Amplitude estimation method

An amplitude estimation method comprising executing, by processing circuitry, operations comprising:

• performing an operation of embedding a parameter θ into an amplitude in a quantum state using an operator A;
• amplifying, using a Grover operators, the amplitude in the quantum state on which the embedding operation has been performed by the operator A;
• measuring the quantum state after the amplitude has been amplified by the Grover operator G;
• estimating the parameter θ and a noise parameter p using a result obtained by measuring the quantum state, the noise parameter p indicating an intensity of noise generated in an operation;
• constructing a variational quantum circuit that adjusts a measurement basis for the quantum state after the amplitude has been amplified, the variational quantum circuit being controlled by a parameter θ′;
• setting an initial value of the parameter θ′ in the variational quantum circuit;
• estimating the parameter θ and the noise parameter p by performing a preliminary measurement of the quantum state using the variational quantum circuit in which the initial value has been set;
• reconstructing the variational quantum circuit that adjusts the measurement basis by employing, as the parameter θ′, an estimated value obtained from a result of the preliminary measurement;
• performing, using the reconstructed variational quantum circuit, a subsequent measurement of the quantum state using the adjusted measurement basis;
• and
• estimating the parameter θ and the noise parameter p using a result of the subsequent measurement.