryonic stem cells (ESCs) that maintain a pluripotent potential through a unique network of transcription factors aimed to ensure proliferation and to prevent undesired differentiation onset. Extensive studies have been carried out to characterize the mechanisms behind the maintenance of pluripotent/multipotent states, as well as the mechanistic aspects that govern the timely response to differentiation stimuli.Among the several complexes implicated in ES cells differentiation, Polycomb group of proteins are particularly fascinating, having a major role in controlling epigenetic memory, repressing gene expression, and contribute to cancer.Di Croce’s laboratory shows that the a novel Polycomb-associated factor EPOP/C17orf96 mediates binding of Elongin factors at Polycomb-repressed genomic targets to sustain low-level expression of the corresponding genes.
This articel received that cover from the journal, and highlighted in the New&Views of Ferrari et al 'The Dual Role of EPOP and Elongin BC in Controlling Transcriptional Activity', Molecular Cell, 64, 637-38.