Databases for quantitative history

This paper will propose that, rather than sitting on silos of data, historians that utilise quantitative methods should endeavour to make their data accessible through databases, and treat this as a new form of bibliographic entry. Of course in many instances historical data does not lend itself easily to the creation of such data sets. With this in mind some of the issues regarding normalising raw historical data will be looked at with reference to current work on nineteenth century Irish trade. These issues encompass (but are not limited to) measurement systems, geographic locations, and potential problems that may arise in attempting to unify disaggregated sources. It will discuss the need for a concerted effort by historians to define what is required from digital resources for them to be considered accurate, and to what extent the normalisation requirements for database systems may conflict with the desire for accuracy. Many of the issues that the historian may encounter engaging with databases will be common to all historians, and there would be merit in having defined standards for referencing items, such as people, places, locations, and measurements.

Correlations in low dimensional quantum systems

In this thesis I present the work done during my PhD in the area of low dimensional quantum gases. The chapters of this thesis are self contained and represent individual projects which have been peer reviewed and accepted for publication in respected international journals. Various systems are considered, the first of which is a two particle model which possesses an exact analytical solution. I investigate the non-classical correlations that exist between the particles as a function of the tunable properties of the system. In the second work I consider the coherences and out of equilibrium dynamics of a one-dimensional Tonks-Girardeau gas. I show how the coherence of the gas can be inferred from various properties of the reduced state and how this may be observed in experiments. I then present a model which can be used to probe a one-dimensional Fermi gas by performing a measurement on an impurity which interacts with the gas. I show how this system can be used to observe the so-called orthogonality catastrophe using modern interferometry techniques. In the next chapter I present a simple scheme to create superposition states of particles with special emphasis on the NOON state. I explore the effect of inter-particle interactions in the process and then characterise the usefulness of these states for interferometry. Finally I present my contribution to a project on long distance entanglement generation in ion chains. I show how carefully tuning the environment can create decoherence-free subspaces which allows one to create and preserve entanglement.