Multi‐qubit Superpositions and Operations
Artyom M. Grigoryan, Sos S. Agaian · 2025
This chapter describes the general case of working with qubits, the number of which can exceed two. It considers the multi-qubit superpositions. Each such superposition possibly describes some physical system of particles that can only be observed in a fixed number of states. The theory and application of multi-qubit superpositions are key to the development of quantum computing and image processing. The chapter also introduces important qubit gates such as Toffoli and Fredkin, demonstrating how classical logic functions can be implemented in quantum circuits. It details elementary operations in multi-qubit systems, starting with three-qubit operations using local gates and control bits. The chapter shows a few 3-qubit gates with one control bits and also gives the symbolic designation of the gates. It also shows 3-qubit gates with 2 control bits.