106 research outputs found
Unexpectedly allowed transition in two inductively coupled transmons
We present experimental results in which the unexpected zero-two transition
of a circuit composed of two inductively coupled transmons is observed. This
transition shows an unusual magnetic flux dependence with a clear disappearance
at zero magnetic flux. In a transmon qubit the symmetry of the wave functions
prevents this transition to occur due to selection rule. In our circuit the
Josephson effect introduces strong couplings between the two normal modes of
the artificial atom. This leads to a coherent superposition of states from the
two modes enabling such transitions to occur
Kerr coefficients of plasma resonances in Josephson junction chains
We present an experimental and theoretical analysis of the self- and
cross-Kerr effect of extended plasma resonances in Josephson junction chains.
We calculate the Kerr coefficients by deriving and diagonalizing the
Hamiltonian of a linear circuit model for the chain and then adding the
Josephson non-linearity as a perturbation. The calculated Kerr-coefficients are
compared with the measurement data of a chain of 200 junctions. The Kerr effect
manifests itself as a frequency shift that depends linearly on the number of
photons in a resonant mode. By changing the input power on a low signal level,
we are able to measure this shift. The photon number is calibrated using the
self-Kerr shift calculated from the sample parameters. We then compare the
measured cross-Kerr shift with the theoretical prediction, using the calibrated
photon number.Comment: 10 pages, 9 figure
Evidence of dual Shapiro steps in a Josephson junctions array
The modern primary voltage standard is based on the AC Josephson effect and
the ensuing Shapiro steps, where a microwave tone applied to a Josephson
junction yields a constant voltage ( is Planck's constant and
the electron charge) determined by only the microwave frequency and
fundamental constants. Duality arguments for current and voltage have long
suggested the possibility of dual Shapiro steps -- that a Josephson junction
device could produce current steps with heights determined only on the applied
frequency. In this report, we embed an ultrasmall Josephson junction in a high
impedance array of larger junctions to reveal dual Shapiro steps. For multiple
frequencies, we detect that the AC response of the circuit is synchronised with
the microwave tone at frequency , and the corresponding emergence of flat
steps in the DC response with current , equal to the tunnelling of a
Cooper pair per tone period. This work sheds new light on phase-charge duality,
omnipresent in condensed matter physics, and extends it to Josephson circuits.
Looking forward, it opens a broad range of possibilities for new experiments in
the field of circuit quantum electrodynamics and is an important step towards
the long-sought closure of the quantum metrology electrical triangle.Comment: 14 pages, 11 figure
Revealing the finite-frequency response of a bosonic quantum impurity
Quantum impurities are ubiquitous in condensed matter physics and constitute
the most stripped-down realization of many-body problems. While measuring their
finite-frequency response could give access to key characteristics such as
excitations spectra or dynamical properties, this goal has remained elusive
despite over two decades of studies in nanoelectronic quantum dots. Conflicting
experimental constraints of very strong coupling and large measurement
bandwidths must be met simultaneously. We get around this problem using cQED
tools, and build a precisely characterized quantum simulator of the boundary
sine-Gordon model, a non-trivial bosonic impurity problem. We succeeded to
fully map out the finite frequency linear response of this system. Its reactive
part evidences a strong renormalisation of the nonlinearity at the boundary in
agreement with non-perturbative calculations. Its dissipative part reveals a
dramatic many-body broadening caused by multi-photon conversion. The
experimental results are matched quantitatively to a resummed diagrammatic
calculation based on a microscopically calibrated model. Furthermore, we push
the device into a regime where diagrammatic calculations break down, which
calls for more advanced theoretical tools to model many-body quantum circuits.
We also critically examine the technological limitations of cQED platforms to
reach universal scaling laws. This work opens exciting perspectives for the
future such as quantifying quantum entanglement in the vicinity of a quantum
critical point or accessing the dynamical properties of non-trivial many-body
problems.Comment: 39 pages, 14 figure
Observation of two-mode squeezing in a traveling wave parametric amplifier
Traveling wave parametric amplifiers (TWPAs) have recently emerged as
essential tools for broadband near quantum-limited amplification. However,
their use to generate microwave quantum states still misses an experimental
demonstration. In this letter, we report operation of a TWPA as a source of
two-mode squeezed microwave radiation. We demonstrate broadband entanglement
generation between two modes separated by up to 400 MHz by measuring
logarithmic negativity between 0.27 and 0.51 and collective quadrature
squeezing below the vacuum limit between 1.5 and 2.1 dB. This work opens
interesting perspectives for the exploration of novel microwave photonics
experiments with possible applications in quantum sensing and continuous
variable quantum computing
Exploration of plant genomes in the FLAGdb++ environment
Background : In the contexts of genomics, post-genomics and systems biology approaches, data integration presents a major concern. Databases provide crucial solutions: they store, organize and allow information to be queried, they enhance the visibility of newly produced data by comparing them with previously published results, and facilitate the exploration and development of both existing hypotheses and new ideas. Results : The FLAGdb++ information system was developed with the aim of using whole plant genomes as physical references in order to gather and merge available genomic data from in silico or experimental approaches. Available through a JAVA application, original interfaces and tools assist the functional study of plant genes by considering them in their specific context: chromosome, gene family, orthology group, co-expression cluster and functional network. FLAGdb++ is mainly dedicated to the exploration of large gene groups in order to decipher functional connections, to highlight shared or specific structural or functional features, and to facilitate translational tasks between plant species (Arabidopsis thaliana, Oryza sativa, Populus trichocarpa and Vitis vinifera). Conclusion : Combining original data with the output of experts and graphical displays that differ from classical plant genome browsers, FLAGdb++ presents a powerful complementary tool for exploring plant genomes and exploiting structural and functional resources, without the need for computer programming knowledge. First launched in 2002, a 15th version of FLAGdb++ is now available and comprises four model plant genomes and over eight million genomic features
Alcoholic fermentation drives the selection of Oenococcus oeni strains in wine but not in cider
Oenococcus oeni is the predominant lactic acid bacteria species in wine and cider, where it performs the malolactic fermentation (MLF). The O. oeni strains analyzed to date form four major genetic lineages named phylogroups A, B, C and D. Most of the strains isolated from wine, cider, or kombucha belong to phylogroups A, B + C, and D, respectively, although B and C strains were also detected in wine. This study was performed to better understand the distribution of the phylogroups in wine and cider. Their population dynamics were determined by qPCR all through wine and cider productions, and the behavior of the strains was analyzed in synthetic wines and ciders. Phylogroups A, B and C were all represented in grape must and throughout the alcoholic fermentation, but on the transition to MLF, only phylogroup A remained at high levels in all wine productions. In the case of cider, phylogroups A, B and C were detected in stable levels during the process. When they were tested in synthetic wine and cider, all phylogroups performed MLF, but with different survival rates depending on the ethanol content. In this sense, ethanol and fermentation kinetics are the main agent that drives the selection of phylogroup A strains in wine, while B and C strains dominates in cider containing less ethanol
Identification of Restricted Subsets of Mature microRNA Abnormally Expressed in Inactive Colonic Mucosa of Patients with Inflammatory Bowel Disease
International audienceBACKGROUND: Ulcerative Colitis (UC) and Crohn's Disease (CD) are two chronic Inflammatory Bowel Diseases (IBD) affecting the intestinal mucosa. Current understanding of IBD pathogenesis points out the interplay of genetic events and environmental cues in the dysregulated immune response. We hypothesized that dysregulated microRNA (miRNA) expression may contribute to IBD pathogenesis. miRNAs are small, non-coding RNAs which prevent protein synthesis through translational suppression or mRNAs degradation, and regulate several physiological processes. METHODOLOGY/FINDINGS: Expression of mature miRNAs was studied by Q-PCR in inactive colonic mucosa of patients with UC (8), CD (8) and expressed relative to that observed in healthy controls (10). Only miRNAs with highly altered expression (>5 or 100 -fold and 0.05-0.19 -fold for over- and under- expression, respectively; 0.00
Patterns of sequence polymorphism in the fleshless berry locus in cultivated and wild Vitis vinifera accessions
<p>Abstract</p> <p>Background</p> <p>Unlike in tomato, little is known about the genetic and molecular control of fleshy fruit development of perennial fruit trees like grapevine (<it>Vitis vinifera </it>L.). Here we present the study of the sequence polymorphism in a 1 Mb grapevine genome region at the top of chromosome 18 carrying the <it>fleshless berry </it>mutation (<it>flb</it>) in order, first to identify SNP markers closely linked to the gene and second to search for possible signatures of domestication.</p> <p>Results</p> <p>In total, 62 regions (17 SSR, 3 SNP, 1 CAPS and 41 re-sequenced gene fragments) were scanned for polymorphism along a 3.4 Mb interval (85,127-3,506,060 bp) at the top of the chromosome 18, in both <it>V. vinifera cv</it>. Chardonnay and a genotype carrying the <it>flb </it>mutation, <it>V. vinifera cv</it>. Ugni Blanc mutant. A nearly complete homozygosity in Ugni Blanc (wild and mutant forms) and an expected high level of heterozygosity in Chardonnay were revealed. Experiments using qPCR and BAC FISH confirmed the observed homozygosity. Under the assumption that <it>flb </it>could be one of the genes involved into the domestication syndrome of grapevine, we sequenced 69 gene fragments, spread over the <it>flb </it>region, representing 48,874 bp in a highly diverse set of cultivated and wild <it>V. vinifera </it>genotypes, to identify possible signatures of domestication in the cultivated <it>V. vinifera </it>compartment. We identified eight gene fragments presenting a significant deviation from neutrality of the Tajima's D parameter in the cultivated pool. One of these also showed higher nucleotide diversity in the wild compartments than in the cultivated compartments. In addition, SNPs significantly associated to berry weight variation were identified in the <it>flb </it>region.</p> <p>Conclusions</p> <p>We observed the occurrence of a large homozygous region in a non-repetitive region of the grapevine otherwise highly-heterozygous genome and propose a hypothesis for its formation. We demonstrated the feasibility to apply BAC FISH on the very small grapevine chromosomes and provided a specific probe for the identification of chromosome 18 on a cytogenetic map. We evidenced genes showing putative signatures of selection and SNPs significantly associated with berry weight variation in the <it>flb </it>region. In addition, we provided to the community 554 SNPs at the top of chromosome 18 for the development of a genotyping chip for future fine mapping of the <it>flb </it>gene in a F2 population when available.</p
Evolution of Surface Hydrology in the Sahelo-Sudanian Strip: An Updated Review
In the West African Sahel, two paradoxical hydrological behaviors have occurred during the last five decades. The first paradox was observed during the 1968â1990s âGreat Droughtâ period, during which runoff significantly increased. The second paradox appeared during the subsequent period of rainfall recovery (i.e., since the 1990s), during which the runoff coefficient continued to increase despite the general re-greening of the Sahel. This paper reviews and synthesizes the literature on the drivers of these paradoxical behaviors, focusing on recent works in the West African Sahelo/Sudanian strip, and upscaling the hydrological processes through an analysis of recent data from two representative areas of this region. This paper helps better determine the respective roles played by Land Use/Land Cover Changes (LULCC), the evolution of rainfall intensity and the occurrence of extreme rainfall events in these hydrological paradoxes. Both the literature review and recent data converge in indicating that the first Sahelian hydrological paradox was mostly driven by LULCC, while the second paradox has been caused by both LULCC and climate evolution, mainly the recent increase in rainfall intensity
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