Summary: The paper presents the principles of operation of quantum computers. Competitive advantages of quantum computing are shown and some variants of a construction of an ideal quantum computer proposed. We analyze also the computational process in a quantum computer from the point of view of the complexity of algorithms. Implementation of nodes of a quantum computer is exemplified based on quantum communication schemes. The operation of Bloch sphere and visualization of the state of the qubit are described. Major obstacles to the creation of quantum computers are considered.