##
Preparation
of quantum mechanical states

**Preparation** means the production of certain initial conditions
on a physical object. An example is the production of light of a certain
color in Newton`s prism experiment:
The light that is prepared in this experiment possesses a certain **dynamical
property** (color or wavelength). By preparation, physical objects with
definite dynamical properties are produced. When a system has a certain
property this property will show up in a test measurement (in the prism
experiment, this can be performed by a second prism). Only if it is possible
to predict with certainty that an object will show a certain property in
a test is one allowed to ascribe this property to the physical object
itself. In this case (and *only* in this case) does the object *really
possess this property*.
Complete preparation leads to reproducible predictions about the probabilities
of all possible measurements on the physical object. To make this connection
between preparation and measured probability distributions more explicit,
one introduces the notion of the **quantum mechanical state**. The state
is identified with the specification of a probability distribution for
each possible measurement. Mathematically, a quantum mechanical state is
described by a **wave function**. With certain mathematical operations,
it is possible to extract from the wave fuction the probabilities of all
conceivable experiments. The conceptual connection between preparation,
state, wave function and probability distribution is illustrated in the
graphics below.

More detailed information on this subject (Lesson
on preparation)

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