  The equivalence postulate of quantum mechanics offers an axiomatic approach
to quantum field theories and quantum gravity. The equivalence hypothesis can
be viewed as adaptation of the classical Hamilton-Jacobi formalism to quantum
mechanics. The construction reveals two key identities that underly the
formalism in Euclidean or Minkowski spaces. The first is a cocycle condition,
which is invariant under $D$--dimensional Mobius transformations with Euclidean
or Minkowski metrics. The second is a quadratic identity which is a
representation of the D-dimensional quantum Hamilton--Jacobi equation. In this
approach, the solutions of the associated Schrodinger equation are used to
solve the nonlinear quantum Hamilton-Jacobi equation. A basic property of the
construction is that the two solutions of the corresponding Schrodinger
equation must be retained. The quantum potential, which arises in the
formalism, can be interpreted as a curvature term. I propose that the quantum
potential, which is always non-trivial and is an intrinsic energy term
characterising a particle, can be interpreted as dark energy. Numerical
estimates of its magnitude show that it is extremely suppressed. In the
multi--particle case the quantum potential, as well as the mass, are
cumulative.
