This thesis analyzes competing theories of constitutional interpretation. Originalism as traditionally understood maintains that proper constitutional interpretation involves consulting the historical record for what the words meant at the time of ratification. This position is in stark opposition to moral reading, which views certain constitutional provisions as embodying broad philosophical principles that must be interpreted according to the best understanding of our constitutional commitments. Originalism seeks historical truths of constitutional meaning whereas moral reading aims primarily toward ethical adjudication and constitutional perfection. I track the origins of originalism and its development in American legal scholarship while analyzing the interpretive shortcomings and ethical dilemmas the theory poses. I ultimately reject originalisms as traditionally conceived as antithetical to American constitutional ideals, as blind to the teachings of this Nation’s jurisprudential history, and as more theoretically problematic than the moral reading it attempts to combat. I further contend that the newest wave of originalist thinking, which recognizes broad constitutional commitments, is no more than moral reading in disguise. I conclude that moral reading is a more defensible theory of constitutional interpretation and that new originalists ultimately agree.

Thesis (Ed.M.)--Boston University

Magnetic memory technology, especially hard disk drives are the leading technology for storing data. Increasing demand for improved storage density, along with faster processing times and low power consumption, have led to the invention and exploration of more sophisticated technologies based on magnetism. In these state of the art technologies, the primary aim is to manipulate the magnetisation state of the material in order to store information. In the next generation of magnetic memory technologies, the manipulation of the magnetisation state by an external magnetic field has been replaced with electric current or electric field. More recently, the use of strain mediated magnetoelastic coupling to change the magnetisation has attracted a lot of interest for development of energy efficient logical processing and information storage devices. One method to demonstrate this is to use a hybrid piezoelectric/ferromagnetic device. A voltage across the piezoelectric transducer induces a mechanical strain in the ferromagnetic layer and results in the manipulation of the magnetic anisotropy via the inverse magnetostriction effect. In this thesis, hybrid structures of a piezoelectric transducer and a magnetostrictive ferromagnet alloy of Fe 1−x Ga x have been used to investigate the strain manipulation and control of magnetisation. The Fe rich Fe-Ga alloy has demonstrated enhanced values of magnetostriction and has been shown to be very magnetically sensitive to strain both in bulk crystals and in thin film cases. Due to a very high magnetostriction value of (3/2) λ100 = 395 ppm, and no rare earth constituents, the material is a competitive candidate for strain mediated magnetic storage devices. The investigations described in the thesis are on 5 nm bilayer films of Fe 1−x Ga x deposited on GaAs (001) substrates by the magnetron sputter deposition technique. The ferromagnetic layers were separated by either a Cu or Al spacer layer of thickness 5 nm or 10 nm. The grown ferromagnetic layers had different Ga concentration so that they demonstrate different magnetostriction value and the magnetisation reversal process in each layer will be unique and independent. SQUID magnetometry along with ferromagnetic resonance experiments and mathematical modelling of minimising the free magnetic energy, revealed that there is a strong cubic magnetocrystalline anisotropy in the individual layers which was approximately equal for all the samples. The uniaxial anisotropy varied in each of the grown samples due to variation in the interface bonds between the substrate and the metallic stack. By modelling each of the layers to be independent, and solving at the switching field regions, the domain wall depinning energies for each layers have also been estimated. It is revealed that the domain wall depinning energies for the layers grown on the substrate is weaker than the layer grown on the metallic stacks. Ferromagnetic resonance experiments along with mathematical modelling were also used to investigate the dynamic properties of these bilayer films. The role of magnetic anisotropies and spacer type and thickness on the magnetisation precession in terms of the resonance frequency, Gilbert damping and linewidth have been investigated. A narrow linewidth of 3.8 mT and 4.7 mT for the top and bottom layers with a low Gilbert damping value of approximately 0.015 and 0.019 have been obtained which makes these films a competitive candidate for applications of microwave spintronic devices. An investigation of the effects of strain on the magnetisation reversal is described in chapter 4, by employing magnetotransport measurements on processed Hall bar devices mounted on piezoelectric transducers. The measured transport data containing contributions from the anisotropic magnetoresistance and giant magnetoresistance effects arising from distinct magnetisation reversal processes of each layer which were independent for each layer and dependent on the voltage induced strain. This strain-mediated modification of the measured resistances was different for all the samples. The induced strain changed the switching fields of the individual layers and was found to be higher for the 5 nm Al spacer samples than the 5 nm Cu spacer samples. However, the 5 nm Cu sample demonstrated a higher giant magnetoresistance contribution to the measured longitudinal resistance. Finally, the working parameters for a multi-level memory cell operated by voltage-induced strain and based on the layers studied in this thesis have been determined. The conceptualised device is an attractive candidate for high density magnetic information storage. The extension to more than one layer would increase the possible storage density by utilising the third spatial dimension to stack storage elements.

The fast development of quantum technologies requires a new theoretical effort to characterize their performance in practical scenarios. By studying both discrete and continuous variable systems, we will explore several research lines, such as control theory, quantum metrology and non-Markovianity. The thread connecting these different fields will be an approach that attempts to determine the limits and the potentiality of quantum performance in the presence of noise and scarcity of resources. Indeed, the goal of this thesis is to investigate whether quantum features can enhance the performance of particular instances of quantum protocols, and, if this is the case, how this enhancement is affected when some restrictions on the practical implementation of these protocols are in place.

In this thesis we explore aspects of dynamics of open quantum systems related to coherence and quantum correlations - necessary resources for enhanced quantum metrology and quantum computation. We first discuss limits to the precision of parameter estimation when using a quantum system in the presence of noise. To this end we introduce a variational principle for the quantum Fisher information (QFI) bounding the estimation errors of any measurement, which motivates an efficient iterative algorithm for finding optimal system preparations for noisy estimation experiments. Furthermore, we investigate influence of noise correlations on the precision in phase and frequency estimation, by delivering bounds for both spatially and temporarily correlated (non-Markovian) dephasing noise. This allows us to prove the Zeno limit in frequency estimation, conjectured in Phys. Rev. A 84, 012103 (2011) and Phys. Rev. Lett. 109, 233601 (2012). The enhanced estimation precision in quantum metrology can be, however, achieved only using highly entangled states. We propose a scheme of generating such highly correlated states as outputs of Markovian open quantum systems near first-order dynamical phase transitions. We show that the quadratic scaling of the QFI with time is present for experiments within the correlation time of the dynamics and describe a theoretical scheme for quantum enhanced estimation of an optical phase-shift using the photons being emitted from an intermittent quantum system. Finally, we establish the basis for a theory of metastability in Markovian open quantum systems, by extending methods from classical stochastic dynamics. We argue that the partial relaxation into long-lived metastable states - distinct from the asymptotic stationary state - may preserve initial coherences within decoherence-free subspaces or noiseless subsystems, thus allowing for quantum computation during the metastable regime.

Atom chips are an excellent tool for studying ultracold degenerate quantum gases, due to the high degree of controllability afforded by the precise potentials generated from the current-carrying microfabricated wires on the chip surface. The geometries of the trapping potentials are inherently capable of realising extreme aspect ratios, and therefore creating model systems with effectively reduced dimensionality, particularly the theoretically-tractable one-dimensional Bose gas. In addition, the temporal tunability makes it possible to impart non-adiabatic changes on the trapping potentials, allowing experimental investigation of samples which have been brought out of equilibrium - a situation which is not fully theoretically understood. This thesis describes the implementation, development and characterisation of an experimental system for producing the first Bose-Einstein condensates of atomic rubidium 87 gas trapped on the surface of an atom chip in Nottingham. Such an apparatus is very complex and requires careful characterisation in order to run in a stable and reliable way. Details of the experimental setup are thoroughly outlined, including the vacuum system, lasers, electronics, computer control and timing, and the optical imaging system. A newly installed compact two-dimensional magneto-optical trap provides an loading rate of 5e7 atoms per second for loading a three-dimensional mirror-magneto-optical trap with 1.5e8 atoms, at a temperature of 300uK within 10s. The cloud is then sub-Doppler cooled to 50uK, and spin-polarised with 96% purity into the |F=2,mF=+2 > ground state within 5ms, in preparation for loading a purely magnetic trap. A millimeter sized copper Z-shaped conductor located beneath the atom chip surface creates a Ioffe-Pritchard magnetic trap, into which the laser cooled cloud is loaded with 70% efficiency, and can be held with a vacuum-limited lifetime of 40s. Evaporative cooling then pre-cools the sample to below 20uK within 10s, to allow the subsequent loading into potentials created by the atom chip with 100% efficiency. A final evaporation stage then cools the cloud below the phase transition temperature of 800nK, resulting finally in pure BECs with $10^5$ atoms confined using the atom chip. Key measurements of various properties of the trapped condensates are presented, which are important in order to characterise the system fully, and to compare with theoretical expectations. In particular, included are the variation of condensate fraction with temperature, the BEC expansion dynamics, and the condensate lifetime in the trap, for example. Finally, it is demonstrated how BECs can be produced on the atom chip without the use of external macroscopic coils, achieved by using novel, integrated sheet structures located beneath the chip surface - unique to this experimental system - to create the necessary bias fields.

The description of a quantum system follows a fundamentally different paradigm to that of a classical system, leading to unique yet counter-intuitive properties. In this thesis we consider some of these unique properties, here termed simply the quantum. We focus on understanding some important types of the quantum: quantum coherence and quantum correlations, as well as quantum entanglement as an important subclass of quantum correlations. Our objective is to investigate how to quantify the quantum, what it can be used for, and how it can be preserved in the adverse presence of noise. These findings help to clarify the frontier between quantum and classical systems, a crucial endeavour for understanding the applications and advantageous features of the quantum world.

A highly integrated device capable of interfacing light and matter on a chip is presented. 1e7 caesium-133 atoms are captured from a hot vapour into a magneto-optical trap held close to a chip-mounted single-mode fibre. Sub-Doppler optical molasses cools the atoms and transfers them into a tightly focused 18W vertical optical dipole trap which intersects a 30um void that has been laser etched through the single-mode fibre. Thus, the optically trapped atoms are tightly confined in the path of fibre-guided photons for maximum overlap. Such a system is capable of writing, reading and storing quantum information and clearly has massive implications for quantum information technologies. The device presented is adaptable, scalable and highly integrated making it the ideal building block for quantum computing. Developments and modifications made to a system for producing ultracold samples of lithium-6, caesium-133 and mixtures thereof is also presented. Feshbach molecules have major applications in quantum computing, particularly in the modelling of complex many-body quantum systems. The large dipolar moment of the lithium-caesium Feshbach molecule is the largest of all the alkali dimers producing rich long-range anisotropic dipole-dipole interactions. By use of the broad Feshbach resonance situated at 834G we associate fermionic lithium-6 atoms into bosonic lithium-6-2 Feshbach molecules. Subsequent evaporative cooling drives a phase transition in the diffuse lithium gas to produce a molecular Bose-Einstein Condensate containing up to 1e4 atoms, the first to be produced in the UK. This thesis documents the construction of the quantum integrated light and matter interface (QuILMI) in its entirety from inception to realisation. An enormous amount of work has gone into the design and subsequent development of various vacuum, laser and magnetic systems that work seamlessly in tandem via a programmable control system. The system is now in a position to demonstrate to the world that atom-photon coupling on a chip is the way forward. For the lithium-caesium mixture experiment, a versatile dual-species oven has been meticulously designed, constructed and thoroughly characterised to replace one that significantly malfunctioned and harmed the experiment. The oven is capable of tuning the axial fluxes of lithium and caesium through several orders of magnitude via PID temperature controlled reservoirs. An array of fifteen 0.51mm diameter microtubes highly collimate the dual-species atomic beam such that little flux is wasted prolonging the life of both the source and the vacuum ion pumps. This source will return the system to its former glory such that the ultimate goal of realising ultracold lihtium-caesium Feshbach molecules can once again be pursued.

General Relativity (GR) has been extremely successful experimentally. However there are several reasons to consider that GR is not the complete theory of gravity. Although directly probing quantum gravity in the near future seems highly unlikely observations of the non- perturbative regime of classical gravity is improving, so any classical modification of gravity may well be testable. In this thesis we will focus on two interesting depatures from GR inspired by quantum gravity: violations of Lorentz symmetry and the weak equivalence principle. Lorentz violating (LV) gravity theories are interesting for various reasons. For example: they may have improved UV behaviour as quantum theories. Additionally testing principles which are fundamental to our understanding of nature is extremely important. We demonstrate how the causality of certain types of LV theories is realised. We then show how the relationship between two different LV theories could be used to find whether or not black holes can truly form from collapse, at least in spherical symmetry. One may be worried about whether or not LV in gravity can spoil the Lorentz invariance of matter. We generalise some known results about this problem in Horava gravity and then consider the viability of one proposal to correct this problem. Weak equivalence principle violations alter the structure of matter. By developing a simple model we demonstrate that one can maintain the weak equivalence principle in the solar system, while breaking it in high-curvature regimes. We go on to demonstrate the efficacy of the mechanism. This thesis is largely aimed at tackling questions related to the strong field regime in alternative theories of gravity: a topic of increasing interest.

Ultracold atomic gases can be utilised as extremely sensitive probes of their surrounding environment. In particular, samples of ultracold atoms confined using chip-based microtraps are an ideal tool for mapping electric and magnetic field landscapes. Over the course of this thesis, a new experiment capable of performing surface microscopy using magnetically trapped clouds of cold rubidium-87 atoms has been built. The focus of the work is on the design and construction of the experimental system, which must incorporate many different aspects for manipulating thermal atomic gases, with a view to positioning them at sub-micron distances from special surfaces. This reduced atom-surface separation is necessary for implementing a high resolution, high sensitivity magnetic field sensor with cold atoms. Although current microfabrication techniques easily enable trapping at distances on the order of micrometres, several distance-dependent surface effects - such as the Casimir-Polder force, Johnson-Nyquist noise, and stray potentials - eventually impede magnetic trapping at the sub-micron level. These surface effects can greatly modify the confining potentials, which reduces the trap depth and consequently leads to an additional loss rate of atoms from the trap. We have explored the possibility of using special surfaces such as nano-membranes of silicon nitride and graphene, which have reduced atom- surface interactions, to enable trapping distances at the sub-micron level. A multilayer printed circuit board chip has been designed to form an initial magnetic trap and then transport the cloud of atoms to a desired location over the samples. This chip, along with various samples, is mounted on a custom-made electrical feedthrough designed to make connections to all conductor that are inside the vacuum chamber. The initial cloud of cold atoms can then be prepared in the central region of the chip and delivered to the location of the samples on either side. The experimental system is able to routinely capture over 10^8 rubidium-87 atoms at a temperature of 80 micro-Kelvin in a magneto-optical trap using a novel scheme of five laser beams. A method is demonstrated for enhancing the atom number in the magneto-optical traps by a factor of two by using laser beams with two slightly different frequencies. Atoms from the magneto-optical trap are then transferred to a purely magnetic trap formed by the wires on the printed circuit board chip. Time-dependent currents in the chip wires then create a dynamic potential, which is shown to successfully transport the atomic sample over a distance of 12 millimetre with minimal atom loss. This thesis describes the development of the apparatus in detail, along with careful characterisation of the cold cloud at various stages of the experimental sequence. Initial results on the long distance atom transport are presented. Finally, the experimental results of the two frequency magneto-optical trap for atom number improvement are discussed.