Nanosecond gating of superconducting nanowire single-photon detectors using cryogenic bias circuitry
Thomas Hummel, Alex Widhalm, Jan Philipp Höpker, Klaus D. Jöns, Jin Chang, Andreas Fognini, Stephan Steinhauer, Val Zwiller, A. Zrenner, Tim J. Bartley
Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3 K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.
Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3 K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.
Superconducting Nanowire Single-Photon Detectors (SNSPDs) are well known for their single-photon sensitivity, low jitter, and high efficiency. Their dynamic range is generally limited either to zero or one (no photon, or a photon absorbed), and if single-photon sensitivity is needed in the vicinity of a strong light pulse, a counteraction like gating needs to be deployed. In such a scheme, we aim at the fastest possible transition time which is helpful to increase sensitivity, to temporally filter any strong laser excitation, and further suppress dark counts. Here, we present our work of time-gated SNSPDs where the detection current can be switched on- and off to allow the detector not to be saturated. We start our discussion by introducing the simplest gating scheme based on a square wave resulting in switch-off-switching transition times of ≈50ns. Then we present a new method to improve this relatively slow transition time to the sub-nanosecond range. Latest measurements of efficiency recovery and jitter are presented, and we show that a 1550nm light pulse with 100’000 photons within 500ns, applied right before the on-transition of the SNSPD, does not yet affect the performance in the on-state.
Superconducting nanowire single-photon detectors (SNSPDs), owing to their unique performance, are currently the standard detector in most demanding single-photon experiments. One important metric for any single-photon detector is the recovery time, which defines the minimum temporal separation between consecutive detection events. In SNSPDs, the recovery time is more subtle, as the detection efficiency does not abruptly drop to zero when the temporal separation between detection events gets smaller, instead, it increases gradually as the SNSPD current recovers. SNSPD's recovery time is dominated by its kinetic inductance, the readout impedance, and the degree of saturation of internal efficiency. Decreasing the kinetic inductance or increasing the readout impedance can accelerate the recovery process. Significant reduction of the SNSPD recovery time, by, for example, adding a series resistor in the readout circuitry, is possible but can lead to detector latching, which hinders further detector operation or enforces underbiasing and hence a reduction in detection efficiency. Previous research has demonstrated passive resistive networks for the reduction of recovery time that rely on trial and error to find the appropriate resistance values. Here, we show that, using a cryogenically compatible and tunable resistor technology, one can find the optimized impedance values, delivering fast SNSPD recovery time while maintaining maximum internal detection efficiency. Here, we show an increase of around twofold in both maximum achievable detection rates and the achievable detection efficiency at high photon fluxes, demonstrating detection rates close to 114 Mcps with no loss of internal detection efficiency.
Superconducting strip single-photon detectors (SSPDs) have demonstrated superior performance in quantum key distribution, high-speed optical communication and et al. However, these applications are constrained by latching effects, dark count rates, and speed of detection, and the rapid detection of single photon events in the target time range requires proper readout means to control. This study presents a nanosecond-level gating filtering circuit with high reliability based on direct current biasing, enabling window-selective photon detection through time-controlled bias current modulation while maintaining superconductivity with reduced current during non-gate intervals. Experimental results show that the proposed scheme achieves a 3 ns–500 ns adjustable gating window and preserving high system detection efficiency and low timing jitter under specific windows. Compared to conventional approaches, the dark count rate is reduced by nearly one orders of magnitude, and the photon dynamic range is significantly expanded.
Scalable superconducting nanowire single photon detector (SNSPDs) arrays require cryogenic digital circuits for multiplexing the output detection pulses. Among existing superconducting digital devices, superconducting nanowire cryotron (nTron) is a three-terminal device with an ultra-compact size, which is promising for large scale monolithic integration. In this report, in order to evaluate the potential and possibility of using nTrons for reading and digitizing SNSPD signals, we characterized the grey zone, speed, timing jitter and power dissipation of a proper designed nTron. With a DC bias on the gate, the nTron can be triggered by a few μA high and nanoseconds wide input signal, showing the nTron was capable of reading an SNSPD pulse at the same signal level. The timing jitter depended on the input signal level. For a 20 μA high and 5 ns wide input pulse, the timing jitter was 33.3 ps, while a typical SNSPD's jitter was around 50 ps. With removing the serial inductors and operating it in an AC bias mode. The nTron was demonstrated to be operated at a clock frequency of 615.4 MHz, which was faster than the maximum counting rate of a typical SNSPD. In additional, with a 50 Ω bias resistor and biased at 17.6 μA, the nTron had a total power dissipation of 19.7 nW. Although RSFQ circuits are faster than nTrons, for reading SNSPD or other detector arrays that demands less operation speed, our results suggest a digital circuit made from nTrons could be another promising alternative.
High detection efficiency and low intrinsic dark count rate are two advantages of superconducting nanowire single photon detectors (SNSPDs). However, the stray photons penetrated into the fiber would cause the extrinsic dark count rate, owing to the free running mode of SNSPDs. In order to improve the performance of SNSPDs in realistic scenarios, stray photons should be investigated and suppression methods should be adopted. In this study, we demonstrate the pulse-gated mode, with 500 kHz gating frequency, of a commercial SNSPD system for suppressing the response of stray photons about three orders of magnitude than its free-running counterpart on the extreme test conditions. When we push the gating frequency to 8 MHz, the dark count rate still keeps under 4% of free-running mode. In experiments, the intrinsic dark count rate is also suppressed to 4.56 × 10−2 counts per second with system detection efficiency of 76.4372%. Furthermore, the time-correlated single-photon counting analysis also approves the validity of our mode in suppressing the responses of stray photons.
Superconducting nanowire single-photon detectors (SNSPDs) are integral to the fields of quantum information and quantum communication, offering high efficiency, low dark count rate, high count rate, and minimal timing jitter. However, a common challenge with SNSPDs is their propensity for latching and nonlinear count rate increase under high incident photon fluxes due to the traditional external readout circuitry. This issue is primarily caused by large dynamic inductance and the ac-coupled effects of the bias and amplifier capacitors. In this study, we carefully selected a commercial SNSPD with an efficiency of over 95%. To address the aforementioned challenges, we implemented a resistor–inductor-type filter structure, which is directly coupled to a low-temperature amplifier, and their operating temperature is 40 K. Experimental results revealed that the enhanced SNSPD readout circuit achieves a count rate that is approximately 3.5 times greater than that of the traditional circuit. Moreover, the timing jitter of the SNSPD was optimized, decreasing by approximately 3.6 times under high incident photon fluxes. These performance enhancements could significantly improve high-speed optical communication and quantum precision measurement.