The study shows that rapid change of a system parameter (nonadiabatic modulation) can convert virtual quantum excitations into real radiation. Near a quantum critical point, photon flux and the nonclassical character of radiation are sharply enhanced, even when thermal fluctuations dominate. Remarkably, even weak modulation activates multiphoton processes, for which a general approach has been developed. Criticality acts as a powerful amplifier of vacuum fluctuations—like a microscope that makes the invisible visible.
The quantum vacuum is not emptiness, but a tautly stretched string, where particles constantly appear and vanish. Abruptly changing conditions—like shifting the mirrors of a microcavity—causes the 'string' to emit real photons. Near a quantum phase transition, the critical point where matter's state changes abruptly, the effect intensifies. Even a tiny disturbance triggers an avalanche of photons flying at the speed of light. Thermal disorder usually silences quantum effects, but here it only whip-flicks the string, without quenching the glow. This gives rise to non-classical light, impossible with ordinary sources.
This opens the door to hypersensitive detectors and new emitters based on vacuum flashes. Spectroscopy—analyzing light by wavelength—reads quantum states like the sheet music of a vibrating string.
🎯 Quantum vacuum fluctuations are so real that they create a subtle attractive force between two closely spaced mirrors—the Casimir effect.