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.

Stability and stabilization of unstable condensates

“…Low dimensional superfluid circuits are of current experiment interest [18]. Periodically driven BEC circuits and the stabilization of nonequilibrium condensates is of special interest too [19,20].…”

Effective dynamics of cold atoms flowing in two ring-shaped optical potentials with tunable tunneling

“…In the Ref. [15] it was evidenced that the program can be indeed realized, constructing the qubit with bosons loaded in single ring lattice interrupted by a weak link.…”

“…Ring shaped optical lattices, in particular, allow us to engineer textbook periodic boundary conditions in many body systems, and pave the way for exploiting the currents in the lattices as 'degrees of freedom' for new quantum devices. Such optical lattices can be generated by employing Laguerre-Gauss laser beams [12,13], by using a rapidly-moving laser beam that paints a time averaged optical dipole potential [14], or by a spatial light modulator (SLM) which imprints a controlled phase onto a collimated laser beam [15]. Light fields of different circular structure has been theoretically proposed [11] by making use of Bessel laser beams.…”

Hysteresis of noninteracting and spin-orbit-coupled atomic Fermi gases with relaxation

“…The ring trap can be constructed by using Laguerre-Gaussian (LG) beams for azimuthal confinement and a pair of laser sheets for tight vertical confinement [32,33]. Atoms propagating in a ring-shape trap with periodic boundary conditions could further allow cold-atom studies of entanglement between boson species [34] and persistent current of interacting bosons [6].…”