Quantum computing implementations with neutral particles

We review quantum information processing with cold neutral particles, that is, atoms or polar molecules. First, we analyze the best suited degrees of freedom of these particles for storing quantum information, and then we discuss both single- and two-qubit gate implementations. We focus our discussion mainly on collisional quantum gates, which are best suited for atom-chip-like devices, as well as on gate proposals conceived for optical lattices. Additionally, we analyze schemes both for cold atoms confined in optical cavities and hybrid approaches to entanglement generation, and we show how optimal control theory might be a powerful tool to enhance the speed up of the gate operations as well as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on Neutral Particles

Speeding up the spatial adiabatic passage of matter waves in optical microtraps by optimal control

We numerically investigate the performance of atomic transport in optical microtraps via the so called spatial adiabatic passage technique. Our analysis is carried out by means of optimal control methods, which enable us to determine suitable transport control pulses. We investigate the ultimate limits of the optimal control in speeding up the transport process in a triple well configuration for both a single atomic wave packet and a Bose-Einstein condensate within a regime of experimental parameters achievable with current optical technology.Comment: 17 pages, 14 figure

Rationally designed oral vaccines can set an evolutionary trap for Salmonella Typhimurium

Secretory antibody responses (Immunoglobulin A, IgA) against repetitive bacterial surface glycans, such as O-antigens and capsules, can protect against intestinal pathogenic Enterobacteriaceae . However, efficacy of such immune responses has been limited by rapid glycan evolution and phase-variation. Here, we track IgA-driven O-antigen variation in Salmonella Typhimurium, and use this to assemble an oligovalent oral vaccine which sets an evolutionary trap. IgA targeting all fitness-neutral O-antigen escape variants of Salmonella Typhimurium rapidly selected for mutants with very short O-antigen: a phenotype known to display major fitness costs and virulence attenuation in naive hosts. Evolutionary trap vaccination therefore represents an alternative concept in vaccine design. This approach capitalizes on the inevitable and rapid evolution of bacteria in the gut, and can combine protection of the individual with elimination of virulent enteropathogen reservoirs