arXiv subjects

Omar Morandi

Publications and source records attributed to Omar Morandi.

8 recordsLinked to original sources

arXiv2026

Synthetic Seismograms from Particle Bed Interactions and Turbulent River Flow: Modeling and Comparison with Observations

We present a physics based numerical model that estimates the seismic radiation generated by water sediment flows in gravel-bed rivers. The model reproduces the trajectories of individual particles, evaluates impact and rolling forces from grain scale dynamics, and accounts for broadband turbulence and vortex shedding in the water column. Synthetic seismic signals are propagated to the receivers using the Rayleigh wave Green s function approach and synthetic ground-velocity signals are estimated. Application to a controlled test case shows how intermittent, size selective sediment transport mechanisms produce distinct spectral signatures. Comparison with seismic data from a flood event in a mountain torrent in the Tuscan Apennines displays general agreement with the observed frequency bands and clarifies the relative width of particle collisions and turbulent flow. These results show that resolved grain scale dynamics provides a framework for discriminating sediment transport and flow induced contributions to river seismic noise.

math-ph↗

arXiv2025

Deterministic classical limit of the optimal control problem of quantum particles with spin

We study the optimal control problem applied to a gas of particles with spin confined in a material with Rashba spin-orbit coupling effect, in the presence of an external magnetic field. The evolution of the particle gas is described in the Wigner formalism. We investigate the classical limit of the optimal control problem, and we prove the convergence of the solution of the quantum problem toward the solution of a simplified optimal control model, based on an ODE description of the particle gas in terms of a single spin vector traveling along a classical trajectory in the phase-space.

math.OC↗

arXiv2025

Optimal control of geometric phase in pairs of interacting atoms traveling along two-dimensional closed paths

Universal quantum gates whose operation depends on the manipulation of the geometric phase of atomic systems are promising candidates for implementation of quantum computing. We propose a scheme inducing a non-trivial Aharonov-Anandan geometric phase in pairs of atoms interacting via dipole-dipole potential. Our protocol relies on mobile optical trap technology and consists of steering a single atom along a closed loop. The trajectory of the atom is controlled by a mobile optical trap, and the shape of the path is designed by applying an optimal control procedure. The geometric phase is generated as a residual of the two-atom entanglement induced by the dipole-dipole interaction. The stability of our scheme in the presence of noise or experimental imperfections is discussed.

quant-ph↗

arXiv2025

Optimal control in phase space applied to minimal-time transfer of thermal atoms in optical traps

We present an optimal control procedure for the non-adiabatic transport of ultracold neutral thermal atoms in optical tweezers arranged in a one-dimensional array, with focus on reaching minimal transfer time. The particle dynamics are modeled first using a classical approach through the Liouville equation and second through the quantum Wigner equation to include quantum effects. Both methods account for typical experimental noise described as stochastic effects through Fokker-Planck terms. The optimal control process is initialized with a trajectory computed for a single classical particle and determines the phase-space path that minimizes transport time and ensures high transport fidelity to the target trap. This approach provides the fastest and most efficient method for relocating atoms from an initial configuration to a desired target arrangement, minimizing time and energy costs while ensuring high fidelity. Such an approach may be highly valuable to initialize large atom arrays for quantum simulation or computation experiments.

quant-ph↗

arXiv2017

Chirped-Frequency Excitation of Gravitationally Bound Ultracold Neutrons

Ultracold neutrons confined in the Earth's gravitational field display quantized energy levels that have been observed for over a decade. In recent resonance spectroscopy experiments [T. Jenke et al., Nature Phys. 7, 468 (2011)], the transition between two such gravitational quantum states was driven by the mechanical oscillation of the plates that confine the neutrons. Here we show that, by applying a sinusoidal modulation with slowly varying frequency (chirp), the neutrons can be brought to higher excited states by climbing the energy levels one by one. The proposed experiment should make it possible to observe the quantum-classical transition that occurs at high neutron energies. Furthermore, it provides a technique to realize superpositions of gravitational quantum states, to be used for precision tests of gravity at short distances.

quant-ph↗

arXiv2014

Semiclassical Vlasov and fluid models for an electron gas with spin effects

We derive a four-component Vlasov equation for a system composed of spin-1/2 fermions (typically electrons). The orbital part of the motion is classical, whereas the spin degrees of freedom are treated in a completely quantum-mechanical way. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function. This hydrodynamic model is closed using a maximum entropy principle in the case of three or four constraints on the fluid moments, both for Maxwell-Boltzmann and Fermi-Dirac statistics.

physics.plasm-ph↗

arXiv2014

A multi-band semiclassical model for surface hopping quantum dynamics

In the paper we derive a semiclassical model for surface hopping allowing quantum dynamical non-adiabatic transition between different potential energy surfaces in which cases the classical Born-Oppenheimer approximation breaks down. The model is derived using the Wigner transform and Weyl quantization, and the central idea is to evolve the entire Wigner matrix rather than just the diagonal entries as was done previously in the adiabatic case. The off-diagonal entries of the Wigner matrix suitably describe the non-adiabatic transition, such as the Berry connection, for avoided crossings. We study the numerical approximation issues of the model, and then conduct numerical experiments to validate the model.

math.NA↗

arXiv2006

A multiband envelope function model for quantum transport in a tunneling diode

We present a simple model for electron transport in semiconductor devices that exhibit tunneling between the conduction and valence bands. The model is derived within the usual Bloch-Wannier formalism by a k-expansion, and is formulated in terms of a set of coupled equations for the electron envelope functions. Its connection with other models present in literature is discussed. As an application we consider the case of a Resonant Interband Tunneling Diode, demonstrating the ability of the model to reproduce the expected behaviour of the current as a function of the applied voltage

cond-mat.mes-hall↗