The Experimental Observation of Replica Symmetry Breaking in Random Lasers

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 revealed by the shape of the probability distribution function of an order parameter named the Parisi overlap. However, a direct experimental evidence in any field of research was nevere reported.

Pulse-to-pulse fluctuations in random lasers, and  a measurement of the Parisi overlap in independent experimental realizations of the same disordered sample, unveil that the distribution undergoes a transition to a glassy light phase compatible with a replica symmetry breaking.

This is the first evidence of Replica Symmetry Breaking and the first direct measurment 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)


Designing Beauty: The Art of Cellular Automata

A new book on the Game of Life, and specifically on the Art of the Game of Life has been published by Springer. Edited by A. Adamatzky and Genaro J. Martinez, the book is entitled part of the Series on Emergence, Complexity and Computation with artistic representations from simple mathematical models at the edge of physics and biology. The book contains a contribution by C. Conti on the Enlightened Game of Life.


Quantum X Waves with Orbital Angular Momentum in Nonlinear Dispersive Media

Marco Ornigotti, Claudio Conti and Alex Szameit develop a rigorous theory of propagation invariant “X-wave” pulses with orbital angular momentum. These new photon states form and propagate in quadratic and cubic nonlinear media, and represent a novel tool for quantum information and entanglement. X-waves also allow a new 3D+1 representation of the propagation of light in nonlinear media as a spinning quantum fluid.

Solitons and quantum gravity in the Hawking radiation

The fact that solitons may have a role in quantum gravity is intriguing.

In a paper in ArXiv, by Leone Di Mauro Villari, Giulia Marcucci, Maria Chiara Braidotti (all of them top complexlight students), and CC, a toy model concerning Hawking radiation by moving black holes is proposed.

Within a simple one-dimensional theory, based on solitons of the Sine-Gordon equation, the authors claim that Hawking emission may be extracted by the concomitant observation of gravitational and electromagnetic waves emitted by colliding black holes. The effect is due to the black-hole-velocity dependent emission spectrum (figure above), which results into an electromagnetic frequency chirp detected by the observer.


Shenzhen-Roma Joint Laboratory on Nonlinear Photonics

A new joint laboratory between Dr. Lifu Zhang of Center for Optoelectronic Science & Technology at Shenzhen University (China) and Prof. Claudio Conti at the Department of Physics of Sapienza is being settled. The laboratory will study theoretical and experimental nonlinear photonics with emphasis on supercontinuum generation, spatio-temporal, and high-field phenomena.

Several joint post-doctoral positions are available in this initiative and open to researchers with a Ph.D. in Optics and Photonics with outstanding track record.

Please contact the team:

Dr. Lifu Zhang (, SZU International Cooperation Laboratory

Prof. Claudio Conti, Dep. of Physics Sapienza, Rome