title: Quantum walks and wavepacket dynamics on a lattice with twisted photons.
abstract: The "quantum walk" has emerged recently as a paradigmatic process for the dynamic simulation of complex quantum systems, entanglement production and quantum computation. Hitherto, photonic implementations of quantum walks have mainly been based on multipath interferometric schemes in real space. We report the experimental realization of a discrete quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons. In contrast to previous implementations, the whole process develops in a single light beam, with no need of interferometers; it requires optical resources scaling linearly with the number of steps; and it allows flexible control of input and output superposition states. Exploiting the latter property, we explored the system band structure in momentum space and the associated spin-orbit topological features by simulating the quantum dynamics of Gaussian wavepackets. Our demonstration introduces a novel versatile photonic platform for quantum simulations.
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Cardano
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Massa
authors.affiliation: Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: Hammam
authors.initials: H
authors.lastname: Qassim
authors.affiliation: Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Karimi
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Sergei
authors.initials: S
authors.lastname: Slussarenko
authors.affiliation: CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Paparo
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy. ; CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Corrado
authors.initials: C
authors.lastname: de Lisio
authors.affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Roma 00185, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Sciarrino
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Santamato
authors.affiliation: Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Boyd
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy. ; CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Marrucci
keywords: Orbital angular momentum of light; Periodic quantum systems; Quantum optics; Quantum simulations; Quantum walk; Spin-orbit effects