Qubit-photon interactions in a cavity: Measurement-induced dephasing and number splitting

By Jay M. Gambetta, Alexandre Blais, David I. Schuster, Andreas Wallraff, Luigi Frunzio, J. Majer, Michel H. Devoret, Steven M. Girvin, Robert J. Schoelkopf. 2006

395 citations recorded by the source corpus.

We theoretically study measurement-induced dephasing of a superconducting qubit in the circuit QED architecture and compare the results to those obtained experimentally by Schuster et al. [Phys. Rev. Lett. 94, 123602 (2005)]. Strong coupling of the qubit to the resonator leads to a significant ac Stark shift of the qubit transition frequency. As a result, quantum fluctuations in the photon number populating the resonator cause dephasing of the qubit. We find good agreement between the predicted line shape of the qubit spectrum and the experimental results. Furthermore, in the strongly dispersive limit, where the Stark shift per photon is large compared to the cavity decay rate and the qubit linewidth, we predict that the qubit spectrum will be split into multiple peaks, with each peak corresponding to a different number of photons in the cavity.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/9ece15a7707d68426452dd96b804fb7925f88168

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Citations in the corpus

Rapid High-Fidelity Single-Shot Dispersive Readout of Superconducting Qubits (2017, background): “We attribute the remaining part to measurement induced mixing [33].”
Rapid High-fidelity Multiplexed Readout of Superconducting Qubits (2018, methodology): “Such unintentional resonator population causes additional dephasing of untargeted qubits [40].”
New class of quantum error-correcting codes for a bosonic mode (2016, background): “In the strong-dispersive limit, where the strength of the dispersive coupling χ is greater than the decay rates of the qubit and the cavity, one can drive the qubit conditioned on given photon number states of the cavity [116,117].”
Microwave photonics with superconducting quantum circuits (2017, background): “7, its transition frequency experiences a Stark shift 2χn when there are n photons inside the resonator, and a vacuum Lamb shift χ, which is present even when there are no photons inside the resonator [364, 365].”