Efficient Guiding of Cold Atoms though a Photonic Band Gap Fiber

We demonstrate the first guiding of cold atoms through a 88 mm long piece of photonic band gap fiber. The guiding potential is created by a far-off resonance dipole trap propagating inside the fiber with a hollow core of 12 mu m. We load the fiber from a dark spot 85-Rb magneto optical trap and observe a peak flux of more than 10^5 atoms/s at a velocity of 1.5 m/s. With an additional reservoir optical dipole trap, a constant atomic flux of 1.5 10^4 atoms/s is sustained for more than 150\,ms. These results open up interesting possibilities to study nonlinear light-matter interaction in a nearly one-dimensional geometry and pave the way for guided matter wave interferometry.Comment: 8 pages, 3 figure

Adiabatic Transfer of Electrons in Coupled Quantum Dots

We investigate the influence of dissipation on one- and two-qubit rotations in coupled semiconductor quantum dots, using a (pseudo) spin-boson model with adiabatically varying parameters. For weak dissipation, we solve a master equation, compare with direct perturbation theory, and derive an expression for the `fidelity loss' during a simple operation that adiabatically moves an electron between two coupled dots. We discuss the possibility of visualizing coherent quantum oscillations in electron `pump' currents, combining quantum adiabaticity and Coulomb blockade. In two-qubit spin-swap operations where the role of intermediate charge states has been discussed recently, we apply our formalism to calculate the fidelity loss due to charge tunneling between two dots.Comment: 13 pages, 8 figures, to appear in Phys. Rev.

Dicke Effect in the Tunnel Current through two Double Quantum Dots

We calculate the stationary current through two double quantum dots which are interacting via a common phonon environment. Numerical and analytical solutions of a master equation in the stationary limit show that the current can be increased as well as decreased due to a dissipation mediated interaction. This effect is closely related to collective, spontaneous emission of phonons (Dicke super- and subradiance effect), and the generation of a `cross-coherence' with entanglement of charges in singlet or triplet states between the dots. Furthermore, we discuss an inelastic `current switch' mechanism by which one double dot controls the current of the other.Comment: 12 pages, 6 figures, to appear in Phys. Rev.

Spinons and Holons with Polarized Photons in a Nonlinear Waveguide

We show that the spin-charge separation predicted for correlated fermions in one dimension, could be observed using polarized photons propagating in a nonlinear optical waveguide. Using coherent control techniques and employing a cold atom ensemble interacting with the photons, large nonlinearities in the single photon level can be achieved. We show that the latter can allow for the simulation of a strongly interacting gas, which is made of stationary dark-state polaritons of two species and then shown to form a Luttinger liquid of effective fermions for the right regime of interactions. The system can be tuned optically to the relevant regime where the spin-charge separation is expected to occur. The characteristic features of the separation as demonstrated in the different spin and charge densities and velocities can be efficiently detected via optical measurements of the emitted photons with current optical technologies.Comment: To appear in New Journal of Physic

Diamonds, gold and crime displacement: Hatton Garden, and the evolution of organised crime in the UK

The 2015 Hatton Garden Heist was described as the ‘largest burglary in English legal history’. However, the global attention that this spectacular crime attracted to ‘The Garden’ tended to concentrate upon the value of the stolen goods and the vintage of the burglars. What has been ignored is how the burglary shone a spotlight into Hatton Garden itself, as an area with a unique ‘upperworld’ commercial profile and skills cluster that we identify as an incubator and facilitator for organised crime. The Garden is the UK’s foremost jewellery production and retail centre and this paper seeks to explore how Hatton Garden’s businesses integrated with a fluid criminal population to transition, through hosting lucrative (and bureaucratically complex) VAT gold frauds from 1980 to the early 1990s, to become a major base for sophisticated acquisitive criminal activities. Based on extensive interviews over a thirty year period, evidence from a personal research archive and public records, this paper details a cultural community with a unique criminal profile due to the particularities of its geographical location, ethnic composition, trading culture, skills base and international connections. The processes and structures that facilitate criminal markets are largely under-researched (Antonopoulos et al. 2015: 11), and this paper considers how elements of Hatton Garden’s ‘upperworld’ businesses integrated with project criminals, displaced by policing strategies, to effect this transition

Deglacial and Holocene sea-ice and climate dynamics in the Bransfield Strait, northern Antarctic Peninsula

The reconstruction of past sea-ice distribution in the Southern Ocean is crucial for an improved understanding of ice–ocean–atmosphere feedbacks and the evaluation of Earth system and Antarctic ice sheet models. The Antarctic Peninsula (AP) has been experiencing a warming since the start of regular monitoring of the atmospheric temperature in the 1950s. The associated decrease in sea-ice cover contrasts the trend of growing sea-ice extent in East Antarctica. To reveal the long-term sea-ice history at the northern Antarctic Peninsula (NAP) under changing climate conditions, we examined a marine sediment core from the eastern basin of the Bransfield Strait covering the last Deglacial and the Holocene. For sea-ice reconstructions, we focused on the specific sea-ice biomarker lipid IPSO25, a highly branched isoprenoid (HBI), and sea-ice diatoms, whereas a phytoplankton-derived HBI triene (C25:3) and warmer open-ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraethers (GDGTs) and diatom assemblages and compare our sea-ice and temperature records with published marine sediment and ice core data. A maximum ice cover is observed during the Antarctic Cold Reversal 13 800–13 000 years before present (13.8–13 ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3 ka. An overall decreasing sea-ice trend throughout the Middle Holocene coincides with summer ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by highly variable winter sea-ice concentrations and a sustained decline in the duration and/or concentration of spring sea ice. Overall diverging trends in GDGT-based TEX86L and RI-OH' subsurface ocean temperatures (SOTs) are found to be linked to opposing spring and summer insolation trends, respectively.</p

Regional Sanctions Against Burundi: A Powerful Campaign and Its Unintended Consequences

This paper examines the impact of regionally imposed sanctions on the trajectory of the Burundian regime and its involvement in the peace process following the 1996 coup in the country. Despite the country's socioeconomic and geopolitical vulnerability, the Buyoya government withstood the pressure from the sanctions. Through a vocal campaign against these sanctions, the new government mitigated the embargo's economic consequences and partially reestablished its international reputation. Paradoxically, this campaign planted the seed for comprehensive political concessions in the long term. While previous literature has attributed the sanctions' success in pressuring the government into negotiations to their economic impact, the government actually responded to the sanction senders' key demand to engage in unconditional, inclusive peace talks under the auspices of the regional mediator once the economy had already started to recover. The regime's anti-sanctions campaign, with its emphasis on the government's willingness to engage in peace talks, backfired, with Buyoya forced to negotiate after having become entrapped in his own rhetoric