1,720,977 research outputs found
Schlieren-style stroboscopic nonscan imaging of the field-amplitudes of acoustic whispering gallery modes
No full textWe report a schlieren-style stroboscopic phase-contrast field-amplitude imaging of two-dimensional acoustic whispering gallery modes in a circular shell cavity immersed in liquid. A schlieren signal is combined with a presplit reference beam to enable nonscan field-amplitude imaging. Excitation mechanisms of standing and traveling eigenmodes, respectively, are analyzed with acoustic ray simulations presented in a Poincare surface of sections. The time evolutions for both standing and traveling eigenmodes are reconstructed using the stroboscopic capability. (C) 2020 Optical Society of AmericaN
Observation of scalable sub-Poissonian-field lasing in a microlaser
No full textSub-Poisson field with much reduced fluctuations in a cavity can boost quantum precision measurements via cavity-enhanced light-matter interactions. Strong coupling between an atom and a cavity mode has been utilized to generate highly sub-Poisson fields. However, a macroscopic number of optical intracavity photons with more than 3 dB variance reduction has not been possible. Here, we report sub-Poisson field lasing in a microlaser operating with hundreds of atoms with well-regulated atom-cavity coupling and interaction time. Its photon-number variance was 4 dB below the standard quantum limit while the intracavity mean photon number scalable up to 600. The highly sub-Poisson photon statistics were not deteriorated by simultaneous interaction of a large number of atoms. Our finding suggests an effective pathway to widely scalable near-Fock-state lasing at the macroscopic scale.Y
Observation of efficient sub-Doppler cooling under a nonzero magnetic field in a moving optical lattice
No full textWe observed efficient sub-Doppler cooling of Rb-85 atoms under a nonzero magnetic field in a moving optical lattice formed in a bichromatic magneto-optical trap. Trap laser detunings were biased or set differently for the counterpropagating laser beams so that the atoms could be trapped where the magnetic field was nonzero. We investigated the center position and the temperature of the atomic cloud. We found that the sub-Doppler cooling effect, known to decrease as the nonzero magnetic field increases in a magneto-optical trap, would in fact increase under a particular trap-laser detuning difference. We first derived the condition under theoretical considerations and then verified it experimentally by conducting nondestructive measurement of atomic temperature.OAIID:RECH_ACHV_DSTSH_NO:T201831685RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A075185CITE_RATE:2.909DEPT_NM:물리·천문학부EMAIL:[email protected]_YN:NN
Maximal Shannon entropy in the vicinity of an exceptional point in an open microcavity
No full textAbstract The Shannon entropy as a measure of information contents is investigated around an exceptional point (EP) in an open elliptical microcavity as a non-Hermitian system. The Shannon entropy is maximized near the EP in the parameter space for two interacting modes, but the exact maximum position is slightly off the EP toward the weak interaction region while the slopes of the Shannon entropies diverge at the EP. The Shannon entropies also show discontinuity across a specific line in the parameter space, directly related to the exchange of the Shannon entropy as well as the mode patterns with that line as a boundary. This feature results in a nontrivial topological structure of the Shannon entropy surfaces
Coherent single-atom superradiance
No full textBuilding up to superradiance, one by one
Superradiance is a quantum phenomenon that occurs when emitters are sufficiently close to change spontaneous emission. Controlling the position and state of emitters within an atomic ensemble, however, is technically challenging. Kim
et al.
show that spatial correlations can be replaced by temporal correlations to achieve superradiance (see the Perspective by Meschede). They dropped prepared atoms into a high-quality optical cavity and found that the number of photons within the cavity built up superradiantly as the atoms dropped through one by one. The method provides a versatile platform for generating nonclassical states of light.
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Bell-inequality tests with entanglement between an atom and a coherent state in a cavity
No full textWe study Bell-inequality tests with entanglement between a coherent-state field in a cavity and a two-level atom. In order to detect the cavity field for such a test, photon on-off measurements and photon number parity measurements, respectively, are investigated. When photon on-off measurements are used, at least 50% of detection efficiency is required to demonstrate violation of the Bell inequality. Photon number parity measurements for the cavity field can be effectively performed using ancillary atoms and an atomic detector, which leads to large degrees of Bell violations up to Cirel'son's bound. We also analyze decoherence effects in both field and atomic modes and discuss conditions required to perform a Bell inequality test free from the locality loophole.Y
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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