The interaction of matter and light is one of the fundamental processes occurring in nature, and its most elementary form is realized when a single atom interacts with a single photon. Reaching this regime has been a major focus of research in atomic physics and quantum optics for several decades and has generated the field of cavity quantum electrodynamics. Here we perform an experiment in which a superconducting two-level system, playing the role of an artificial atom, is coupled to an on-chip cavity consisting of a superconducting transmission line resonator. We show that the strong coupling regime can be attained in a solid-state system, and we experimentally observe the coherent interaction of a superconducting two-level system with a single microwave photon. The concept of circuit quantum electrodynamics opens many new possibilities for studying the strong interaction of light and matter. This system can also be exploited for quantum information processing and quantum communication and may lead to new approaches for single photon generation and detection.

Superconducting circuits based on Josephson junctions are regarded as one of the most promising technologies for the implementation of scalable quantum computers. This review presents the basic principles of superconducting qubits and shows the progress of quantum computing and quantum simulation based on superconducting qubits in recent years. The experimental realization of gate operations, readout, error correction codes, as well as some quantum algorithms are summarized, followed by an introduction of quantum simulation. And then some important applications in fields including condensed matter physics, quantum annealing, and quantum chemistry are discussed.

Superconducting transition edge sensor (TES) bolometers require superconducting films to have controllable transition temperatures T c in different practical applications. The value of T c strongly affects thermal conductivity and thermal noise performance of TES detectors. Al films doped with Mn (Al–Mn) of different concentrations can accomplish tunable T c. A magnetron sputtering machine is used to deposit the Al–Mn films in this study. Fabrication parameters including sputtering pressure and annealing process are studied and their influences on T c and superconducting transition width ΔT c are optimized. The Al–Mn films with ΔT c below 1.0 mK for T c in a range of 520 mK–580 mK are successfully fabricated.

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