arXiv subjects

Ferruccio Renzoni

Publications and source records attributed to Ferruccio Renzoni.

27 records · Page 2Linked to original sources

arXiv2014

Irrationality and quasiperiodicity in driven nonlinear systems

We analyse the relationship between irrationality and quasiperiodicity in nonlinear driven systems. To that purpose we consider a nonlinear system whose steady-state response is very sensitive to the periodic or quasiperiodic character of the input signal. In the infinite time limit, an input signal consisting of two incommensurate frequencies will be recognised by the system as quasiperiodic. We show that this is in general not true in the case of finite interaction times. An irrational ratio of the driving frequencies of the input signal is not sufficient for it to be recognised by the nonlinear system as quasiperiodic, resulting in observations which may differ by several orders of magnitude from the expected quasiperiodic behavior. Thus, the system response depends on the nature of the irrational ratio, as well as the observation time. We derive a condition for the input signal to be identified by the system as quasiperiodic. Such a condition also takes into account the sub-Fourier response of the nonlinear system.

cond-mat.stat-mech↗

arXiv2013

Magnetic induction measurements using an all-optical $^{87}$Rb atomic magnetometer

In this work we propose, and experimentally demonstrate, the use of a self-oscillating all-optical atomic magnetometer for magnetic induction measurements. Given the potential for miniaturization of atomic magnetometers, and their extreme sensitivity, the present work shows that atomic magnetometers may play a key role in the development of instrumentation for magnetic induction tomography.

physics.atom-ph↗

arXiv2013

Control of transport in higher dimensional systems via dynamical decoupling of degrees of freedom with quasiperiodic driving fields

We consider the problem of the control of transport in higher dimensional periodic structures by applied ac fields. In a generic crystal, transverse degrees of freedom are coupled, and this makes the control of motion difficult to implement. We show, both with simulations and with an analytical functional expansion on the driving amplitudes, that the use of quasiperiodic driving significantly suppresses the coupling between transverse degrees of freedom. This allows a precise control of the transport, and does not require a detailed knowledge of the crystal geometry.

cond-mat.stat-mech↗

arXiv2013

Collective strong coupling in multimode cavity QED

We study an atom-cavity system in which the cavity has several degenerate transverse modes. Mode-resolved cavity transmission spectroscopy reveals well-resolved atom-cavity resonances for several cavity modes, a signature of collective strong coupling for the different modes. Furthermore, the experiment shows that the cavity modes are coupled via the atomic ensemble contained in the cavity. The experimental observations are supported by a detailed theoretical analysis. The work paves the way to the use of interacting degenerate modes in cavity-based quantum information processing, where qubits corresponding to different cavity modes interact via an atom shared by the two modes. Our results are also relevant to the experimental realization of quantum spin glasses with ultracold atoms.

physics.atom-ph↗

arXiv2003

Phase-control of directed diffusion in a symmetric optical lattice

We demonstrate the phenomenon of directed diffusion in a symmetric periodic potential. This has been realized with cold atoms in a one-dimensional dissipative optical lattice. The stochastic process of optical pumping leads to a diffusive dynamics of the atoms through the periodic structure, while a zero-mean force which breaks the temporal symmetry of the system is applied by phase-modulating one of the lattice beams. The atoms are set into directed motion as a result of the breaking of the temporal symmetry of the system.

quant-ph↗

arXiv2003

Damping rates of the atomic velocity in Sisyphus cooling

We present a theoretical and experimental study of the damping process of the atomic velocity in Sisyphus cooling. The relaxation rates of the atomic kinetic temperature are determined for a 3D lin$\perp$lin optical lattice. We find that the damping rates of the atomic temperature depend linearly on the optical pumping rate, for a given depth of the potential wells. This is at variance with the behavior of the friction coefficient as calculated from the spatial diffusion coefficients within a model of Brownian motion. The origin of this different behavior is identified by distinguishing the role of the trapped and traveling atoms.

quant-ph↗

arXiv2003

Rayleigh Scattering and Atomic Dynamics in Dissipative Optical Lattices

We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals (S. Guibal {\it et al}, Phys. Rev. Lett. {\bf 78}, 4709 (1997); C. Jurczak {\it et al}, Phys. Rev. Lett. {\bf 77}, 1727 (1996)), we study whether the Rayleigh resonance originates from the diffraction on a density grating, and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance.

quant-ph↗

arXiv2002

Dark propagation modes in optical lattices

We examine the stimulated light scattering onto the propagation modes of a dissipative optical lattice. We show that two different pump-probe configurations may lead to the excitation, via different mechanisms, of the same mode. We found that in one configuration the scattering on the propagation mode results in a resonance in the probe transmission spectrum while in the other configuration no modification of the scattering spectrum occurs, i.e. the mode is dark. A theoretical explanation of this behaviour is provided.

quant-ph↗

arXiv2002

Stochastic resonance in periodic potentials: realization in a dissipative optical lattice

We have observed the phenomenon of stochastic resonance on the Brillouin propagation modes of a dissipative optical lattice. Such a mode has been excited by applying a moving potential modulation with phase velocity equal to the velocity of the mode. Its amplitude has been characterized by the center-of-mass (CM) velocity of the atomic cloud. At Brillouin resonance, we studied the CM-velocity as a function of the optical pumping rate at a given depth of the potential wells. We have observed a resonant dependence of the CM velocity on the optical pumping rate, corresponding to the noise strength. This corresponds to the experimental observation of stochastic resonance in a periodic potential in the low-damping regime.

quant-ph↗