Birth of Light from the Quantum Void express
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.
Original abstract
as written by the authors arXiv:2604.10406
Equilibrium quantum phase transitions profoundly reshape the ground state of light-matter systems; yet, the resulting quantum correlations, such as squeezing and entanglement, remain experimentally inaccessible since they involve virtual ground state excitations. We investigate how a nonadiabatic modulation of a Hamiltonian parameter can convert these virtual excitations into real photons, enabling quantum vacuum radiation. We show that proximity to the critical point strongly enhances the emitted photon flux and the non-classical nature of the emitted radiation, even when thermal fluctuations are expected to dominate. In addition, higher-order processes become relevant even for small modulation amplitudes, and we develop a framework that systematically incorporates them. Our results reveal that criticality can act as an efficient amplifier of vacuum fluctuations, offering new routes to probe and exploit quantum critical ground states.
Quantum vacuum fluctuations are so real that they create a subtle attractive force between two closely spaced mirrors, the Casimir effect.