Underground experiment rules out gravity as cause of quantum decoherence

September 21, 2026 at 03:00 PM1 min

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An experiment at Italy's Gran Sasso National Laboratory has eliminated a gravity-based explanation for quantum decoherence. The findings, published in the New Journal of Physics in June 2026, found no evidence for the faint radiation predicted by the Károlyházy model. The result narrows the search for why quantum behavior disappears in the macroscopic world.

Key Facts

The experiment was conducted at the INFN Gran Sasso National Laboratory, the world's largest underground laboratory for fundamental physics, beneath 1.4 kilometers of rock.
The findings were published in the New Journal of Physics in June 2026.
The Károlyházy model predicts that spacetime fluctuations cause charged particles to emit extremely faint electromagnetic radiation.
The experiment found no evidence for the predicted radiation, eliminating the gravity-based decoherence model.
FQxI member Catalina Curceanu, director of research at INFN-LNF, is spokesperson for the VIP Collaboration.

The Experiment

Researchers tested a model in which gravity destroys quantum superpositions through tiny spacetime fluctuations. The model was proposed by Hungarian physicist Frigyes Károlyházy in the 1960s and recently revived by FQxI's Angelo Bassi and colleagues. The experiment searched for faint electromagnetic radiation that charged particles would emit if spacetime fluctuated. The Gran Sasso laboratory's 1.4 kilometers of rock shielding blocks cosmic rays and other background radiation.

Quantum Decoherence

Quantum mechanics allows particles to exist in superpositions of states, as in Schrödinger's cat being both alive and dead. Physicists call the loss of these quantum effects decoherence, and its cause remains an open question. The new experiment eliminates one prominent gravity-based explanation for decoherence. Catalina Curceanu, director of research at INFN-LNF, describes the disappearance of quantum behavior as one of the deepest questions in modern physics.