title: Superfluid qubit systems with ring shaped optical lattices.
abstract: We study an experimentally feasible qubit system employing neutral atomic currents. Our system is based on bosonic cold atoms trapped in ring-shaped optical lattice potentials. The lattice makes the system strictly one dimensional and it provides the infrastructure to realize a tunable ring-ring interaction. Our implementation combines the low decoherence rates of neutral cold atoms systems, overcoming single site addressing, with the robustness of topologically protected solid state Josephson flux qubits. Characteristic fluctuations in the magnetic fields affecting Josephson junction based flux qubits are expected to be minimized employing neutral atoms as flux carriers. By breaking the Galilean invariance we demonstrate how atomic currents through the lattice provide an implementation of a qubit. This is realized either by artificially creating a phase slip in a single ring, or by tunnel coupling of two homogeneous ring lattices. The single qubit infrastructure is experimentally investigated with tailored optical potentials. Indeed, we have experimentally realized scaled ring-lattice potentials that could host, in principle, n ~ 10 of such ring-qubits, arranged in a stack configuration, along the laser beam propagation axis. An experimentally viable scheme of the two-ring-qubit is discussed, as well. Based on our analysis, we provide protocols to initialize, address, and read-out the qubit.
authors.affiliation: CNR-MATIS-IMM & Dipartimento di Fisica e Astronomia, Via S. Sofia 64, 95127 Catania, Italy Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Institute of Advanced Studies, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616.
authors.forename: Luigi
authors.initials: L
authors.lastname: Amico
authors.affiliation: Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543.
authors.forename: Davit
authors.initials: D
authors.lastname: Aghamalyan
authors.affiliation: Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Division of Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Filip
authors.initials: F
authors.lastname: Auksztol
authors.affiliation: Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Division of Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Herbert
authors.initials: H
authors.lastname: Crepaz
authors.affiliation: Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Division of Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Rainer
authors.initials: R
authors.lastname: Dumke
authors.affiliation: Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and National Institute of Education and Institute of Advanced Studies, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616.
authors.forename: Leong Chuan
authors.initials: LC
authors.lastname: Kwek