With the advancement of non-classical light sources such as single-photon and entangled-photon sources, innovative microscopy based on the quantum principles has been proposed over traditional microscopy. This paper introduces the experimental demonstration of a quantum polarization microscopic technique that incorporates a quantum-entangled photon source. Although the point that employs the variation of polarization angle due to reflection or transmission at the sample is similar to classical polarization microscopy, the method for constructing image contrast is significantly different. Image contrast is constructed by the coincidence count of signal and idler photons. In the case that coincidence count is recorded from both the signal and idler photons, the photon statistics resemble a thermal state, similar to the blackbody radiation, but with a significantly higher peak intensity in the second order autocorrelation function at zero delay that is derived from coincidence count. While, when the coincidence count is taken from either the signal or idler photon only, though the photon state exhibits a thermal state again, the photon statistics become more dispersive and result in a lower peak intensity of the autocorrelation function. These different thermal states can be switched by slightly changing the photon polarization, which is suddenly aroused within narrow range of analyzer angle. This polarization microscopic technique can provide a superior imaging technique compared to the classical method, opening a new frontier for research in material sciences, biology, and other fields requiring high-resolution imaging.
With the advancement of non-classical light sources such as single-photon and entangled-photon sources, innovative microscopy based on the quantum principles has been proposed over traditional microscopy. This paper introduces the experimental demonstration of a quantum polarization microscopic technique that incorporates a quantum-entangled photon source. Although the point that employs the variation of polarization angle due to reflection or transmission at the sample is similar to classical polarization microscopy, the method for constructing image contrast is significantly different. Image contrast is constructed by the coincidence count of signal and idler photons. In the case that coincidence count is recorded from both the signal and idler photons, the photon statistics resemble a thermal state, similar to the blackbody radiation, but with a significantly higher peak intensity in the second order autocorrelation function at zero delay that is derived from coincidence count. While, when the coincidence count is taken from either the signal or idler photon only, though the photon state exhibits a thermal state again, the photon statistics become more dispersive and result in a lower peak intensity of the autocorrelation function. These different thermal states can be switched by slightly changing the photon polarization, which is suddenly aroused within narrow range of analyzer angle. This polarization microscopic technique can provide a superior imaging technique compared to the classical method, opening a new frontier for research in material sciences, biology, and other fields requiring high-resolution imaging.
With the advancement of non-classical light sources such as single-photon and entangled-photon sources, innovative microscopy based on quantum principles has been proposed for traditional microscopy. This paper introduces the experimental demonstration of a quantum polarization microscopic technique that incorporates a quantum-entangled photon source. Although the point that employs the variation in polarization angle due to reflection or transmission at the sample is similar to classical polarization microscopy, the method for constructing the image contrast is significantly different. The image contrast is constructed by the coincidence count of signal and idler photons. In the case that the coincidence count is recorded from both the signal and idler photons, the photon statistics resemble a thermal state, similar to the blackbody radiation, but with a significantly higher peak intensity in the second-order autocorrelation function at zero delay that is derived from the coincidence count, while, when the coincidence count is taken from either the signal or idler photon only, although the photon state exhibits a thermal state again, the photon statistics become more dispersive and result in a lower peak intensity of the autocorrelation function. These different thermal states can be switched by slightly changing the photon polarization, which is suddenly aroused within a narrow range of the analyzer angle. The autocorrelation function g2(0) at the thermal state exhibits a sensitivity that is three times higher compared to the classical coincidence count rate, and this concept can be effectively utilized to enhance the contrast of the image. One of the key achievements of our proposed method is ensuring a low power of illumination (in the order of Pico-joules) for constructing the image. In addition, the robustness without any precise setup is also favorable for practical use. This polarization microscopic technique can provide a superior imaging technique compared to the classical method, opening a new frontier for research in material sciences, biology, and other fields requiring high-resolution imaging.
Abstract Quantum imaging is an advanced method for microscopy or investigating the optical properties of materials or bio-medical inspections with high accuracy, low noise, and extremely low photo-damage. In previous work, we proposed a quantum imaging technique, in which variations in polarization angle due to reflection or transmission at the sample enhance image contrast in the second-order autocorrelation function at zero delay g 2(0). However, the image resolution observed was not satisfactory. In this report, to improve the image quality, the parameters such as coincidence window was optimized to distinguish photon statistics effectively due to change in polarization angle and the objective lens was utilized to focus the entangled photon beams. These modifications enabled optical imaging by accurately detecting slight polarization variations in different media. Although this method is effective for various samples, it has certain limitations for samples that exhibit polarization disturbances, such as those involving photon scattering. Nevertheless, the proposed approach demonstrates superior imaging performance under noisy conditions and low illumination, offering promising possibilities for high-quality quantum imaging applications.
Quantum imaging is an advanced method for microscopy or investigating the optical properties of materials or bio-medical inspections with high accuracy, low noise, and extremely low photo-damage. In previous work, we proposed a quantum imaging technique, in which variations in polarization angle due to reflection or transmission at the sample enhance image contrast in the second-order autocorrelation function at zero delay g2(0). However, the image resolution observed was not satisfactory. In this report, to improve the image quality, the parameters such as coincidence window was optimized to distinguish photon statistics effectively due to change in polarization angle and the objective lens was utilized to focus the entangled photon beams. These modifications enabled optical imaging by accurately detecting slight polarization variations in different media. It is suggested that the proposed method enables a superior imaging performance even in the presence of noise and low-power illumination requirement, offering new possibilities for high-quality imaging applications.
Two-photon interference in a Hong-Ou-Mandel (HOM) interferometer can be used as a quantum sensing mechanism due to the sensitivity of the interference dip to perturbations of the photon indistinguishability. In particular, recent works have generalized this concept to microscopy setups, but the sensitivity to optical path differences constrains its application to samples with thickness variation typically below a few micrometers if tracking changes in the coincidences at a fixed delay. Extending the concept to polarization microscopy and circumventing this limitation, this manuscript explores the use of a narrowband photon pair source with coherence length >1 mm to broaden the HOM dip. Thus, realistic sample-thickness variations introduce negligible temporal distinguishability, and changes in coincidence rate at the dip centre are then dominated by sample-induced polarization effects. To compute the polarization rotation, we develop a statistical model for the interferometer, derive the Fisher information, and establish a maximum-likelihood estimator for the local fast-axis angle. Recording dip and baseline frames at each sample position via raster scanning, the experimental results validate the framework, agreeing with classical polarized-intensity images while demonstrating operation at a maximum-precision regime and insensitiveness to layer thickness. Overall, the approach enclosed provides a quantum-based quantitative imaging of birefringent structures, which can motivate further advantageous applications, including enhanced signal-to-noise ratio and lower damage imaging of photosensitive samples.
Polarization entanglement of single photons is a key element to enable quantum 2.0 applications, such as quantum computing, quantum networks, and quantum sensing. Verification and fidelity assessment of the entanglement state are typically performed by sequential coincidence measurements with single-pixel photon detectors. Quantum imaging techniques that use single-photon imaging cameras for visualizing an entangled biphoton state and calculating Bell's inequality have been reported. Their performances are limited for practical use due to low photon flux and low speed. Here, we introduce a new approach to image polarization-entangled biphoton states using radial polarizations, which enables rapid high-performance entanglement measurement. An intensified single-photon counting camera (SPCC) captures a single image with multiple polarizations imposed by a radial wave plate, which converts a linear polarization of single photons to radial polarizations. The coincidence photon image is rapidly taken with the SPCC in the integrate-on-chip mode, which is triggered by the idler photons set at a specific polarization angle. Bell's inequality is calculated directly from four coincidence images that show polarization correlation. Our technique not only visualizes the entangled polarization state but also enables fast full Bell-type evaluation of photonic polarization entanglement. We envision that our approach may be instrumental for developing advanced polarization-entangled photon sources and polarization-entangled quantum systems, which in turn would advance fundamental research involving dynamic photon-matter interactions.
Technological advancements in the creation, manipulation and detection of quantum states of light have motivated the application of such states to overcome classical limits in sensing and imaging. In particular, there has been a surge of recent interest in super-resolution imaging based on principles of quantum optics. However, the application of such schemes for practical imaging of biological samples is demanding in terms of signal-to-noise ratio, speed of acquisition and robustness with respect to sample labeling. Here, we re-introduce the concept of quantum image scanning microscopy (Q-ISM), a super-resolution method that enhances the classical image scanning microscopy (ISM) method by measuring photon correlations. Q-ISM was already utilized to achieve super-resolved images of a biological sample labeled with fluorescent nanoscrystals whose contrast is based entirely on a quantum optical phenomenon, photon antibunching. We present here an experimental demonstration of the method and discuss with further details its prospects for application in life science microscopy.