门控下InGaAs/InP单光子探测器用于符合测量的时域滤波特性研究

Temporal filtering characteristics of gated InGaAs/InP singlephoton detectors for coincidence measurement

基于砷化镓/磷化铟雪崩光电二极管(InGaAs/InP APD)的半导体单光子探测器因工作在通信波段,且具有体积小、成本低、操作方便等优势,在实用化量子通信技术中发挥了重要作用.为尽可能避免暗计数和后脉冲对单光子探测的影响,InGaAs/InP单光子探测器广泛采用门控技术来快速触发和淬灭雪崩效应,有效门宽通常在纳秒量级.本文研究揭示了门控下单光子探测器可测量的最大符合时间宽度受限于门控脉冲的宽度,理论分析与实验结果良好拟合.该研究表明,门控下InGaAs/InP单光子探测器用于双光子符合测量具有显著的时域滤波特性,限制了其在基于双光子时间关联测量的量子信息技术中的应用.

Semiconductor single-photon avalanche detectors(SPADs)have played an important role in practical quantum communication technology due to their advantages of small size,low cost and easy operation.Among them,InGaAs/InP SPADs have been widely used in fiber-optic quantum key distribution systems due to their response wavelength range in a near-infrared optical communication band.In order to avoid the influence of dark count and afterpulsing on single photon detection,the gated quenching technologies are widely applied to the InGaAs/InP SPADs.Typically,the duration of gate pulse is set to be as short as a few nanoseconds or even less.As the detection of the arrival of single photons depends on the coincidence between the arrival time of gate pulse and the arrival time of photon,the gate pulse duration of the InGaAs/InP SPADs inevitably affects the effective detection of the single photons.Without the influence of dispersion,the temporal width of the transmitted photons is usually on the order of picoseconds or even less,which is much shorter than the gate width of the InGaAs/InP SPAD.Therefore,the gate width normally has no influence on the temporal measurement of the detected photons.However,in quantum systems involving large dispersion,such as the long-distance fiber-optic quantum communication system,the temporal width of the transmitted photons is significantly broadened by the experienced dispersion so that it may approach to or even exceed the gate width of the single-photon detector.As a result,the effect of the gate width on the recording of the arrival time of the dispersed photons should be taken into account.In this paper,the influence of the gate width coupled to the InGaAs/InP single photon detectors on the measurement of the two-photon coincidence time width is studied both theoretically and experimentally.The theoretical analysis and experimental results are in good agreement with each other,showing that the finally measured coincidence time width of the two-photon state after dispersion is not more than half of the effective gate pulses width.The maximum observable coincidence time width based on the gated single photon detector is fundamentally limited by the gate width,which restricts its applications in quantum information processing based on the two-photon temporal correlation measurement.