Quantum imaging protocols have traditionally relied on spatially resolving detector arrays or multi-pixel cameras whose noise floors, limited detection efficiencies, and timing jitter fundamentally constrain image quality. Here we report a fibre-integrated architecture that reconstructs full two-dimensional quantum images using only a single superconducting nanowire single-photon detector, replacing spatial resolution with temporal multiplexing and compressive measurement. Correlated photon pairs generated by parametric down-conversion illuminate the target through one arm while the partner photon is retained as a temporal reference; non-local dispersion engineered across the two arms suppresses uncorrelated background while preserving pair timing. A compressive sensing algorithm exploiting sparsity in the Fourier domain then recovers 50×50-pixel images from far fewer measurements than conventional raster scanning would require. Operating over several kilometres of standard single-mode fibre at the eye-safe wavelength of 1550 nm, the system produces images of comparable fidelity to classical illumination while using 95 dB less optical power, achieves sub-shot-noise performance with a 7.9 dB signal-to-noise ratio improvement, and sustains useful image quality under injected noise exceeding the signal by 10 dB. The same temporal correlation data yield a timing precision of 1.2 ps, corresponding to sub-millimetre ranging resolution. These results establish single-detector temporal multiplexing as a viable and scalable route to practical quantum imaging over deployed telecommunications infrastructure.
Quantum imaging protocols have traditionally relied on spatially resolving detector arrays or multi-pixel cameras whose noise floors, limited detection efficiencies, and timing jitter fundamentally constrain image quality. Here we report a fibre-integrated architecture that reconstructs full two-dimensional quantum images using only a single superconducting nanowire single-photon detector, replacing spatial resolution with temporal multiplexing and compressive measurement. Correlated photon pairs generated by parametric down-conversion illuminate the target through one arm while the partner photon is retained as a temporal reference; non-local dispersion engineered across the two arms suppresses uncorrelated background while preserving pair timing. A compressive sensing algorithm exploiting sparsity in the Fourier domain then recovers 50×50-pixel images from far fewer measurements than conventional raster scanning would require. Operating over several kilometres of standard single-mode fibre at the eye-safe wavelength of 1550 nm, the system produces images of comparable fidelity to classical illumination while using 95 dB less optical power, achieves sub-shot-noise performance with a 7.9 dB signal-to-noise ratio improvement, and sustains useful image quality under injected noise exceeding the signal by 10 dB. The same temporal correlation data yield a timing precision of 1.2 ps, corresponding to sub-millimetre ranging resolution. These results establish single-detector temporal multiplexing as a viable and scalable route to practical quantum imaging over deployed telecommunications infrastructure.
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.
A two-dimensional single-photon imaging system with high sensitivity and high time resolution is the ultimate camera and useful in a wide range of fields. A superconducting nanowire single-photon detector (SSPD or SNSPD) is one of the best candidates for realizing such an ultimate camera due to its high detection efficiency in a wide spectral range, low dark count rate without after-pulsing, and excellent time resolution. Here we propose a new readout scheme to realize a large-scale imaging array based on SSPD, where a row-column readout architecture is combined with a digital signal processor based on a single-flux-quantum (SFQ) circuit. A 16-pixel row-column readout SSPD array is fabricated and measured with an SFQ digital signal processor. We successfully acquired spatial information as encoded digital bit codes with the temporal information of the photon detection. The system timing jitter was measured as <80 ps for all 16 pixels even through the SFQ signal processor, indicating the potential for an imaging array with an extremely high time resolution.
We implement a double-pixel compressive-sensing camera to efficiently characterize, at high resolution, the spatially entangled fields that are produced by spontaneous parametric down-conversion.This technique leverages sparsity in spatial correlations between entangled photons to improve acquisition times over raster scanning by a scaling factor up to n 2 = logðnÞ for n-dimensional images.We image at resolutions up to 1024 dimensions per detector and demonstrate a channel capacity of 8.4 bits per photon.By comparing the entangled photons' classical mutual information in conjugate bases, we violate an entropic Einstein-Podolsky-Rosen separability criterion for all measured resolutions.More broadly, our result indicates that compressive sensing can be especially effective for higher-order measurements on correlated systems.
A broad range of scientific and industrial disciplines require precise optical measurements at very low light levels. Single-photon detectors combining high efficiency and high time resolution are pivotal in such experiments. By using relatively thick films of NbTiN (8-11\,nm) and improving the pattern fidelity of the nano-structure of the superconducting nanowire single-photon detectors (SNSPD), we fabricated devices demonstrating superior performance over all previously reported detectors in the combination of efficiency and time resolution. Our findings prove that small variations in the nanowire width, in the order of a few nanometers, can lead to a significant penalty on their temporal response. Addressing these issues, we consistently achieved high time resolution (best device 7.7\,ps, other devices $\sim$10-16\,ps) simultaneously with high system detection efficiencies (80−90%) in the wavelength range of 780-1000\,nm, as well as in the telecom bands (1310-1550\,nm). The use of thicker films allowed us to fabricate large-area multi-pixel devices with homogeneous pixel performance. We first fabricated and characterized a 100×100μm2 16-pixel detector and showed there was little variation among individual pixels. Additionally, to showcase the power of our platform, we fabricated and characterized 4-pixel multimode fiber-coupled detectors and carried out photon correlation experiments on a nanowire quantum dot resulting in g2(0) values lower than 0.04. The multi-pixel detectors alleviate the need for beamsplitters and can be used for higher order correlations with promising prospects not only in the field of quantum optics, but also in bio-imaging applications, such as fluorescence microscopy and positron emission tomography.
We report a 16-pixel (4×4) superconducting nanowire single-photon detector (SNSPD) array featuring pixel-level photon-number-resolving capability. This multidimensional sensing is enabled by integrating a compact four-element series nanowire architecture into each spatial pixel, allowing direct discrimination of one to four photons. Under single-mode fiber illumination, the device achieves a total system detection efficiency of 41.5%, given the array geometrical fill factor of 53%. Across all channels, the device exhibits reliable multiphoton discrimination, maintaining minimum readout fidelities of 96%, 89%, 73%, and 77% for one- to four-photon states, respectively. Furthermore, independent channel evaluations reveal low timing jitter and negligible inter-channel crosstalk (<0.1 % ). By implementing differentiating pulse shaping for high-flux operation, a maximum single-channel −3 dB count rate of 984 MHz is achieved, establishing an aggregated array bandwidth potential of 8.9 GHz. This sensing architecture may provide a viable pathway toward high-flux single-photon imaging, offering potential applications in quantum optics and light detection and ranging (LiDAR) systems.
The quality of an image is limited to the signal-to-noise ratio of the output from sensors. As the background noise increases much more than the signal, which can be caused by either a huge attenuation of light pulses after a long-haul transmission or a blinding attack with a strong flood illumination, an imaging system stops working properly. Here we built a superconducting single-photon infrared camera of negligible dark counts and 60 ps timing resolution. Combining with an adaptive 3D slicing algorithm that gives each pixel an optimal temporal window to distinguish clustered signal photons from a uniformly distributed background, we successfully reconstructed 3D single-photon images at both a low signal level (∼1 average photon per pixel) and extremely high noise background (background-to-signal ratio = 200 within a period of 50 ns before denoising). Among all detection events, we were able to remove 99.45% of the noise photons while keeping the signal photon loss at 0.74%. This Letter is a direct outcome of quantum-inspired imaging that asks for a co-development of sensors and computational methods. We envision that the proposed methods can increase the working distance of a long-haul imaging system or defend it from blinding attacks.