Generation of Entangled Photon Pairs from a Silicon Bichromatic Photonic Crystal Cavity

<p>Integrated quantum photonics leverages the on-chip generation of nonclassical states of light to realize key function-<br>alities of quantum devices. Typically, the generation of such nonclassical states relies on whispering gallery mode<br>resonators, such as integrated optical micro-rings, which enhance the efficiency of the underlying spontaneous non-<br>linear processes. While this kind of resonators excel in maximizing either the temporal confinement or the spatial<br>overlap between different resonant modes, they are usually associated with large mode volumes, imposing an intrin-<br>sic limitation on the device efficiency and footprint. Here, we engineer a source of time-energy entangled photon<br>pairs based on a silicon photonic crystal cavity, implemented in a fully CMOS-compatible platform. In this device,<br>resonantly enhanced spontaneous four-wave mixing converts pump photon pairs into signal/idler photon pairs at the<br>energy-conserving condition in the telecommunication C-band. The design of the resonator is based on an effective<br>bichromatic confinement potential, allowing to achieve up to 9 close-to-equally spaced modes in frequency, while pre-<br>serving small mode volumes, and the whole chip, including grating couplers and access waveguides, is fabricated in<br>a single run on a silicon-on-insulator platform. Besides demonstrating efficient photon pair generation, we also im-<br>plement a Franson-type interference experiment, demonstrating entanglement between signal and idler photons with<br>a Bell inequality violation exceeding 5 standard deviations. The high generation efficiency combined with the small<br>device footprint in a CMOS-compatible integrated structure opens a pathway towards the implementation of compact<br>quantum light sources in all-silicon photonic platforms.</p>