  In these notes, we discuss squeezed states using the elementary quantum
language based on one-dimensional Schr\"odinger equation. No operators are
used. The language of quantum optics is mentioned only for a hint to solve a
differential equation. Sections II and III (squeezed vacuum and pure squeezed
states) can be used in a standard undergraduate course on quantum mechanics
after discussion of a harmonic oscillator. Section IV discusses density matrix
of mixed squeezed states in $x$-representation. These notes present explicit
(therefore somewhat lengthy) step-by-step derivations. These notes are not
intended for publication as a journal paper.
