Experimental observation of quantum‑vacuum–seeded amplification from a rotating absorber

Demonstrate experimentally the amplification of quantum fluctuations by a rotating absorber predicted by the Zel'dovich effect, i.e., establish spontaneous generation and amplification of electromagnetic radiation seeded solely by the quantum vacuum rather than classical noise.

Background

Zel'dovich predicted that a rotating absorbing body, such as a conductive cylinder, can superradiantly amplify incident electromagnetic waves when the rotational Doppler‑shifted co‑rotating mode frequency becomes negative. The effect extends to the quantum field, where vacuum fluctuations interacting with the rotating absorber can be amplified, leading to spontaneous radiation and extraction of rotational energy.

In this work the authors experimentally demonstrate classical amplification and a black‑hole‑bomb‑like instability in an electromagnetic system using a three‑phase stator and a rotating metallic cylinder, including noise‑seeded self‑oscillation and runaway growth. However, the experiments were performed at room temperature and the signals were seeded by classical (thermal and electronic) noise, not by vacuum fluctuations. The authors explicitly note that observing amplification seeded by the quantum vacuum has not yet been achieved and remains a key milestone.