High-performance electronic cooling with superconducting tunnel junctions
Publication date: Available online 20 August 2016 Source:Comptes Rendus Physique Author(s): Hervé Courtois, Hung Q. Nguyen, Clemens B. Winkelmann, Jukka P. Pekola When biased at a voltage just below a superconductor's energy gap, a tunnel junction between this superconductor and a normal metal cools the latter. While the study of such devices has long been focused to structures of submicron size and consequently cooling power in the picowatt range, we have led a thorough study of devices with a large cooling power up to the nanowatt range. Here we describe how their performance can be optimized by using a quasi-part...
Source: Comptes Rendus Physique - August 19, 2016 Category: Physics Source Type: research
Quantum-interference-enhanced thermoelectricity in single molecules and molecular films
Publication date: Available online 18 August 2016 Source:Comptes Rendus Physique Author(s): Colin J. Lambert, Hatef Sadeghi, Qusiy H. Al-Galiby We provide a brief overview of recent measurements and predictions of thermoelectric properties of single-molecules and porous nanoribbons and discuss some principles underpinning strategies for enhancing their thermoelectric performance. The latter include (a) taking advantage of steep slopes in the electron transmission coefficient T ( E ) , (b) creating structures with delta-function-like transmission coefficients and (c) utilising step-like features in T ( E ) . To achieve...
Source: Comptes Rendus Physique - August 18, 2016 Category: Physics Source Type: research
Quantum trajectories of superconducting qubits
Publication date: Available online 18 August 2016 Source:Comptes Rendus Physique Author(s): Steven J. Weber, Kater W. Murch, Mollie E. Kimchi-Schwartz, Nicolas Roch, Irfan Siddiqi In this review, we discuss recent experiments that investigate how the quantum sate of a superconducting qubit evolves during measurement. We provide a pedagogical overview of the measurement process, when the qubit is dispersively coupled to a microwave frequency cavity, and the qubit state is encoded in the phase of a microwave tone that probes the cavity. A continuous measurement record is used to reconstruct the individual quantum traj...
Source: Comptes Rendus Physique - August 18, 2016 Category: Physics Source Type: research
Thermoelectrics with Coulomb-coupled quantum dots
Publication date: Available online 17 August 2016 Source:Comptes Rendus Physique Author(s): Holger Thierschmann, Rafael Sánchez, Björn Sothmann, Hartmut Buhmann, Laurens W. Molenkamp In this article we review the thermoelectric properties of three terminal devices with Coulomb-coupled quantum dots (QDs) as observed in recent experiments [1,2]. The system we consider consists of two Coulomb-blockade QDs, one of which can exchange electrons with only a single reservoir (heat reservoir), while the other dot is tunnel coupled with two reservoirs at a lower temperature (conductor). The heat reservoir and the conductor ...
Source: Comptes Rendus Physique - August 17, 2016 Category: Physics Source Type: research
Towards strongly correlated photons in arrays of dissipative nonlinear cavities under a frequency-dependent incoherent pumping
We report a theoretical study of a quantum optical model consisting of an array of strongly nonlinear cavities incoherently pumped by an ensemble of population-inverted two-level atoms. Projective methods are used to eliminate the atomic dynamics and write a generalized master equation for the photonic degrees of freedom only, where the frequency-dependence of gain introduces non-Markovian features. In the simplest single cavity configuration, this pumping scheme gives novel optical bistability effects and allows for the selective generation of Fock states with a well-defined photon number. For many cavities in a weakly no...
Source: Comptes Rendus Physique - August 12, 2016 Category: Physics Source Type: research
Foreword – Strong light–matter coupling in solid-state systems: A historical perspective
Publication date: Available online 11 August 2016 Source:Comptes Rendus Physique (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - August 11, 2016 Category: Physics Source Type: research
Superposition of fiber Bragg and LPG gratings for embedded strain measurement
Publication date: Available online 11 August 2016 Source:Comptes Rendus Physique Author(s): Romain Guyard, Dominique Leduc, Yann Lecieux, Cyril Lupi When a fiber Bragg grating strain sensor is embedded inside a structure, the interaction of the sensor with the host material can lead to spurious results if the radial strain is neglected. In this article, we use numerical simulations to show that the axial and radial strains can be simultaneously measured with a single fiber in which a Bragg grating and a long-period grating are superimposed. Moreover, we present an optimal architecture of the sensor. (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - August 11, 2016 Category: Physics Source Type: research
Microwave imaging of magnetohydrodynamic instabilities in fusion plasma
Publication date: Available online 12 August 2016 Source:Comptes Rendus Physique Author(s): Roland Sabot, Didier Elbèze, Woochang Lee, Yoonbum Nam, Hyeon Park, Junsong Shen, Gunsu Yun, Minjun Choi, Jean-Claude Giacalone, Timothée Nicolas, Christine Bottereau, Frédéric Clairet, Philippe Lotte, Diego Molina Microwave imaging diagnostics are extremely useful for observing magnetohydrodynamic (MHD) instabilities in magnetic fusion plasmas. Two imaging diagnostics will be available on the WEST tokamak. A method was developed to reconstruct electron density maps from electron density profiles measured by ultr...
Source: Comptes Rendus Physique - August 11, 2016 Category: Physics Source Type: research
Combined complex-source beam and spherical-multipole analysis for the electromagnetic probing of conical structures
Publication date: Available online 12 August 2016 Source:Comptes Rendus Physique Author(s): Ludger Klinkenbusch, Hendrik Brüns The paper addresses the combination of the spherical-multipole analysis in sphero-conal coordinates with a uniform complex-source beam (CSB) in order to analyze the scattering of a localized electromagnetic plane wave by any desired part of a perfectly conducting elliptic cone. The concept of uniform CSB is introduced and rigorously applied to the diffraction by a semi-infinite elliptic cone. The analysis takes into account the fact that the incident CSB does not satisfy the radiation conditio...
Source: Comptes Rendus Physique - August 11, 2016 Category: Physics Source Type: research
Exact solution of the Dirac –Weyl equation in graphene under electric and magnetic fields
Publication date: Available online 10 August 2016 Source:Comptes Rendus Physique Author(s): Mahdi Eshghi, Hosein Mehraban In this paper, we have obtained exact analytical solutions for the bound states of a graphene Dirac electron in magnetic fields with various q-parameters under an electrostatic potential. In order to solve the time-independent Dirac–Weyl equation, the Nikoforov–Uvarov (NU) and Frobenius methods have been used. We have also investigated the thermodynamic properties by using the Hurwitz zeta function method for one of the states. Finally, some of the numerical results are also shown. (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - August 10, 2016 Category: Physics Source Type: research
Comets at radio wavelengths
We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe. (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - August 10, 2016 Category: Physics Source Type: research
The thermoelectric working fluid: Thermodynamics and transport
Publication date: Available online 10 August 2016 Source:Comptes Rendus Physique Author(s): Giuliano Benenti, Henni Ouerdane, Christophe Goupil Thermoelectric devices are heat engines, which operate as generators or refrigerators using the conduction electrons as a working fluid. The thermoelectric heat-to-work conversion efficiency has always been typically quite low, but much effort continues to be devoted to the design of new materials boasting improved transport properties that would make them of the electron crystal–phonon glass type of systems. On the other hand, there are comparatively few studies where a pro...
Source: Comptes Rendus Physique - August 10, 2016 Category: Physics Source Type: research
Scattering properties of a stratified air/snow/sea ice medium. Small slope approximation
Publication date: Available online 10 August 2016 Source:Comptes Rendus Physique Author(s): Richard Dusséaux, Saddek Afifi, Monique Dechambre The sea-ice thickness, a key parameter in Arctic studies, is derived from radar altimeter height measurements of the freeboard, taking into account not only snow load, but also the penetration depth of the electromagnetic waves inside the snow—this is the not generally the case. Within the framework of the small slope approximation method, we study in Ku-band ( f = 13 GHz , λ = 2.31 cm in the air) the electromagnetic signature of an air/snow/sea ice rough layered mediu...
Source: Comptes Rendus Physique - August 10, 2016 Category: Physics Source Type: research
Introduction to parametric amplification of quantum signals with Josephson circuits
Publication date: Available online 10 August 2016 Source:Comptes Rendus Physique Author(s): Ananda Roy, Michel Devoret This short and opinionated review starts with the concept of quantum signals at microwave frequencies and focuses on the principle of linear parametric amplification. This process emerges from the dispersive nonlinearity of Josephson junctions driven with appropriate tones. We discuss two defining characteristics of the corresponding amplifying devices: i) the number of modes excited by the signal, idler and pump waves and ii) the number of independent ports through which these waves enter into the cir...
Source: Comptes Rendus Physique - August 10, 2016 Category: Physics Source Type: research
The Riemann tensor and the Bianchi identity in 5D space –time
Publication date: Available online 5 August 2016 Source:Comptes Rendus Physique Author(s): Mehran Taki, Abolfazl Mirjalili The initial assumption of theories with extra dimension is based on the efforts to yield a geometrical interpretation of the gravitation field. In this paper, using an infinitesimal parallel transportation of a vector, we generalize the obtained results in four dimensions to five-dimensional space–time. For this purpose, we first consider the effect of the geometrical structure of 4D space–time on a vector in a round trip of a closed path, which is basically quoted from chapter three of Ref. [5...
Source: Comptes Rendus Physique - August 5, 2016 Category: Physics Source Type: research
