Abstract Measurement process is the key element for the interpretation of the results in quantum mechanics experiments. Here weinvestigate the influence of the detector technical characteristics (e.g. detector’s dead time) upon the photon distribution a inparametric down-conversion experiment. We show that the information on photon counting for signal, idle and coincidencescan be optimized by using a correlation pattern between time-window used of the measurements, detector’s dead time andthe speed of electronic circuits. Fine tuning of these parameters allows for the maximization of information transfer betweenthe quantum system and the experimental device. We prove this by comparing known physical properties of down convertedphotons with those measured with different experimental setups.
Abstract Measurement process is the key element for the interpretation of the results in quantum mechanics experiments. Here weinvestigate the influence of the detector technical characteristics (e.g. detector’s dead time) upon the photon distribution a inparametric down-conversion experiment. We show that the information on photon counting for signal, idle and coincidencescan be optimized by using a correlation pattern between time-window used of the measurements, detector’s dead time andthe speed of electronic circuits. Fine tuning of these parameters allows for the maximization of information transfer betweenthe quantum system and the experimental device. We prove this by comparing known physical properties of down convertedphotons with those measured with different experimental setups.
We used a microcontroller-based setup for the data acquisition in a down-conversion experiment to detect single photon events. This type of setup allows us to compare the effect of the detector's dead time as well as the delay in the data acquisition on the measured data. By using various time windows for the single-photon data acquisition, we estimate the magnitude of the errors in the measuring process as a function of the correlation between the electronics delay and the detector's dead time. Our conclusions are validated by analyzing the particle number, detection rates, and statistical distributions, as well as the correlations between signal and idler photons.
Photon correlated beams, generated by parametric down-conversion in nonlinear crystals (PDC), have been proved successfully for the measurement of quantum efficiency, of single photon detectors [1, 2, 3, 4] and can be used for measuring transmittance, as well. The main feature relies on the realization of two correlated quantum channels yielding coincident events. To reduce uncertainty [4, 5, 6] and determine its ultimate limit, contributions to statistical noise in a real experimental set-up are here investigated, and a general model is proposed to calculate the maximum likelihood best estimators and evaluate the probability of coincidence. In typical measurement scheme a channel is set as trigger (idler, i) and attention is paid to catch at least the same amount of correlated photons in the other channel (signal, s) [4]. Unwanted uncorrelated photons due to PDC itself result in a decreased degree of correlation, noise fluctuations in coincidence measurements and asymmetry between the two channels, whose mean photon rate can be quite different. We indicate by with the mean rate of correlated photons in s and i channels We address the total mean photon rates in both channels as where terms take into account also additive background photon rates due to straylight and detector noise. Actually statistical noise is also due to losses of correlated photons by optical elements, non ideal detectors and electronic devices in both channels. We distinguish, therefore, between optical losses ( transmittance of the correlated photon path), detection losses detectorquantum efficiency), electronic losses associated to the dead times time during which the detection system is unable to detect photons). It is usual to identify dead times as non-extending and extending: in the first case, all photons following a revealed photon within the fixed time interval are ignored, while in the second case any incoming photon produces or prolongs Eventually the finite duration of the time coincidence window, modifies the distribution probability of coincident events. Let us consider the distribution probability of single channel
Intensity correlation measurements form the basis of many experiments based on spontaneous parametric down-conversion. In the most common situation, two single-photon avalanche diodes and coincidence electronics are used in the detection of the photon pairs, and the coincidence count distributions are measured by making use of some scanning procedure. Here we analyze the measurement of intensity correlations using multielement detector arrays. By considering the detector parameters such as the detection and noise probabilities, we found that the mean number of detected photons that maximizes the visibility of the two-photon correlations is approximately equal to the mean number of noise events in the detector array. We provide expressions predicting the strength of the measured intensity correlations as a function of the detector parameters and on the mean number of detected photons. We experimentally test our predictions by measuring far-field intensity correlations of spontaneous parametric down-conversion with an electron multiplying charge-coupled device camera, finding excellent agreement with the theoretical analysis.
Abstract In the case of quantum random number generators based on single photon arrivals, the physical properties of single-photon detectors, such as time-tagger clocks and dead time, influence the stochastic properties of the generated random numbers. This can lead to unwanted correlations among consecutive samples. We present a method based on extending the insensitive periods after photon detections. This method eliminates the unwanted stochastic effects at the cost of reduced generation speed. We calculate performance measures for our presented method and verify its correctness with computer simulations and measurements conducted on an experimental setup. Our algorithm has low complexity, making it convenient to implement in QRNG schemes, where the benefits of having uncorrelated output intervals exceed the disadvantages of the decreased rate.
Time-correlated single photon counting is a technique to record low level light signals with very high time resolution. We first describe the experimental apparatus and briefly outline the statistical interpretation of the measurement series. After, we propose a stochastic model for the formulation of interference patterns based on doubly stochastic autoregressive model class. We suggest the application of optimal filtering technique conceived in [R. J. Elliott et al., (1997)] in order to estimate the underlying intensity process of the Poisson type measurement series. Finally, we present some results of the identification of realistic data that is although in coincidence with the general view of interference experiments, goes beyond the physical interpretation and may deepen our understanding of the quantum world.
Summary form only given. In any optical system, quantum and classical theory yield identical predictions for the mean intensity. The quantum mechanical predictions diverge from the classical theory only for higher order correlations. For this reason, typical quantum-interference experiments are performed by measuring coincidence rates between two or more detectors. The usual approximation, following Glauber, is that a single-photon counter fires at a rate proportional to the intensity, or number of incident photons per unit time. This approximation is so good and so entrenched that one routinely assumes that all singles-detection rates are insensitive to quantum effects. However, if one of these detectors fires, it cannot fire again for a characteristic time, called the dead-time. This characteristic of the detectors makes them highly nonlinear over times shorter than the dead-time, and thus sensitive to the higher order intensity correlations. In other words the detector has a different response for two photons arriving at different times, than for two photons arriving at the same time. We use the process of spontaneous parametric-downconversion (SPDC) to create correlated photon-pairs and send them through a polarization-based Hong-Ou-Mander interferometer. This quantum interferometer allows us to change the photon statistics without changing the intensity of the beams.