title: Coulomb Bound States of Strongly Interacting Photons.
abstract: We show that two photons coupled to Rydberg states via electromagnetically induced transparency can interact via an effective Coulomb potential. This interaction gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasibound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb potential, thus obtaining a photonic analogue of the hydrogen atom. Under certain conditions, the wave function resembles that of a diatomic molecule in which the two polaritons are separated by a finite "bond length." These states propagate with a negative group velocity in the medium, allowing for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms.
authors.affiliation: Joint Quantum Institute and Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Maghrebi
authors.affiliation: Joint Quantum Institute and Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Gullans
authors.affiliation: Institute for Theoretical Physics III, University of Stuttgart, 70550 Stuttgart, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Bienias
authors.affiliation: Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: S
authors.initials: S
authors.lastname: Choi
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: I
authors.initials: I
authors.lastname: Martin
authors.affiliation: Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: O
authors.initials: O
authors.lastname: Firstenberg
authors.affiliation: Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Lukin
authors.affiliation: Institute for Theoretical Physics III, University of Stuttgart, 70550 Stuttgart, Germany.
authors.forename: H P
authors.initials: HP
authors.lastname: Büchler
authors.affiliation: Joint Quantum Institute and Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Gorshkov