  Materials with a zero refractive index support electromagnetic modes that
exhibit stationary phase profiles. While such materials have been realized
across the visible and near-infrared spectral range, radiative and dissipative
optical losses have hindered their development. We reduce losses in zero-index,
on-chip photonic crystals by introducing high-Q resonances via
resonance-trapped and symmetry-protected states. Using these approaches, we
experimentally obtain quality factors of 2.6*10^3 and 7.8*10^3 at near-infrared
wavelengths, corresponding to an order-of-magnitude reduction in propagation
loss over previous designs. Our work presents a viable approach to fabricate
zero-index on-chip nanophotonic devices with low-loss.
