Ferreting out the Fluffy Bunnies: Entanglement constrained by Generalized superselection rules

Entanglement is a resource central to quantum information (QI). In particular, entanglement shared between two distant parties allows them to do certain tasks that would otherwise be impossible. In this context, we study the effect on the available entanglement of physical restrictions on the local operations that can be performed by the two parties. We enforce these physical restrictions by generalized superselection rules (SSRs), which we define to be associated with a given group of physical transformations. Specifically the generalized SSR is that the local operations must be covariant with respect to that group. Then we operationally define the entanglement constrained by a SSR, and show that it may be far below that expected on the basis of a naive (or ``fluffy bunny'') calculation. We consider two examples. The first is a particle number SSR. Using this we show that for a two-mode BEC (with Alice owning mode $A$ and Bob mode $B$), the useful entanglement shared by Alice and Bob is identically zero. The second, a SSR associated with the symmetric group, is applicable to ensemble QI processing such as in liquid-NMR. We prove that even for an ensemble comprising many pairs of qubits, with each pair described by a pure Bell state, the entanglement per pair constrained by this SSR goes to zero for a large ensemble.Comment: 8 pages, proceedings paper for an invited talk at 16th International Conference on Laser Spectroscopy (2003

Political parties in Botswana: Some observations

African Studies Seminar series. Paper presented February 1973Perhaps I could begin by stressing the tentative nature of the paper which I shall be presenting to this seminar. In the main this is due to the inadequacy of source material, relating to Botswana, available in Britain. The country is small (in terms of population) and poor, a situation which does not encourage the generation of much in the way of primary material, especially outside the governmental sector. With one or two exceptions the secondary material concerning Botswana seems to be based on the promise that the most important factor concerning the country is its relationship with the rest of Southern Africa. Thus it is regarded as a rather small pawn in the wider struggle with usually little more than a cursory glance at its internal politics. I am at the moment planning a trip to Botswana for the purposes of field work later in the year, but for the present I acknowledge that there are serious gaps in the paper I shall put before you. In most cases I shall attempt to point to the omissions myself. In spite of this I believe that the paper may be of interest, not only to those few who have a particular interest in Botswana, but to the much wider number who accept that the study of new states is of vital relevance to our understanding of politics. This account rejects the notion of any "single explanation" of the party system in Botswana: it rejects single variable determinism or even dominancy as a core explanatory factor. Thus it regards as simplistic any attempt to use one variable (e.g. tribe, class, region etc.) as a sensible method of understanding the nature of political parties or their interactions, analytically positioned as "party system". What is more, this account argues that the same method cannot be used to explain all the parties, even after allowance has been made for different content variables

Binary Gas Mixture Analysis with an Interdigitated Gate Electrode Field Effect Transistor (IGEFET) Microsensor

Single component and binary gas mixtures of nitrogen dioxide (NO2) and ammonia (NH3) were analyzed with a microsensor composed of an array of interdigitated Gate Electrode Field Effect Transistor (IGEFET) sensor elements coated with copper-, nickel-, and cobalt-phthalocyanine thin films. Improvements in the IGEFET microsensor design and operation facilitated simultaneous measurement of ihe direct current (DC) and alternating current (AC) electrical response of the metal-substituted phthalocyanine (MPc) films to challenge gas exposure. A finite-difference model of the interdigitated gate electrode (IGE) structure confirmed the fundamental operation of the IGEFET microsensor. Principal component analysis (PCA) and multilinear regression were applied to features identified in the IGE structure\u27s normalized DC resistance response, as well as the IGEFET transfer function\u27s gain and phase response, to gas mixtures containing parts-per-billion (ppb) NO2 and parts-per-million (ppm) NH3. The predicted concentrations were generally within 50% of the known concentrations for all gas analyses. The single component analysis of each test gas using the normalized DC resistance data yielded the smallest error (14% for NH3 and 26% for NO2). For the binary gas mixture analysis, the smallest error was achieved with the gain response data (approximately 25% for each component). jg p6

FIGHTING JUVENILE PREJUDICE IN FILM: THE MAKING OF HOUSE I LIVE IN

At a working Hollywood dinner party held shortly before the surrender of the German armies in early May 1945, four progressives brainstormed about making a movie short for young Americans on the democratic significance of the war while its lessons were still timely. One of the reformers present that evening was Frank Sinatra, the bobbysocks singing idol who also spent the war years giving Four Freedom talks to his teenage fans. The other three were Frank Ross, an RKO producer with humanitarian sentiments, Albert Maltz, a screenwriter with unreconstructed Marxist views, and Mervyn LeRoy, a veteran director of social problem films that had inspired Sinatra as a boy