Why do beam splitters experience losses
Devices with metallic coatings typically exhibit higher losses, while those with dichroic coatings can achieve minimal losses. Originally, these were sheets of highly polished metal perforated with holes to obtain the desired ratio of reflection to transmission. Our recent proof for the entanglement properties of states interfering with the vacuum on a beam splitter led to monotonicity and convexity properties for quantum states undergoing photon loss [Lupu-Gladstein et al. In many papers about quantum optics and interferometry, it's assumed or said that "it's well known" that linear optics commutes with uniform losses.
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