Generation of quantum light deterministically and at telecommunications wavelengths has been an insurmountable challenge for execution of quantum networking protocols in a scalable manner, as telecom photons can travel with minimal loss through optical fiber networks, distributing quantum entanglement over long distances. Semiconductor quantum dots have emerged as the most promising platform to generate entangled photons deterministically, enabling scalable quantum networking applications. However, high quality quantum dots operate at wavelengths outside of the telecom bandwidth, and therefore, efficient and low-noise quantum frequency converters are needed to use these quantum emitters for quantum networking purposes. To date, fiber-coupled deterministic entangled photon sources with high efficiency have not been demonstrated, not even at wavelengths other than telecom. This proposal focuses on developing such a source based on quantum dots, coupled to a frequency converter to enable low-loss fiber communications. The focus of this Phase I project is to show the feasibility of developing fiber-coupled quantum emitters and frequency converters separately, and the feasibility for their integration. High-quality-factor optical cavities will be designed and fabricated that, when coupled to quantum dots, ensure efficient extraction of the quantum dot emission into a single-mode fiber. During a separate effort, the feasibility of a frequency converter will be studied, based on a material with ultra-low loss and high nonlinear coefficient, periodically poled thin-film lithium niobate. Thin-film lithium niobate has emerged as a promising platform for integrated quantum photonics, supporting functionalities such as low-loss routing, high-speed switching, and nonlinear quantum processes. Together with high-quality-factor optical cavities, the feasibility of deterministic generation of entangled photon pairs at telecom wavelengths will be shown during Phase I. Anticipated
Benefits: Deterministic entanglement generation and distribution with high quality, rates, and efficiency is a long-lasting challenge and has applications in quantum communications, quantum sensing, and quantum computation. We address this challenge by combining a quantum dot platform for deterministic entanglement generation, with a lithium niobate device that can shift the frequency of the generated photons to telecom wavelength which are compatible with low-loss fiber networks, enabling long-distance entanglement distribution. Our project addresses key concerns about the rate and reach of entanglement distribution. Entangling distant nodes in a quantum network is of interest for quantum networking testbed providers such as Cisco and Oak Ridge National Laboratory, who are keenly interested in using our devices in their networks for data security and sensing applications.
