  A symmetric zero mass tensor of rank two is constructed using the superstring
modes of excitation which satisfies the physical state constraints of a
superstring. These states have one to one correspondence with quantised
operators and are shown to be the absorption and emission quanta of the
Minkowski space Lorentz tensors using the Gupta-Bleuler method of quantisation.
The principle of equivalence makes the tensor identical to the metric tensor at
any arbitrary space-time point. The propagator for the quantised field is
deduced. The gravitational interaction is switched on by going over from
ordinary derivatives to coderivatives.The Riemann-Christoffel affine
connections are calculated and the weak field Ricci tensor $R^{0}_{\mu \nu}$ is
shown to vanish. The interaction part $R^{int}_{\mu \nu}$ is found out and the
exact $R_{\mu \nu}$ of theory of gravity is expressed in terms of the quantised
metric. The quantum mechanical self energy of the gravitational field, in
vacuum, is shown to vanish. It is suggested that quantum gravity may be
renormalisable by the use of the physical ground states of the superstring
theory.
