Abstract Superconducting nanowire-based devices are being hailed as promising single-photon detectors that exhibit excellent combined properties. In particular, their unrivalled time-resolution ability has made these devices potentially revolutionary for the commercial ultrafast single-photon measurement and analysis fields. In this review, we present a detailed summary of the influencing factors and the intrinsic physical mechanism of the temporal resolution in superconducting nanowire single-photon detectors (SNSPDs). We elaborate on the two internal components of temporal resolution, the time response and time jitter, as well as on many measurement methods and device structure modifications attempted to exclude external interference, thus approaching the ultimate limits of time-resolved single photon detection. The investigation of the temporal resolution of SNSPDs not only sheds light on the intrinsic physical mechanism but also contributes to time-related practical engineering applications.
Abstract Superconducting nanowire-based devices are being hailed as promising single-photon detectors that exhibit excellent combined properties. In particular, their unrivalled time-resolution ability has made these devices potentially revolutionary for the commercial ultrafast single-photon measurement and analysis fields. In this review, we present a detailed summary of the influencing factors and the intrinsic physical mechanism of the temporal resolution in superconducting nanowire single-photon detectors (SNSPDs). We elaborate on the two internal components of temporal resolution, the time response and time jitter, as well as on many measurement methods and device structure modifications attempted to exclude external interference, thus approaching the ultimate limits of time-resolved single photon detection. The investigation of the temporal resolution of SNSPDs not only sheds light on the intrinsic physical mechanism but also contributes to time-related practical engineering applications.
Single-photon detectors based on superconducting nanowires (SNSPDs) are promising technologies with good comprehensive performance, especially their excellent temporal resolution for applications in quantum precision measurements and time-varying ultimate detection. The response time of an SNSPD can be characterized by aspects of hotspot thermal relaxation and electrical relaxation, which are also responsible for the time jitter of the SNSPD. The factors affecting the temporal resolution of an SNSPD, the underlying physical mechanism, the intrinsic limit, and possible optimization methods are reviewed. The poor energy resolution and lack of photon number resolution for conventional SNSPDs can be overcome by using high-impedance readouts, novel device structures, characterization methods and, most importantly, SNSPD arrays, which can simultaneously further improve the temporal resolution. The study of the temporal and photon number resolution of SNSPDs helps reveal the underlying physics and is valuable for their new application in various practical engineering areas.
Detecting spatial and temporal information of individual photons is a crucial technology in today's quantum information science. Among the existing single-photon detectors, superconducting nanowire single-photon detectors (SNSPDs) have been demonstrated with a sub-50 ps timing jitter, near unity detection efficiency1, wide response spectrum from visible to infrared and ~10 ns reset time. However, to gain spatial sensitivity, multiple SNSPDs have to be integrated into an array, whose spatial and temporal resolutions are limited by the multiplexing circuit. Here, we add spatial sensitivity to a single nanowire while preserving the temporal resolution from an SNSPD, thereby turning an SNSPD into a superconducting nanowire single-photon imager (SNSPI). To achieve an SNSPI, we modify a nanowire's electrical behavior from a lumped inductor to a transmission line, where the signal velocity is slowed down to 0.02c (where c is the speed of light). Consequently, we are able to simultaneously read out the landing locations and arrival times of the photons from the output electrical pulses using only two connections. We have demonstrated single-photon imaging by using a 19.7 mm long SNSPI, which is meandered into an imaging area of 286 {\mu}m*193 {\mu}m. The nanowire has a temporal resolution of 50 ps for detecting 1.5 {\mu}m photons. The 2D spatial resolution is 13.0 {\mu}m in the vertical direction and 5.6 {\mu}m in the horizontal direction. The maximum number of resolvable locations (i.e., the effective number of pixels) in such a long nanowire is calculated to be 590. Rather than operating an individual detector in a scanning mode or using SPD arrays, this SNSPI gives an alternative approach to taking large-scale single-photon images and measuring temporal and spatial correlation.
Many quantum applications will benefit significantly from photon number resolving detection. However, photon number resolving detectors have been largely experimental devices implemented in laboratory settings. Recent advances in superconducting nanowire device fabrication and readout techniques have enabled the implementation of photon number resolution in widely deployable commercial single-photon detection systems. We will discuss progress in implementing photon number resolved detection with commercially produced superconducting nanowire single photon detectors via spatial multiplexing of independently instrumented detector elements and photon number dependent rise-time changes in single-element nanowire devices.
Superconducting Nanowire Single Photon Detectors (SNSPDs) excel at a wide variety of performance criteria for single photon counting. They combine unprecedented high detection efficiency, high timing resolution, high count rates, low intrinsic dark count rates, and are sensitive to ultraviolet through mid-infrared single-photons. At JPL, we are working on several projects to push the performance limits of SNSPDs to achieve higher maximum count rates, larger active areas, higher timing resolution, and a wider spectral range. Our recent advances enable new applications for dark matter detection, imaging, and space-to-ground communication and provide insight into the fundamental physics of single-photon detection in superconducting nanowires.
The topic of latency in superconducting nanowire single-photon detectors (SNSPDs, the fastest type of such sensors) is of interest for understanding the absolute limits of timing performance in these devices, but so far no model of the detection mechanism could quantitatively explain recent measurements of intrinsic jitter and latency. This analysis of the connection between detector latency and timing jitter in the presence of Fano fluctuations and spatial nonuniformity provides a framework for studying the intrinsic jitter in SNSPDs, and suggests that intrinsic jitter could be reduced by enhancing scattering to suppress superconductivity as quickly as possible.
In this review, we present recent advances relating to superconducting nanowire single-photon detectors (SSPDs or SNSPDs) and their broad range of applications. During a period exceeding ten years, the system performance of SSPDs has been drastically improved, and lately excellent detection efficiencies have been realized in practical systems for a wide range of target photon wavelengths. Owing to their advantages such as high system detection efficiency, low dark count rate, and excellent timing jitter, SSPDs have found application in various research fields such as quantum information, quantum optics, optical communication, and also in the life sciences. We summarize the photon detection principle and the current performance status of practical SSPD systems. In addition, we introduce application examples in which SSPDs have been applied.