Strongly correlated fluids of light in a Bose-Hubbard circuit

Manipulating quantum systems composed of interacting particles represents a central challenge of modern quantum science, with applications from quantum computation to many-body physics. I will present our recent work in constructing low-entropy quantum fluids of light by employing particle-resolved assembly combined with robust adiabatic preparation [1]. This experiment is performed in a 1D Bose-Hubbard circuit implemented with an array of capacitively coupled transmon qubits. We leverage strong lattice disorder to inject individual photons into known localized eigenstates, then adiabatically remove this disorder to melt the photons into a fluid via tunneling-induced quantum fluctuations. Site-resolved readout allows us to characterize these multi-particle fluids. Inter-site entanglement measurements reveal that the particles are delocalized, and two-body density correlation measurements demonstrated that they also avoid one another, revealing Friedel oscillations characteristic of a Tonks-Girardeau gas. Finally, I will describe our efforts in investigating out-of-equilibrium dynamics in this quantum system, by leveraging the precise time- and space-resolved control of the lattice potential landscape. We employ many-body spectroscopic techniques to probe the quasiparticle excitations of the fluid, using perturbations in the lattice potential. These controlled perturbations can be applied coherently in our favor, allowing us to prepare superpositions of many-body states and observe the propagation of sound excitations of light in the lattice. Furthermore, we probe the many-body dynamics when incorporating integrability-breaking perturbations, to investigate the propagation of quantum entanglement and thermalization.