Fabrication Of Superconducting Quantum Devices Based On Josephson Junction

Quantum computation has interested researchers a lot due to its excellent parallel computation ability.Superconducting quantum computing is one of the most promising architectures to implementing quantum computers.Superconducting quantum chips can be fabricated by conventional micro-/nano-fabrication techniques,their control and measurement can be realized by commercial microwave devices and equipment,and the ultra-low temperature environment can be achieved by a dilution refrigerator.The output signal from a superconducting quantum chip is normally down to single microwave photon level,thus to read the qubits' states out,the signal needs to be amplified inside the dilution refrigerator and at room temperature.Even the state-of-the-art commercial low-temperature low-noise microwave amplifier will introduce tens of noise(microwave)photons,which limit the signal-to-noise ratio and so as the readout fidelity.In order to boost the readout fidelity,an ultra-low temperature compatible quantum-limited(only introduce one noise photon)amplifier needs to be developed.Such a quantum-limited amplifier can be realized by using superconducting Josephson junctions.We designed and fabricated the Josephson narrowband parametric amplifier,the test results basically meet the expected design requirements.In addition,we also designed and fabricated a traveling wave parametric amplifier consists of a chain of Josephson junctions.The measurement results show that the Josephson junction chain made by our micro-/nano-fabrication processes behaves as we expect.Finally,we used the superconducting qubit to simulate the Landau-Zener interference of the two-level system.The experimental results and the theoretical numerical results are in good agreement.