The low-latency requirements of a loophole-free Bell test prohibit time-consuming post-processing steps that are often used to improve the statistical quality of a physical random number generator (RNG). Here we demonstrate a postprocessing-free RNG that produces a random bit within 2.4(2) ns of an input trigger. We use the Allan variance as a tool for characterizing non-idealities in the RNG and designing a feedback mechanism to account for and correct long-term drift. The impact of the feedback on the predictability of the output is less than 6.4 × 10<sup>7</sup> , and results in a system capable of 24 hour operation with output that is statistically indistinguishable from a balanced Bernoulli process.
There are a variety of technologies used for single-photon detection, and within each of these technologies there are multiple device designs. While they differ radically in their nature and operation, in all cases their response to and recovery from a detection event is a complex and temporally evolving process. This makes the state of the detector at any given time dependent on the device's prior history.
For many types of measurements, and particularly high-precision measurements, a detector's complex history dependence can lead to systematic errors that must be accounted for in analysis, and this sort of accounting requires a comprehensive knowledge of the detection system. For a typical non-photon-number-resolving detector accurate characterization includes multiple parameters beyond detection efficiency (afterpulsing, recovery time, etc.) We show that all heretofore explored properties can be described in a unified way with a generalized second-order model of a detector. While empirically proven effective, there are no experimental attempts that check the validity of this approach. We propose and experimentally demonstrate a simple validity test based on calculation of 2nd and 3rd order correlation functions from a single list of detection timestamps. We also accurately calibrate detectors used for this test.