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We present a nonlocal quantum approach to polarimetry, leveraging the phenomenon of entanglement in photon pairs to enhance the precision in sample property determination. By employing two distinct channels, one containing the sample of interest and the other serving as a reference, we explore the conditions under which the inherent correlation between entangled photons can increase measurement sensitivity. Specifically, we calculate the quantum Fisher information (QFI) and compare the accuracy and sensitivity for the cases of single sample channel versus two channel quantum state tomography measurements. The theoretical results are verified by experimental analysis. Our theoretical and experimental framework demonstrates that the nonlocal strategy enables enhanced precision and accuracy in extracting information about sample characteristics more than the local measurements. Depending on the chosen estimators and noise channels present, theoretical and experimental results show that noise-induced bias decreases the precision for the estimated parameter. Such a quantum-enhanced nonlocal polarimetry holds promise for advancing diverse fields including material science, biomedical imaging, and remote sensing, via high-precision measurements through quantum entanglement., Comment: 16 pages, 7 figures

For a wide range of applications a fast, non-destructive, remote, and sensitive identification of samples with predefined characteristics is preferred instead of their full characterization. Here, we report on the experimental implementation of a nonlocal quantum measurement scheme enabling to distinguish different transparent and birefringent samples by means of polarization-entangled photon pairs and remote state preparation. On an example set of more than 80 objects with varying Mueller matrices we show that only two coincidence measurements are already sufficient for successful discrimination in contrast to at least 8 required for a comprehensive inspection. The decreased number of measurements and the sample set significantly exceeding a typical set size for various problems demonstrate the high potential of the method for applications aiming at biomedical diagnostics, remote sensing, and other classification/detection tasks., Comment: 11 pages, 5 figures

Classical polarimetry is a well-established discipline with diverse applications across different branches of science. The burgeoning interest in leveraging quantum resources to achieve highly sensitive measurements has spurred researchers to elucidate the behavior of polarized light within a quantum mechanical framework, thereby fostering the development of a quantum theory of polarimetry. In this work, drawing inspiration from polarimetric investigations in biological tissues, we investigate the precision limits of polarization rotation angle estimation about a known rotation axis, in a quantum polarimetric process, comprising three distinct quantum channels. The rotation angle to be estimated is induced by the retarder channel on the Stokes vector of the probe state. The diattenuator and depolarizer channels, acting on the probe state, can be thought of as effective noise processes. We explore the precision constraints inherent in quantum polarimetry by evaluating the quantum Fisher information (QFI) for probe states of significance in quantum metrology, namely NOON, Kings of Quantumness, and Coherent states. The effects of the noise channels as well as their ordering is analyzed on the estimation error of the rotation angle to characterize practical and optimal quantum probe states for quantum polarimetry. Furthermore, we propose an experimental framework tailored for NOON state quantum polarimetry, aiming to bridge theoretical insights with empirical validation., Comment: 17 pages, 7 figures