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S. Gentilini

Publications and source records attributed to S. Gentilini.

5 recordsLinked to original sources

Precision Hamiltonian Encoding in Full-Aperture Spatial Photonic Ising Machines

Spatial photonic Ising machines (SPIMs) offer compact, room-temperature hardware with inherently parallel, energy-efficient, single-shot optical evaluation of the Ising Hamiltonian. However, accurate operation has been fundamentally limited by optical aberrations and non-uniform illumination, which corrupt phase-based spin encoding and distort coupling representation, forcing operation to a restricted spatial light modulator (SLM) region. Here we introduce a high-precision full-aperture calibration scheme that overcomes these constraints. By implementing wavefront retrieval and correction with $<\lambda/40$ accuracy, we restore faithful phase encoding across the entire SLM area. Furthermore, we introduce an interaction-normalization method, which compensates for amplitude curvature and enables uniform coupling representation. Together, these advances establish a full-aperture SPIM architecture whose faithful Hamiltonian encoding is a prerequisite for photonic Ising computation.

physics.optics

Shock waves in thermal lensing

We review experimental investigation on spatial shock waves formed by the self-defocusing action of a laser beam propagation in a disordered thermal nonlinear media.

physics.optics

Shock waves in disordered media

We experimentally investigate the interplay between spatial shock waves and the degree of disorder during nonlinear optical propagation in a thermal defocusing medium. We characterize the way the shock point is affected by the amount of disorder and scales with wave amplitude. Evidence for the existence of a phase diagram in terms of nonlinearity and amount of randomness is reported. The results are in quantitative agreement with a theoretical approach based on the hydrodynamic approximation.

physics.optics

Shear banding phenomena in a Laponite suspension

Shear localization in an aqueous clay suspension of Laponite is investigated through dynamic light scattering, which provides access both to the dynamics of the system (homodyne mode) and to the local velocity profile (heterodyne mode). When the shear bands form, a relaxation of the dynamics typical of a gel phase is observed in the unsheared band soon after flow stop, suggesting that an arrested dynamics is present during the shear localization regime. Periodic oscillations of the flow behavior, typical of a stick-slip phenomenon, are also observed when shear localization occurs. Both results are discussed in the light of various theoretical models for soft glassy materials.

physics.flu-dyn

Aging after shear rejuvenation in a soft glassy colloidal suspension: evidence for two different regimes

The aging dynamics after shear rejuvenation in a glassy, charged clay suspension have been investigated through dynamic light scattering (DLS). Two different aging regimes are observed: one is attained if the sample is rejuvenated before its gelation and one after the rejuvenation of the gelled sample. In the first regime, the application of shear fully rejuvenates the sample, as the system dynamics soon after shear cessation follow the same aging evolution characteristic of normal aging. In the second regime, aging proceeds very fast after shear rejuvenation, and classical DLS cannot be used. An original protocol to measure an ensemble averaged intensity correlation function is proposed and its consistency with classical DLS is verified. The fast aging dynamics of rejuvenated gelled samples exhibit a power law dependence of the slow relaxation time on the waiting time.

cond-mat.soft