The quantum register s containing these two qubits, potentially the same register, are found within the QuantumComputer 's QuantumRegisterCollection. In section 4, through the lens of an algorithm which swaps the state of two qubits, various modes of usage of the APIs presented in section 3 are presented. Branches Tags. Program code can be put in a Python string or equivalently read in from a file into a string. Entropic uncertainty and measurement reversibility.