Single-photon detection concept is the most crucial factor that determines the performance of quantum key distribution (QKD) systems. In this paper, a simulator with time domain visualizers and configurable parameters using continuous time simulation approach is presented for modeling and investigating the performance of single-photon detectors operating in Gieger mode at the wavelength of 830 nm. The widely used C30921S silicon avalanche photodiode was modeled in terms of avalanche pulse, the effect of experiment conditions such as excess voltage, temperature and average photon number on the photon detection efficiency, dark count rate and afterpulse probability. This work shows a general repeatable modeling process for significant performance evaluation. The most remarkable result emerged from the simulated data generated and detected by commercial devices is that the modeling process provides guidance for single-photon detectors design and characterization. The validation and testing results of the single-photon avalanche detectors (SPAD) simulator showed acceptable results with the theoretical and experimental results reported in related references and the device's data sheets.
Single-photon detection concept is the most crucial factor that determines the performance of quantum key distribution (QKD) systems. In this paper, a simulator with time domain visualizers and configurable parameters using continuous time simulation approach is presented for modeling and investigating the performance of single-photon detectors operating in Gieger mode at the wavelength of 830 nm. The widely used C30921S silicon avalanche photodiode was modeled in terms of avalanche pulse, the effect of experiment conditions such as excess voltage, temperature and average photon number on the photon detection efficiency, dark count rate and afterpulse probability. This work shows a general repeatable modeling process for significant performance evaluation. The most remarkable result emerged from the simulated data generated and detected by commercial devices is that the modeling process provides guidance for single-photon detectors design and characterization. The validation and testing results of the single-photon avalanche detectors (SPAD) simulator showed acceptable results with the theoretical and experimental results reported in related references and the device's data sheets.
Single-photon detection concept is the most crucial and often difficult factor to determine the performance of quantum key distribution (QKD) systems. One solution to facilitate understanding this concept is to create a virtual environment for modeling, analyzing, and investigating the performance of single photon detectors. In this paper, a simulator for superconducting single photon detectors with time domain visualizer and configurable parameters is presented. The widely used ID281SNSPD in the QKD area was theoretically modeled in terms of pulse analysis, the impact of biasing current and the temperature on the dark counts rate and single photon-detection efficiency and influence of the number of photons per pulse on the single photon-detection efficiency. The simulated results were in good agreement with the theoretical results and the simulator demonstrated its adaptability.
Experimental results obtained with silicon single photon avalanche diodes (SPADs) in quantum key distribution (QKD) at short wavelengths reveal remarkable potential for application in local area networks (LAN) and for free-space transmission at high rate. Actual application prospects, however, depend on the performance level and on the suitability of practical systems using the available silicon SPAD devices. They can be essentially divided in two groups: planar p-n junction structures with a thin depletion layer (typically 1 μm); and reach-through structures with a thick depletion layer (from 20 μm to 150μm). The physical mechanisms that control the device behaviour were investigated and the effect on the key parameters of the detector (quantum detection efficiency, dark counting rate, afterpulsing probability and photon-timing jitter) were thoroughly assessed. A quantitative analysis was made of the influence of such parameters on the quantum bit error rate (QBER). Actual parameters were measured and the attainable performance and system suitability of the two device types evaluated. Comparable performance is obtained, but from a system viewpoint thin SPADs appear inherently better suited to high-rate QKD applications, because of their faster response time, ruggedness, low voltage, low power dissipation and fabrication technology, which is simple, efficient, economical and compatible with monolithic integration of detector and associated circuits.
In our experiment, two InGaAs/InP avalanche photodiodes (APD) were used in the quantum key distribution (QKD) system for single-photon detection at telecom communication wavelength (1310/1550 nm). By using properly designed passive-quenching circuit, the photo-detection efficiency of the APD could reach 10% at 1550 nm. In order to decrease the dark count rate efficiently, we designed a coincident counting circuits for single-photon detection. Before the APD signals were sent to the signal processing circuit, the avalanche signals were amplified and shaped into the TTL pulses. In order to obtain an accurate and efficient data acquisition and to transfer synchronically several signals such as the TTL signals and pulses from Random generators, we designed a signal processing circuit with the parallel port whose speed limitation is about 100Kb/s. In our experiments of single-photon interference and quantum cryptography, the electronic designs presented us satisfactory performance and results. To achieve much higher speed for the data acquisition, we also employed the Universal Serial Bus System (USB2.0) to interface our single-photon avalanche detectors and random generators used in our QKD system, which was believed to improve the performance of QKD such as the key distribution speed.
InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in practical applications requiring near-infrared photon counting such as quantum key distribution (QKD). Photon detection efficiency and dark count rate are the intrinsic parameters of InGaAs/InP SPADs, due to the fact that their performances cannot be improved using different quenching electronics given the same operation conditions. After modeling these parameters and developing a simulation platform for InGaAs/InP SPADs, we investigate the semiconductor structure design and optimization. The parameters of photon detection efficiency and dark count rate highly depend on the variables of absorption layer thickness, multiplication layer thickness, excess bias voltage, and temperature. By evaluating the decoy-state QKD performance, the variables for SPAD design and operation can be globally optimized. Such optimization from the perspective of specific applications can provide an effective approach to design high-performance InGaAs/InP SPADs.
The application of quantum key distribution (QKD) has raised particular demands for single-photon detectors. One of the most promising candidates at the low-loss optical fibre communications windows is the planar geometry InGaAs/InP single-photon avalanche diode. These detectors have been modelled, fabricated and characterised at 1.55 µm wavelength. Their performance in terms of single-photon detection efficiency, dark count rate, timing jitter and afterpulsing behaviour are reported and compared with the best commercially available, linear multiplication avalanche photodiodes operated in Geiger-mode. Their use in the application of QKD is discussed.
Twin-field quantum key distribution (TF-QKD) surpasses the repeaterless key-rate bound, offering great promise for long-distance quantum communication. Avalanche-photodiode (APD) single-photon detectors are widely used in practical QKD systems, due to their compactness, cost-effectiveness, and room-temperature operation. However, their non-ideal characteristics-including afterpulse probability, dead time, and dark counts-can severely degrade TF-QKD performance. In this work, we develop a comprehensive TF-QKD simulation model incorporating these APD imperfections, enabling quantitative analysis of their individual impacts. Our results reveal that afterpulse induced by high-intensity reference pulses is the dominant performance-limiting factor. Under identical APD conditions, we compare three representative TF-QKD protocols. The sending-or-not-sending (SNS) protocol demonstrates superior long-distance performance due to its higher signal photon number and enhanced noise tolerance. This study provides practical guidance for the design of compact, APD-based TF-QKD systems and highlights key strategies for performance optimization.