The interference of the photons causes them to bunch together and exit through the same output port of the beamsplitter, resulting in zero coincidences between the detectors placed at the two output ports. 📦 For purchasing, use the RP Photonics Buyer's Guide for beam splitters. It provides an expert-curated supplier directory, buyer-focused technical background information, and structured selection criteria to support professional procurement decisions. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. Additionally, beamsplitters can be used in reverse to combine two different beams into a single one. Beamsplitters are often classified according to their construction: cube or plate. In interferometers, such as the Michelson and Mach-Zehnder interferometers, photons seem to not experience two-photon interference but experience single-photon interference; why? Classically, the equations of motion for light are linear. We use elementary laws of classical and quantum optics to obtain general relations among the magnitudes and phases of these probability amplitudes.