Observation of the Bloch-Siegert shift in a driven quantum-to-classical transition

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  • University of Oulu


We show that the counter-rotating terms of the dispersive qubit-cavity Rabi model can produce relatively large and nonmonotonic Bloch-Siegert shifts in the cavity frequency as the system is driven through a quantum-to-classical transition. Using a weak microwave probe tone, we demonstrate experimentally this effect by monitoring the resonance frequency of a microwave cavity coupled to a transmon and driven by a microwave field with varying power. In the weakly driven regime (quantum phase), the Bloch-Siegert shift appears as a small constant frequency shift, while for a strong drive (classical phase) it presents an oscillatory behavior as a function of the number of photons in the cavity. The experimental results are in agreement with numerical simulations based on the quasienergy spectrum.


Original languageEnglish
Article number020501
Pages (from-to)1-5
JournalPhysical Review B
Issue number2
Publication statusPublished - 7 Jul 2017
MoE publication typeA1 Journal article-refereed

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