Martin Plávala

Quantum mechanics is a linear theory. This property is so fundamental that violating it would mean losing the superposition principle and, consequently, the possibility of superluminal information transfer. But physicists have long suspected that at a deep level, where gravity meets quanta, linearity might not survive.

In 2022, physicists observed gravity shifting the phase of a single atom's wave, the gravitational analog of the Aharonov–Bohm effect. This experiment became part of a long-standing debate: whether gravity must be quantized or remains a classical background in the quantum world.