Coherent multiple scattering of light in (2+1) dimensions

We formulate a multiple scattering theory of light in media spatially disordered along two directions and homogeneous along the third one, without making any paraxial approximation on the wave equation and fully treating the vector character of light. With this formalism, we calculate the distribution of transverse momenta of a beam as it evolves along the optical axis, and unveil a phenomenon not captured by the paraxial equation: a cross-over from a scalar to a vector regime, visible in the coherent backscattering peak as polarization gets randomized.Comment: 10 page

Dynamical phase transition of light in time-varying nonlinear dispersive media

We demonstrate the existence of a prethermal dynamical phase transition (DPT) for fluctuating optical beams propagating in nonlinear dispersive media. The DPT can be probed by suddenly changing in time the dispersion and nonlinearity parameters of the medium (thus realizing a "temporal interface"), a procedure that emulates a quench in a massive $\varphi^4$ model. Above a critical value of the quench identifying the transition, the fluctuating beam after the temporal interface is characterized by a correlation length that diverges algebraically at the transition. Below the critical quench, the beam exhibits an algebraic relaxation and a self-similar scaling. Our analysis also reveals a dimensional cross-over of the critical exponent, a characteristic feature of the optical DPT.Comment: Comments welcom

Bunching and anti-bunching of localised particles in disordered media

We consider pairs of non-interacting quantum particles transmitted through a disordered medium, with emphasis on the role of their quantum statistics. It is shown that particle-number correlations measured in transmission are strikingly sensitive to the quantum nature of the particles when they undergo Anderson localisation, due to bosonic bunching and fermionic anti-bunching in the scattering channels of the medium. The case of distinguishable particles is also discussed.Comment: 5 pages, 3 figure

Quantum kinetics of quenched two-dimensional Bose superfluids

We study theoretically the non-equilibrium dynamics of a two-dimensional (2D) uniform Bose superfluid following a quantum quench, from its short-time (prethermal) coherent dynamics to its long-time thermalization. Using a quantum hydrodynamic description combined with a Keldysh field formalism, we derive quantum kinetic equations for the low-energy phononic excitations of the system and characterize both their normal and anomalous momentum distributions. We apply this formalism to the interaction quench of a 2D Bose gas and study the ensuing dynamics of its quantum structure factor and coherence function, both recently measured experimentally. Our results indicate that in two dimensions, a description in terms of independent quasi-particles becomes quickly inaccurate and should be systematically questioned when dealing with non-equilibrium scenarios.Comment: 14 pages. Most technical details are contained in Sec. III. Secs. IV and V discuss concrete application

Quantum boomeranglike effect of wave packets in random media

We unveil an original manifestation of Anderson localization for wave packets launched with a finite average velocity: after an initial ballistic motion, the center of mass of the wave packet experiences a retroreflection and slowly returns to its initial position, an effect that we dub "Quantum Boomerang" and describe numerically and analytically in dimension 1. In dimension 3, we show numerically that the quantum boomerang is a genuine signature of Anderson localization: it exists if and only if the quantum dynamics if localized.Comment: Published versio