Oscillation apparatus, quantum computer, and control method

A control method comprising:

• setting a coupling strength between an oscillator and a read-out circuit for reading out an internal state of the oscillator to a first coupling strength, and making the oscillator perform parametric oscillation, the oscillator comprising a resonator and a magnetic-field generating circuit, the resonator comprising a loop circuit and a capacitor, the loop circuit comprising a first superconducting line, a first Josephson junction, a second superconducting line, and a second Josephson junction connected in a ring shape, and the magnetic-field generating circuit being configured to apply a magnetic field to the loop circuit;
• and
• then, setting the coupling strength between the oscillator and the read-out circuit to a second coupling strength larger than the first coupling strength, and reading out, by the reading-out circuit, the internal state of the oscillator, wherein
• the resonator is connected to the read-out circuit through a circuit component in which the coupling strength between the oscillator and the read-out circuit is variable, and the circuit component is:
• a variable filter of which a bandwidth in which transmission of a signal is restricted is variable, or
• a variable capacitor having a variable capacitance.