Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hamiltonian of a flux qubit-LC oscillator circuit in the
  deep-strong-coupling regime   We derive the Hamiltonian of a superconducting circuit that comprises a
single-Josephson-junction flux qubit and an LC oscillator. If we keep the
qubit's lowest two energy levels, the derived circuit Hamiltonian takes the
form of the quantum Rabi Hamiltonian, which describes a two-level system
coupled to a harmonic oscillator, regardless of the coupling strength. To
investigate contributions from the qubit's higher energy levels, we numerically
calculate the transition frequencies of the circuit Hamiltonian. We find that
the qubit's higher energy levels mainly cause an overall shift of the entire
spectrum, but the energy level structure up to the seventh excited states can
still be fitted well by the quantum Rabi Hamiltonian even in the case where the
coupling strength is larger than the frequencies of the qubit and the
oscillator, i.e., when the qubit-oscillator circuit is in the
deep-strong-coupling regime. We also confirm that some of the paradoxical
properties of the quantum Rabi Hamiltonian in the deep-strong-coupling regime,
e.g. the non-negligible number of photons and the nonzero expectation value of
the flux in the oscillator in the ground state, arise from the circuit
Hamiltonian as well.

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The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th