This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Somewhere between the microscopic realm of elementary particles and the macroscopic world of human beings, something strange happens: The rules of quantum physics, which work so exquisitely for tiny atoms, seem to lose their grip as objects grow larger. Pondering where and how this shift from small-scale quantum fuzziness to everyday sharp certainty happens gives rise to thought-experiment oddities like Schrödinger's famous dead-and-alive cat.
The process by which quantum phenomena like superposition—the paradoxical affliction of Schrödinger's cat—fade into the classical reality we experience is known as decoherence. Now, a new experiment has narrowed the field of possible explanations for decoherence, in particular ruling out a prominent theory linking gravity to the process. The results appeared in a paper in the New Journal of Physics in June 2026.
"One of the deepest questions in modern physics is why the strange quantum behavior that governs atoms and elementary particles seems to disappear in the macroscopic world we experience every day," says FQxI member Catalina Curceanu, director of research and spokesperson for the VIP Collaboration at the National Laboratory of Frascati of the National Institute for Nuclear Physics (INFN-LNF) in Italy. Conducted at the INFN Gran Sasso National Laboratory (INFN-LNGS), the world's largest underground laboratory for fundamental physics research, the experiment tested one model in which decoherence is caused by gravity. Einstein's general theory of relativity states that gravity manifests due to the warping of spacetime's fabric around massive objects.
In the 1960s, the Hungarian theoretical physicist Frigyes Károlyházy posited that spacetime is constantly rippling with tiny fluctuations that gradually erode quantum superpositions, preventing macroscopic objects from existing in the kind of quantum combinations imagined in Schrödinger's famous cat paradox. His model continues to intrigue physicists and was recently revived, refined and reformulated by FQxI's Angelo Bassi and colleagues. The fluctuations predicted by Károlyházy can't be observed directly but, if they exist, they should cause charged particles to jiggle and accelerate randomly, giving telltale trails of electromagnetic radiation.
This radiation would be so faint that it could easily be lost in electromagnetic background noise from sources like cosmic rays. That makes the Gran Sasso National Laboratory, which is tucked beneath 1.4 kilometers (0.9 miles) of radiation-dampening rock, an ideal place to conduct the search. "The natural shielding provided by the rock creates one of the quietest environments on Earth for detecting extremely rare physical phenomena," says Curceanu.
The researchers used a detector made up of a coffee-mug-sized piece of high-purity germanium crystal, surrounded by layers of copper and lead shielding. They collected data for a total of 62 days. Then, they subtracted the expected background radiation from their measurements and looked for a signature that matched that predicted by the model.
Extract — continue reading at the source.
