An Ultra-Low Noise Telecom Wavelength Free Running Single Photon Detector Using Negative Feedback Avalanche Diode

TL;DR

This paper introduces a novel free-running single photon detector at 1550 nm using NFADs with ultra-low noise, high efficiency, and good timing, enabling long-distance quantum key distribution.

Contribution

The paper presents a new readout system for NFADs that achieves low dark counts, high detection efficiency, and good timing at 193 K, suitable for quantum communication.

Findings

Dark counts ~100 CPS at 193 K

Detection efficiency ~10% at 1550 nm

QKD over 400 km of telecom fiber feasible

Abstract

It is challenging to implement genuine free running single photon detectors for the 1550 nm wavelength range with simultaneously high detection efficiency (DE), low dark noise, and good time resolution. We report a novel read out system for the signals from a negative feedback avalanche diode (NFAD) which allows useful operation of these devices at a temperature of 193 K and results in very low dark counts (~100 CPS), good time jitter (~30 ps), and good DE (~10%). We characterized two NFADs with a time correlation method using photons generated from weak coherent pulses (WCP) and photon pairs produced by spontaneous parametric down conversion (SPDC). The inferred detector efficiencies for both types of photon sources agree with each other. The best noise equivalent power of the device is estimated to be 8.1 x 10^(-18) W Hz^(-1/2), more than 10 times better than typical InP/InGaAs SPADs show in free running mode. The afterpulsing probability was found to be less than 0.1% per ns at the optimized operating point. In addition, we studied the performance of an entanglement-based quantum key distribution (QKD) using these detectors and develop a model for the quantum bit error rate (QBER) that incorporates the afterpulsing coefficients. We verified experimentally that using these NFADs it is feasible to implement QKD over 400 km of telecom fibre. Our NFAD photon detector system is very simple, and is well suited for single-photon applications where ultra-low noise and free-running operation is required, and some afterpulsing can be tolerated.