Correlated Exciton Transport in Rydberg-Dressed-Atom Spin Chains

We investigate the transport of excitations through a chain of atoms with non-local dissipation introduced through coupling to additional short-lived states. The system is described by an effective spin-1/2 model where the ratio of the exchange interaction strength to the reservoir coupling strength determines the type of transport, including coherent exciton motion, incoherent hopping and a regime in which an emergent length scale leads to a preferred hopping distance far beyond nearest neighbors. For multiple impurities, the dissipation gives rise to strong nearest-neighbor correlations and entanglement. These results highlight the importance of non-trivial dissipation, correlations and many-body effects in recent experiments on the dipole-mediated transport of Rydberg excitations.Comment: 5 page

Quantum simulation of energy transport with embedded Rydberg aggregates

We show that an array of ultracold Rydberg atoms embedded in a laser driven background gas can serve as an aggregate for simulating exciton dynamics and energy transport with a controlled environment. Spatial disorder and decoherence introduced by the interaction with the background gas atoms can be controlled by the laser parameters. This allows for an almost ideal realization of a Haken-Reineker-Strobl type model for energy transport. Physics can be monitored using the same mechanism that provides control over the environment. The degree of decoherence is traced back to information gained on the excitation location through the monitoring, turning the setup into an experimentally accessible model system for studying the effects of quantum measurements on the dynamics of a many-body quantum system.Comment: 5 pages, 4 figures, 3 pages supp. in

Semi-analytical model for nonlinear light propagation in strongly interacting Rydberg gases

Rate equation models are extensively used to describe the many-body states of laser driven atomic gases. We show that the properties of the rate equation model used to describe nonlinear optical effects arising in interacting Rydberg gases can be understood by considering the excitation of individual super-atoms. From this we deduce a simple semi-analytic model that accurately describes the Rydberg density and optical susceptibility for different dimensionalities. We identify the previously reported universal dependence of the susceptibility on the Rydberg excited fraction as an intrinsic property of the rate equation model that is rooted in one-body properties. Benchmarking against exact master equation calculations, we identify regimes in which the semi-analytic model is particularly reliable. The performance of the model improves in the presence of dephasing which destroys higher order atomic coherences.Comment: 7 pages, 4 figure

Variations in the earth's electric field

The nature and causes of variations in the atmospheric electric field as measured at the earth's surface at Durham are investigated. Determinations of the horizontal velocity of travel of variations of periods less than one hour, are made from simultaneous field measurements, using two rotating electrostatic fluxmetera, at two points approximately 100m apart. In fair weather the horizontal speed of the variations is about 1.2 times that of the wind at 10m, suggesting that they are due primarily to the motion of windborne space charges contained in the first 100m of atmosphere. In general the magnitude of the field variations appears to be dependent on the vertical stability of the lower atmosphere. Certain distinctive variations are believed to originate from charged locomotive steam while others appear related to atmospheric convective motion. Measurements in mist and fog support the view that the undulatory nature of the field is due to the horizontal drift of fog of varying thickness or density. Frequently fields below layer clouds show wave-like variations, these are shown to be due to the horizontal motion of cloud layers which contain a periodic spatial distribution of charges. This charge distribution appears to be closely related to visible structural variations in cloud thickness or density. Reasons are given for suggesting that, in stratus cloud, charge is separated by the Wilson process. It is shown that the field disturbances below shower clouds are due mainly to the horizontal drift of the charge system associated with the cloud. Such systems may be complex for appreciable charges appear to exist outside the cloud bounderies. Examples are given of the modification of surface fields by space charges liberated by point discharge processes and it is shown that surface measurements may be critically dependent on the location of the measuring instruments relative to discharging points

Setting the Sun on the British Empire: British Economic Interests and the Decolonization of Hong Kong

From 1843 to 1997, the United Kingdom ruled Hong Kong, which included Hong Kong Island and the Kowloon Peninsula, as a Crown Colony and British Dependent Territory. Spurred by their initial interests in controlling the opium trade, the British began their colonial role after obtaining Hong Kong from Qing China after the First Opium War and Treaty of Nanking in 1842. Under Britain’s 154 years of rule, the stable nature of British government systems and thorough economic investments caused Hong Kong to become a stable, wealthy international trade center in the twentieth century. How did Britain’s economic focus on Hong Kong, i.e. the development and implementation of its capitalist economic system, influence the decolonization process between the mid-1980s and 1990s? With rapid decolonization and the rise of communism in East Asia threatening Britain’s leading world role by the mid twentieth century, officials recognized the role Hong Kong played in Britain’s economic interests and investments, including with the potential of the developing East Asian market. With this realization, Britain aimed to protect these interests by preserving elements of Hong Kong’s capitalist economic system during the decolonization negotiations and resulting legislation in the 1980s

A Return to Camelot?: British Identity, The Masculine Ideal, and the Romanticization of the Royal Flying Corps Image

My research focuses on the intersection between gender, social identity, and memory in the British military during the First World War. Focusing on the Royal Flying Corps, I explore how the image of the Royal Flying Corps stemmed from three primary avenues: Britain’s pre-war infatuation with aviation, the anonymous nature of industrial warfare in the trenches impacting public morale, and targeted recruitment tactics and medical examination criteria. These three avenues directly correlated with the British upper class perception of the ideal “masculine man”, whose characteristics of chivalry, obedience, courage, and emotional strength were directly projected onto RFC servicemen. Through an examination of pilots’ personal correspondence/memoirs and post-war films, I argue that although the general public and military officials emphasized RFC pilots as the collected, reckless, “ideal” British male, this romanticization hid the reality of this new form of warfare, in which pilots suffered from a lack of aviation medicine practice and the oppression of this “masculine ideal”. Post-war film presents an interesting perspective on this RFC image, showing RFC life as one of an “artificial” camaraderie, formulated in the creation of an “us” vs “them” mentality, as a direct result of attempting to uphold this masculine ideal. Though their character dynamics in scenes varies by individual film, the overall film genre focused on the Royal Flying Corps creates a series of “us” vs “them” relationships. These different mentalities reflect a collectivism formed under the factors of war and united on a certain set of ideals formed and defined against another set of ideals, “an other” based upon one’s respective emotional reactions to war. As there is not just one “us” vs “them” relationship present in each plot, these film representations are not only informative on how the public perceived the Royal Flying Corps, but also provide a social commentary on the time period by showing how these perceptions were interpreted to fit their own ideas of the “ideal”