The physical universe and the mind are complimentary, in that the physical universe exists and is independent of the mind, but it is the mind which allows us to translate this physical universe into our expriences of it.
What you have called 'Buddhism' is actually mysticism. I agree that 'oneness' exists in Buddhist philosophy, but it is not as you describe - a mystic state - but instead is a state of awareness of the universe as a system. Modern Buddhism has evolved from it's ancient roots and is largely no longer the 'search for the mystic dream state' often promoted by Western practitioners who have not grasped the reality of Buddhist thought.
This would be useful if the double-slit experiment was relevant to atoms, but it is not. Being part of Quantum Physics, the double-slit experiment is relevant to quantum particles - which an atom is not. Specifically, the double-slit experiment was conducted using photons - quantum particles of light.
Secondly, the quantum particle does not exist in a 'waveform state' if unobserved. The wavefunction is merely descriptive of all states a quantum particle may exist in, but does not describe what state it does exist in.