Integrated Photonic Chips for Generating Entangled Photon Triplets

Harvard University, Cambridge MA

Investigators

Abstract

Quantum information technologies are a driving force for the advancement of fundamental physics and enable large-scale secure communication, unprecedented processor speeds, and higher resolution measurement techniques. These applications require a source of entangled photons, which act as bits of information with interesting quantum properties, as well as circuits that can manipulate and measure these photons. An almost unexplored approach is to generate triplets of entangled photons in a single step. This scheme significantly simplifies the generation of larger entangled states, enabling exciting quantum experiments and filling a huge gap in the development of quantum computers. In this project, the investigator and his students will use titanium dioxide (TiO2) integrated photonic circuits to produce triplets in a robust, scalable, and commercially viable format. Leveraging their expertise in TiO2, nonlinear optics and integrated photonic devices, the group will develop a source that directly produces entangled triplet photons at telecommunications wavelengths. Maturation of TiO2 and photonic integrated quantum circuits will move the field of quantum information science in the direction of commercializable products. While advancing the discoveries in the fields described above, this project will also contribute to the training of future multidisciplinary scientists and engineers through research-based education of undergraduate and graduate students. Quantum information technologies are a driving force for the advancement of fundamental theories and can enable large-scale secure networks, quantum information processors, and enhanced measurement and lithographic techniques. Photonics is an ideal platform for such technologies; however, the generation, manipulation, and detection of single and entangled photons remain a challenge. While sources of spontaneous single and pairs of photons are widespread, triplet-photon sources are almost completely unexplored and represent the missing link for fundamental tests in quantum theory and heralded photon pairs for quantum communication and computation. Furthermore, a triplet-photon source significantly simplifies the generation of larger entangled states. This project will seek to developm a source that can directly produce entangled triplet photons at telecommunications wavelengths (e.g., 1500 nm) at a rate of 4,000 triplets/sec (six orders of magnitude greater than current experimental efforts) using third-order spontaneous parametric down-conversion. By coupling to a resonant cavity, the group will further enhance the emission rate by an additional order of magnitude and improve spectral control. TiO2 is the ideal material for this process because of its high transparency, large nonlinearity, high linear refractive indices, and negligible fluorescence. The group will exploit the strong, sustained nonlinearity and tight light-confinement in TiO2 devices to achieve unprecedented triplet-photon generation rates directly on chip, where they can readily be routed, manipulated, and then measured using integrated detectors.