39 research outputs found
Thermometry by correlated dephasing of impurities in a 1D Fermi gas
We theoretically investigate the pure dephasing dynamics of two static
impurity qubits embedded within a common environment of ultracold fermionic
atoms, which are confined to one spatial dimension. Our goal is to understand
how bath-mediated interactions between impurities affect their performance as
nonequilibrium quantum thermometers. By solving the dynamics exactly using a
functional determinant approach, we show that the impurities become correlated
via retarded interactions of the Ruderman-Kittel-Kasuya-Yosida type. Moreover,
we demonstrate that these correlations can provide a metrological advantage,
enhancing the sensitivity of the two-qubit thermometer beyond that of two
independent impurities. This enhancement is most prominent in the limit of low
temperature and weak collisional coupling between the impurities and the gas.
We show that this precision advantage can be exploited using standard Ramsey
interferometry, with no need to prepare correlated initial states nor to
individually manipulate or measure the impurities. We also quantitatively
assess the impact of ignoring these correlations when constructing a
temperature estimate, finding that acceptable precision can still be achieved
from a simplified model of independent impurities. Our results demonstrate the
rich nonequilibrium physics of impurities dephasing in a common Fermi gas, and
may help to provide better temperature estimates at ultralow temperatures.Comment: v1: 16 pages, 6 figures. Comments and feedback welcome as always v2:
included temperature dependent decoherence and added reference
Heteromysis cocoensis n. sp. (Crustacea: Mysida: Mysidae) from coastal waters of Isla del Coco, Costa Rica
A survey of the invertebrate fauna of coral reef hard bottom communities in the shallow waters of Isla del Coco yielded a new species of mysid belonging to the genus Heteromysis S. I. Smith, 1873. Heteromysis (Olivemysis) cocoensis, n. sp. was collected from coral rubble at depths of 8 to 34 m. It differs from its congeners by having male pleopods 1, 3, and 4 with modified setae. Within the subgenus Olivemysis Băcescu, 1968, the new species is morphologically most similar to Heteromysis. ekamako Wittmann and Chevaldonne, 2017 from the Pacific, Heteromysis. gomezi Băcescu, 1970, H. mayana Brattegard, 1970, and H. rubrocinta, Băcescu, 1968 from the Western Atlantic, and Heteromysis. dardani Wittmann, 2008, Heteromysis. wirtzi Wittmann, 2008, and Heteromysis. sabelliphila Wittmann and Wirtz, 2017 from the Eastern Atlantic. However, H. cocoensis n. sp. is distinguished from these six apparently closely related species by the following combination of characters: flagellate, modified setae on articles 1 and 3 of the antennular peduncle, and setation of thoracic endopod 3, male pleopods 1, 3 and 4, uropodal endopods, and the apical and lateral margins of the telson. A diagnostic table separating these eight species is given.Universidad de Costa Rica/[]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
Programme to assess the ecological effects of oil spills in coastal areas of Norway
The basic biological effects of oil spillage on coastal ecosystems is quite
well documented following the Torrey Canyon and the Santa Barbara, California
spills. Both these areas can be expected to be quite different biologically
from the Norwegian coasts. The Torrey Canyon oil affected areas of Britain
and Brittany are characterised by large tidal ranges and rapid tidal currents,
whilst the Pacific coast of the U.S.A. has considerably different ecosystems.
Thus although the experience of the above cited spills can be used the biological
effects will need to be monitored anew in Norway. The following plan
draws on the reports of the above two disasters