Spontaneous emission of an atom with two close upper levels and one lower level in a multilayer dielectric medium, and quantum interference between transitions from the upper levels to the lower one, are considered. Since the medium is inhomogeneous along the direction normal to the interfaces of the dielectric layers, the vacuum has an anisotropic spatial structure, and quantum intereference between the two decay channels can appear even if the two dipole matrix elements are orthogonal to each other. If the atom is placed in a three-layer dielectric plate cavity, a strong quantum interference...
