Inline SNSPDs coupled to photonic bound states for advanced on-chip detection functionalities
Filippo Martinelli, Anton N. Vetlugin, Shuyu Dong +4 more
We present the concept of inline detection with integrated superconducting nanowire single-photon detectors (SNSPDs), a promising approach to miniaturize quantum photonic circuits. By cascading multiple nanowires with controlled partial absorption along a single waveguide, complex detection functionalities can be realized within a compact footprint. To enable inline detectors, we developed an unconventional integration platform based on photonic bound states in etchless polymer waveguides that mitigates parasitic losses at the detectors termination. We demonstrate integrated devices with on-chip efficiency exceeding 80%, recovery time of less than 2 ns, and intrinsic jitter of less than 70 ps. As a proof of principle, we implement an inline Hanbury Brown and Twiss interferometry and photon number resolving detector. With a footprint of 60 × 6 µm², it is one of the most compact demonstrations of its kind to date. The concept of inline quantum measurements could be further developed to support miniaturization of more complex circuit functionalities, such as higher-order correlation measurements, quantum state tomography, and multi-photon subtraction within a compact footprint.
Quantum Computing, Communication, and Simulation•Mar 5, 2026•0 citations