Question

Have gravitons been detected through experiment?

Answer 1

Although the graviton hasn’t been experimentally detected yet, most of the
quantum gravity models posit a neutral spin-2 particle, appearing carrier (gauge
boson) of the gravity. Similarly to the case with the neutrino before 1998, the
prevailing current opinion is that the graviton is massless. This opinion is
connected with Einstein’s theory of general relativity, where the gravity is
described by a massless field of spin 2 in a generally covariance manner.

Answer 2

Gravitons are indeed very similar in concept to photons. Both represent the quantized field of a fundamental force: photons the electromagnetic field and gravitons the gravitational field. Both are forces with infinite range -- hence both involve massless particles that travel at the speed of light. The field equations governing the propagation and interaction of these particles are different, of course, but the basic properties are the same.