This study discusses the correction factors in detection efficiency measurements based on spontaneous parametric down-conversion (SPDC) and coincidence counting. To address the coincidence loss induced by relative delays between two detection channels, this study proposes an accurate calculation analysis based on counting probability statistics derived from coincidence events. Additionally, an approximate method utilizing histograms and the photon count rate of detectors is proposed, which can effectively reduce the errors in coincidence loss corrections. Furthermore, the study discusses the dead time of single-photon detectors (SPDs) and proposes a weighted-average method applicable for correcting the influence of dead time.
This study discusses the correction factors in detection efficiency measurements based on spontaneous parametric down-conversion (SPDC) and coincidence counting. To address the coincidence loss induced by relative delays between two detection channels, this study proposes an accurate calculation analysis based on counting probability statistics derived from coincidence events. Additionally, an approximate method utilizing histograms and the photon count rate of detectors is proposed, which can effectively reduce the errors in coincidence loss corrections. Furthermore, the study discusses the dead time of single-photon detectors (SPDs) and proposes a weighted-average method applicable for correcting the influence of dead time.
With the aim to realize Quantum Efficiency(QE) measurement of photon detectors based on Spontaneous Parametric Down-conversion(SPDC),two type of coincidence count systems were set up,the correction factors of coincidence count were analyzed and the real experimental methods of correction factors were given.Firstly,the principle of SPDC and the technique using SPDC to calibrate the QE of photo detectors were introduced.Then the design of two type of coincidence count systems,gated dual-photon counter coincidence count system and TAC/MCA coincidence count system,were introduced.Finally,the main correction factors,accidental coincidence,missing coincidence,dead time of counters and detectors were analyzed,and the calculation and test methods were also given.Experimental results show that the deviation between this two type of coincidence setups is less than 0.4% after correction,which indicates that the two setups can satisfy the requirement of QE measurement.
A new method of absolute measurement of photodetector quantum efficiency based on spontaneous parametric down- conversion (SPDC) biphoton field is discussed. The process of SPDC is studied theoretically. The single photon detection probability and two-photon coincidence probability are derived and the measurement principle of photodetectors is explained. An experimental system has been set up. The quantum efficiency of a photon-counting photomultiplier tube was measured, and the results were compared with that obtained using conventional method.
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
Single-photon detectors (SPDs) are ubiquitous in many protocols for quantum imaging, sensing, and communications. Many of these protocols critically depend on the precise knowledge of their detection efficiency. A method for the calibration of SPDs based on sources of quantum-correlated photon pairs uses single-photon detection to generate heralded single photons, which can be used as a standard of radiation at the single-photon level. These heralded photons then allow for precise calibration of SPDs in absolute terms. In this work, we investigate the absolute calibration of avalanche photodiodes based on a portable, commercial bi-photon source, and investigate the effects of multi-photon events from the spontaneous parametric down conversion (SPDC) process in these sources. We show that the multi-photon character of the bi-photon source, together with system losses, has a significant impact on the achievable accuracy for the calibration of SPDs. However, modeling the expected photon counting statistics from the squeezed vacuum in the SPDC process allows for accurate estimation of the efficiency of SPDs, assuming that the system losses are known. This study provides essential information for the design and optimization of portable bi-photon sources for their application in on-site calibration of SPDs with high accuracy, without requiring any other reference standard.
This work presents a probability theory of coincidence detection to address the detection limit of time-correlated photon sources. We use Bayes’ theorem to model instruments as a noisy communication channel and apply statistical inference to identify the minimum detectable coincidence rate. Photon triplet generation is considered as a case study to illustrate the application of coincidence detection theory for time-correlated photon sources that are based on spontaneous parametric down-conversion. A triplet generation rate of 1–100 Hz is required for source characterization performed over 1–72 hours using superconducting nanowire single-photon detectors. We envision the connection between Bayes’ theorem and coincidence detection opens up a new avenue for applying signal processing techniques available in information theory to photon coincidence measurements.
Fast characterization of pulsed spontaneous parametric down conversion (SPDC) sources is important for applications in quantum information processing and communications. We propose a simple method to perform this task, which only requires measuring the counts on the two output channels and the coincidences between them, as well as modeling the filter used to reduce the source bandwidth. The proposed method is experimentally tested and used for a complete evaluation of SPDC sources (pair emission probability, total losses, and fidelity) of various bandwidths. This method can find applications in the setting up of SPDC sources and in the continuous verification of the quality of quantum communication links.