Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Visualising Berry phase and diabolical points in a quantum
  exciton-polariton billiard   Diabolical points (degeneracies) can naturally occur in spectra of
two-dimensional quantum systems and classical wave resonators due to simple
symmetries. Geometric Berry phase is associated with these spectral
degeneracies. Here, we demonstrate a diabolical point and the corresponding
Berry phase in the spectrum of hybrid light-matter quasiparticles --
exciton-polaritons in semiconductor microcavities. It is well known that
sufficiently strong optical pumping can drive exciton-polaritons to quantum
degeneracy, whereby they form a macroscopically populated quantum coherent
state similar to a Bose-Einstein condensate. By pumping a microcavity with a
spatially structured light, we create a two-dimensional quantum billiard for
the exciton-polariton condensate and demonstrate a diabolical point in the
spectrum of the billiard eigenstates. The fully reconfigurable geometry of the
potential walls controlled by the optical pump enables a striking experimental
visualisation of the Berry phase associated with the diabolical point. The
Berry phase is observed and measured by direct imaging of the macroscopic
exciton-polariton wavefunctions.

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The categories of this paper are: math-ph
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph
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The categories of this paper are: patt-sol