Unitary and Nonunitary Evolution of Qubit States in Probability Representation of Quantum Mechanics.

Review of the probability representation of qubit states and observables is presented as well as the picture of states of two-level systems in terms of Triada of Malevich's squares. A new relation of introduced probability parameters is obtained. Also, it is offered a method to visualize the quantum channel's maps of qubit states. Evolution of the two-level system is considered in terms of Triada of Malevich's squares in case of Rabi and Demkov models. [ABSTRACT FROM AUTHOR]