Phys. Rev. Lett. 94, 123602 (2005) [4 pages]ac Stark Shift and Dephasing of a Superconducting Qubit Strongly Coupled to a Cavity FieldSee Also: Erratum Received 16 August 2004; published 30 March 2005 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. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.123602
DOI:
10.1103/PhysRevLett.94.123602
PACS:
42.50.Pq, 32.60.+i, 42.50.Lc, 85.35.Gv
See AlsoErratum: D. I. Schuster, A. Wallraff, A. Blais, L. Frunzio, R.-S. Huang, J. Majer, S. M. Girvin, and R. J. Schoelkopf, Erratum: ac Stark Shift and Dephasing of a Superconducting Qubit Strongly Coupled to a Cavity Field [Phys. Rev. Lett. 94, 123602 (2005)], Phys. Rev. Lett. 98, 049902 (2007). |
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