Control And Readout Of The Superconducting Circuit Quantum Electrodynamics System

As artificial atoms, superconducting qubits are not only promising candidates to realize quantum computation but also excellent systems to explore fundamental quan-tum phenomena. Recently, a new kind of qubit, developing from cavity quantum elec-trodynamics system, becomes a hot spot for its long decoherence time. It is called su-perconducting circuit quantum electrodynamics system. Differed from previous qubits, it applies microwave cavities as its readout scheme, which reduces fluctuations from the environment and provides a new kind of quantum measurement:quantum non-demolition measurement. Besides, the structure of superconducting circuit quantum electrodynamics system has advantages in multi-qubit integration. Therefore, it is al-most the best superconducting qubits in the present.In this thesis, we will first introduce basic concepts about quantum computing, quantum measurement, and the "traditional" superconducting qubits, namely charge qubits, flux qubits, and phase qubits. Then superconducting circuit quantum electro-dynamics system will be introduced. It has three parts, including artificial atoms, mi-crowave cavities, and their interactions. We use three types of artificial atoms here, which are 3D transmon,2D transmon, and 3D flux qubit, respectively. The microwave cavities are rectangular waveguide cavities made by aluminium or oxygen free copper and coplanar waveguide cavities made by aluminium. When we put the atoms near the cavities and let them couple together, we get the superconducting circuit quantum elec-trodynamics system. After that, the measurement setup will be introduced in detail. And two kinds of quantum measurements, high power readout scheme and quantum nondemolition measurement, will also be referred. At last, some experimental results will be introduced. According to the different energy levels we used, we separate these experiments into two chapters, namely two levels system and three levels system. In the chapter of two levels system, we use the Rabi oscillation, Ramsey interference, spin echo, quantum tomography to test our qubit and measurement system. In the chapter of three levels system, we introduce the experiments on dark state, coherent popula-tion trapping, Autler-Townes splitting, and electromagnetically induced transparency. In the experiments of dark state and coherent population trapping, we used two mi-crowaves to control the qutrit. When the phases and powers of two microwaves were satisfied certain conditions, the state of the qutrit did not evolve in time domain. It was then in dark state. By controlling the microwaves, we are able to "freeze" any state of a qutrit, which offers a new way to control quantum information processing. In the experiments of Autler-Townes splitting and electromagnetically induced transparency, we measured the level splitting when one of the microwaves was on resonance of the (?) type energy structure. The results agreed well with the numerical simulations. In or-der to satisfy the conditions of electromagnetically induced transparency, we induced some noise to the system to suppress the energy relaxation time. Although we did not observe the electromagnetically induced transparency, the system was indeed in the electromagnetically induced transparency region according to its conditions.