Observation of the Bloch-Siegert shift in a driven quantum-to-classical transition
Pietikäinen, I.; Danilin, S.; Kumar, K. S.; Vepsäläinen, A.; Golubev, D. S.; Tuorila, J.; Paraoanu, G. S. (2017-07-07)
I. Pietikäinen, S. Danilin, K. S. Kumar, A. Vepsäläinen, D. S. Golubev, J. Tuorila, and G. S. Paraoanu Phys. Rev. B 96, 020501, https://doi.org/10.1103/PhysRevB.96.020501
© 2017 American Physical Society. Published in this repository with the kind permission of the publisher.
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.
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