236 research outputs found

    Reply to "Comment on `Inference with minimal Gibbs free energy in information field theory'" by Iatsenko, Stefanovska and McClintock

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    We endorse the comment on our recent paper [En{\ss}lin and Weig, Phys. Rev. E 82, 051112 (2010)] by Iatsenko, Stefanovska and McClintock [Phys. Rev. E 85 033101 (2012)] and we try to clarify the origin of the apparent controversy on two issues. The aim of the minimal Gibbs free energy approach to provide a signal estimate is not affected by their Comment. However, if one wants to extend the method to also infer the a posteriori signal uncertainty any tempering of the posterior has to be undone at the end of the calculations, as they correctly point out. Furthermore, a distinction is made here between maximum entropy, the maximum entropy principle, and the so-called maximum entropy method in imaging, hopefully clarifying further the second issue of their Comment paper.Comment: 1 page, no figures, Reply to Comment pape

    Inference with minimal Gibbs free energy in information field theory

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    Non-linear and non-Gaussian signal inference problems are difficult to tackle. Renormalization techniques permit us to construct good estimators for the posterior signal mean within information field theory (IFT), but the approximations and assumptions made are not very obvious. Here we introduce the simple concept of minimal Gibbs free energy to IFT, and show that previous renormalization results emerge naturally. They can be understood as being the Gaussian approximation to the full posterior probability, which has maximal cross information with it. We derive optimized estimators for three applications, to illustrate the usage of the framework: (i) reconstruction of a log-normal signal from Poissonian data with background counts and point spread function, as it is needed for gamma ray astronomy and for cosmography using photometric galaxy redshifts, (ii) inference of a Gaussian signal with unknown spectrum and (iii) inference of a Poissonian log-normal signal with unknown spectrum, the combination of (i) and (ii). Finally we explain how Gaussian knowledge states constructed by the minimal Gibbs free energy principle at different temperatures can be combined into a more accurate surrogate of the non-Gaussian posterior.Comment: 14 page

    Size-independent Young's modulus of inverted conical GaAs nanowire resonators

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    We explore mechanical properties of top down fabricated, singly clamped inverted conical GaAs nanowires. Combining nanowire lengths of 2-9 μ\mum with foot diameters of 36-935 nm yields fundamental flexural eigenmodes spanning two orders of magnitude from 200 kHz to 42 MHz. We extract a size-independent value of Young's modulus of (45±\pm3) GPa. With foot diameters down to a few tens of nanometers, the investigated nanowires are promising candidates for ultra-flexible and ultra-sensitive nanomechanical devices

    Scurvy presenting as vulvar folliculitis, a case report and review of the literature

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    This case examines clinical features and care of a patient with scurvy presenting with vulvar folliculitis

    Optical detection of a BCS transition of Lithium-6 in harmonic traps

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    We study the detection of a BCS transition within a sample of Lithium--6 atoms confined in a harmonic trap. Using the local density approximation we calculate the pair correlation function in the normal and superfluid state at zero temperature. We show that the softening of the Fermi hole associated with a BCS transition leads to an observable increase in the intensity of off--resonant light scattered from the atomic cloud at small angles.Comment: 7 pages, 3 figures, submitted to Europhysics Letter

    State tomography of capacitively shunted phase qubits with high fidelity

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    We introduce a new design concept for superconducting quantum bits (qubits) in which we explicitly separate the capacitive element from the Josephson tunnel junction for improved qubit performance. The number of two-level systems (TLS) that couple to the qubit is thereby reduced by an order of magnitude and the measurement fidelity improves to 90%. This improved design enables the first demonstration of quantum state tomography with superconducting qubits using single shot measurements.Comment: submitted to PR

    Anisotropic optical conductivity of the putative Kondo insulator CeRu4_4Sn6_6

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    Kondo insulators and in particular their non-cubic representatives have remained poorly understood. Here we report on the development of an anisotropic energy pseudogap in the tetragonal compound CeRu4_4Sn6_6 employing optical reflectivity measurements in broad frequency and temperature ranges, and local density approximation plus dynamical mean field theory calculations. The calculations provide evidence for a Kondo insulator-like response within the aaa-a plane and a more metallic response along the c axis and qualitatively reproduce the experimental observations, helping to identify their origin

    Optomechanics for quantum technologies

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    The ability to control the motion of mechanical systems through interaction with light has opened the door to a plethora of applications in fundamental and applied physics. With experiments routinely reaching the quantum regime, the focus has now turned towards creating and exploiting interesting non-classical states of motion and entanglement in optomechanical systems. Quantumness has also shifted from being the very reason why experiments are constructed to becoming a resource for the investigation of fundamental physics and the creation of quantum technologies. Here, by focusing on opto- and electromechanical platforms we review recent progress in quantum state preparation and entanglement of mechanical systems, together with applications to signal processing and transduction, quantum sensing and topological physics, as well as small-scale thermodynamics
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