Entangled photons on a chip

Dongpeng Kang, Nima Zareian, Amr Saher Helmy

Generating entangled photons on monolithic chips is a significant progress towards real-life applications of optical quantum information processing such as quantum key distribution and quantum computing. Here we present our recent achievements in generating polarization entangled photons on monolithic III-V semiconductor chips without any off-chip component. We demonstrate the direct generation of broadband polarization entangled photons from a semiconductor chip for the first time with a record degree of entanglement. We also show an alternative approach for polarization entangled photon generation on the same epitaxial structure, which enabled a single chip generating both co-polarized and cross-polarized entangled photons. With recent progress on pump laser integration, our results pave the way for fully integrated entangled photon sources in the foreseeable future.

Filippo Cardano, Lorenzo Marrucci

Alexander S. Solntsev, Andrey A. Sukhorukov

Photon entanglement has a range of applications from secure communication to the tests of quantum mechanics. Utilizing optical nonlinearity for the generation of entangled photons remains the most widely used approach due to its quality and simplicity. The on-chip integration of entangled light sources has enabled the increase of complexity and enhancement of stability compared to bulk optical implementations. Entanglement over different optical paths is uniquely suited for photonic chips, since waveguides are typically optimized for particular wavelength and polarization, making polarization- and frequency-entanglement less practical. In this review we focus on the latest developments in the field of on-chip nonlinear path-entangled photon sources. We provide a review of recent implementations and compare various approaches to tunability, including thermo-optical, electro-optical and all-optical tuning. We also discuss a range of important technical issues, in particular the on-chip separation of the pump and generated entangled photons. Finally, we review different quality control methods, including on-chip quantum tomography and recently discovered classical-quantum analogy that allows to characterize entangled photon sources by performing simple nonlinear measurements in the classical regime.

Andreas Reinhard, Thomas Volz, Martin Winger +4 more

Jianwei Wang, Damien Bonneau, Matteo Villa +12 more

We demonstrate high-fidelity distribution of entanglement across two integrated silicon photonic chips, by observing a violation of a Bell-type inequality of 2.638±0.039. Entanglement states are generated and measured on-chip, and coherently distributed between chips.

Giacomo Prando