A method, apparatus, and product comprising: obtaining a representation of a quantum circuit; determining that a qubit is a candidate auxiliary qubit by estimating that a state of the qubit at a first cycle is identical to a state of the qubit at a second cycle; identifying a function section in the quantum circuit based on the qubit, the function section commencing at a beginning cycle, the beginning cycle is ordered before the second cycle, the function section ending at an ending cycle, the ending cycle is ordered after the first cycle, the ending cycle is ordered after the commencing cycle, the function section utilizing the qubit as an auxiliary qubit; and outputting an indication of the function section.