  Classical linear wave superposition produces the appearance of interference.
This observation can be interpreted in two equivalent ways: one can assume that
interference is an illusion because input components remain unperturbed, or
that interference is real and input components undergo energy redistribution.
Both interpretations entail the same observable consequences at the macroscopic
level, but the first approach is considerably more popular. This preference was
established before the emergence of quantum mechanics. Unfortunately, it
requires a non-classical underlying mechanism and fails to explain well-known
microscopic observations. Classical physics appears to collapse at the quantum
level. On the other hand, quantum superposition can be described as a classical
process if the second alternative is adopted. The gap between classical
mechanics and quantum mechanics is an interpretive problem.
