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arXiv:1208.0127 · Review of Scientific Instruments

Fully integrated InGaAs/InP single-photon detector module with gigahertz sine wave gating

Xiao-Lei Liang, Jian-Hong Liu, Quan Wang, De-Bing Du, Jian Ma, Ge Jin, Zeng-Bing Chen, Jun Zhang, Jian-Wei Pan

Published Aug 1, 2012• 39 citations
arXivHTMLPDF

Abstract

InGaAs/InP single-photon avalanche diodes (SPADs) working in the regime of GHz clock rates are crucial components for the high-speed quantum key distribution (QKD). We have developed for the first time a compact, stable, and user-friendly tabletop InGaAs/InP single-photon detector system operating at a 1.25 GHz gate rate that fully integrates functions for controlling and optimizing SPAD performance. We characterize the key parameters of the detector system and test the long-term stability of the system for continuous operation of 75 h. The detector system can substantially enhance QKD performance and our present work paves the way for practical high-speed QKD applications.

DOI
10.1063/1.4746291

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We discuss high-speed electronics that support the use of single-photon avalanche diodes (SPADs) in gigahertz singlephoton communications systems. For InGaAs/InP SPADs, recent work has demonstrated reduced afterpulsing and count rates approaching 500 MHz can be achieved with gigahertz periodic-gating techniques designed to minimize the total avalanche charge to less than 100 fC. We investigate afterpulsing in this regime and establish a connection to observations using more conventional techniques. For Si SPADs, we report the benefits of improved timing electronics that enhance the temporal resolution of Si SPADs used in a free-space quantum key distribution (QKD) system operating in the GHz regime. We establish that the effects of count-rate fluctuations induced by daytime turbulent scintillation are significantly reduced, benefitting the performance of the QKD system.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Dec 7, 2010•2 citations
InGaAs/InP single-photon avalanche diodes (SPADs) working in the regime of GHz clock rates are crucial components for the high-speed quantum key distribution (QKD). We have developed for the first time a compact, stable, and user-friendly tabletop InGaAs/InP single-photon detector system operating at a 1.25 GHz gate rate that fully integrates functions for controlling and optimizing SPAD performance. We characterize the key parameters of the detector system and test the long-term stability of the system for continuous operation of 75 h. The detector system can substantially enhance QKD performance and our present work paves the way for practical high-speed QKD applications.
We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose a useful way to characterize the afterpulsing distribution for rapid gating that allows for easy comparison with conventional gating regimes. We compare the performance of this rapid gating scheme with free-running detector and superconducting single-photon detector (SSPD) for the coherent one-way quantum key distribution (QKD) protocol. The rapid gating system is well suited for both high-rate and long-distance QKD applications, in which Mbps key rates can be achieved for distances less than 40km with 50 ns deadtime and the maximum distance is limited to ~190km with 5 μs deadtime. These results illustrate that the afterpulsing is no longer a limiting factor for QKD.
InGaAs/InP Single-Photon Avalanche Diodes (SPADs) are widely employed in quantum optics applications, particularly in Quantum Key Distribution (QKD), due to their high sensitivity in the near-infrared range. In QKD, low noise and high timing resolution are essential to ensure secure and high-rate key exchange. One of the main limitations of InGaAs/InP SPADs is afterpulsing, which degrades the quantum bit error rate (QBER), limits the maximum count rate, and can compromise both the security and throughput of QKD systems. Reducing afterpulsing is thus crucial for enabling high-speed, reliable quantum communication. We present a newly developed gating and quenching circuit that significantly reduces afterpulsing. The circuit is located entirely outside the detector package, maintaining compatibility with any InGaAs/InP SPAD, and supports both gated and free-running operation. Unlike integrated ASIC-based solutions, which offer low parasitics but are often limited by process constraints (e.g., low maximum voltages), our approach uses high-speed discrete components, allowing high excess bias operation and design flexibility. While discrete designs are typically more prone to parasitics, our compact layout effectively mitigates these effects and preserves signal integrity. Experimental results show a strong afterpulsing reduction compared to our current commercial module. Additionally, the measured SPAD current highlights that the avalanche is completely quenched in less than a nanosecond after sensing. Eventually, the small footprint of the design paves the way for a new generation of compact, low-afterpulsing InGaAs/InP SPAD modules suitable for high-performance quantum optics applications.
Photonic integration is a promising route to miniaturise the hardware of quantum key distribution (QKD), yet the monolithic integration of single-photon detectors remains a significant challenge. QKD receiver chips integrating superconducting detectors have been demonstrated, but their requirement for cryogenic cooling restricts their practical applications. High-frequency gated single-photon avalanche diodes (SPADs) provide a mature non-cryogenic alternative, and their fabrication into compact arrays would enable scalable hybrid integration. However, this faces several challenges related to efficient GHz array gating, inter-pixel crosstalk, and scalable waveguide coupling, which to date remain unaddressed. Here, we overcome the key challenges and develop GHz-gated InGaAs/InP SPAD arrays with performance viable for QKD and negligible inter-pixel crosstalk. We combine the arrays with low-loss silica waveguide chips to produce compact hybrid QKD receivers and perform BB84 protocol experiments, achieving secure key rates over 2 Mbps at short distances and 15 kbps over 100 km of fibre. Our work provides a method for flexible and scalable integration of waveguide-coupled SPADs for quantum information processing applications.
Gated single-photon avalanche diodes (SPADs) are practical solutions for quantum key distribution (QKD) applications. However, the gating frequency is limited by time jitter and afterpulse probability when SPADs operate at a frequency higher than 2 GHz. We find that filter distortion and variation of signal amplitude are the dominant mechanisms for time jitter in high-frequency scenarios, and design a specific low-pass filter (LPF) and a zero crossing discriminator to reduce the time jitter effectively. Specifically, the LPF extracts avalanche signals and forms accurate zero crossing points by its impulse response, and the zero crossing discriminator correctly discriminates avalanche signals to achieve low time jitter. When the SPAD is operated at a gating frequency of 2.5 GHz with a detection efficiency of 21%, the time jitter and afterpulse probability are 44 ps and 1.4%, respectively. Our results pave the way to practical QKD systems at higher clock rates.
We discuss high-speed electronics that support the use of single-photon avalanche diodes (SPADs) in gigahertz singlephoton communications systems. For InGaAs/InP SPADs, recent work has demonstrated reduced afterpulsing and count rates approaching 500 MHz can be achieved with gigahertz periodic-gating techniques designed to minimize the total avalanche charge to less than 100 fC. We investigate afterpulsing in this regime and establish a connection to observations using more conventional techniques. For Si SPADs, we report the benefits of improved timing electronics that enhance the temporal resolution of Si SPADs used in a free-space quantum key distribution (QKD) system operating in the GHz regime. We establish that the effects of count-rate fluctuations induced by daytime turbulent scintillation are significantly reduced, benefitting the performance of the QKD system.