Reservoir engineering in circuit quantum electrodynamics

Robin Christian Dekker

Y. N. Srivastava

M. Göppl

Dietrich Marcuse

Eric C. Holland

Engineered quantum systems are poised to revolutionize information science in the near future. A persistent challenge in applied quantum technology is creating controllable, quantum interactions while preventing information loss to the environment, decoherence. In this thesis, we realize mesoscopic superconducting circuits whose macroscopic collective degrees of freedom, such as voltages and currents, behave quantum mechanically. We couple these mesoscopic devices to microwave cavities forming a cavity quantum electrodynamics (QED) architecture comprised entirely of circuit elements. This application of cavity QED is dubbed Circuit QED and is an interdisciplinary field seated at the intersection of electrical engineering, superconductivity, quantum optics, and quantum information science. Two popular methods for taming active quantum systems in the presence of decoherence are discrete feedback conditioned on an ancillary system or quantum reservoir engineering. Quantum reservoir engineering maintains a desired subset of a Hilbert space through a combination of drives and designed entropy evacuation. Circuit QED provides a favorable platform for investigating quantum reservoir engineering proposals. A major advancement of this thesis is the development of a quantum reservoir engineering protocol which maintains the quantum state of a microwave cavity in the presence of decoherence. This thesis synthesizes strongly coupled, coherent devices whose solutions to its driven, dissipative Hamiltonian are predicted a priori. This work lays the foundation for future advancements in cavity centered quantum reservoir engineering protocols realizing hardware efficient circuit QED designs.

Alain Sarlette, Zaki Leghtas, M. Brune +2 more

We analyze a quantum reservoir engineering method, originally introduced by Sarlette et al. [Phys. Rev. Lett. 107, 010402 (2011)], for the stabilization of nonclassical field states in high-quality cavities. We generalize the method to the protection of mesoscopic entangled field states shared by two nondegenerate field modes. The reservoir consists of a stream of atoms consecutively interacting with the cavity. Each individual atom-cavity interaction follows the same time-varying Hamiltonian, combining resonant with nonresonant parts. We gain detailed insight into the competition between the engineered reservoir and decoherence. We show that the operation is quite insensitive to experimental imperfections and that it could thus be implemented in the near future in the context of microwave cavity or circuit quantum electrodynamics.