PR_29 Photon-Pair Generation using Coupled Silicon Microring Resonators (1201308-PO)

The physical principles of entangled photon-pair generation in coupled silicon microring resonators were studied theoretically and experimentally. Summary of a Project Outcomes report of research funded by the National Science Foundation under Project Number 1201308.

PR_34 Improved Photon-Pair Generation using Silicon Photonic Micro-resonators (1640968-Y1)

We focus on the development of key building blocks for entangled photon-pair generation using microchips that are cost-effective, compact, energy efficient and leverages modern micro-fabrication platforms such as silicon photonics. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1640968 (Year 1).

PR36 Towards the Integration of Microring-based Photon-Pair Sources in Silicon Photonics (1640968-Y3)

Our research focused on developing integrated pair sources using silicon photonics technology. This device uses a microring resonator for pair generation. Activities performed this year include measurements of silicon photonic entangled-pair and heralded single photon generation using an integrated photonic microchip that includes the pair generation resonator as well as tunable filters. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1640968 (Year 3).

PR37 An Alternative Strategy for Photon-Pair Generation using Integrated Photonics on Silicon Wafers (1640968-Y4)

Research activities include the design, fabrication and poling of a spontaneous parametric down-conversion (SPDC) waveguide in periodically-poled thin-film lithium niobate SPDC device, and measurements of photon-pair generation in it. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1640968 (Year 4).

Four-wave Mixing Using Silicon Microring CROWs (Project Report 0642603-Y4)

This NSF-funded project [0642603] is a five-year (60 months) CAREER (Faculty Early Career Development Program) unified research and education development program. The project’s focus is the science, engineering and applications of low-power (milliwatt class) nonlinear optics using a novel type of waveguide, the Coupled Resonator Optical Waveguide (CROW). Examples of applications of the nonlinear effects that were studied in this project are wavelength conversion of high speed modulated signals and correlated photon-pair generation.

Photon-Pair Generation from Chip-Scale Cs Atomic Vapor Cell

The realization of a narrowband photonic quantum source based on a chip-scale atomic device is considered essential in the practical development of photonic quantum information science and technology. In this study, we present the first step toward the development of a photon-pair source based on a microfabricated chip-scale Cs atomic vapor cell. Time-correlated photon pairs from the millimeter-scale Cs vapor cell are emitted via the spontaneous four-wave mixing process of the cascade-type 6S1/2–6P3/2–8S1/2 transition of 133Cs. The maximum normalized cross-correlation value between the signal and idler photons is measured as 622(8) under a weak pump power of 10 mW. Our photon source violates the Cauchy–Schwartz inequality by a factor of >105. We believe that our approach has very important applications in the context of realizing practical scalable quantum networks based on atom–photon interactions.

Quantum dot technology for quantum repeaters: from entangled photon generation towards the integration with quantum memories

The realization of a functional quantum repeater is one of the major research goals in long-distance quantum communication. Among the different approaches that are being followed, the one relying on quantum memories interfaced with deterministic quantum emitters is considered as one of the most promising solutions. In this work, we focus on the hardware to implement memory-based quantum-repeater schemes that rely on semiconductor quantum dots for the generation of polarization entangled photons. Going through the most relevant figures of merit related to efficiency of the photon source, we select significant developments in fabrication, processing and tuning techniques aimed at combining high degree of entanglement with on-demand pair generation, with a special focus on the progress achieved in the representative case of the GaAs system. We proceed to offer a perspective on integration with quantum memories, both highlighting preliminary works on natural-artificial atomic interfaces and commenting a wide choice of currently available and potentially viable memory solutions in terms of wavelength, bandwidth and noise-requirements. To complete the overview, we also present recent implementations of entanglement-based quantum communication protocols with quantum dots and highlight the next challenges ahead for the implementation of practical quantum networks.

Experimental investigation of a rotor blade tip vortex pair

This paper presents the results of an experimental study of two closely spaced vortices generated by a rotating blade with a modified tip geometry. The experiments are carried out in two water channel facilities and involve a generic one-bladed rotor operating in a regime near hover. It is equipped with a parametric fin placed perpendicular to the pressure surface near the tip, which generates a co-rotating vortex pair having a helical geometry. Based on previous results obtained with a fixed wing, a series of small-scale experiments is first carried out, to validate the method of vortex pair generation also for a rotating blade, and to obtain a qualitative overview of its evolution going downstream. A more detailed quantitative study is then performed in a larger facility at three times the initial scale. By varying the fin parameters, it was possible to obtain a configuration in which the two vortices have almost the same circulation. In both experiments, the vortex pair is found to merge into a single helical wake vortex within one blade rotation. Particle image velocimetry measurements show that the resulting vortex has a significantly larger core radius than the single tip vortex from a blade without fin. This finding may have relevance in the context of blade–vortex interactions, where noise generation and fatigue from fluid–structure interactions depend strongly on the vortex core size.