  We obtain experimental chimera states in the minimal network of three
identical mechanical oscillators (metronomes), by introducing phase-lagged
all-to-all coupling. For this, we have developed a real-time model-in-the-loop
coupling mechanism that allows for flexible and online change of coupling
topology, strength and phase-lag. The chimera states manifest themselves as a
mismatch of average frequency between two synchronous and one desynchronized
oscillator. We find this kind of striking chimeric behavior is robust in a wide
parameter region. At other parameters, however, chimera state can lose
stability and the system behavior manifests itself as a heteroclinic switching
between three saddle-type chimeras. Our experimental observations are in a
qualitative agreement with the model simulation.
