A study reports the emergence of dynamical superfluid and Bose-insulator phases in quantized microcavity lattices. The work explores how light trapped in micrometre-scale structures can organize into collective states analogous to those of ultracold atomic gases, opening a route to study the superfluid-to-insulator transition with photons instead of atoms.

The transition between a superfluid, in which particles flow without friction, and a Bose insulator, in which they become localized by interactions and disorder, is one of the most studied phenomena of quantum condensed matter. Reproducing it with photons in microcavities makes it possible to control parameters such as the coupling between cavities and the optical nonlinearity more accessibly than in atomic setups.

The term 'dynamical' in the title indicates that the phases are characterized by their time evolution within the cavity lattice, rather than by a single steady state. Quantization of the field in each microcavity allows the system to be described with Bose-Hubbard-type models, where photons play the role of bosons with effective repulsion.

The results fit into the line of polaritonics and quantum simulation with light, which seeks to use photonic devices as testbeds for condensed-matter phenomena. The microcavity platform also offers a route towards optical circuits in which quantum coherence can be maintained and manipulated on a chip.