TY - JOUR
T1 - Inversion of Qubit Energy Levels in Qubit-Oscillator Circuits in the Deep-Strong-Coupling Regime
AU - Yoshihara, F.
AU - Fuse, T.
AU - Ao, Z.
AU - Ashhab, S.
AU - Kakuyanagi, K.
AU - Saito, S.
AU - Aoki, T.
AU - Koshino, K.
AU - Semba, K.
N1 - Funding Information:
We thank Masahiro Takeoka for stimulating discussions. Z. A. acknowledges the Leading Graduate Program in Science and Engineering, Waseda University from MEXT, Japan. This work was supported by Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (KAKENHI) (Grants No. JP25220601 and No. JP16K05497), and Japan Science and Technology Agency Core Research for Evolutionary Science and Technology (Grant No. JPMJCR1775).
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/5/3
Y1 - 2018/5/3
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevLett.120.183601
DO - 10.1103/PhysRevLett.120.183601
M3 - Article
C2 - 29775324
AN - SCOPUS:85046532529
VL - 120
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 18
M1 - 183601
ER -