Fig. 1. Superconducting nanowire single-photon detector (SNSPD). (a) Typical meandered nanowire; (b) equivalent circuit of SNSPD; (c) waveform of output pulse

Fig. 2. Schematic of reading the spatial and temporal information of a photon in a superconducting nanowire delay line

Fig. 3. Microwave characteristics of a superconducting nanowire. (a) Characteristic impedance and velocity of superconducting coplanar waveguides (The superconducting film is NbN with a kinetic inductance of 80 pH/square. The substrate is thermal dioxide silicon. The gap between signal line and ground is fixed at 500 nm.); (b) characteristic impedance and velocity of coplanar waveguides made from normal metal (no kinetic inductance); (c) ratio of kinetic inductance to geometric inductance

Fig. 4. Different geometries of superconducting nanowire delay line imagers. (a) A single nanowires both acts as a detector and a delay line^[20]; (b) detectors and delay lines are separated to build a two-dimensional array, and the delay lines are made from wide nanowires while detectors are made from 3-SNAPs^[21]; (c) simulated current distribution in a 3-SNAP; (d) detectors and delay lines are separated to build a linear array

Fig. 5. Schematic of the readout circuit for a SNSPI

Fig. 6. Characteristics of the spatial and temporal detections with a SNSPI^[21]. (a) Waveforms of output pulses from the two terminals; (b) 1D histogram of the differential times; (c) enlarged view of the 1D histogram; (d) 2D map of the normalized photon counts; (e) histogram of the normalized photon counts for all 256 pixels; (f) histogram of the photon arrival times (The timing jitter is defined as the FWHM of the histogram, which is 60 ps)

Fig. 7. Single-photon imaging system^[21]. (a) Photo of the imaging setup; (b) schematic of the imaging system

Fig. 8. Block diagram of the algorithmicprocess^[21]

Fig. 9. Comparison of the 3D slicing denoising algorithm with the other methods^[21]

Fig. 10. Imaging results at different background levels

Fig. 11. Simulation of the denoising performance at different timing jitters^[21]. (a) Average width of all pixelwise gates versus the timing jitter; (b) remaining signal photon number and noise photon number per pixel on average versus the timing jitter; (c) signal-to-noise selectivity ratio versus the timing jitter