Inversion of Qubit Energy Levels in Qubit-Oscillator Circuits in the Deep-Strong-Coupling Regime

F. Yoshihara, T. Fuse, Z. Ao, S. Ashhab, K. Kakuyanagi, S. Saito, Takao Aoki, K. Koshino, K. Semba

    Research output: Contribution to journalArticle

    15 Citations (Scopus)

    Abstract

    We report on experimentally measured light shifts of superconducting flux qubits deep-strongly coupled to LC oscillators, where the coupling constants are comparable to the qubit and oscillator resonance frequencies. By using two-tone spectroscopy, the energies of the six lowest levels of each circuit are determined. We find huge Lamb shifts that exceed 90% of the bare qubit frequencies and inversions of the qubits' ground and excited states when there are a finite number of photons in the oscillator. Our experimental results agree with theoretical predictions based on the quantum Rabi model.

    Original languageEnglish
    Article number183601
    JournalPhysical Review Letters
    Volume120
    Issue number18
    DOIs
    Publication statusPublished - 2018 May 3

    ASJC Scopus subject areas

    • Physics and Astronomy(all)

    Fingerprint Dive into the research topics of 'Inversion of Qubit Energy Levels in Qubit-Oscillator Circuits in the Deep-Strong-Coupling Regime'. Together they form a unique fingerprint.

  • Cite this

    Yoshihara, F., Fuse, T., Ao, Z., Ashhab, S., Kakuyanagi, K., Saito, S., Aoki, T., Koshino, K., & Semba, K. (2018). Inversion of Qubit Energy Levels in Qubit-Oscillator Circuits in the Deep-Strong-Coupling Regime. Physical Review Letters, 120(18), [183601]. https://doi.org/10.1103/PhysRevLett.120.183601