We demonstrate theoretically the existence of a Stern-Gerlach effect for single photons in a pumped quadratic nonlinear medium hosting a sum-frequency generation process. The two-frequency basis acts as the equivalent of the spin-1/2 subspace, and the nonlinear coupling takes the role of a magnetic field. A transverse gradient in the latter then deflects the field operators into two discrete directions, thus enabling the spatial separation of orthogonal frequency superposition states by the projection of an incident state onto a transverse basis on the Bloch sphere. The latter observation might open new possibilities for the manipulation of bichromatic qubits for quantum information applications. A further emergent phenomenon is the 2-photon interference demonstrating a new manifestation of the frequency-domain Hong-Ou-Mandel effect, namely the generation of frequency superposition NOON states. We then discuss the generalization of the quantum-optical SternGerlach effect to higher spin dimensions through the use of cascaded processes, thus enabling the generation of polychromatic qutrits, and possibly even qudits. Since a principally similar analysis can be formulated in terms of the classical coupled wave equations describing sum grequency generation of macroscopic light beams, we employ our well-established simulation tools to validate and optimize a possible scheme for realizing the proposed optical Stern-Gerlach deflector, in aim for an experimental realization in the near future.