Addressable refraction and curved soliton waveguides using electric interfaces

A great deal of interest over the years has been directed to the optical space solitons for the possibility of realizing 3D waveguides with very low propagation losses. A great limitation in their use for writing complex circuits is represented by the impossibility of making curved structures. In the past, solitons in nematic liquid crystals, called nematicons, were reflected on electrical interfaces, and recently on photorefractive spatial solitons as well. In the present work we investigate refraction and total reflection of spatial solitons with saturable electro-optic nonlinearity, such as the photorefractive ones, on an electric wall acting as a reflector. Using a custom FDTD code, the propagation of a self-confined beam was analyzed as a function of the applied electric bias. The electrical reflector has been simulated by applying different biases in two adjacent volumes. We have observed both smaller and larger angles of refraction, up to the critical π/2-refraction condition and then total reflection. The radii of curvature of the associated guides can be varied from centimeters down to hundreds of microns. The straight guides showed losses down to 0.07 dB/cm as previously observed, while the losses associated with single curves were estimated down to 0.2 dB

Solid-State Quantum Communication With Josephson Arrays

Josephson junction arrays can be used as quantum channels to transfer quantum information between distant sites. In this work we discuss simple protocols to realize state transfer with high fidelity. The channels do not require complicate gating but use the natural dynamics of a properly designed array. We investigate the influence of static disorder both in the Josephson energies and in the coupling to the background gate charges, as well as the effect of dynamical noise. We also analyze the readout process, and its backaction on the state transfer

Steady-state entanglement activation in optomechanical cavities

Quantum discord, and a number of related indicators, are currently raising a relentless interest as a novel paradigm of non-classical correlations beyond entanglement. Beside merely fundamental aspects, various works have shown that discord is a valuable -- so far largely unexplored -- resource in quantum information processing. Along this line, quite a striking scheme is {entanglement activation}. An initial amount of discord between two disentangled parties of a multipartite system affects the dynamics so as to establish entanglement across a bipartition, which would not arise otherwise. To date, such a process was proven to be achievable only dynamically, i.e., with no guarantee of a stationary entanglement throughput in the presence of noise. Here, we discover a {\it discord-activated mechanism yielding steady-state entanglement} production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.Comment: 5+4 pages, 5+1 figures (main text + supplementary materials

Study of magnetic switch for surface plasmon-polariton circuits

In recent years, technological development has focused on the construction of ever smaller devices, characterized by dimensions limited to the nanometer order and by a very low energy requirement to be able to function. This allows them to be integrated into chips, which are then able to perform many tasks from filtering to computation. Here, we present a magnetic switch capable of working with surface plasmon polaritons

Supervised learning of soliton X-junctions in lithium niobate films on insulator

In this Letter, the first implementation, to our knowledge, of X-junctions between photorefractive soliton waveguides in lithium niobate-on-insulator (LNOI) films is reported. The experiments were performed on 8 μm thick films of congru- ent undoped LiNbO3. Compared with bulk crystals, the use of films reduces the soliton formation time, allows more con- trol over the interaction between the injected soliton beams, and opens a route to integration with silicon optoelectronics functions. The created X-junction structures show effective supervised learning, directing the signals propagated inside the soliton waveguides into the output channels highlighted by the control assigned by the external supervisor. Thus, the obtained X-junctions have behaviors analogous to biological neurons

Plasmonic-Solitonic coupling structure

The applications of optics, in particular non-linear optics, have joined the electrical ones in many contexts, often equaling or exceeding them thanks to the characteristics ensured by the physical nature of light such as high speed of propagation and low losses. In recent years, nanotechnologies combined with plasmon propagation are shaping a new development scenario that touches areas such as medicine, robotics or neurobiology. In fact, nano-devices are able to reproduce a very large number of functions ensuring very small dimensions. Among these, the applications of surface plasmon polariton waves are becoming more and more important, thanks to their peculiar behavior both as an electric wave and as a light wave. In this work we present an innovative structure consisting of a nano metallic waveguide on which it is possible to propagate a surface-plasmon- polariton signal at the interface with a photorefractive dielectric material. At the end of the guide, the diffracting light can generate, under suitable conditions, a self-confined light beam (bright-screening-photorefractive soliton). In this way the polariton plasmon waves propagating at the interface are automatically coupled within a soliton-based optical waveguide. By definition, soliton guides have very low propagation losses, opening the possibility of using this type of hybrid interconnection in extended complex circuits, for example as memories, thanks to the intrinsic plasticity of the photorefractive nonlinear refractive index

Adiabatic dynamics in open quantum critical many-body systems

The purpose of this work is to understand the effect of an external environment on the adiabatic dynamics of a quantum critical system. By means of scaling arguments we derive a general expression for the density of excitations produced in the quench as a function of its velocity and of the temperature of the bath. We corroborate the scaling analysis by explicitly solving the case of a one-dimensional quantum Ising model coupled to an Ohmic bath.Comment: 4 pages, 4 figures; revised version to be published in Phys. Rev. Let

Quantum Effects on the Synchronization Dynamics of the Kuramoto Model

The Kuramoto model serves as a paradigm for describing spontaneous synchronization in a system of classical interacting rotors. In this study, we extend this model to the quantum domain by coupling quantum interacting rotors to external baths following the Caldeira-Leggett approach. Studying the mean-field model in the overdamped limit using Feynman-Vernon theory, we show how quantum mechanics modifies the phase diagram. Specifically, we demonstrate that quantum fluctuations hinder the emergence of synchronization, albeit not entirely suppressing it. We examine the phase transition into the synchronized phase at various temperatures, revealing that classical results are recovered at high temperatures while a quantum phase transition occurs at zero temperature. Additionally, we derive an analytical expression for the critical coupling, highlighting its dependence on the model parameters, and examine the differences between classical and quantum behavior.Comment: 14 pages, 5 figure

Full Counting Statistics in Strongly Interacting Systems: Non-Markovian Effects

We present a theory of full counting statistics for electron transport through interacting electron systems with non-Markovian dynamics. We illustrate our approach for transport through a single-level quantum dot and a metallic single-electron transistor to second order in the tunnel-coupling strength, and discuss under which circumstances non-Markovian effects appear in the transport properties.Comment: 4 pages, 2 figures, LaTeX; typos added, references adde