CORDIS - Forschungsergebnisse der EU

Processing of biomolecular targets for interferometric quantum experiments

Final Report Summary - PROBIOTIQUS (Processing of biomolecular targets for interferometric quantum experiments)

The ERC project PROBIOTIQUS was focused on processing biomolecular targets for quantum interference experiments, operating at the interface between quantum optics, physical chemistry, nanotechnology and biomolecular physics.
We have studied the feasibility of preparing and observing quantum delocalized states of biomolecules, which one often colloquially refers to as each of these biomolecules ‘being’ in two or more places at once. As of to date the QNP group at the University of Vienna is still the only group in the world to have achieved this feat.

The matter-wave schemes, harnessed and developed in the context of Probiotiqus, comprise for instance textbook like diffraction of mood-stimulating agents or antibiotics at nanomechanical and optical gratings rendering their wave-particle duality intuitively visual in fluorescence imaging schemes. These experiments also taught us that quantum control over the position of polar biomolecules is best achieved using optical elements, specifically optical gratings which can be act either as periodic absorptive masks – using photo-induced ionization, fragmentation or other depletion mechanisms – or as phase shifting gratings.

Optical gratings were used in three interferometer configurations, to first prove and then utilize the delocalized quantum wave nature of objects of biological relevance, such as vitamins, antibiotics and biopolymers or even clusters of biomolecules.

The results of PROBIOTIQUS touch on our fundamental understanding of physics and our philosophical views on the world. We must ask ourselves, ever more than before, what we mean when we use our everyday notions of reality, space-time, locality or Aristotelian logic to assign interpretations to experimental observations in quantum physics.

PROBIOTIQUS shares this puzzle with many fundamental quantum experiments, since it draws on the same principles of quantum superposition and the wave nature of matter. PROBIOTIQUS, however, went beyond any prior quantum experiment by showing that even molecules and materials that we digest in our human body on a daily basis or commonly find in nature, do behave in this highly non-classical, quantum mechanical fashion, when they are properly isolated from the environment.

The matter-wave interferometers of PROBIOTIQUS are also unique in the way they contribute to quantum enhanced measurements of electronic, magnetic, optical or structural properties of complex molecules.

We have determined some electronic properties of the (pre)vitamins A, E and K in Kapitza-Dirac-Talbot Lau interferometry, using the fact that matter-wave fringes are free-flying ‘rulers’ made of molecular probability density, whose position can be read out in dedicated experiments and this with nanometer precision. This way one can track the absorption of on average less than a single-photon per molecule to determine a reliable and precise absorption cross section, simply by following the momentum exchange between light and matter. Related ideas now allow new ways of spectroscopy or sorting of molecules by their internal properties. The experiments have reached a force sensitivity way below the yN level.

PROBIOTIQUS, like no other project anywhere else, has demonstrated the universality of de Broglie’s matter-wave concept and the feasibility to study its philosophical and metrological consequences in application to a vast range of diverse molecules, that play also a fundamental role in life.

A central element of PROBIOTIQUS was also to develop molecular beam methods, to improve the volatilization, manipulation and detection of neutral biomolecules for advanced quantum experiments. Laser-assisted acoustic desorption was shown to release very slow but also very sparse beams biomolecules. Pulsed laser desorption of polypeptides into an adiabatically expanding noble gas allowed generating neutral beams of biopolymers matching the needs of advanced interferometers.

Quantum interference with large biomolecular nanomatter at the edge to life has remained an outstanding goal and challenge throughout the last two decades. PROBIOTIQUS contributed to separating the impossible from the conceivable for future experiments with viruses, too.