gravity is a force, however Einstien did not agree with this and instead went on with the space-time warp theory. But I have always heard that quantum mechanics justifes gravity as a force. Now my question is what does quantum mechancis states that clearly justifies gravity?

Lol, no reply?

We don't currently have a quantum theory of gravity. Such a theory, to fit into the standard model of particle physics, would have to involve a "force" mediated by spin-2 bosons, called "gravitons".

It is difficult to see how this could be reconciled with Einstein's spacetime curvature. However, I am no expert in the field of quantum gravity.

But there is at least a quantum gravity theory that possibly don't require the graviton. For example, in Loop Quantum Gravity

"It remains open to debate whether loop quantum gravity requires, or does not require, the graviton, or whether the graviton can be accounted for in its theoretical framework. As of today, the appearance of smooth space and gravitons in LQG has not been demonstrated, and hence questions about graviton scattering cannot be answered."

http://en.wikipedia.org/wiki/Loop_quantum_gravity

There's much obsession with String Theory, but is not the only player in the game