Circuit QED Photonics

Alicia J. Kollár

Matthias Baur, Peter Leek, Andreas J. Wallraff

Thomas P. Pearsall

Blake Johnson

Controlling Photons in Superconducting Electrical Circuits Blake Robert Johnson 2011 Circuit quantum electrodynamics (circuit QED) is a system that allows for strong coupling between microwave photons in transmission line cavities and superconducting qubits or artificial atoms. While circuit QED is often studied in the context of quantum information processing, it also provides an attractive platform for performing quantum optics experiments on-a-chip, because the level of control and coupling strengths available in circuit QED opens a vast array of possibilities for the creation, manipulation, and detection of quantum states of light. In this thesis, the extension of circuit QED to two cavities is examined, including design issues for cavities with very different Q-factors, and a new qubit design is proposed that couples to both cavities. The qubit-cavity interaction, while providing much of the utility of circuit QED, also introduces additional qubit relaxation. A powerful formalism for calculating this energy decay due to the classical admittance of the electromagnetic environment is presented in the context of circuit QED. Measurements of a wide range of samples validate this theory as providing an effective model for relaxation. A new circuit element, called the ‘Purcell filter’, is introduced and demonstrated to decouple the relationship between cavity Q and qubit relaxation. Finally, a new method for performing quantum nondemolition measurements of microwave photons is demonstrated. Controlling Photons in Superconducting Electrical Circuits A Dissertation Presented to the Faculty of the Graduate School of Yale University in Candidacy for the Degree of Doctor of Philosophy by Blake Robert Johnson Dissertation Director: Professor Robert J. Schoelkopf

Xi Jiang, ziqiu zhang, Shi-Qing Tang

Circuit QED based on superconducting circuit structure is similar to the model of interaction between cavity field and atoms, and is solidified on the substrate, so it is more suitable for integration, expansion and control. The circuit QED system consists of resonators and superconducting qubits, the length of the resonators much larger than width, so it can be regarded as a one-dimensional linear planar structure in theory. We propose a theoretical model to realizing two-qubit photonic phase gate, we use two superconducting resonators to couple a magnetic flux qutrit via two capacitors in circuit QED system, and choose an appropriate interaction time, it turns out that a two-qubit photonic phase gate can be realized by one step.

Thomas P. Pearsall