The technology of integrated photonic quantum chips has successfully enabled the on-chip preparation, manipulation, and detection of photonic quantum states, thereby significantly accelerating the advancement of quantum communication, quantum computing, and quantum information technologies. Within photonic quantum chip systems, single-photon detectors play a pivotal role by accurately identifying single-photon statistics and measuring quantum states of photons, ensuring efficient readout of quantum information. Detection efficiency quantifies the probability that a detector successfully captures an incident photon. In multi-photon detection tasks involving n photons, the overall detection probability is given by the detection efficiency raised to the n th power. Even minor reductions in detection efficiency can lead to a dramatic decline in multi-photon detection probability as n increases. Consequently, in large-scale photonic quantum computing applications, enhancing multi-photon detection capability necessitates the on-chip integration of large-scale single-photon detector arrays, wherein each detector must operate at a detection efficiency approaching the theoretical maximum of 100%.
In a newly published paper in * Light: Science & Applications *, a collaborative team from Nanjing University and Peking University has developed an innovative approach to achieve an on-chip detection efficiency exceeding 99%, representing a breakthrough in photon detection performance. A novel comb-like structure was proposed, in which the nanowires were oriented transversely with respect to the optical waveguide. Compared to the conventional hairpin configuration, the corners of the comb nanowires are positioned outside the waveguide region, thereby eliminating efficiency loss—an often-overlooked factor that becomes increasingly significant as detection efficiency approaches unity. However, due to the absence of mechanical support, this comb structure is incompatible with conventional bottom-up planar fabrication techniques.
To address this limitation, the research team implemented a hybrid integration strategy, fabricating the detector as a flexible membrane device and subsequently transferring it onto the waveguide chip. Moreover , to maximize the detection efficiency, two comb nanowire detectors were integrated on a signle waveguide so that the missing photon passing through the first detector can be detected again by the second one. By incorporating self-calibration, the team could precisely measure the absorption rate, achieving a detection efficiency of 99.73%. This result significantly advances the capabilities of SNSPDs, making them ideal candidates for scalable quantum photonic chip applications.
Light Science & Applications
Surpassing 99% detection efficiency by cascading two superconducting nanowires on one waveguide with self-calibration