Quantum Optics with Superconducting Circuits

Yale University, New Haven CT

Investigators

Abstract

One of the test bed systems for the study of the light-matter interactions is cavity quantum electrodynamics (cavity QED), in which a single two-level atom is coupled to a single mode of the electromagnetic field. The "strong coupling regime" of cavity QED is of particular interest, because the interaction between atom and photon is more rapid than the rates of dissipation and decoherence, and so the atom photon interactions are coherent and reversible. In this regime, the atom creates significant nonlinearities at the single photon level, revealing many of the quantum aspects of the electromagnetic field, and allowing manipulations and measurements of individual photons. This project uses a paradigm for cavity QED studies known as "circuit QED," which accesses the strong coupling physics of cavity QED in a novel superconducting integrated circuit, consisting of a superconducting transmission line resonator (the cavity for microwave photons) coupled to a single Josephson junction qubit (the two level atom). Previous experiments have focused on using the cavity as probe of the qubit's coherence, and on employing the cavity as an entanglement bus to realize quantum logic gates between qubits. In this project, previous work will be extended in new directions to use this system to generate, manipulate, and detect single microwave photons on a chip. In particular, experiments will be performed in which a qubit is simultaneously and strongly coupled to two independent cavities. In this device, the properties of one cavity affect the other via the interaction with the qubit, inducing significant photon-photon nonlinearities, and permitting quantum non-demolition measurements of a single microwave photon. This project constitutes fundamental experiments in quantum optics that have not so far been possible with traditional systems from atomic and optical physics. This work will open a new area for fundamental studies of the quantum nature of the electromagnetic field, as well as develop new technology for integrated circuits which operate at the single quantum level. 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 forges new connections between the quantum optics and condensed matter physics communities. This project also supports education of graduate students at Yale University.