A landmark of statistical mechanics, spin-glass theory describes critical phenomena in disordered systems that range from condensed matter to biophysics and social dynamics. The most fascinating concept is the breaking of replica symmetry: identical copies of the randomly interacting system that manifest completely different dynamics. Replica symmetry breaking has been predicted in nonlinear wave propagation, including Bose-Einstein condensates and optics, but it has never been observed. Here, we report the experimental evidence of replica symmetry breaking in optical wave propagation, a phenomenon that emerges from the interplay of disorder and nonlinearity. When mode interaction dominates light dynamics in a disordered optical waveguide, different experimental realizations are found to have an anomalous overlap intensity distribution that signals a transition to an optical glassy phase. The findings demonstrate that nonlinear propagation can manifest features typical of spin-glasses and provide a novel platform for testing so-far unexplored fundamental physical theories for complex systems.
OUTNANO is a Marie Curie Fellowship in the H2020 program funding activity on Out of Equilibrium Nano-photonics
The Marie Curie Fellow is Andrea Marini, a top level young scientist with an extended research career in Nonlinear Photonics.
A new approach for studying novel optical materials in out-of-equilibrium ultrafast dynamics is the goal of this interdisciplinary projects committing together ideas of statical mechanics of complex systems and nonlinear photonics. We will conceive a new generation of nonlinear devices operating at the fastest achievable speeds for classical and quantum applications.
Team of the OUTNANO project
The school brings together experts in emerging photonic technologies and fundamental physics to share with young researchers their knowledge and interdisciplinary approaches for understanding and designing complex photonic systems. The areas covered by the school include: complexity of optical communication systems, in particular topics such as the nonlinear Fourier transform and transmission over multimode fibres, complexity in quantum systems emulated in photonics (including optical computing), PT-symmetric systems, complexity of emerging novel materials and components like meta-surfaces and micro-resonators. Importantly, the complexity in bio-medical photonic applications will be also considered as a high priority topic.
The cascade of resonant topological structures with PT-symmetry breaking is shown to emit laser light with a frequency-comb spectrum. We consider optically active topological Aubry-Andr\’e-Harper lattices supporting edge-modes at regularly spaced frequencies. When the amplified resonances in the PT-broken regime match the edge modes of the topological gratings, we predict the emission of discrete laser lines. A proper design enables to engineer the spectral features for specific applications. The robustness of the topological protection makes the system very well suited for a novel generation of compact frequency comb emitters for spectroscopy, metrology, and quantum information.
Pilozzi and Conti, arXiv:1707.09191
Spin-glass theory is one of the leading paradigms of complex physics and describes condensed matter, neural networks and biological systems, ultracold atoms, random photonics, and many other research fields. According to this theory, identical systems under identical conditions may reach different states and provide different values for observable quantities. This effect is known as Replica Symmetry Breaking and is theoretically revealed by the change in shape of the probability distribution function of an order parameter named the Parisi overlap.
Despite the profound implications in the new physics of complexity, a direct experimental evidence of the Replica Symmetry Breaking transition, in any field of research was never reported.
C. Conti and coworkers show that pulse-to-pulse fluctuations in random lasers, and a direct measurement of the Parisi overlap, unveil a transition to a glassy light phase in random lasers compatible with a Replica Symmetry Breaking.
This is the first evidence of Replica Symmetry Breaking and the first direct measurement of the Parisi overlap.
N. Ghofraniha, I. Viola, F. Di Maria, G. Barbarella, G. Gigli, L. Leuzzi and C. Conti reported on the first evidence of Replica Symmetry Breaking in Random Lasers by the direct measurement of the Parisi overlap distribution function (arXiv:1407.5428, Nature Communications 2015)