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We investigate the effect of a mirror-symmetry plane in multiple-scattering media under plane-wave illumination along the symmetry plane. Designed and fabricated samples' optical transport properties are compared quantitatively with three-dimensional modeling. Strong polarization-dependent deviations of the bulk speckle-averaged intensity distribution at the symmetry plane are observed, showing either up to a factor two enhancement or complete suppression of the ensemble-averaged intensities. We derive analytical expressions for the ensemble-averaged intensity profiles near the symmetry plane. Apart from their interest in fundamental light propagation studies, applications of mirror-symmetric scattering media are envisioned in anti-counterfeiting.

Reliable randomness is a core ingredient in algorithms and applications ranging from numerical simulations to statistical sampling and cryptography. The outcomes of measurements on entangled quantum states can violate Bell inequalities, thus guaranteeing their intrinsic randomness. This constitutes the basis for certified randomness generation. However, this certification requires spacelike separated devices, making it unfit for a compact apparatus. Here we provide a general method for certified randomness generation on a small-scale application-ready device and perform an integrated photonic demonstration combining a solid-state emitter and a glass chip. In contrast to most existing certification protocols, which in the absence of spacelike separation are vulnerable to loopholes inherent to realistic devices, the protocol we implement accounts for information leakage and is thus compatible with emerging compact scalable devices. We demonstrate a 2-qubit photonic device that achieves the highest standard in randomness yet is cut out for real-world applications. The full 94.5-hour-long stabilized process harnesses a bright and stable single-photon quantum-dot based source, feeding into a reconfigurable photonic chip, with stability in the milliradian range on the implemented phases and consistent indistinguishability of the entangled photons above 93%. Using the contextuality framework, we certify private randomness generation and achieve a rate compatible with randomness expansion secure against quantum adversaries., Comment: 20 pages, 11 figures. Improved manuscript, close to published version