Quantum Gravity

The simplest of string theories are the ones that live in ten dimensions and are observed to be supersymmetric. The sum over string theory which are emphasized with Feynman diagrams can be performed and yields finite results. At considerable low energies to the likes of energies lower than mass of the massive string states E ≪ 1/ls the only excitation we will have are gravitons and other massless particles. The interactions of these particles are those of some massless fields and also of Einstein gravity fields.This is exactly how string theory quantize the gravity. The description above is nothing except the perturbative quantization of the theory.