446 research outputs found
Parity-dependent State Engineering and Tomography in the ultrastrong coupling regime
Reaching the strong coupling regime of light-matter interaction has led to an
impressive development in fundamental quantum physics and applications to
quantum information processing. Latests advances in different quantum
technologies, like superconducting circuits or semiconductor quantum wells,
show that the ultrastrong coupling regime (USC) can also be achieved, where
novel physical phenomena and potential computational benefits have been
predicted. Nevertheless, the lack of effective decoupling mechanism in this
regime has so far hindered control and measurement processes. Here, we propose
a method based on parity symmetry conservation that allows for the generation
and reconstruction of arbitrary states in the ultrastrong coupling regime of
light-matter interactions. Our protocol requires minimal external resources by
making use of the coupling between the USC system and an ancillary two-level
quantum system.Comment: Improved version. 9 pages, 5 figure
Magnetic order, spin waves and fluctuations in the triangular antiferromagnet La2Ca2MnO7
We report magnetic susceptibility, specific heat and muon spin relaxation
(muSR) experiments on the triangular antiferromagnet La2Ca2MnO7 which develops
a genuine two-dimensional, three-sublattice \sqrt{3} \times \sqrt{3} magnetic
order below T_N = 2.8 K. From the susceptibility and specific heat data an
estimate of the exchange interaction is derived. A value for the spin-wave gap
is obtained from the latter data. The analysis of a previously reported
inelastic neutron scattering study yields values for the exchange and spin-wave
gap compatible with the results obtained from macroscopic measurements. An
appreciable entropy is still missing at 10 K that may be ascribed to intense
short-range correlations. The critical paramagnetic fluctuations extend far
above T_N, and can be partly understood in terms of two-dimensional spin-wave
excitations. While no spontaneous muSR field is observed below T_N, persistent
spin dynamics is found. Short-range correlations are detected in this
temperature range. Their relation to a possible molecular spin substructure and
the observed exotic spin fluctuations is discussed.Comment: 9 pages, 6 figure
Forest Resources Digital Information System
Forestry Images, the digitized documented forest health image archive, was developed with the aim to gather, create, maintain, and distribute digital information as tools to enhance and complement information exchange and educational activities. The Forestry Images System exists under the umbrella of Bugwood Network (Bargeron, Douce, & Moorhead, 2000). The increased volume of images and its usage statistics required major changes to enhance the system access, better content management, and security. The enhanced system is standard compliant based on recommendations from the World Wide Web Consortium (W3C) and the U.S. government Section 508
Localization of a 64-kDa phosphoprotein in the lumen between the outer and inner envelopes of pea chloroplasts
The identification and localization of a marker protein for the intermembrane space between the outer and inner chloroplast envelopes is described. This 64-kDa protein is very rapidly labeled by [γ-32P]ATP at very low (30 nM) ATP concentrations and the phosphoryl group exhibits a high turnover rate. It was possible to establish the presence of the 64-kDa protein in this plastid compartment by using different chloroplast envelope separation and isolation techniques. In addition comparison of labeling kinetics by intact and hypotonically lysed pea chloroplasts support the localization of the 64-kDa protein in the intermembrane space. The 64-kDa protein was present and could be labeled in mixed envelope membranes isolated from hypotonically lysed plastids. Mixed envelope membranes incorporated high amounts of 32P from [γ-32P]ATP into the 64-kDa protein, whereas separated outer and inner envelope membranes did not show significant phosphorylation of this protein. Water/Triton X-114 phase partitioning demonstrated that the 64-kDa protein is a hydrophilic polypeptide. These findings suggest that the 64-kDa protein is a soluble protein trapped in the space between the inner and outer envelope membranes. After sonication of mixed envelope membranes, the 64-kDa protein was no longer present in the membrane fraction, but could be found in the supernatant after a 110000 × g centrifugation
From the Bloch sphere to phase space representations with the Gottesman-Kitaev-Preskill encoding
In this work, we study the Wigner phase-space representation of qubit states
encoded in continuous variables (CV) by using the Gottesman-Kitaev-Preskill
(GKP) mapping. We explore a possible connection between resources for universal
quantum computation in discrete-variable (DV) systems, i.e. non-stabilizer
states, and negativity of the Wigner function in CV architectures, which is a
necessary requirement for quantum advantage. In particular, we show that the
lowest Wigner logarithmic negativity of qubit states encoded in CV with the GKP
mapping corresponds to encoded stabilizer states, while the maximum negativity
is associated with the most non-stabilizer states, H-type and T-type quantum
states.Comment: (v1) Accepted for publication in the Springer's "Mathematics for
Industry" series. (v2) Typo in the abstract fixed; URL of the conference
where the paper has been presented added: International Symposium on
Mathematics, Quantum Theory, and Cryptography (MQC), held in September 2019
in Fukuoka, Japan (https://www.mqc2019.org/mqc2019/program
Continuous-variable sampling from photon-added or photon-subtracted squeezed states
We introduce a new family of quantum circuits in Continuous Variables and we
show that, relying on the widely accepted conjecture that the polynomial
hierarchy of complexity classes does not collapse, their output probability
distribution cannot be efficiently simulated by a classical computer. These
circuits are composed of input photon-subtracted (or photon-added) squeezed
states, passive linear optics evolution, and eight-port homodyne detection. We
address the proof of hardness for the exact probability distribution of these
quantum circuits by exploiting mappings onto different architectures of
sub-universal quantum computers. We obtain both a worst-case and an
average-case hardness result. Hardness of Boson Sampling with eight-port
homodyne detection is obtained as the zero squeezing limit of our model. We
conclude with a discussion on the relevance and interest of the present model
in connection to experimental applications and classical simulations.Comment: 11 pages, 6 figure
Cloning and sequence analysis of cDNAs encoding the cytosolic precursors of subunits GapA and GapB of chloroplast glyceraldehyde-3-phosphate dehydrogenase from pea and spinach
Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is composed of two different subunits, GapA and GapB. cDNA clones containing the entire coding sequences of the cytosolic precursors for GapA from pea and for GapB from pea and spinach have been identified, sequenced and the derived amino acid sequences have been compared to the corresponding sequences from tobacco, maize and mustard. These comparisons show that GapB differs from GapA in about 20% of its amino acid residues and by the presence of a flexible and negatively charged C-terminal extension, possibly responsible for the observed association of the enzyme with chloroplast envelopes in vitro. This C-terminal extension (29 or 30 residues) may be susceptible to proteolytic cleavage thereby leading to a conversion of chloroplast GAPDH isoenzyme I into isoenzyme II. Evolutionary rate comparisons at the amino acid sequence level show that chloroplast GapA and GapB evolve roughly two-fold slower than their cytosolic counterpart GapC. GapA and GapB transit peptides evolve about 10 times faster than the corresponding mature subunits. They are relatively long (68 and 83 residues for pea GapA and spinach GapB respectively) and share a similar amino acid framework with other chloroplast transit peptides
Seronegative patients vaccinated with cytomegalovirus gB-MF59 vaccine have evidence of neutralising antibody responses against gB early post-transplantation
Background
Human cytomegalovirus (HCMV) causes a ubiquitous infection which can pose a significant threat for immunocompromised individuals, such as those undergoing solid organ transplant (SOT). Arguably, the most successful vaccine studied to date is the recombinant glycoprotein-B (gB) with MF59 adjuvant which, in 3 Phase II trials, demonstrated 43–50% efficacy in preventing HCMV acquisition in seronegative healthy women or adolescents and reduction in virological parameters after SOT. However, the mechanism of vaccine protection in seronegative recipients remains undefined.
Methods
We evaluated samples from the cohort of seronegative SOT patients enroled in the Phase II glycoprotein-B/MF59 vaccine trial who received organs from seropositive donors. Samples after SOT (0–90 days) were tested by real-time quantitative PCR for HCMV DNA. Anti-gB antibody levels were measured by ELISA. Neutralization was measured as a decrease in infectivity for fibroblast cell cultures revealed by expression of immediate-early antigens.
Findings
Serological analyses revealed a more rapid increase in the humoral response against gB post transplant in vaccine recipients than in those randomised to receive placebo. Importantly, a number of patient sera displayed HCMV neutralising responses – neutralisation which was abrogated by pre-absorbing the sera with recombinant gB.
Interpretation
We hypothesise that the vaccine primed the immune system of seronegative recipients which, when further challenged with virus at time of transplant, allowed the host to mount rapid immunological humoral responses even under conditions of T cell immune suppression during transplantation
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