Geometries for universal quantum computation with matchgates

Matchgates are a group of two-qubit gates associated with free fermions. They are classically simulatable if restricted to act between nearest neighbors on a one-dimensional chain, but become universal for quantum computation with longer-range interactions. We describe various alternative geometries with nearest-neighbor interactions that result in universal quantum computation with matchgates only, including subtle departures from the chain. Our results pave the way for new quantum computer architectures that rely solely on the simple interactions associated with matchgates.Comment: 6 pages, 4 figures. Updated version includes an appendix extending one of the result

Associação entre medidas morfométricas e ultrassonograficas e a produção de leite de caprinos.

Resumo: O objetivo do presente estudo foi avaliar as associações entre medidas morfométricas e ultrassonográficas e a produção de leite em caprinos, para identificar animais com melhor eficiência de produção. Foram utilizadas trinta e seis cabras, sendo 18 da raça Saa-nen e 18 da raça Anglo-nubiana. As características morfológicas mensuradas foram pro-fundidade do úbere (PU), largura do úbere (LAR), distância do teto ao solo (DTS), dis-tância entre tetos (DET), comprimento (CT) e diâmetro do teto (DT). As características avaliadas por ultrassonografia foram comprimento do canal do teto (CCT), diâmetro do teto (DTU), espessura da parede do teto (ESPT), área da cisterna do teto (ARCT) e área da cisterna da glândula (ARCG). A produção de leite diária (PL) foi representada pela média dos últimos três controles leiteiros. Houve poucas associações significativas entre as características morfológicas/ultrassonográficas com a produção de leite nas duas ra-ças. Somente ARCG foi correlacionada com PL (r = 0,57; P<0,05), na raça Anglo-nubiana, e LAR (r = 0,48; P<0,05) na raça Saanen. Na raça Anglo-nubiana, tetos mais compridos e com maior diâmetro tendem a aumentar a proximidade do úbere ao solo, enquanto isso é mais evidente em úberes mais profundos, na raça Saanen. Em ambas as raças, tetos mais compridos também apresentam maior diâmetro. A análise de correlação canônica demonstrou que os conjuntos de características morfométricas e ultrasso-nográficas apresentam alta associação (r = 0,9455). O primeiro par canônico explicou 93,21% da variação total contida no conjunto de dados. As características DT, CT e DTS foram as mais associadas com o conjunto de variáveis canônicas ultrassonográficas, enquanto DT e ARCT foram as mais associadas com o conjunto de variáveis canônicas morfológicas. As características morfológicas a serem mensuradas para auxiliar a PL de cabras dependem da raça em consideração, o que pode estar em função do histórico seletivo desta raça. As mensurações realizadas nos tetos apresentam maiores cor-respondências com as realizadas com o ultrassom do que aqueles mensuradas no úbere. Comprimento e diâmetro dos tetos e sua distância ao solo são as que mais devem ser consideradas como auxiliares à seleção para produção de leite em caprinos. [Association between morphometric and ultrasound-graphic measures and the production of goat milk]. Abstract: The aim of this study was to evaluate the associations between morphometric and ultra-sound measurements and the milk yield of goats, to identify of animals with better production efficiency. Thirty-six does 18 from Saanen breed and 18 from Anglo-Nubian breed. The measured morphological traits were: udder depth (UD), udder width (UW), distance from the teat to the ground (DCG), distance between teat (DBT), length (LT) and diameter of the teat (DT). The ultra-sonographic traits analyzed were: teat canal length (TCL), teat diameter (TD), wall thickness of the teat (WTC), cistern area of the teat (CAT) and cistern area of the gland (CAG). Daily milk yield (MY) was estimated as the average of the last test-day milk yield. In both breeds, there was no significant associations between morphometric/ultra-sonographic traits and the milk yield. Only CAG was correlated with MY (r = 0.57; P <0.05), in the Anglo-Nubian breed, and UW (r = 0.48; P <0.05) in Saanen breed. In the Anglo-Nubian breed, longer and larger diam-eter teat tend to increase the proximity of the udder to the ground, while this is more evident in deeper udders in Saanen breed. In both breeds, longer teat also feature larger diameter. The canonical correlation analysis showed that the sets of morphometric and ultra-sonographic traits present high association (r = 0.9455). The first canonical pair explained 93.21% of the total variation contained in the data set. DC, LC and DCG traits were the most associated with the set of ultra-sonographic canonical variables, while DC and CAT were most associated with the set of morphological canonical varia-bles. The morphological traits to be measured to aid the production of goat milk depend on the breed into consideration, which may be a function of up selective history of this breed. The measurements carried out on the teat have higher correspondence with those performed with ultrasound than those measured in the udder. Length and diameter of the teat and its ground clearance are the most should be considered as an aid to selection for milk production in goats.Dissertação (Mestrado em Zootecnia) - Centro de Ciência Agrárias, Universidade Federal do Ceará, Fortaleza. Orientador: Raimundo Nonato Braga Lôbo (CNPC)

Spin-orbit mode transfer via a classical analog of quantum teleportation

We translate the quantum teleportation protocol into a sequence of coherent operations involving three degrees of freedom of a classical laser beam. The protocol, which we demonstrate experimentally, transfers the polarisation state of the input beam to the transverse mode of the output beam. The role of quantum entanglement is played by a non-separable mode describing the path and transverse degrees of freedom. Our protocol illustrates the possibility of new optical applications based on this intriguing classical analogue of quantum entanglement.Comment: 5 pages, 7 figure

Evaluation of Bone Remodeling in Hemodialysis Patients: Serum Biochemistry, Circulating Cytokines and Bone Histomorphometry

BACKGROUND: To optimize the noninvasive evaluation of bone remodeling, we evaluated, besides routine serum markers, serum levels of several cytokines involved in bone turnover. METHODS: A transiliac bone biopsy was performed in 47 hemodialysis patients. Serum levels of intact parathyroid hormone (iPTH; 1-84), total alkaline phosphatases (tAP), calcium, phosphate and aluminum (Al) were measured. Circulating levels of interleukin-6 (IL-6), IL-1 receptor antagonist (IL-1Ra) and soluble IL-6 receptor (sIL-6r) were determined using ELISA. Circulating IL-1beta, IL-6, IL-8, IL-10, IL-12p70 and tumor necrosis factor-alpha (TNF-alpha) were simultaneously quantified by flow cytometric immunoassay. RESULTS: Patients with low/normal bone formation rate (L/N-BFR) had significantly lower serum iPTH (p300 pg/mL in association with tAP >120 U/L showed low sensitivity (58.8%) and low negative predictive value (44.0%) for the diagnosis of high BFR disease. An iPTH <300 pg/mL in association with normal or low tAP, <120 U/L, was associated with low sensitivity (66.7%) but high specificity (97.1%) for the diagnosis of L/N-BFR. Serum IL-1, IL-6, IL-12p70 and TNF-alpha were positively correlated with BFR, serum IL1-Ra and IL-10 with bone area, and by multiple regression analysis, tAP and IL-6 were independently predictive of BFR. CONCLUSIONS: Significant associations were found between several circulating cytokines and bone histomorphometry in dialysis patients. The usefulness of these determinations in the noninvasive evaluation of bone remodeling needs to be confirmed in larger dialysis populations

A Quantum solution to the Byzantine agreement problem

We present a solution to an old and timely problem in distributed computing. Like Quantum Key Distribution (QKD), quantum channels make it possible to achieve taks classically impossible. However, unlike QKD, here the goal is not secrecy but agreement, and the adversary is not outside but inside the game, and the resources require qutrits.Comment: 4 pages, 1 figur

Classicality in discrete Wigner functions

Gibbons et al. [Phys. Rev. A 70, 062101(2004)] have recently defined a class of discrete Wigner functions W to represent quantum states in a Hilbert space with finite dimension. We show that the only pure states having non-negative W for all such functions are stabilizer states, as conjectured by one of us [Phys. Rev. A 71, 042302 (2005)]. We also show that the unitaries preserving non-negativity of W for all definitions of W form a subgroup of the Clifford group. This means pure states with non-negative W and their associated unitary dynamics are classical in the sense of admitting an efficient classical simulation scheme using the stabilizer formalism.Comment: 10 pages, 1 figur

Podolsky Electromagnetism at Finite Temperature: Implications on Stefan-Boltzmann Law

In this work we study Podolsky electromagnetism in thermodynamic equilibrium. We show that a Podolsky mass-dependent modification to the Stefan-Boltzmann law is induced and we use experimental data to limit the possible values for this free parameter.Comment: 13 pages, submitted to Physical Review