Excitons guided by polaritons

Abstract

Abstract We show that an exciton on a discrete chain of sites can be guided by effective measurements induced by an ambient, non-equilibrium medium that is synchronised to the exciton transport. For experimental verification, we propose a hybrid cold atom platform, carrying the exciton as electronic excitation on a chain of atoms, which are surrounded by a slow light medium supporting polaritons. The chain is coupled to the medium through long-range Rydberg interactions. Despite the guiding mechanism being incoherent, the exciton pulse can be coherently transported with high fidelity, relying on effective quantum non-demolition measurements. These are enacted by the medium, measuring those parts of the Hilbertspace that are instantaneously not helpful for transport, which are thus effectively removed through a quantum Zeno effect. The implementation requires careful alignment of chain and medium but then no further time-dependent control. In addition to guidance, the same mechanism can also be utilized to incoherently switch coherent transport. Our concept can be ported to other exciton and polariton carrying media or devices, and will enable switches and waveguides operating with the two quasi particles involved, as we demonstrate.