  The subject of this thesis are various properties of quantum states that make
them "non-classical" and their behaviour under unitary operations. In chapter 2
some basic concepts of quantum mechanics and quantum information are reviewed.
In chapter 3 properties of quantum states analysed in the literature are
identified. I chapter 4 relations between them are analysed: whether possessing
of one property by a given state implies possessing another property by the
same state. In chapter 5 the central notion of the thesis is introduced, namely
possessing a given property in absolute vs. non-absolute way. A property is
possessed by a given state in an absolute way if it is preserved under
arbitrary unitary operation on this state. This will be applied notion to all
properties listed in chapter 3. Two main questions asked here are as follows:
Can a given property be possessed both in an absolute way and in a non-absolute
way (by different classes of states)? If yes, what are necessary and sufficient
conditions for a state possessing a given property in an absolute way?
