Over the past two decades, the fast development of superconducting nanowire single photon detector (SNSPD) has made them the detector of choice for modern stringent quantum optics experiments. SNSPD offers remarkably high efficiencies, approching unity efficiency, a few pico-second time resolution, and gigahertz counting rates. The recovery time$\tau$of the SNSPD is one of the key parameters influencing its efficiency at high photon fluxes. Here we report on preliminary results of controlling the response speed of the SNSPD by introducing a tunable resistor$R_{S}$in the electric circuit.
Over the past two decades, the fast development of superconducting nanowire single photon detector (SNSPD) has made them the detector of choice for modern stringent quantum optics experiments. SNSPD offers remarkably high efficiencies, approching unity efficiency, a few pico-second time resolution, and gigahertz counting rates. The recovery timeτof the SNSPD is one of the key parameters influencing its efficiency at high photon fluxes. Here we report on preliminary results of controlling the response speed of the SNSPD by introducing a tunable resistorRSin the electric circuit.
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 nanowire single photon detectors (SNSPDs) have separately demonstrated high efficiency, low noise, and extremely high speed when detecting single photons. However, achieving all of these simultaneously has been limited by detector subtleties and tradeoffs. Here, we report an SNSPD system with <80 ps timing resolution, kHz noise count rates, and 76% fiber-coupled system detection efficiency in the low-flux limit at 1550 nm. We present a model for determining the detection efficiency penalty due to the detection recovery time, and we validate our method using experimental data obtained at high count rates. We demonstrate improved performance tradeoffs, such as 68% system detection efficiency, including losses due to detector recovery time, when coupled to a Poisson source emitting 100 million photons per second. Our system can provide limited photon number resolution, continuous cryogen-free operation, and scalability to future imaging and GHz-count-rate applications.
One of the key properties of single-photon detectors is their recovery time, i.e. the time required for the detector to recover its nominal efficiency. In the case of superconducting nanowire single-photon detectors (SNSPDs), which can feature extremely short recovery times in free-running mode, a precise characterization of this recovery time and its time dynamics is essential for many quantum optics or quantum communication experiments. We introduce a fast and simple method to characterize precisely the recovery time of SNSPDs. It provides full information about the recovery of the efficiency in time for a single or several consecutive detections. We also show how the method can be used to gain insight into the behavior of the bias current inside the nanowire after a detection, which allows predicting the behavior of the detector and its efficiency in any practical experiment using these detectors.
One of the key properties of single-photon detectors is their recovery time, i.e., the time required for the detector to recover its nominal efficiency. In the case of superconducting nanowire single-photon detectors (SNSPDs), which can feature extremely short recovery times in free-running mode, a precise characterization of this recovery time and its time dynamics is essential for many quantum optics or quantum communication experiments. We introduce a fast and simple method to characterize precisely the recovery time of SNSPDs. It provides full information about the recovery of the efficiency in time for a single or several consecutive detections. We also show how the method can be used to gain insight into the behavior of the bias current inside the nanowire after a detection, which allows predicting the behavior of the detector and its efficiency in any practical experiment using these detectors.
Superconducting nanowire single-photon detectors (SNSPDs) are an attractive technology for applications which benefit from high-count rate photon detection such as quantum communication protocols, photon-starved classical communications, metrology of single-emitters, and photonic quantum computing. However, at high-count rates, a significant portion of photons may be incident during recovery intervals following prior detection events. After detection, the device efficiency recovers over nanoseconds to tens of nanoseconds before reaching a steadystate value. Therefore, for a given SNSPD bias current setpoint, a single efficiency and recovery time specification may not be sufficient to characterize the performance of a device at high count rates. Here we present and experimentally validate a model of the recovery time as a function of bias current for any given system efficiency. These results may be used to improve analysis of measurements performed using SNSPDs operating in the high count rate regime.
Superconducting nanowire single-photon detectors are set apart from other photon counting technologies above all else by their extremely high speed, with few-ten-ps timing resolution, and recovery times τR ≲ 10 ns after a detection event. In this work, however, we identify in the conventional electrical readout scheme a nonlinear interaction between the detector and its readout which can make stable, high-efficiency operation impossible at count rates even an order-of-magnitude less than τR−1. We present detailed experimental confirmation of this, and a theoretical model which quantitatively explains our observations. Finally, we describe an improved readout which circumvents this problem, allowing these detectors to be operated stably at high count rates, with a detection efficiency penalty determined purely by their inductive reset time.