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M. Abbarchi, A. Amo, V.G. Sala, D. Solnyshkov, H. Flayac, L. Ferrier, I. Sagnes, E. Galopin, A. Lemaitre, G. Malpuech and J. Bloch
Nature Physics 9, 275-279 (2013)

The coupling of two macroscopic quantum states through a tunnel barrier forms a Josephson Junction, which
displays such phenomena as Rabi oscillations, a.c. and d.c. Josephson effects, or macroscopic self-trapping,
depending on whether it is the tunnelling or interactions that dominate. Nonlinear Josephson physics (when
the interaction energy is sufficiently high) was first observed in superfluid helium and atomic condensates,
but has remained inaccessible in photonic systems because it requires large photon–photon interactions. A
goal has been to demonstrate it in such a context.

In their paper Abbarchi and colleagues report on the observation of nonlinear Josephson oscillations in a
highly nonlinear photonic system. In particular they show the passage from coherent oscillations to trapping
in a single site. Their results open the way to the experimental study of highly nonlinear regimes in photonic
systems, such as chaos or symmetry-breaking bifurcations.