Super-Resolving Quantum Radar: Coherent-State Sources with Homodyne Detection Suffice to Beat the Diffraction Limit

There has been much recent interest in quantum metrology for applications to sub-Raleigh ranging and remote sensing such as in quantum radar. For quantum radar, atmospheric absorption and diffraction rapidly degrades any actively transmitted quantum states of light, such as N00N states, so that for this high-loss regime the optimal strategy is to transmit coherent states of light, which suffer no worse loss than the linear Beer's law for classical radar attenuation, and which provide sensitivity at the shot-noise limit in the returned power. We show that coherent radar radiation sources, coupled with a quantum homodyne detection scheme, provide both longitudinal and angular super-resolution much below the Rayleigh diffraction limit, with sensitivity at shot-noise in terms of the detected photon power. Our approach provides a template for the development of a complete super-resolving quantum radar system with currently available technology.Comment: 23 pages, content is identical to published versio

Quantum Computation as Geometry

Quantum computers hold great promise, but it remains a challenge to find efficient quantum circuits that solve interesting computational problems. We show that finding optimal quantum circuits is essentially equivalent to finding the shortest path between two points in a certain curved geometry. By recasting the problem of finding quantum circuits as a geometric problem, we open up the possibility of using the mathematical techniques of Riemannian geometry to suggest new quantum algorithms, or to prove limitations on the power of quantum computers.Comment: 13 Pages, 1 Figur

Generation of Large Number-Path Entanglement Using Linear Optics and Feed-Forward

We show how an idealised measurement procedure can condense photons from two modes into one, and how, by feeding forward the results of the measurement, it is possible to generate efficiently superpositions of components for which only one mode is populated, commonly called ``N00N states''. For the basic procedure, sources of number states leak onto a beam splitter, and the output ports are monitored by photodetectors. We find that detecting a fixed fraction of the input at one output port suffices to direct the remainder to the same port with high probability, however large the initial state. When instead photons are detected at both ports, Schr\"{o}dinger cat states are produced. We describe a circuit for making the components of such a state orthogonal, and another for subsequent conversion to a N00N state. Our approach scales exponentially better than existing proposals. Important applications include quantum imaging and metrology

Sentencing Discretion in Pennsylvania: Has the Pendulum Returned to the Trial Judge?

Sentencing philosophies and the power to determine a convict\u27s fate have been topics of much debate in recent years. Pennsylvania\u27s experiment with sentencing guidelines, designed to reduce disparity in sentencing, has witnessed a surfacing of tensions between the trial judge, whose foremost concern is to impose a sentence that meets the competing demands placed on him by the community in general and the courtroom participants in particular, and the appellate courts, whose overriding objective is uniformity. As a result, sentencing appeals have often been remanded because of unexplained deviations from the guidelines. The guidelines were dealt a temporary setback by a recent decision of our Supreme Court which declared them unconstitutional for reasons unrelated to their substance. Though the legislature was quick to reenact them, this decision made it clear that the new guidelines cannot be mandatory without a change in the enabling legislation. Sentencing discretion has thereby been returned to the trial judge, who should no longer be reversed absent a genuine abuse of discretion

Strong violations of Bell-type inequalities for Werner-like states

We investigate the violation of Bell-type inequalities for two-qubit Werner-like states parametrized by the positive parameter 0<p<1. We use an unbalanced homodyne detection scheme to obtain the quantum mechanical probabilities. A violation of the Bell-Wigner and Janssens inequalities is obtained for a large range of the parameter p. The range given by these inequalities is greater than the one given by the Clauser-Horne inequality. The range in which a violation is attained actually coincides with the range where the Werner-like states are known to be nonseparabel, i.e., for p>1/3. However, the improvement over the Clauser-Horne inequality is achieved at the price of restricting the class of possible local hidden variable theories.Comment: Revised manuscript, accepted for publication in PR

A psycho-social examination of the developing mastery phase within English Premier League football

In recent years, the youth to senior transition in football has been considered something of a hot topic (Finn & Mckenna, 2010), particularly in England due to the lack of home-grown players becoming established first team football players in the English Premier League (EPL) clubs (Green, 200). However, the work of Richardson, Relvas and Littlewood (2013) suggested there is a longer, potentially more complex phase that exists beyond this transitional phase, labelled the ‘developing mastery phase’ due to it being a prolonged period in-between the developing phase and mastery phase of development (Bloom, 1985; van Rossum, 2001). The current applied thesis examines the development mastery phase within EPL football through a psycho-social perspective with a focus on talent development, transitions and identity (Erikson, 1968). The use of a qualitative research design (semi-structured interviews, ethnography and longitudinal research) allowed the opportunity to capture perspectives, feelings, emotions and thoughts of coaches, players and other support staff over a more protracted period of time. Patton (2002) argues by carrying out qualitative enquiry, researches are better able to understand other people’s points of view, experiences and perspectives without being constrained by the fixed focus of many quantitative methods. Study One utilised semi-structured interviews with six Under21 English Premier League development coaches to explore the structures, roles, responsibilities and practices of coaches working within this phase of development. Results suggested that under21 development coaches were situated, culturally and sometimes physically, inbetween the academy and first team environments, trapped between two distinct cultures. Under21 development coaches also have contrasting views and approaches with regards to the development of under21 players. Study Two adopted an ethnographic approach to explore the day-to-day practices and working environment for both coaches and players alike at the developing mastery phase, with a specific focus on identity (Eriskon, 1968). Results from Study Two highlighted a range of social and psychological issues relating to meaning, purpose, self-motivation and identity. The results specifically demonstrated that as time progresses and players are still in this phase of development, they begin to lose meaning and struggle with motivation at this phase of development. Study Three utilised a longitudinal qualitative approach to interview four players over the course of two seasons with a total of sixteen interviews. The study took a narrative approach to tell the story of two players journey’s as they progressed through this phase of development with a focus on identity development and narrative identity (McAdams, 1985). The results showed the impact of culture and cultural narratives within football on the development of identity in young players and how this can impact how players are perceived within their respective clubs. The results further demonstrate why players may either live, or resist the performance narrative (Carless & Douglas, 2012)