56 research outputs found
Non-Gaussian two-mode squeezing and continuous variable entanglement of linearly and circularly polarized light beams interacting with cold atoms
We investigate how entangled coherent states and superpositions of low
intensity coherent states of non-Gaussian nature can be generated via
non-resonant interaction between either two linearly or circularly polarized
field modes and an ensemble of X-like four-level atoms placed in an optical
cavity. We compare our results to recent experimental observations and argue
that the non-Gaussian structure of the field states may be present in those
systems.Comment: 10 pages, 7 figures, replaced with final published versio
Unconditional Bell-type state generation for spatially separate trapped ions
We propose a scheme for generation of maximally entangled states involving
internal electronic degrees of freedom of two distant trapped ions, each of
them located in a cavity. This is achieved by using a single flying atom to
distribute entanglement. For certain specific interaction times, the proposed
scheme leads to the non-probabilistic generation of a perfect Bell-type state.
At the end of the protocol, the flying atom completely disentangles from the
rest of the system, leaving both ions in a Bell-type state. Moreover, the
scheme is insensitive to the cavity field state and cavity losses. We also
address the situation in which dephasing and dissipation must be taken into
account for the flying atom on its way from one cavity to the other, and
discuss the applicability of the resulting noisy channel for performing quantum
teleportation.Comment: 5 pages, 1 figure, detailed comments on the practical implementation
of the scheme is added to replaced version, minor typos fixed, added
references with comment
Role of cellulose oxidation in the yellowing of ancient paper
The yellowing of paper on aging causes major aesthetic damages of cultural heritage. It is due to cellulose oxidation, a complex process with many possible products still to be clarified. By comparing ultraviolet-visible reflectance spectra of ancient and artificially aged modern papers with ab initio time-dependent density functional theory calculations, we identify and estimate the abundance of oxidized functional groups acting as chromophores and responsible of paper yellowing. This knowledge can be used to set up strategies and selective chemical treatments preventing paper yellowing
Qualitative aspects of entanglement in the Jaynes-Cummings model with an external quantum field
We present a mathematical procedure which leads us to obtain analytical
solutions for the atomic inversion and Wigner function in the framework of the
Jaynes-Cummings model with an external quantum field, for any kinds of cavity
and driving fields. Such solutions are expressed in the integral form, with
their integrands having a commom term that describes the product of the
Glauber-Sudarshan quasiprobability distribution functions for each field, and a
kernel responsible for the entanglement. Considering two specific initial
states of the tripartite system, the formalism is then applied to calculate the
atomic inversion and Wigner function where, in particular, we show how the
detuning and amplitude of the driving field modify the entanglement. In
addition, we also obtain the correctComment: 15 pages and 21 figure
Factors influencing overall survival rates for patients with pineocytoma
Given its rarity, appropriate treatment for pineocytoma remains variable. As the literature primarily contains case reports or studies involving a small series of patients, prognostic factors following treatment of pineocytoma remain unclear. We therefore compiled a systematic review of the literature concerning post-treatment outcomes for pineocytoma to better determine factors associated with overall survival among patients with pineocytoma. We performed a comprehensive search of the published English language literature to identify studies containing outcome data for patients undergoing treatment for pineocytoma. Kaplan–Meier analysis was utilized to determine overall survival rates. Our systematic review identified 168 total patients reported in 64 articles. Among these patients, 21% underwent biopsy, 38% underwent subtotal resection, 42% underwent gross total resection, and 29% underwent radiation therapy, either as mono- or adjuvant therapy. The 1 and 5 year overall survival rates for patients receiving gross total resection versus subtotal resection plus radiotherapy were 91 versus 88%, and 84 versus 17%, respectively. When compared to subtotal resection alone, subtotal resection plus radiation therapy did not offer a significant improvement in overall survival. Gross total resection is the most appropriate treatment for pineocytoma. The potential benefit of conventional radiotherapy for the treatment of these lesions is unproven, and little evidence supports its use at present
Feshbach resonances and mesoscopic phase separation near a quantum critical point in multiband FeAs-based superconductors
High Tc superconductivity in FeAs-based multilayers (pnictides), evading
temperature decoherence effects in a quantum condensate, is assigned to a
Feshbach resonance (called also shape resonance) in the exchange-like interband
pairing. The resonance is switched on by tuning the chemical potential at an
electronic topological transition (ETT) near a band edge, where the Fermi
surface topology of one of the subbands changes from 1D to 2D topology. We show
that the tuning is realized by changing i) the misfit strain between the
superconducting planes and the spacers ii) the charge density and iii) the
disorder. The system is at the verge of a catastrophe i.e. near a structural
and magnetic phase transition associated with the stripes (analogous to the 1/8
stripe phase in cuprates) order to disorder phase transition. Fine tuning of
both the chemical potential and the disorder pushes the critical temperature Ts
of this phase transition to zero giving a quantum critical point. Here the
quantum lattice and magnetic fluctuations promote the Feshbach resonance of the
exchange-like anisotropic pairing. This superconducting phase that resists to
the attacks of temperature is shown to be controlled by the interplay of the
hopping energy between stripes and the quantum fluctuations. The
superconducting gaps in the multiple Fermi surface spots reported by the recent
ARPES experiment of D. V. Evtushinsky et al. arXiv:0809.4455 are shown to
support the Feshbach scenario.Comment: 31 pages, 7 figure
Microstructural and mechanical characterisation of laser-welded high-carbon and stainless steel
The final publication is available at Springer via http://dx.doi.org/10.1007/s00170-015-7111-5Laser welding is becoming an important joining technique for welding of stainless steel to carbon steel and is extensively used across various sectors, including aerospace, transportation, power plants, electronics and other industries. However, welding of stainless steel to high-carbon steel is still at its early stage, predominantly due to the formation of hard brittle phases, which undermine the mechanical strength of the joint. This study reports a scientific investigation on controlling the brittle phase formation during laser dissimilar welding of high-carbon steel to stainless steel. Attempts have been made to tailor the microstructure and phase composition of the fusion zone through influencing the alloying composition and the cooling rate. Results show that the heat-affected zone (HAZ) within the high-carbon steel has significantly higher hardness than the weld area, which severely undermines the weld quality. To reduce the hardness of the HAZ, a new heat treatment strategy was proposed and evaluated using a finite element analysis-based numerical simulation model. A series of experiments has been performed to verify the developed thermo-metallurgical finite element analysis (FEA) model, and a qualitative agreement of predicted martensitic phase distribution is shown to exist
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