Researchers from ETH Zurich and the Institute of Photonic Sciences in Barcelona have successfully demonstrated controlled quantum delocalization in a silica nanoparticle, a significant step toward bridging the quantum and macroscopic worlds.
The experiment, published in Physical Review Letters, addresses the challenge of observing quantum interference in larger objects, which is typically limited by zero-point motion. The team employed a modulated optical tweezers system to dynamically adjust the confinement of the light trap, effectively increasing the nanoparticle's coherence length by over threefold, from approximately 21 picometers to over 70 picometers under optimal conditions. This extended coherence length is crucial for a particle to exhibit quantum interference and its wave-like behavior.
While the distances involved are minute, the breakthrough proves that controlled expansion is feasible without compromising the particle's quantum integrity. This opens new avenues for studying phenomena previously confined to atomic or molecular systems, bringing quantum mechanics closer to practical applications.
The QnanoMECA project, supported by the European Research Council, has also contributed by reducing the mechanical energy of quantum nanomechanical oscillators, bringing them nearer to the quantum regime of individual phonons. This progress enhances the manipulation of quantum states at larger scales.
Beyond fundamental significance, this technique holds promise for developing highly sensitive quantum force sensors capable of detecting minute variations in electric or gravitational fields with unprecedented precision. It also offers new pathways for exploring the connection between quantum mechanics and gravity, with theoretical frameworks suggesting that two delocalized quantum masses could generate gravitational entanglement.
These advancements are expected to contribute to a new generation of sophisticated mechanical sensors for applications ranging from navigation systems to seismology, marking a monumental leap in understanding and applying quantum mechanics at macroscopic scales.