Reaching the intrinsic performance limits of superconducting nanowire single-photon detectors up to 0.1 mm wide

Superconducting nanowire single-photon detectors combine high detection efficiency, low noise, and excellent timing resolution, making them a leading platform for photon-counting applications. However, despite decades of materials and fabrication research, detector performance has never been shown to match theoretical performance expectations. Here, we demonstrate for the first time in situ tuning of a detector from its typical, suboptimal operation, to a regime limited only by material quality, allowing the device to reach its intrinsic performance limit. Our approach is based on current-biased superconducting “rails” placed on either side of the detector that redistribute current across its width to achieve peak performance. This technique not only reduces the dark count rate by ten orders of magnitude, but also enables future detectors to overcome the Pearl limit for device width, paving the way for arbitrarily large detectors. We show operation at this intrinsic performance limit for devices up to 0.1 mm wide, and also demonstrate near-unity internal detection efficiency at a wavelength of 4 μm for a 20 μm-wide detector—a factor of 20 wider than the current state of the art.