Circuit QED with multi-pole microwave cavity filters

David C. McKay, Ravi Naik, Lev S. Bishop +1 more

S. Haroche, Auffeves, Meunier +5 more

Jin‐Xuan Han, Jin‐Lei Wu, Yan Wang +3 more

We present a one-step scheme in circuit quantum electrodynamics (QED) to realize multi-target controlled phase gates by using one microwave cavity that is coupled capacitively to a superconducting flux qutrit which plays the control role and simultaneously controls n target qutrits embedded in the microwave cavity. A strong classical field is imposed on the control qutrit so as to yield two dressed states, one of which is coded as a logical state. The controlled phase gates can be employed to achieve the creation of entangled states deterministically without any measurement, including the Bell state, the GHZ state, and the cluster state. Numerical simulations demonstrate that the high-fidelity creation of the entangled state is feasible with the constructed controlled phase gate under the present circuit QED technology.

Blake Johnson, Andrew Houck, Jay Gambetta +4 more

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

Sébastien Leger, Javier Puertas, Karthik Srikanth Bharadwaj +12 more