1,721,239 research outputs found
Postselected quantum hypothesis testing
Full text linkWe study a variant of quantum hypothesis testing wherein an additional \u27inconclusive\u27 measurement outcome is added, allowing one to abstain from attempting to discriminate the hypotheses. The error probabilities are then conditioned on a successful attempt, with inconclusive trials disregarded. We completely characterise this task in both the single-shot and asymptotic regimes, providing exact formulas for the optimal error probabilities. In particular, we prove that the asymptotic error exponent of discriminating any two quantum states and is given by the Hilbert projective metric in asymmetric hypothesis testing, and by the Thompson metric in symmetric hypothesis testing. This endows these two quantities with fundamental operational interpretations in quantum state discrimination. Our findings extend to composite hypothesis testing, where we show that the asymmetric error exponent with respect to any convex set of density matrices is given by a regularisation of the Hilbert projective metric. We apply our results also to quantum channels, showing that no advantage is gained by employing adaptive or even more general discrimination schemes over parallel ones, in both the asymmetric and symmetric settings. Our state discrimination results make use of no properties specific to quantum mechanics and are also valid in general probabilistic theories.31 pages. v2: corrected proof of Lemma 9, added minor clarifications. Close to published versio
Britten in Scotland: Naxos 8.572706
No full textBenjamin Britten's songs to texts in Scots or by Scottish poets
Songs and Sonnets:bilingual songs from the reign of Queen Victoria: EM Records CD054
No full textWilliam Sterndale Bennett was the first to publish sets of songs where the originals were variously in German and English (translations into the other language being provided in each case). This innovation preceded the widespread practice of providing existing German songs (by Schubert or Schumann, for example) with subsequent English translations: notable exponents of this branch of poetry were Maria X. Hayes, Natalia MacFarren, & A.H. Fox-Strangways. This CD, however, traces a purer path from WSB’s innovation. Battison Haynes’s Vier Lieder continue the theme of German poems being set by an Englishman (published with English singing translations). Astonishingly enough, Parry’s settings of four Shakespeare Sonnets were originally made to Bodenstedt’s unmetrical translation, with the vocal line subsequently entirely re-written to carry Shakespeare’s original – a perfectly unique procedure whose implications my liner-note discusses in detail. We recorded both versions of Parry in full, Battison Haynes only in the original German, and the Sterndale Bennett songs in a mixture of original and translation, so that in the course of a single CD we could give samples of each possibility of original tongue and singing translation. This is the only complete recording of WSB’s songs (four songs are recorded elsewhere, all in English), the only recording of the Battison Haynes, and the only recording of Parry’s German original.The instrument used dates from the time of composition of the Parry & Battison Haynes songs. The liner notes discuss this in the context of period performance style
Union bound for quantum information processing
Full text linkIn this paper, we prove a quantum union bound that is relevant when performing a sequence of binary-outcome quantum measurements on a quantum state. The quantum union bound proved here involves a tunable parameter that can be optimized, and this tunable parameter plays a similar role to a parameter involved in the Hayashi-Nagaoka inequality (Hayashi & Nagaoka 2003 IEEE Trans. Inf. Theory49, 1753-1768. (doi:10.1109/TIT.2003.813556)), used often in quantum information theory when analysing the error probability of a square-root measurement. An advantage of the proof delivered here is that it is elementary, relying only on basic properties of projectors, Pythagoras' theorem, and the Cauchy-Schwarz inequality. As a non-trivial application of our quantum union bound, we prove that a sequential decoding strategy for classical communication over a quantum channel achieves a lower bound on the channel's second-order coding rate. This demonstrates the advantage of our quantum union bound in the non-asymptotic regime, in which a communication channel is called a finite number of times. We expect that the bound will find a range of applications in quantum communication theory, quantum algorithms and quantum complexity theory
Exact solution for the quantum and private capacities of bosonic dephasing channels
Full text linkThe capacities of noisy quantum channels capture the ultimate rates of information transmission across quantum communication lines, and the quantum capacity plays a key role in determining the overhead of fault-tolerant quantum computation platforms. In the case of bosonic systems, central to many applications, no closed formulas for these capacities were known for bosonic dephasing channels, a key class of non-Gaussian channels modelling, e.g., noise affecting superconducting circuits or fiber-optic communication channels. Here we provide the first exact calculation of the quantum, private, two-way assisted quantum, and secret-key agreement capacities of all bosonic dephasing channels. We prove that that they are equal to the relative entropy of the distribution underlying the channel to the uniform distribution. Our result solves a problem that has been open for over a decade, having been posed originally by [Jiang & Chen, Quantum and Nonlinear Optics 244, 2010].10+20 pages, 6 figures. v2 is close to the published versio
Elgar Songs & Piano Music Pitt, Wilde, Savidge, AvieAV2129 2007
No full textNot only two world premieres (not merely premiere recordings) but the liner notes give new information on the songs, especially on the original version of 'Sea Pictures', here recorded for the first time
Overcoming entropic limitations on asymptotic state transformations through probabilistic protocols
Full text linkThe quantum relative entropy is known to play a key role in determining the
asymptotic convertibility of quantum states in general resource-theoretic
settings, often constituting the unique monotone that is relevant in the
asymptotic regime. We show that this is no longer the case when one allows
stochastic protocols that may only succeed with some probability, in which case
the quantum relative entropy is insufficient to characterize the rates of
asymptotic state transformations, and a new entropic quantity based on a
regularization of the Hilbert projective metric comes into play. Such a
scenario is motivated by a setting where the cost associated with
transformations of quantum states, typically taken to be the number of copies
of a given state, is instead identified with the size of the quantum memory
needed to realize the protocol. Our approach allows for constructing
transformation protocols that achieve strictly higher rates than those imposed
by the relative entropy. Focusing on the task of resource distillation, we give
broadly applicable strong converse bounds on the asymptotic rates of
probabilistic distillation protocols, and show them to be tight in relevant
settings such as entanglement distillation with non-entangling operations. This
generalizes and extends previously known limitations that only applied to
deterministic protocols. Our methods are based on recent results for
probabilistic one-shot transformations as well as a new asymptotic
equipartition property for the projective relative entropy.Comment: 7+18 pages, 2 figures. v2: minor clarifications and additions. v3:
close to published versio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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