Is There a Gravitational Wave in the Universe?

We don't know how to do gravitational calculations for a quantum object, that requires a theory of quantum gravity. And we can't really do those experiments very easily because particles have almost no detectable gravity and gravity is so weak. But maybe all those particles out there are sort of like humming in gravity, and we can pick up like the sum of them. This would be like a finger print for generating gravitational waves in the universe. Would tell us something about gravity and the composition of the universe.