Your search for "ornigotti" returned 13 results

Linearized stochastic nanomechanical systems operating at nonzero temperatures and constant frequency and damping are restricted in their capacity to reduce noise in nonlinear combinations of the canonical variables. Nonlinear dynamics are then required in order to overcome these limits. Here we demonstrate how to make these limits explicit in the form of a threshold for nonlinear squeezing of the motional variables. Noise suppression below the threshold cannot be explained by linearized dynamics and is helpful in low-noise nonlinear devices at an ambient temperature. We predict that a state of the art levitating particle, exposed to cubic or quartic trapping potentials for a short interval will display nonlinear squeezing of stochastic motion that cannot be replicated by linear motion.

The Bloch sphere representation is a geometric model for all possible quantum states of a two-level system that can be used to describe the time dynamics of a qubit. As explicit application, we consider the time dynamics of a particle in a double-well potential. In particular, we adopt a recent method for off-resonant excitations, the so-called SUPER principle (Swing Up of the quantum emitter population) driven by periodic electromagnetic fields, to the context of quantum tunnelling. We show that the tunnelling probability can be enhanced significantly when an appropriate oscillation of the potential height is introduced. Driven by a collaborative approach we call educator-developer dialogue, an updated version of the software Quantum Composer is presented. For educational purposes, we map the two lowest energy states of the 1D-Schrödinger equation to the Bloch sphere representation, leading to a rather clear and intuitive physical picture for the pertinent time dynamics.

The evolution of entanglement in a non-Hermitian quantum system may behave differently compared to its Hermitian counterpart. In this paper, we investigate the entanglement dynamics of two coupled and driven non-Hermitian qubits. Through calculating the concurrence of the system, we find that the evolution of the bipartite entanglement manifests two distinct patterns in the parameter space. In the low non-Hermiticity regime, the concurrence oscillates significantly, while in the opposite regime the same quantity would trend to a stable value. We attribute this phenomenon to parity-time ($\mathcal{PT}$) symmetry phase transition. We also study the effect of decoherence on the entanglement dynamics. Our work provides a method to stabilize entanglement by exploiting non-Hermiticity.

The intrinsic connection between the transverse photonic spin Hall effect (PSHE) and the Imbert–Fedorov shift has been well characterized. However, physical insights into the longitudinal photonic spin splitting associated with the Goos-Hänchen (GH) shift remain elusive. This paper aims to expand the theory of the PSHE generation mechanism from the transverse to the longitudinal case by examining the reflection of each spin component from an arbitrarily linearly polarized incident Gaussian beam on the air-dielectric interface. Unlike the transverse case, both spin-maintained and spin-flipped modes exhibit non-zero longitudinal displacements, with the latter being affected by the second-order expansion term of the Fresnel reflection coefficient with respect to the in-plane wave-vector component. Meanwhile, the polarization angle plays a crucial role in determining the longitudinal PSHE since each reflected total spin component is a coherent superposition of these two corresponding modes. Remarkably, the imaginary part of the relative permittivity of the dielectric significantly affects the symmetry of the longitudinal PSHE. Furthermore, the GH shift results from a superposition of individual spin states' longitudinal displacements, taking into account their energy weights. By incorporating the corresponding extrinsic orbital angular momentum, we explore the generation mechanism of the symmetric/asymmetric longitudinal PSHE. The unified physical framework elucidating the longitudinal photonic spin splitting and GH shift provides a comprehensive understanding of the fundamental origin of the PSHE and beam shifts, paving the way for potential applications in spin-controlled nanophotonics.

A novel formulation of the Lie-Darboux method of obtaining the Riccati equations for the spatial curves in Euclidean three-dimensional space is presented. It leads to two Riccati equations that differ by the sign of torsion. The case of cylindrical helices is used as an illustrative example. Possible applications in Physics are suggested.

We provide a method to obtain a complete set of eigenstates analytically and the corresponding eigenvalues in one type of N-multiple well potentials. The quantum well profile can be adjusted by many different parameters, which could be applicable to many different physical situations. We demonstrate explicitly the series of eigenstates in double and triple well potentials, which can be used to describe Josephson oscillations and other tunneling dynamics conveniently. The analytic solutions can be used to discuss the topological vector potential hidden in the eigenstates of quantum wells, through performing our recently proposed method of extending Dirac's monopole theory to a complex plane. Our results suggest that each node of eigenfunctions corresponds to the merging of a pair of magnetic monopoles with inverse charge. The underlying monopoles can be used to determine the phase jump of a pure real wave function with nodes, as observed from an experimental viewpoint.

The effect of surface phonon polaritons (SPhPs) on Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts of reflected rotating elliptical Gaussian beams (REGBs) is investigated in the Otto configuration with a naturally hyperbolic material (NHM) substrate. The spatial shifts are enhanced significantly and adjusted by tuning the REGBs and the optical axis orientation of NHM. The magnitude of GH and IF shifts is easily evaluated by timing the elliptical parameter ${b}_{0}^{2}$ on the basis of the spatial shift at ${b}_{0}=1.0$ when $\eta (={a}_{0}/{b}_{0})\geqslant 2.0.$ The attenuation total reflection (ATR) spectra are simulated for a hexagonal boron nitride (hBN) substrate. To better understand the impact of SPhPs on the GH and IF shifts, the dispersion curves of SPhPs are calculated. The features of GH and IF shifts around SPhPs can be observed through the frequency scanning along the dispersion curves at a fixed incident angle. The comparison between the ATR spectra and the dispersion curves demonstrates that the enhancement of GH and IF shifts with higher reflection always occurs in the reststrahlen bands (RBs) of NHM once SPhPs are excited. In RB-I, the magnitudes of GH and IF shifts attributable to the SPhPs are located between the peak and dip of a shift curve within a very narrow frequency region. However, in RB-II, the positive maximum values of GH and IF shifts just coincide with the SPhPs. As a result, it is predicted that a relatively large spatial shift will be observed along the frequency scanning line. The large shifts accompanied by the higher reflection may show potential applications in optical or optoelectronic technologies.

We construct the exact solution of a non-Hermitian $\mathscr{PT}$-symmetric isotropic Heisenberg spin chain with integrable boundary fields. We find that the system exhibits two types of phases named A and B. In the B type phase, the $\mathscr{PT}$ symmetry remains unbroken and it comprises of eigenstates with only real energies, whereas the A type phase exhibits both $\mathscr{PT}$ symmetry broken and unbroken sectors, comprising of eigenstates with only complex and real energies respectively. The $\mathscr{PT}$-symmetry broken sector comprises of pairs of eigenstates whose energies are complex conjugates of each other. The existence of two sectors in the A type phase is associated with the exponentially localized bound states at the edges with complex energies which are described by boundary strings. We find that both A and B type phases can be further divided into sub-phases which exhibit different ground states. We also compute the bound state wavefunction in one magnon sector and find that as the imaginary value of the boundary parameter is increased, the exponentially localized wavefunction broadens thereby protruding more into the bulk, which indicates that exponentially localized bound states may not be stabilized for large imaginary values of the boundary parameter.

We introduce a two-parameter ensemble of generalized $2\times 2$ real symmetric random matrices called the β-Rosenzweig–Porter ensemble (β-RPE), parameterized by β, a fictitious inverse temperature of the analogous Coulomb gas model, and γ, controlling the relative strength of disorder. β-RPE encompasses RPE from all of the Dyson's threefold symmetry classes: orthogonal, unitary and symplectic for $\beta = 1,2,4$. Firstly, we study the energy correlations by calculating the density and 2nd moment of the nearest neighbor spacing (NNS) and robustly quantify the crossover among various degrees of level repulsions. Secondly, the dynamical properties are determined from an exact calculation of the temporal evolution of the fidelity enabling an identification of the characteristic Thouless and the equilibration timescales. The relative depth of the correlation hole in the average fidelity serves as a dynamical signature of the crossover from chaos to integrability and enables us to construct the phase diagram of β-RPE in the γ-β plane. Our results are in qualitative agreement with numerically computed fidelity for $N\gg2$ matrix ensembles. Furthermore, we observe that for large N the 2nd moment of NNS and the relative depth of the correlation hole exhibit a second order phase transition at γ = 2.

We report on an experimental investigation of the Goos–Hänchen (GH) optical beam shift in the vicinity of the critical angle of incidence at an air–glass interface using a weak value amplification (WVA) technique for two mutually orthogonal first order Hermite–Gaussian (HG) modes (HG₁₀ and HG₀₁) of a light beam at 633 nm generated by a phase-only reflective spatial light modulator. We have developed a mathematical approach to visualize the beam shaping due to the WVA scheme of beam shifts for the HG modes. The study reveals the angle of incidence dependency of the GH shift in the total internal reflection condition. For both modes, a detailed study of the horizontal and transverse beam shift values with varied post-selection angles is also reported. In addition, a comparison of the beam shift values for both of the selected modes with the fundamental mode (HG₀₀) has been demonstrated. We found a significant enhancement (about two to three times) in the beam shifts for the first order HG₁₀ and HG₀₁ modes compared to the fundamental mode (HG₀₀). Our results clearly demonstrate the advantages of the HG modes of the light beam-exploiting WVA technique and thus may contribute significantly to this field and open up important applications in photonic manipulation and future technologies.