Polarization-based sensing proved highly effective for studying complex samples that exhibit strong scattering. This elevated the classical polarimetry as a well-acknowledged technique, especially for biomedical diagnostics [1]. Revisiting polarization-based sensing with non-classical states of light reveals the potential of the improved sensitivity [2] and enhanced accuracy [3] of the measurement compared to the classical sensing scenario. Our recent proof-of-concept experiments with photons entangled in polarization unveiled the potential of such states for quantitative characterization of scattering in tissue-mimicking phantoms [4]. In this study, we further explore the evolution of the polarization-entangled states in a turbid environment. In particular, we explore which properties of such states could be used for sensing purposes as monitoring parameters.
Polarization-based sensing proved highly effective for studying complex samples that exhibit strong scattering. This elevated the classical polarimetry as a well-acknowledged technique, especially for biomedical diagnostics [1]. Revisiting polarization-based sensing with non-classical states of light reveals the potential of the improved sensitivity [2] and enhanced accuracy [3] of the measurement compared to the classical sensing scenario. Our recent proof-of-concept experiments with photons entangled in polarization unveiled the potential of such states for quantitative characterization of scattering in tissue-mimicking phantoms [4]. In this study, we further explore the evolution of the polarization-entangled states in a turbid environment. In particular, we explore which properties of such states could be used for sensing purposes as monitoring parameters.
ABSTRACT Polarimetry with quantum light promises improved measurements for various scenarios. However, fundamental understanding of quantum photonic state transport in complex, real media, and tools to interpret the state after interaction with the sample are still lacking. Here, we theoretically and experimentally explore the evolution of polarization‐entangled states in a turbid medium on example of tissue phantoms. By elaborating mathematical relationship between Wolf's coherency matrix and density matrix, we introduce a versatile framework describing the transfer of entangled photons in turbid environments with polarization tracking and resulting quantum state representation with the density operator. Experimentally, we reveal a robust trend in the state evolution depending on the reduced scattering coefficient of the medium. Our theoretical predictions correlate with experimental findings, while the model extends the study by photonic states with different degrees of entanglement. The presented results pave the way for quantitative quantum photonic sensing enabling applications ranging from biomedical diagnostics to remote sensing.
It takes some convincing to realize that light has a polarization degree of freedom, as our eyes are usually ignorant of light's polarization. Since overcoming this hurdle of intuition, polarization has become a fantastic resource that can be easily manipulated both physically and mathematically, opening the door to a wide variety of applications. We have only recently begun to appreciate how many more doors are opened by the quantum mechanical degrees of freedom inherent to optical polarization. One use of optical polarization is for polarimetry: measuring the changes in light's polarization after it interacts with a material is an excellent procedure for nondestructively probing the characteristics and composition of the intervening material. More sensitive measurements require brighter probe light; however, sufficiently intense light will begin to destroy the sample being probed. In this thesis, we seek to provide more sensitive polarimetry without resorting to bright beams of light. Tailoring the quantum properties of various states of light has been shown to increase their usefulness for other estimation protocols and we show how to extend this paradigm to quantum enhancements in polarimetry. We begin by finding the quantum states underlying classical polarization. Each particular set of classical polarization properties corresponds to a large variety of quantum states. Next, we establish quantum descriptions of classical polarization transformations corresponding to arbitrary Jones and Mueller matrices, including quantum mechanical insights into the distinction between processes that can and cannot be described by Jones matrices. We propose candidates for the most likely quantum states underlying classical decompositions into polarized and unpolarized fractions, carefully inspecting how these quantum states behave under polarization transformations. This language allows us to inspect quantum-enhanced sensing in the multiparameter context of polarimetry. We show the dramatic possibilities for quantum enhancements in any metrological scenario that is mathematically equivalent to a rotation, of which polarization rotations are a primary example; in contrast, we also show most attenuating and depolarizing polarization transformations to forbid such dramatic enhancements. Finally, we discuss polarization and its generalizations in the context of generating quantum entanglement via linear optics. These applications serve as mere examples of the usefulness promised by light’s quantum polarization degrees of freedom.
Polarimetric imaging, a technique that captures the invisible polarization-related properties of given materials, has broad applications from fundamental physics to advanced fields such as target recognition, stress detection, biomedical diagnosis and remote sensing. The introduction of quantum sources into classical imaging systems has demonstrated distinct advantages, yet few studies have explored their combination with polarimetric imaging. In this study, we present a quantum polarimetric imaging system that integrates polarization-entangled photon pairs into a polarizer-sample-compensator-analyzer-typed polarimeter. Our system visualizes the birefringence properties of a periodical-distributed anisotropic material under decreasing illumination levels and diverse disturbing light sources. Compared to the classical system, the quantum approach reveals the superior sensitivity and robustness in low-light conditions, particularly useful in biomedical studies where the low illumination and non-destructive detection are urgently needed. The study also highlights the nonlocality of entangled photons in birefringence measurement, indicating the potential of quantum polarimetric system in the remote sensing domain.
Probing the polarization response of an object with the well-acknowledged technique of optical polarimetry enables determination of the specimen's inner properties. Prominent examples include the measurement of the chirality of proteins and molecules [1] or the induced anisotropy of disease-affected cells and tissues [2]. Aiming for better signal-to-noise ratio, lower photon flux of the probing beam and non-local diagnostics, polarimetric approaches employing the quantum nature of light and entanglement are currently rapidly developing [3]–[6]. In the present work we study the experimental feasibility of the non-local identification of different polarizing samples by performing only few coincidence measurements [6] without necessity for full density matrix reconstruction of the quantum state.
Polarimetric imaging, a technique that captures the invisible polarization-related properties of given materials, has broad applications from fundamental physics to advanced fields such as target recognition, stress detection, biomedical diagnosis and remote sensing. The introduction of quantum sources into classical imaging systems has demonstrated distinct advantages, yet few studies have explored their combination with polarimetric imaging. In this study, we present a quantum polarimetric imaging system that integrates polarization-entangled photon pairs into a polarizer-sample-compensator-analyzer (PSRA)-type polarimeter. Our system visualizes the birefringence properties of a periodical-distributed anisotropic material under decreasing illumination levels and diverse disturbing light sources. Compared to the classical system, the quantum approach reveals the superior sensitivity and robustness in low-light conditions, particularly useful in biomedical studies where the low illumination and non-destructive detection are urgently needed. The study also highlights the nonlocality of entangled photons in birefringence measurement, indicating the potential of quantum polarimetric system in the remote sensing domain.
Developing advanced technologies for sensing and imaging biological samples is crucial for medical applications, making quantum-enhanced methods particularly valuable, as they promise significant benefits over classical techniques. An important aspect of biological imaging is the characterization of tissue, which often involves resolving complex structural information such as birefringence and diattenuation. These measures require polarization-sensitive sensing which remains largely unaddressed in quantum-imaging techniques with undetected light. However, the bicolor nature and supreme phase sensitivity of nonlinear interferometers make them particularly advantageous for biological sensing. Hence, we theoretically introduce controllable polarizations of the interrogating light in a quantum-imaging setup and show the potential of nonlinear interferometers to simultaneously sense birefringence and diattenuation with undetected light while discussing both the low- and high-gain regime.