Quantenphotons

Quantenphotons, or quantum photons, are the fundamental quanta of the electromagnetic field. In quantum electrodynamics they carry discrete energy E = hf and momentum p = h/λ, and they always travel at the speed of light in vacuum. Photons are massless gauge bosons with spin 1 and, in free space, possess two independent polarization states corresponding to helicities ±1. As quanta of the field, photons can be created or annihilated by interactions with matter, and their quantum states can be described using photon-number (Fock) states or coherent superpositions across different modes.

Quantum optics treats light as excitations of field modes rather than as particles in a classical sense. Photons obey Bose statistics, and their interference and correlations reveal nonclassical behavior. Polarization, timing, frequency, and spatial mode structure provide independent degrees of freedom that can be entangled. The indistinguishability of photons underlies phenomena such as Hong-Ou-Mandel interference, a signature of two-photon quantum interference that has become a standard test in quantum optics. Entangled photon pairs enable protocols in quantum communication and teleportation.

Photon sources range from heralded photons produced by spontaneous parametric down-conversion to on-demand emitters such as quantum dots or color centers in solids. Detection relies on highly efficient photon counters and timing, including superconducting nanowire detectors and avalanche photodiodes, as well as homodyne or heterodyne techniques for field measurements. Applications of quantum photons span fundamental tests of quantum mechanics, secure quantum communication, photonic quantum computing, and precision metrology.