ac Stark Shift and Dephasing of a Superconducting Qubit Strongly Coupled to a Cavity Field

2004/08/16 by D. I. Schuster, David Schuster, A. Wallraff +12 · 9 citations
Computer Science · Physics and Astronomy · #Mechanical and Optical Resonators #Quantum Information and Cryptography #Quantum and electron transport phenomena #cond-mat.mes-hall #cond-mat.supr-con #quant-ph

paper · pdf · doi:10.1103/physrevlett.94.123602

published as Phys. Rev. Lett. 94, 123602 (2005) · 4 pages, 5 figures, submitted to Physical Review Letters, version with high resolution figures available at http://www.eng.yale.edu/rslab/Andreas/content/science/PubsPapers.html

arxiv created 2004/08/16 · openalex publication_date 2005/03/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30

Abstract

We have performed spectroscopy of a superconducting charge qubit coupled nonresonantly to a single mode of an on-chip resonator. The strong coupling induces a large ac Stark shift in the energy levels of both the qubit and the resonator. The dispersive shift of the resonator frequency is used to nondestructively determine the qubit state. Photon shot noise in the measurement field induces qubit level fluctuations leading to dephasing which is characteristic for the measurement backaction. A crossover in line shape with measurement power is observed and theoretically explained. For weak measurement a long intrinsic dephasing time of T2>200 ns of the qubit is found.

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