A comparative analysis of InGaAs SPADs and SNSPDs in entanglement-based Quantum communications

We present experimental results from a Quantum Key Distribution (QKD) setup based on entanglement, where polarization entangled photon pairs are distributed after narrowband filtering and followed by detection employing polarization-based receivers. A comparative analysis of the performance of InGaAs single photon avalanche detectors (SPADs) and superconducting nanowire single photon detectors (SNSPDs), reveals a notable advantage of SNSPDs for QKD applications. The entangled photon pairs are generated using a Sagnac-based polarization entanglement source, and subsequently split by Dense Wavelength Division Multiplexers (DWDMs). These entangled photon pairs are sent to two polarization-based receivers facilitating the comparison between the detection using InGaAs SPADs and SNSPDs. The results emphasize the superior performance of SNSPDs reflected in an around 80 times higher coincidence rate, therefore tolerating around 8 dB higher attenuation values. For both configurations and all considered attenuation levels, the fidelity and quantum bit error rate (QBER) are well inside the respective bounds for secure key generation. This work provides valuable insights for the optimization of QKD systems.