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I have two questions about normal mode splitting in cavity.

  1. Is this splitting available when an atom in the cavity is in the ground state? I've seen many text books but their initial condition is that the atom is in the excited state. So, I have wondered whether the atom should be excited to make Vacuum Rabi Splitting.

  2. Is normal mode splitting related with Electromagnetically Induced Transparency? When I saw absorption spectrums of both phenomenons, they were the same. For this reason, I'm a bit confused about it.

Please help me out.

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  1. The problem of Rabi splitting indeed is usually considered when an atom is in the excited state. Roughly speaking, the Rabi splitting results from an energy exchange between an excited atom and a cavity. The atom emits a photon, which is reflected by the cavity, absorbed by the atom, and so on. More rigorously, quantum mechanics considers this problem as an interaction between two oscillators, that, of course, SHOULD POSSESS ENERGY: vacuum fluctuations of the cavity and THE EXCITED ATOM.

  2. Electromagnetically Induced Transparency (EIT) is completely another phenomenon resulting from the INTERFERENCE BETWEEN DIFFERENT TRANSITIONS in an atom.

If you are interested to go for more details I would recommend this article: https://arxiv.org/abs/1404.5941

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  • $\begingroup$ Let's imagine, that you want to measure the splitting in the experiment, how to do it? Basically, splitting means new states of the system: it is not bare "cavity" and "atom", but mixed states. (so-called dressed states). As usually, eigenstates of a physical system could be "probed" by light, i.e. measuring absorption or reflection spectra. It means that in order to measure the splitting you SHOULD excite the system. Note that, it means that you excite the atom only indirectly, as I said the system cannot be considered as the bare atom and the bare cavity anymore. $\endgroup$
    – Anton Baranikov
    Commented May 4, 2020 at 14:21
  • $\begingroup$ Yes, initially it should be excited in the experiment. If you ask about the exact time of the splitting it is a very complicated question. I am not sure whether it can be measured and whether it makes sense. You initially prepare the system with the splitting, so the dressed states already exist. $\endgroup$
    – Anton Baranikov
    Commented May 4, 2020 at 14:55
  • $\begingroup$ Appreciate, if you vote:) $\endgroup$
    – Anton Baranikov
    Commented May 5, 2020 at 4:00

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