Fig. 2: Trajectory of bound photons.
From: Formation of robust bound states of interacting microwave photons
a, Time- and site-resolved photon occupancy on a 24-qubit ring for photon numbers nph = 1–5. To measure a nph photon bound state, nph adjacent qubits are prepared in the \(\left|1\right\rangle \) state. b, Schematic and example of bitstrings in \({\mathcal{T}}\) and \({\mathcal{S}}\). Centre of mass is defined as the centre of nph adjacent occupied sites. c, Evolution of the centre of mass of nph bound states. Each trajectory is similar to the single-photon case, highlighting the composite nature of the bound states. d, Extracted maximum (Max.) group velocity from the trajectory of the centre of mass. Black line, theoretical prediction. Exp., experimental. e, Decay of the bound state into the single excitations continuum due to dephasing. For all panels, θ = π/6 and ϕ = 2π/3, and the trajectories are averaged over all possible initial states. Data are postselected for number of excitations equal to nph.
