Suppression of external noise in on-chip photon-pair sources

Quantum photonic integrated circuits are ideal for photon-based complex quantum information systems due to their size, stability, and scalability. Photon-pair sources integrated into these circuits help reduce connection losses. These pairs are generated by pumping strong light through optical fibers into the chip, which can introduce unwanted noise photons, lowering the performance of quantum sources. Here, we studied photon pairs generated solely from on-chip sources to improve quantum photonic applications. External filtering often fails due to environmental influences, leading us to propose on-chip filters before and after photon-pair generation to mitigate external noise. We fabricated silicon waveguides with and without on-chip asymmetric Mach–Zehnder interferometer filters and analyzed photon pair properties through experiments. The results showed that on-chip filters effectively eliminate external noise, tripling the coincidence-to-accidental coincidence ratio. This suggests that on-chip filtering holds significant promise for enhancing quantum photonic applications like quantum communications and computations.