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Do photon-number-resolving detectors provide valid evidence for the discrete nature of light?

Morgan Williamson, Gabriel D. Ko, Brian R. La Cour

Published Oct 8, 2021• 0 citations
OpenAlex

Abstract

We consider the question of whether photon-number-resolving (PNR) detectors provide compelling evidence for the discrete nature of light; i.e., whether they indicate the prior presence of a certain number of discrete photons. To answer this question, we reveal the insufficient signal-to-noise ratio (SNR) of existing PNR detectors, and propose an alternative interpretation for the analysis of PNR detector output that is consistent with a wave picture of light and does not rely on the presumption of light particles. This interpretation is based on the aggregation of correlated or accidentally coincident detections within a given detector coincidence window. Our interpretation accounts for the arbitrary character of detector coincidence windows and includes connections to established treatments of intensity interferometers. To validate our interpretation, we performed an experiment on a multiplexed PNR detector and examined the dependence of photon number on the coincidence window via post-processing. These observations were then compared to a fully classical wave model based on amplitude threshold detection, and the results were found to be in excellent agreement. We find that results from low SNR PNR detectors, such as those existing in the literature, are able to be described by classical descriptions, and therefore do not demonstrate evidence for the discrete nature of light.

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We consider the question of whether photon-number-resolving (PNR) detectors provide compelling evidence for the discrete nature of light; i.e., whether they indicate the prior presence of a certain number of discrete photons. To answer this question, we reveal the insufficient signal-to-noise ratio (SNR) of existing PNR detectors, and propose an alternative interpretation for the analysis of PNR detector output that is consistent with a wave picture of light and does not rely on the presumption of light particles. This interpretation is based on the aggregation of correlated or accidentally coincident detections within a given detector coincidence window. Our interpretation accounts for the arbitrary character of detector coincidence windows and includes connections to established treatments of intensity interferometers. To validate our interpretation, we performed an experiment on a multiplexed PNR detector and examined the dependence of photon number on the coincidence window via post-processing. These observations were then compared to a fully classical wave model based on amplitude threshold detection, and the results were found to be in excellent agreement. We find that results from low SNR PNR detectors, such as those existing in the literature, are able to be described by classical descriptions, and therefore do not demonstrate evidence for the discrete nature of light.
We consider the question of whether photon-number-resolving (PNR) detectors provide compelling evidence for the discrete nature of light; i.e., whether they indicate the prior presence of a certain number of discrete photons. To answer this question, we reveal the insufficient signal-to-noise ratio (SNR) of existing PNR detectors, and propose an alternative interpretation for the analysis of PNR detector output that is consistent with a wave picture of light and does not rely on the presumption of light particles. This interpretation is based on the aggregation of correlated or accidentally coincident detections within a given detector coincidence window. Our interpretation accounts for the arbitrary character of detector coincidence windows and includes connections to established treatments of intensity interferometers. To validate our interpretation, we performed an experiment on a multiplexed PNR detector and examined the dependence of photon number on the coincidence window via post-processing. These observations were then compared to a fully classical wave model based on amplitude threshold detection, and the results were found to be in excellent agreement. We find that results from low SNR PNR detectors, such as those existing in the literature, are able to be described by classical descriptions, and therefore do not demonstrate evidence for the discrete nature of light.
We develop a comprehensive model for the effective two-photon density matrix produced by a parametric source of entangled-photon pairs under a variety of detector configurations commonly seen in a laboratory setting: two and four photon-number-resolving (PNR) and threshold detectors. We derive the probability of obtaining a single coincidence assuming Poisson-distributed photon pairs, nonunit detection efficiency, and dark counts; obtain the effective density matrix; and use this quantity to compute the fidelity of this state with respect to the maximally entangled ideal. The four-detector PNR case admits an analytic result valid for any combination of parameters, while all other cases leverage low-efficiency approximations to arrive at closed-form expressions. Interestingly, our model reveals appreciable fidelity improvements from four detectors as opposed to two but minimal advantages for PNR over threshold detectors in the regimes explored. Overall, our work provides a valuable tool for the quantitative design of two-photon experiments under realistic nonidealities.
Abstract We investigate the operation of a photon-number-resolving (PNR) detector consisting of a cascade of waveguide-coupled Λ-type emitters, where each waveguide-coupled emitter extracts a single photon from the input light and sends it to a single-photon detector. Using Green’s function and input-output formalisms, we derive the scattering matrices and photon–photon correlators for individual scatterers. By cascading these results, we obtain a closed-form expression for the detector’s precision in the linear regime and predict how correlations generated by nonlinear photon–photon interactions influence this precision. To evaluate the performance of this PNR detector in the nonlinear regime, we apply the quantum trajectory method to the cascaded setup, calculating the achievable precision and analyzing its dependence on key system parameters, such as the number of emitters and their coupling strength to the waveguide. We compare the performance of the proposed PNR detector with that of a conventional PNR scheme based on spatial demultiplexing via beamsplitters. Our results indicate that the proposed scheme can outperform conventional detectors under realistic conditions, making it a promising candidate for next-generation PNR detection.
This work is devoted to the development of novel photon-detector models at room temperature using quantum optics elements. This work comprises of two photon-number-resolving detector (PNRD) models, and the application of PNRD in LIDAR. The first model is based on using a two-mode squeezing device to resolve photon number at room temperature. In this model we study the average intensity-intensity correlations signal at the output of a two-mode squeezing device with |N> and |α> as the two input modes. We show that the input photon-number can be resolved from the average intensity-intensity correlations. In particular, we show jumps in the average intensity-intensity correlations signal as a function of input photon-number N. Therefore, we propose that such a device may be deployed as photon-number-resolving detector at room temperature with high efficiency. In the second model we study the atom-vapor based PNRD from first principles, including quantum mechanical treatment of the electromagnetic field. We analyze a photon detector model that combines coherently controlled absorption of light and resonance fluorescence to achieve photon counting at room temperature. In particular we identify the fundamental limits to this particular scheme of photon detection. We show that there exists a time-energy uncertainty between the incident pulse strength and the time period of the incident pulse. We verify the role of a large ensemble of atoms in boosting the efficiency of such a detector. Lastly, we show the application of PNRD technique to enhance laser range finding and light detection and ranging. We present a technique that improves the signal-to-noise-ratio (SNR) of range-finding, sensing, and other light-detection applications. The technique filters out low photon numbers using PNRD. This technique has no classical analog and cannot be achieved with classical detectors. We investigate the properties of our technique and show under what conditions the scheme surpasses the classical SNR. Finally, we simulate the operation of a rangefinder, showing improvement with a low number of signal samplings and confirming the theory with a high number of signal samplings.
Photon-number-resolving (PNR) detectors are essential components of photonic quantum technologies, yet thus far, no practical metric exists to certify how many photons they can genuinely resolve in a single measurement. Here we introduce an operational framework for quantifying the capability of a PNR detector to distinguish between different numbers of photons, i.e. its genuine resolution. In turn, we develop a practical and scalable protocol for certifying the genuine resolution of a detector, which is based on coherent state probes. We apply the method to a 28-pixel photon-number-resolving superconducting nanowire single-photon detector (PNR-SNSPD) and certify genuine four-outcome resolution. Our work highlights the critical requirements in terms of detector efficiency towards achieving high genuine resolution. This approach provides an operational benchmark for PNR detectors and fills a crucial gap in the characterization of photonic quantum devices.
We present a technique that improves the signal-to-noise-ratio (SNR) of range-finding, sensing, and other light-detection applications. The technique filters out low photon numbers using photon-number-resolving detectors. This technique has no classical analog and cannot be done with classical detectors. We investigate the properties of our technique and show under what conditions the scheme surpasses the classical SNR. Finally, we simulate the operation of a rangefinder, showing improvement with a low number of signal samplings and confirming the theory with a high number of signal samplings.