In general, quantum theory is not directly used to calculate the gravitational force between objects. The current understanding of gravity is described by general relativity, which is a classical theory of gravity formulated by Albert Einstein. General relativity describes gravity as the curvature of spacetime caused by mass and energy.
Quantum theory, on the other hand, deals with the behavior of particles and fields at the microscopic level and is primarily concerned with the realm of subatomic particles and their interactions. Quantum mechanics provides a framework for understanding the behavior of particles such as electrons, photons, and quarks, but it does not incorporate gravity into its formalism.
The challenge lies in reconciling general relativity and quantum mechanics into a unified theory, often referred to as quantum gravity. Various approaches, such as string theory, loop quantum gravity, and others, have been proposed to bridge this gap and provide a consistent description of both gravity and quantum phenomena. However, a complete and experimentally validated theory of quantum gravity is still an active area of research, and there is no widely accepted framework at present.
While some aspects of quantum theory and gravitational interactions have been explored, such as quantum field theory in curved spacetime, the full understanding of quantum gravity and its application to calculating gravitational forces between objects is still an open question.