Time-bin entanglement at telecom wavelengths from a hybrid photonic integrated circuit

Mass-deployable implementations for quantum communication require compact, reliable, and low-cost hardware solutions for photon generation, control and analysis. We present a fiber-pigtailed hybrid photonic circuit comprising nonlinear waveguides for photon-pair generation and a polymer interposer reaching \({68}\,\hbox {dB}\) $68\text{dB}$ of pump suppression and photon separation based on a polarizing beam splitter with \(>{25}\,\hbox {dB}\) $>25\text{dB}$ polarization extinction ratio. The optical stability of the hybrid assembly enhances the quality of the entanglement, and the efficient background suppression and photon routing further reduce accidental coincidences. We thus achieve a \(\left( 96_{-8}^{+3}\right) \%\) $\left({96}_{-8}^{+3}\right)\%$ concurrence and a \(\left( 96_{-5}^{+2}\right) \%\) $\left({96}_{-5}^{+2}\right)\%$ fidelity to a Bell state. The generated telecom-wavelength, time-bin entangled photon pairs are ideally suited for distributing Bell pairs over fiber networks with low dispersion.