We study the phase ordering of parametrically and incoherently driven microcavity polaritons after an infinitely rapid quench across the critical region. We confirm that the system, despite its driven-dissipative nature, satisfies the dynamical scaling hypothesis for both driving schemes by exhibiting self-similar patterns for the two-point correlator at late times of the phase ordering. We show that polaritons are characterized by the dynamical critical exponent z≈2 with topological defects playing a fundamental role in the dynamics, giving logarithmic corrections both to the power-law decay of the number of vortices and to the associated growth of the characteristic length scale.
The rapid development
of artificial neural networks and applied
artificial intelligence has led to many applications. However, current
software implementation of neural networks is severely limited in
terms of performance and energy efficiency. It is believed that further
progress requires the development of neuromorphic systems, in which
hardware directly mimics the neuronal network structure of a human
brain. Here, we propose theoretically and realize experimentally an
optical network of nodes performing binary operations. The nonlinearity
required for efficient computation is provided by semiconductor microcavities
in the strong quantum light-matter coupling regime, which exhibit
exciton–polariton interactions. We demonstrate the system performance
against a pattern recognition task, obtaining accuracy on a par with
state-of-the-art hardware implementations. Our work opens the way
to ultrafast and energy-efficient neuromorphic systems taking advantage
of ultrastrong optical nonlinearity of polaritons.
We study the dynamics of a two-dimensional Bose gas after an instantaneous quench of an initially ultracold thermal atomic gas across the Berezinskii-Kosterlitz-Thouless phase transition, confirming via stochastic simulations that the system undergoes phase ordering kinetics and fulfills the dynamical scaling hypothesis at late-time dynamics. Specifically, we find in that regime the vortex number decaying in time as Nv ∝ t −1 , consistent with a dynamical critical exponent z ≈ 2 for both temperature and interaction quenches. Focusing on finite-size box-like geometries, we demonstrate that such an observation is within current experimental reach. arXiv:1905.05263v1 [cond-mat.quant-gas]
We study the collective modes of the confined unitary Fermi gas under anisotropic harmonic confinement as a function of the number of atoms. We use the equations of extended superfluid hydrodynamics, which take into account a dispersive von Weizsäcker-like term in the equation of state. We also discuss the inclusion of a backflow term in the extended superfluid Lagrangian and the effects of this anomalous term on sound waves and the Beliaev damping of phonon
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