We present a proposal for creating high-dimensional entangled photon pairs in a tapered silicon waveguide through intermodal four-wave mixing. We show that 4D Bell states can be obtained with 98 % fidelity.
Silicon photonics is rapidly emerging as a promising, scalable platform for quantum information applications. As the technology matures, sources of high-quality quantum-optical states are increasingly important. We discuss the use of intermodal four-wave mixing in silicon waveguides for creating entangled photon pairs. We describe a framework to numerically analyze the state of produced photon pairs and discuss a scheme for generating photon pairs that are purely entangled in their transverse waveguide mode. Using this scheme, we find a theoretical fidelity of 99.6 % to a true Bell state in the transverse mode with no spectral correlations.
Abstract Integrated entangled photon pair source is an essential resource for both fundamental investigations and practical applications of quantum information science. Currently there have been several types of entanglement, among which the transverse-mode entanglement is becoming attractive because of its unique advantages. Here, we report an on-chip transverse-mode entangled photon pair source via the spontaneous four-wave mixing processes in a multimode silicon waveguide. Transverse-mode photon pairs are verified over multiple frequency channels within a bandwidth of ~2 THz, and a maximally entangled Bell state is also produced with a net fidelity of 0.96 ± 0.01. Our entangled photon pair source is the key element for quantum photonics based on transverse-mode, and also has the possibility to extend to higher-dimensional Hilbert space. Furthermore, the transverse-mode entanglement can be converted coherently to path and polarization entanglement, which paves the way to realizing highly complex quantum photonic circuits with multiple degrees of freedom.