The 'photographers' of the attosegundo, Frontiers of Knowledge Award in Basic Sciences

Paul Corkum, Ferenc Krausz and Anne L'Huillier. / BBVA Foundation

The winners have made it possible to observe the movements of electrons in the trillionth part of a second, approximately the time it takes light to pass through an atom

José A. González

Although the scientific community disagrees, the human eye is capable of seeing 30 frames per second (fps) or 60 fps. The world's fastest camera captures, at 70 trillion fps, "the path of light in all its splendor," experts say. But, even so, it is not possible to "see processes of nature in a very short time," says Carlos Hernández García, a tenured professor at the University of Salamanca. Can they be seen, measured? Also. How long does a blink last? And the flutter of a hummingbird? Technology has made it possible to fragment time into seconds, milliseconds (thousandth of a second), microsecond (millionth of a second, nanosecond (billionth of a second), picosecond (billionth of a second), femtosecond (billionth of a second and how to compare a second with 100 million of years) and attoseconds (trillionths). "Cameras can reach milliseconds or nanoseconds," explains Hernandez. "Underneath it can only be optics," he adds. And this is what Anne L'Huillier, Paul Corkum have achieved and Ferenc Krausz, new BBVA Foundation Frontiers of Knowledge Awards.

These three laureates have managed to develop cutting-edge techniques that allow physicists to observe the movement of electrons in an atom on the scale of one attosecond. "This is a brutal frontier of knowledge that we have crossed," says the tenured professor at the University of Salamanca. "This allows us to see how time varies in such short processes," he says. "In the shortest space of time that exists," he adds. As much as 0.000000000000001 seconds.

"This is the time scale at which the electrons move in all the atoms that make up matter, including our own bodies," points out Fernando Martín, professor of Physical Chemistry at the Autonomous University of Madrid, scientific director of IMDEA. -Nanoscience and nominator of the three winners. "If we have made computers by controlling the movement of electrons in nanoseconds, imagine what we could do by controlling a million seconds faster," answers Hernandez.

atomic revolution

The first step in this revolutionary discovery came in the workspace of Anne L'Huillier at the University of Lund (Sweden) at the end of the 1980s. French physics reached the highest frequency ever achieved by interacting pulses of laser light with matter.

A discovery that came after wanting to see what happened when subjecting atoms to brief and intense pulses of infrared laser light. The result was not as expected, but he was surprised to find that the atoms seemed to emit light waves at very high frequencies. "It was very fascinating, it was the first step in generating an attosecond pulse," says L'Huillier. «The laser acts on the atoms like sea waves on a seaweed attached to a rock. Each time a wave arrives, the alga fully extends, only to retract when the wave recedes. This is why the algae oscillate up and down in tune with the waves. In the same way, the arrival of a laser pulse caused the electrons, which surround the atoms, to move away, and later return to their initial position when the laser pulse withdrew », he explains.

This theoretical basis is what years later Paul Corkum (University of Ottawa in Canada) and Ferenc Krausz (Max Planck Institute for Quantum Optics) concluded "could be the basis for generating the shortest light pulses ever created." Both kept in mind that, in general, short pulses of light were the vehicle to get to observe the universe of the small.

However, not everything was successful, since the pulses, despite being brief, came in a succession of many in a row. “Having the full pulse train is more or less like having a camera that has a very high shutter speed. But instead of opening the shutter just once, it opens and closes it all the time, and that's usually not very helpful. What you want is to be able to open the shutter once and close it very quickly, to take a single photo,” reveals Krausz.

To isolate this pulse of light, they decided to shorten the initial pulse of infrared light, the one that makes the sea wave following the example of L'Huillier, so that the electron, in this case the algae, went up and down just once. "This is how they obtained a single pulse of light lasting about one hundred attoseconds," the BBVA Foundation details in a statement. "This is the birth of experimental attophysics," says Krausz.

future applications

Now that the physics of attoseconds has clearly demonstrated its potential, the winners are trying to get the most out of it in order to gain an in-depth understanding of the matter that nature is made of and develop possible applications in fields such as electronics and biomedicine. "This field of research is expanding in many directions," says L'Huillier.

"I am more cautious in the application," says Hernández. "Now we are discovering what it is and we are making like movies, for example, of a chemical reaction," he details. "If you see it, maybe later you can replicate it and that is very interesting and very important," she adds.

Krausz sets his sights on the field of computing. 'Electrons play an extremely important role in nanocircuits, they are responsible for switching electrical current on and off and thus processing information at ever increasing speeds. If we want to speed up signal processing to build ever more powerful computers”, he narrates. "It can also be essential to know how heat is dissipated in a material and advance in the subject of semiconductors" adds Carlos Hernández.

However, the work of Ferenc Krausz goes beyond this scope and already explores the biomedical potential of these pulses to diagnose diseases. "With this technique we have been able to detect eight different types of cancer," says the Hungarian-Austrian physicist. These measurements, according to the scientist, could be very useful in the future to diagnose many diseases early. Krausz is currently trying to validate the results through a clinical trial with 10,000 people over several years, and his hope is that it could be applied within a decade.