Photon-number resolved detection with superconducting nanowire single-photon detectors (SNSPDs) attracts increasing interest, but lacks a systematic framework for interpreting and benchmarking this capability. In this work, we combine principal component analysis (PCA) with a new readout technique to explore the photon-number resolving capabilities of SNSPDs and find that the information of the photon number is contained in a single principal component which approximates the time derivative of the average response trace. We introduce a new confidence metric based on the Bhattacharyya coefficient to quantify the photon-number-resolving capabilities of a detector system and show that this metric can be used to compare different systems. Our analysis and interpretation of the principal components imply that photon-number resolution in SNSPDs can be achieved with moderate hardware requirements in terms of both sample rate (5 GSample/sec) and analog bandwidth (3 GHz) and could be implemented in an FPGA, giving a highly scalable solution for real-time photon counting.
Photon-number resolved detection with superconducting nanowire single-photon detectors (SNSPDs) attracts increasing interest, but lacks a systematic framework for interpreting and benchmarking this capability. In this work, we combine principal component analysis (PCA) with a new readout technique to explore the photon-number resolving capabilities of SNSPDs and find that the information of the photon number is contained in a single principal component which approximates the time derivative of the average response trace. We introduce a new confidence metric based on the Bhattacharyya coefficient to quantify the photon-number-resolving capabilities of a detector system and show that this metric can be used to compare different systems. Our analysis and interpretation of the principal components imply that photon-number resolution in SNSPDs can be achieved with moderate hardware requirements in terms of both sample rate (5 GSample/sec) and analog bandwidth (3 GHz) and could be implemented in an FPGA, giving a highly scalable solution for real-time photon counting.
We apply principal component analysis (PCA) to a set of electrical output signals from a commercially available superconducting nanowire single-photon detector (SNSPD) to investigate their photon-number-resolving capability. We find that the rising edge as well as the amplitude of the electrical signal have the most dependence on photon number. Accurately measuring the rising edge while simultaneously measuring the voltage of the pulse amplitude maximizes the photon-number resolution of SNSPDs. Using an optimal basis of principal components, we show unambiguous discrimination between one- and two-photon events, as well as partial resolution up to five photons. This expands the use case of SNSPDs to photon-counting experiments, without the need of detector multiplexing architectures. Published by the American Physical Society 2024
Superconducting series nanowire single-photon detectors (SNDs) have been used for resolving photon numbers. But it can also exhibit a higher counting rate than a single superconducting nanowire single-photon detector (SNSPD), because the serial architecture allows multiple detectors working in parallel and the inductance of each pixel is reduced. In this paper, we found each pixel of the SND could reset fast although the whole detector took a much longer time for recovering. Therefore, the speed of an SND with a large kinetic inductance of 1.25 μH was characterized and compared to a standard SNSPD with the same total inductance. By measuring the detected photon rate over the input photon rate, we obtained a photon counting rate enhancement by 7.5 times. Meanwhile, the timing jitter of the SND was 63 ps at single photon detection regime. Our results show that the series structure and the readout scheme are quite practical in realizing high speed single-photon detectors besides resolving photon numbers.
Since their first demonstration in 2001 [Gol’tsman et al., Appl. Phys. Lett. 79, 705–707 (2001)], superconducting-nanowire single-photon detectors (SNSPDs) have witnessed two decades of great developments. SNSPDs are the detector of choice in most modern quantum optics experiments and are slowly finding their way into other photon-starved fields of optics. Until now, however, in nearly all experiments, SNSPDs were used as “binary” detectors, meaning that they could only distinguish between 0 and >=1 photons, and photon number information was lost. Recent research has demonstrated proof-of-principle photon-number resolution (PNR) SNSPDs counting 2–5 photons. The photon-number-resolving capability is highly demanded in various quantum-optics experiments, including Hong–Ou–Mandel interference, photonic quantum computing, quantum communication, and non-Gaussian quantum state preparation. In particular, PNR detectors at the wavelength range of 850–950 nm are of great interest due to the availability of high-quality semiconductor quantum dots (QDs) [Heindel et al., Adv. Opt. Photonics 15, 613–738 (2023)] and high-performance cesium-based quantum memories [Ma et al., J. Opt. 19, 043001 (2017)]. In this paper, we demonstrate NbTiN-based SNSPDs with >94% system detection efficiency, sub-11 ps timing jitter for one photon, and sub-7 ps for 2 photons. More importantly, our detectors resolve up to 7 photons using conventional cryogenic electric readout circuitry. Through theoretical analysis, we show that the PNR performance of demonstrated detectors can be further improved by enhancing the signal-to-noise ratio and bandwidth of our readout circuitry. Our results are promising for the future of optical quantum computing and quantum communication.
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.
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.
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.