A quantum computer includes: a setting unit configured to set a parameter group of n layers based on each coefficient in a linear sum of unitary operators whose number is 2 to the n-th power, wherein the parameter group of k-th (2≤k≤n) layer is recursively set based on the parameter group of (k−1)-th layer; a quantum gate having n+m qubits including n auxiliary qubits and m target qubits, and configured to execute a predetermined calculation on an input value input to each qubit based the parameter group of n layers; and a specification unit configured to specify the linear sum of the unitary operators based on a calculation result of the quantum gate.