Linear wave dynamics explains observations attributed to dark-solitons in a polariton quantum fluid

We investigate the propagation and scattering of polaritons in a planar GaAs microcavity in the linear regime under resonant excitation. The propagation of the coherent polariton wave across an extended defect creates phase and intensity patterns with identical qualitative features previously attributed to dark and half-dark solitons of polaritons. We demonstrate that these features are observed for negligible nonlinearity (i.e., polariton-polariton interaction) and are, therefore, not sufficient to identify dark and half-dark solitons. A linear model based on the Maxwell equations is shown to reproduce the experimental observations.Comment: Article + Supplementary Information (tot. 18 pages

Core promoter short tandem repeats as evolutionary switch codes for primate speciation

Alteration in gene expression levels underlies many of the phenotypic differences across species. Because of their highly mutable nature, proximity to the +1 transcription start site (TSS), and the emerging evidence of functional impact on gene expression, core promoter short tandem repeats (STRs) may be considered an ideal source of variation across species. In a genome-scale analysis of the entire Homo sapiens protein-coding genes, we have previously identified core promoters with at least one STR of ≥6-repeats, with possible selective advantage in this species. In the current study, we performed reverse analysis of the entire Homo sapiens orthologous genes in mouse in the Ensembl database, in order to identify conserved STRs that have shrunk as an evolutionary advantage to humans. Two protocols were used to minimize ascertainment bias. Firstly, two species sharing a more recent ancestor with Homo sapiens (i.e. Pan troglodytes and Gorilla gorilla gorilla) were also included in the study. Secondly, four non-primate species encompassing the major orders across Mammals, including Scandentia, Laurasiatheria, Afrotheria, and Xenarthra were analyzed as out-groups. We introduce STR evolutionary events specifically identical in primates (i.e. Homo sapiens, Pan troglodytes, and Gorilla gorilla gorilla) vs. non-primate out-groups. The average frequency of the identically shared STR motifs across those primates ranged between 0.00005 and 0.06. The identified genes are involved in important evolutionary and developmental processes, such as normal craniofacial development (TFAP2B), regulation of cell shape (PALMD), learning and long-term memory (RGS14), nervous system development (GFRA2), embryonic limb morphogenesis (PBX2), and forebrain development (APAF1). We provide evidence of core promoter STRs as evolutionary switch codes for primate speciation, and the first instance of identity-by-descent for those motifs at the interspecies level. © 2014 Wiley Periodicals, Inc

Novel designs for Penning ion traps

We present a number of alternative designs for Penning ion traps suitable for quantum information processing (QIP) applications with atomic ions. The first trap design is a simple array of long straight wires which allows easy optical access. A prototype of this trap has been built to trap Ca+ and a simple electronic detection scheme has been employed to demonstrate the operation of the trap. Another trap design consists of a conducting plate with a hole in it situated above a continuous conducting plane. The final trap design is based on an array of pad electrodes. Although this trap design lacks the open geometry of the traps described above, the pad design may prove useful in a hybrid scheme in which information processing and qubit storage take place in different types of trap. The behaviour of the pad traps is simulated numerically and techniques for moving ions rapidly between traps are discussed. Future experiments with these various designs are discussed. All of the designs lend themselves to the construction of multiple trap arrays, as required for scalable ion trap QIP.Comment: 11 pages, 10 figure

Driven-dissipative spin chain model based on exciton-polariton condensates

An infinite chain of driven-dissipative condensate spins with uniform nearest-neighbor coherent coupling is solved analytically and investigated numerically. Above a critical occupation threshold the condensates undergo spontaneous spin bifurcation (becoming magnetized) forming a binary chain of spin-up or spin-down states. Minimization of the bifurcation threshold determines the magnetic order as a function of the coupling strength. This allows control of multiple magnetic orders via adiabatic (slow ramping of) pumping. In addition to ferromagnetic and anti-ferromagnetic ordered states we show the formation of a paired-spin ordered state $\left|\dots \uparrow \uparrow \downarrow \downarrow \dots \right. \rangle$ as a consequence of the phase degree of freedom between condensates

Novel designs for Penning ion traps

Project supported by the European Commission within the FP5 RTD programmes HITRAP and QGATES and the Integrated Project FET/QIPC “SCALA” FP6. We also acknowledge the support from the EPSRC. JRCP acknowledges the support by CONACyT, SEP and the ORS Awards

Molecular study of PKD1 & PKD2 genes by linkage analysis and determining the genotype/phenotype correlations in several Iranian families with autosomal dominant polycystic kidney disease

Background: Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder with genetic heterogeneity. Up to three loci are involved in this disease, PKD1 on chromosome 16p 13.3, PKD2 on 4q21, and a third locus of unknown location. Methods: Here we report the first molecular genetic study of ADPKD and the existence of locus heterogeneity for ADPKD in the Iranian population by performing linkage analysis on 15 affected families. Results: Eleven families showed linkage to PKD1 and two families showed linkage to PKD2. In two families, PKD1 markers are common in all affected members but PKD2 markers were not informative. Conclusion: The results of this study demonstrate significant locus heterogeneity in autosomal dominant PKD in Iran. Analysis of clinical data confirms a milder ADPKD phenotype for PKD2 families. Our results showed relatively high heterozygosity rates and PIC values for some markers, while the most informative markers were KG8 and 16AC2.5 for PKD1 gene and AFM224x6 for PKD2 gene

Robust platform for engineering pure-quantum-state transitions in polariton condensates

We report on pure-quantum-state polariton condensates in optical annular traps. The study of the underlying mechanism reveals that the polariton wavefunction always coalesces in a single pure-quantum-state that, counter-intuitively, is always the uppermost confined state with the highest overlap to the exciton reservoir. The tunability of such states combined with the short polariton lifetime allows for ultrafast transitions between coherent mesoscopic wavefunctions of distinctly different symmetries rendering optically confined polariton condensates a promising platform for applications such as many-body quantum circuitry and continuous-variable quantum processing.Comment: 5 pages, 5 figure

Nontrivial phase coupling in polariton multiplets

We investigate the phase coupling between spatially separated polariton condensates under nonresonant optical pulsed excitation. In the simple case of two condensates, we observe phase locking either in symmetric or antisymmetric states. We demonstrate that the coupling symmetry depends both on the separation distance and outflow velocity from the condensates. We interpret the observations through stimulated relaxation of polaritons to the phase configuration with the highest occupation. We derive an analytic criterion for the phase locking of a pair-polariton condensate and extend it to polariton multiplets. In the case of three condensates, we predict theoretically and observe experimentally either in-phase locking or the appearance of phase winding with phase differences of �2π/3 between neighbors. The latter state corresponds to a vortex of winding number �1 across the three polariton condensates..P. G. L. and A. V. K. acknowledge EPSRC through Programme Grant on Hybrid Polaritonics EP/M025330/1 and EP/F026455/1 for co-supporting this work. N. G. B acknowledges financial support by the Ministry of Education and Science of the Russian Federation 1425320 (Project DOI: RFMEFI58114X0006). Y. G. R. acknowledges financial support by CONACYT (Mexico) under Grant No. 251808

Cooling atoms particles and polarisable objects using dissipative dipole forces

Optical cooling methods are generally applicable to a very restricted range of species. As a means of overcoming this problem, we explore the effect of the retarded interaction of any polarisable particle (an atom, a molecule or even a micromirror) with itself, similarly to cavity-mediated cooling. We use the transfermatrix method, extended to allow us to handle moving scatterers, to explore the most general configuration of a mobile particle interacting with any 1D combination of fixed optical elements. Remarkably, this model allows a solution in closed form for the force acting on the particle, without any a priori restriction on the nature of the particle