Textbook Standard Quantum Mechanics StdQM can be viewed to be a form of voodoo physics in the sense that symbolic formalism has taken over the physical realism of classical physics. This is expressed by the icon of StdQM in the form of a (real or complex-valued) wave function $\Psi (x_1,...,x_N)$ for an atomic system with $N$ electrons depending on $N$ 3d spatial variables $x_i$ in 3d Euclidean space $\Re^3$ for $i=1,...,N$, each variable somehow associated with possible positions of an electron. We can collect the spatial variables $x_i$ into $x=(x_1,...,x_N)\in\Re^{3N}$ and thus exhibit $\Psi (x)$ as depending on a coordinate $x$ in $3N$ dimensional Euclidean space, referred to as configuration space of possibilities with a misleading connection to classical particle mechanics with actual positions of $N$ particles specified by $x$.
For example, for a single $H_2O$ molecule, we have $N=10$ and so representation of the possible values of $\Psi (x)$ for a very modest resolution of 100 in each $\Re$, would require specification of $100^{30}$ numbers which compares with the number of atoms in the Solar system. To account for $100$ possible values in each of $30$ coordinates as $100^{30}=10^{60}$ as wave function specification in StdQM, is clearly overwhelming, to be compared with $30$ actual values as classical configuration. The step from actual to possible is a step out into the unknowable. Interaction of actual realities is thinkable as real (more or less deterministic physics), but not interaction of all possibilities without any form of causality. The meaning as physics is lacking.
Physics as physical interaction between actualities can make sense. Physics as physical interaction between possibilities does not make sense. The actuality of a coin ending with heads up can take physical form. The possibility of heads cannot interact with possibilities of tails.
We understand that $\Psi (x)$ from both physical and computational point of view is a disaster and so represents voodoo science as purely formalistic science. Recall that a voodoo magician puts a stick through a doll representing your enemy and asks for your money to give result. A physicist speaks about $\Psi (x)$ with $x\in\Re^{3N}$ and asks for a grant.
In any case $\Psi (x)$ is expected to satisfy a Schrödinger Equation SE and so describe some atom physics. In SE the 3d variables $x_i$ have a double role of both representing presence of electrons around coordinate $x_i$ in a common physical $\Re^3$, and also the spread of each electron in each private $\Re^3$ as given by the presence of a Laplacian acting with respect to $x_i$. The construction is indeed very strange.
In any case, to get a computable model the wave function is dimensionally reduced to consist of sums of products of wave functions $\Psi_i(x_i)$ depending on only one spatial variable $x_i$, typically products with two factors, which are symmetrized into (with $i\neq j$):
- $\Psi(x_i,x_j)=\Psi_i(x_i)\Psi_j(x_j)+\Psi_i(x_j)\Psi_j(x_i)$
- electrons are indistinguishable.
- $\int\Psi H\Psi dx$
- $\int\Psi_i(x_i)\Psi_j(x_i)H\Psi_j(x_i)\Psi_j(x_i)dx$
as exchange terms characteristic of StdQM. A major mystery of StdQM is the physical meaning of the exchange terms, which have no counterparts in classical physics.
In RealQM physical $\Re^3$ is subdivided into domains $\Omega_i$ acting as support for electronic wave function $\Psi_i(x)$ with $x\in\Re^3$, in which case the exchange terms vanish, and $\Psi (x)=\sum_i\Psi_i(x)$ with $x\in\Re^3$ making $\Psi (x)$ computable.
The generalisation of SE from $N=1$ to $N>1$ was made on purely formalistic grounds and it became necessary to introduce physics by dimensional reduction. RealQM appears as a natural model based on non-overlapping one-electron charge densities, which can be seen as an elaboration of Density Functional Theory DFT as extreme reduction into a single common electron density. RealQM avoids the complication of the exchange terms appearing in DFT.

