Why QM Needs Time-Reversibility & Unitarity Explained

[sadegh4137]

i read a text at www.askmathmacian.com, and i don't understood this

"QM requires that time-reversibility (or “unitarity”, to a professional) holds"

why QM need time-reversibility?
and what's relation between time-reversibility and unitarity?

 

[Jano L.]

More transparent statement:

The time-dependent Schroedinger equation is time-symmetric. This means that for any its solution

$$
\psi(r,t)
$$
and any $t_0$ the function

$$
\psi^*(r, t_0- t)
$$

is also its solution.