This paper presents a new optical system for detecting light signals associated with the change in incoming photon number. The system employs quantum correlation of photon pairs created via spontaneous parametric down-conversion (SPDC). The signal, if present, will perturb the flux of the incident photon stream. The perturbed photon stream is first projected through a birefringent crystal where SPDC occurs, converting a single high-energy photon into a pair of low-energy photons. The photons in each pair eventually arrive at separate detectors. By examining the biphoton correlation using the probability distribution of the photons at the detectors, which varies depending on the displacement of the main “pump” photon stream and the change in the number of photons, the small optical displacement of the photon stream and its variance can be determined. The change in incident photon number, in other words, the presence of light signal does not influence the average of the measured optical displacement values. Nevertheless, the change in optical displacement measurement variance when the number of incident photons has changed detects the light signal. This optical setup enables the detection of light signals with low noise and remarkably high precision and sensitivity using quantum correlation. The proposed technique has potential application for axion-like particle search in experimental high energy physics.
This paper presents a new optical system for detecting light signals associated with the change in incoming photon number. The system employs quantum correlation of photon pairs created via spontaneous parametric down-conversion (SPDC). The signal, if present, will perturb the flux of the incident photon stream. The perturbed photon stream is first projected through a birefringent crystal where SPDC occurs, converting a single high-energy photon into a pair of low-energy photons. The photons in each pair eventually arrive at separate detectors. By examining the biphoton correlation using the probability distribution of the photons at the detectors, which varies depending on the displacement of the main “pump” photon stream and the change in the number of photons, the small optical displacement of the photon stream and its variance can be determined. The change in incident photon number, in other words, the presence of light signal does not influence the average of the measured optical displacement values. Nevertheless, the change in optical displacement measurement variance when the number of incident photons has changed detects the light signal. This optical setup enables the detection of light signals with low noise and remarkably high precision and sensitivity using quantum correlation. The proposed technique has potential application for axion-like particle search in experimental high energy physics.
Taking advantage of our previous experimental results and calculations that establish a new approach to the calibration of photo detectors using correlated photon pairs, we developed an experimental setup with a fast electronic control unit for the direct measurement of photon statistics. The most convenient source for generating such correlated photon pairs is a nonlinear optical process of spontaneous parametric down conversion (SPDC). When a photon of the pump beam is incident to a nonlinear crystal with phase matching condition, a pair of photons (signal and idler) is created at the same time. The photons are detected in the signal beam, and a controllable shutter is placed in the idler beam. When a detection event is made in the signal beam the fast optical shutter opens for a certain (pre-programmed) time. While the opening time of the shutter is adjustable with good time resolution, the time interval between the photons in the idler beam can be scanned, so the photon statistics can be determined.
We propose a way to use optical tools from quantum imaging and quantum communication to search for physics beyond the standard model.Spontaneous parametric down-conversion (SPDC) is a commonly used source of entangled photons in which pump photons convert to a signal-idler pair.We propose to search for "dark-SPDC" (dSPDC) events in which a new dark-sector particle replaces the idler.Though it does not interact, the presence of a dark particle can be inferred by the properties of the signal photon.Examples of dark states include axionlike particles and dark photons.We show that the presence of an optical medium opens the phase space of the down-conversion process, or decay, which would be forbidden in a vacuum.Search schemes are proposed that employ optical imaging and/or spectroscopy of the signal photons.The signal rates in our proposal scales with the second power of the small coupling to new physics, as opposed to light-shining-through-wall experiments, the signal of which scales with coupling to the fourth power.We analyze the characteristics of the optical media needed to enhance dSPDC and estimate the rate.
Spontaneous Parametric Down-Conversion (SPDC) is a cornerstone phenomenon in nonlinear optics, where an incident high-energy photon is transformed into a pair of lower-energy photons. This quantum process serves as a fundamental tool for generating entangled photon pairs, heralded single photons, and squeezed light, making it indispensable in the realms of quantum communication, quantum computing, and precision metrology. In this paper, we present a comprehensive study on the theoretical foundations and practical realization of an SPDC experimental setup, developed for the first time at the Photonics Research Laboratory at Amirkabir University of Technology. Our setup features a self-grown potassium dihydrogen phosphate (KDP) nonlinear crystal, illuminated by a 450 nm blue laser, to achieve parametric down-conversion into infrared photon pairs at 900 nm. By integrating a custom-designed transimpedance amplifier with a BPX65 photodiode, we have successfully amplified and detected the weak SPDC signal, demonstrating the feasibility of achieving high sensitivity with low-cost, widely available components. The experimental results align closely with theoretical predictions, showcasing the effectiveness of the system in detecting photon pairs with minimal resources. This study underscores the accessibility and scalability of SPDC technology, providing a blueprint for constructing versatile quantum optics experiments in resource-limited settings. By bridging the gap between theoretical insight and experimental realization, we aim to inspire further exploration of SPDC's potential in both foundational research and practical applications, laying the groundwork for future innovations in quantum technologies.
Spontaneous Parametric Down-Conversion (SPDC) is a cornerstone phenomenon in nonlinear optics, where an incident high-energy photon is transformed into a pair of lower-energy photons. This quantum process serves as a fundamental tool for generating entangled photon pairs, heralded single photons, and squeezed light, making it indispensable in the realms of quantum communication, quantum computing, and precision metrology. In this paper, we present a comprehensive study on the theoretical foundations and practical realization of an SPDC experimental setup, developed for the first time at the Photonics Research Laboratory at Amirkabir University of Technology. Our setup features a self-grown potassium dihydrogen phosphate (KDP) nonlinear crystal, illuminated by a 450 nm blue laser, to achieve parametric down-conversion into infrared photon pairs at 900 nm. By integrating a custom-designed transimpedance amplifier with a BPX65 photodiode, we have successfully amplified and detected the weak SPDC signal, demonstrating the feasibility of achieving high sensitivity with low-cost, widely available components. The experimental results align closely with theoretical predictions, showcasing the effectiveness of the system in detecting photon pairs with minimal resources. This study underscores the accessibility and scalability of SPDC technology, providing a blueprint for constructing versatile quantum optics experiments in resource-limited settings. By bridging the gap between theoretical insight and experimental realization, we aim to inspire further exploration of SPDC's potential in both foundational research and practical applications, laying the groundwork for future innovations in quantum technologies.
A method to measure the correlation function of a biphoton field, which does not require single-photon detectors and photocount coincidence schemes, has been proposed and experimentally approved. It is based on the statistical analysis of current data from analog detectors. On an example of the operation of a scheme with analog photomultiplier tubes in the signal and idler channels of degenerate parametric down conversion, it has been shown that this new approach allows one to obtain correlation function values coinciding with the results of the standard photon counting technique. It has been shown how the absolute values of photon numbers and radiation power in the signal channel of the down conversion scheme are determined from the measured correlation function. Analog detection can expand the spectral and dynamic ranges of electromagnetic radiation for the application of quantum optic technologies. A method for the reference-free measurement of the spectral sensitivity of an analog photosensor module has been demonstrated as the first example of application.
Recent years have seen the development of quantum sensing concepts utilizing nonlinear interferometers based on correlated photon pairs generated by spontaneous parametric down-conversion (SPDC). Using SPDC far from frequency degeneracy allows a “division of labor” between the mid-infrared photon for the strongest sample interaction and the correlated near-infrared photon for low-noise detection. The small number of photons provided by SPDC and the resulting inferior signal-to-noise ratio are, however, a limiting factor preventing the wide applicability of the novel sensing concept. Here, we demonstrate a nonlinear interferometer based on pump-enhanced SPDC with strongly improved emission rates while maintaining broadband spontaneous emission. For validation of the concept, we demonstrate high-resolution mid-infrared spectroscopy with near-infrared detection, showcasing improved accuracy. Although the number of mid-infrared photons is about five orders of magnitude smaller than in classical spectrometers, the sensitivity of the quantum spectrometer becomes comparable, marking an essential step toward real-world applications.