Alpha-phase tantalum film superconducting quantum bit based on niobium film buffer layer

The invention discloses an alpha-phase tantalum film superconducting quantum bit based on a niobium film buffer layer, which comprises a transmission line, a quarter-wavelength readout resonator and a superconducting quantum bit, and is characterized in that one end of the quarter-wavelength readout resonator is coupled with the transmission line, and the other end of the quarter-wavelength readout resonator is coupled with the superconducting quantum bit; the superconducting quantum bit is composed of two capacitor plates and a Josephson structure. The preparation method comprises the following steps: growing a niobium film as a buffer layer on a sapphire substrate at normal temperature through magnetron sputtering equipment, and then continuously growing a tantalum film on the sapphire substrate with the niobium film as the buffer layer at normal temperature to obtain an alpha-phase tantalum film with the niobium film buffer layer; the transmission line, the quarter-wavelength readout resonator and the two