Nonlinear quantum logic with colliding graphene plasmons

Graphene has emerged as a promising platform to bring nonlinear quantum optics to the nanoscale, where a large intrinsic optical nonlinearity enables long-lived and actively tunable plasmon polaritons to strongly interact. Here we theoretically study the collision between two counter-propagating plasmons in a graphene nanoribbon, where transversal subwavelength confinement endows propagating plasmons with %large effective masses a flat band dispersion that enhances their interaction. This scenario presents interesting possibilities towards the implementation of multi-mode polaritonic gates that circumvent limitations imposed by the Shapiro no-go theorem for photonic gates in nonlinear optical fibers. As a paradigmatic example we demonstrate the feasibility of a high fidelity conditional $\pi$ phase shift (CZ), where the gate performance is fundamentally limited only by the single plasmon lifetime. These results open new exciting avenues towards quantum information and many-body applications with strongly-interacting polaritons.Comment: 13 pages, 4 figure

High-harmonic generation enhancement with graphene heterostructures

We investigate high-harmonic generation in graphene heterostructures consisting of metallic nanoribbons separated from a graphene sheet by either a few-nanometer layer of aluminum oxide or an atomic monolayer of hexagonal boron nitride. The nanoribbons amplify the near-field at the graphene layer relative to the externally applied pumping, thus allowing us to observe third- and fifth-harmonic generation in the carbon monolayer at modest pump powers in the mid-infrared. We study the dependence of the nonlinear signals on the ribbon width and spacer thickness, as well as pump power and polarization, and demonstrate enhancement factors relative to bare graphene reaching 1600 and 4100 for third- and fifth-harmonic generation, respectively. Our work supports the use of graphene heterostructures to selectively enhance specific nonlinear processes of interest, an essential capability for the design of nanoscale nonlinear devices

Giant enhancement of third-harmonic generation in graphene-metal heterostructures

Nonlinear nanophotonics leverages engineered nanostructures to funnel light into small volumes and intensify nonlinear optical processes with spectral and spatial control. Due to its intrinsically large and electrically tunable nonlinear optical response, graphene is an especially promising nanomaterial for nonlinear optoelectronic applications. Here we report on exceptionally strong optical nonlinearities in graphene-insulator-metal heterostructures, demonstrating an enhancement by three orders of magnitude in the third-harmonic signal compared to bare graphene. Furthermore, by increasing the graphene Fermi energy through an external gate voltage, we find that graphene plasmons mediate the optical nonlinearity and modify the third-harmonic signal. Our findings show that graphene-insulator-metal is a promising heterostructure for optically-controlled and electrically-tunable nano-optoelectronic components

Automatic 3D Reconstruction of Structured Indoor Environments

Creating high-level structured 3D models of real-world indoor scenes from captured data is a fundamental task which has important applications in many fields. Given the complexity and variability of interior environments and the need to cope with noisy and partial captured data, many open research problems remain, despite the substantial progress made in the past decade. In this tutorial, we provide an up-to-date integrative view of the field, bridging complementary views coming from computer graphics and computer vision. After providing a characterization of input sources, we define the structure of output models and the priors exploited to bridge the gap between imperfect sources and desired output. We then identify and discuss the main components of a structured reconstruction pipeline, and review how they are combined in scalable solutions working at the building level. We finally point out relevant research issues and analyze research trends