Intellectual merit: This award is for a program on fundamental experiments in quantum optics using superconducting integrated circuits. Based on the paradigm of "circuit QED" developed by the PI's group, in which superconducting qubits are combined with microwave resonant cavities to realize the physics of the Jaynes-Cummings model with ultra-strong coupling, we are pursuing the generation, manipulation, and measurement of non-classical states of the electromagnetic field. Using the tools developed for quantum information processing with superconducting devices, we have realized a new 3D version of a "two-cavity" circuit architecture with significantly extended coherence times during the current funding period. Here a single qubit, which provides nonlinearity, is combined with two microwave cavities, allowing new possibilities for nonlinear optics at the single quantum level. We have been able to use these devices to observe new quantum phenomena, such as the single-photon Kerr regime, and to manipulate states of microwave fields in new ways. We have the ability to create interesting non-classical states, including the largest "Schrodinger cat states" (superpositions of Glauber coherent states) ever produced, and measure them with full Wigner state tomography. This opens new possibilities for employing cavities and the physics of continuous variables in quantum information processing. Our main goal with this architecture is to develop real-time quantum non-demolition measurements capable of detecting single quantum jumps, and utilize this to actively stabilize states and perform quantum error correction. The physics and capabilities developed here can have significant impact on the prospects for scalable quantum information processing with solid-state devices.
Broader impacts: This work opens a new area for fundamental studies of the quantum measurement of the electromagnetic field, as well as to develop new technology for integrated circuits which operate at the single quantum level. The experiments employ the novel features of the circuit QED system to observe and study phenomena which are mostly inaccessible with traditional AMO systems in quantum optics. The techniques and capabilities for single photon generation and detection could have major impact on the prospects for scalable quantum computation and communication in these superconducting circuits and also atomic/condensed matter hybrid systems such as ion and molecule chips. This project also continues the trend established by earlier work to forge new connections between atomic and condensed matter physics communities. The project supports graduate student research. Results will be disseminated via publications and presentations at conferences in the areas of AMO physics, quantum information, and condensed matter physics, as well as in tutorials and introductory lectures at summer schools and conferences. This research will take advantage of the infrastructure and technical knowledge for fabrication and measurement of superconducting devices developed as part of the large, applied effort for development of quantum computing at Yale, but allows new and distinct directions of fundamental physical interest.
