Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multi-photon transitions between energy levels in a current-biased
  Josephson tunnel junction   The escape of a small current-biased Josephson tunnel junction from the zero
voltage state in the presence of weak microwave radiation is investigated
experimentally at low temperatures. The measurements of the junction switching
current distribution indicate the macroscopic quantum tunneling of the phase
below a cross-over temperature of $T^{\star} \approx 280 \rm{mK}$. At
temperatures below $T^{\star}$ we observe both single-photon and
\emph{multi-photon} transitions between the junction energy levels by applying
microwave radiation in the frequency range between $10 \rm{GHz}$ and $38
\rm{GHz}$ to the junction. These observations reflect the anharmonicity of the
junction potential containing only a small number of levels.

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The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph