How Light Reveals the Hidden Laws of Open Systems ⚡ экспресс
Non-Hermitian physics describes phenomena in open systems, but many predictions of non-Bloch band theory remained experimentally inaccessible, especially the connection between complex momenta and non-Hermitian bands. In this work, we experimentally investigated spectral deformation in complex momentum space using a non-Hermitian lattice with long-range couplings, realized in the synthetic dimension of photon orbital angular momentum inside a degenerate cavity. Complex momenta were encoded through phase and amplitude modulation of the modes, and specially designed projective detection with complex momentum resolution allowed reconstruction of the spectrum, whose eigenvalues on the complex plane change geometry. This enabled extraction of exceptional points in complex momentum space, spectra under open boundary conditions, and the generalized Brillouin zone. The platform is universal for non-Hermitian physics and, for the first time, allows direct investigation of non-Bloch features in complex momentum space.
Open systems exchange energy with their surroundings, like a guitar string fading into the air. Scientists built such a system out of light, twisting the beams into corkscrews and forming an artificial lattice—a maze where losses can be controlled at every step. Light in this maze always moves at the maximum possible speed, but its energy can fade or grow. By simultaneously measuring the twist and strength of the corkscrew beams, physicists reconstructed the full spectrum (color composition) depending on direction and attenuation. At certain points, two different colors of light merge into one, as if losing their individuality—something impossible in ordinary crystals. This optical technique opens access to effects that were previously only theoretical. It's already helping improve lasers and sensors, and in the future will bring us closer to ultrasensitive quantum devices.
🎯 Light beams with different degrees of twist look like donuts with varying numbers of swirls, and each such donut can act as a separate data transmission channel.