12,481 research outputs found
Violation of a Leggett-Garg inequality with ideal non-invasive measurements
No full textThe quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.</p
Characterization of the APEX2-GARG-1060 proximity biotinylation system.
No full textA. Domain organization of GBF1 and the C-terminally truncated GBF1 constructs fused to EGFP (positive control) and APEX2. Both GBF1 truncated constructs contain the BFA-resistant Sec7 domain from ARNO. B. Polio replicon replication was assessed in the presence or absence of 2μg/ml of BFA in HeLa cells transfected with plasmids expressing the C-terminally truncated GBF1 fusions with APEX2 or EGFP, or an empty vector C. Polio replicon replication assay was performed in control HeLa cells, or HeLa cells stably expressing APEX2-GARG-1060 with or without 2μg/ml of BFA. D. HeLa cells stably expressing APEX2-GARG-1060 were infected (or mock-infected) with 10 PFU/cell of poliovirus, and the biotinylation reaction was performed at 4 h p.i. The cells were processed for visualization of biotinylated proteins with a fluorescent streptavidin conjugate and immunostaining for a poliovirus antigen 3A. E. HeLa cells stably expressing APEX2-GARG-1060 were infected (or mock-infected) with poliovirus and the biotinylation reaction was performed as in D. The cells were stained with a fluorescent streptavidin conjugate and antibodies against a poliovirus antigen 2B and processed for structural illumination superresolution (SIM) microscopy. The arrow shows biotinylation-positive structures identified as stress granules. The scale bar is 10μm. F. HeLa cells stably expressing APEX2-GARG-1060 were infected (PV), or mock-infected (M) with 10 PFU/cell of poliovirus, and protein biotinylation was assessed after performing the biotinylation reaction at 4 h p.i. with biotin-phenol (BP) and hydrogen peroxide (complete reaction), or without one, or both compounds.</p
Comment on 'A scattering quantum circuit for measuring Bell's time inequality:a nuclear magnetic resonance demonstration using maximally mixed states'
No full textA recent paper by Souza, Oliveira and Sarthour (SOS) reports the experimental violation of a Leggett-Garg (LG) inequality (sometimes referred to as a temporal Bell inequality). The inequality tests for quantum mechanical superposition: if the inequality is violated, the dynamics cannot be explained by a large class of classical theories under the heading of macrorealism. Experimental tests of the LG inequality are beset by the difficulty of carrying out the necessary so-called 'non-invasive' measurements (which for the macrorealist will extract information from a system of interest without disturbing it). SOS argue that they nevertheless achieve this difficult goal by putting the system in a maximally mixed state. The system then allegedly undergoes no perturbation during their experiment. Unfortunately, the method is ultimately unconvincing to a skeptical macrorealist and so the conclusions drawn by SOS are unjustified.</p
Enhancing violations of Leggett-Garg inequalities in nonequilibrium correlated many-body systems by interactions and decoherence
No full textWe identify different schemes to enhance the violation of Leggett-Garg inequalities in open many-body systems. Considering a nonequilibrium archetypical setup of quantum transport, we show that particle interactions control the direction and amplitude of maximal violation and that in the strongly-interacting and strongly-driven regime bulk dephasing enhances the violation. Through an analytical study of a minimal model, we unravel the basic ingredients to explain this decoherence-enhanced quantumness, illustrating that such an effect emerges in a wide variety of systems
Universal two-time correlations, out-of-time-ordered correlators, and Leggett-Garg inequality violation by edge Majorana fermion qubits
No full textIn the present work we propose that two-time correlations of Majorana edge localized fermions constitute a novel and versatile toolbox for assessing the topological phases of 1D open lattices. Using analytical and numerical calculations on the Kitaev model, we uncover universal relationships between the decay of the short-time correlations and a particular family of out-of-time-ordered correlators, which provide direct experimental alternatives to the quantitative analysis of the system regime, either normal or topological. Furthermore we show that the saturation of two-time correlations possesses features of an order parameter. Finally, we find that violations of Leggett-Garg inequalities can indicate the topological-normal phase transition by looking at different qubits formed by pairing local and non-local edge Majorana fermions
Sampling hurdles : “Borderline Illegitimate” to legitimate data.
No full textIn this paper the author discusses how sampling access and recruitment problems encountered in an in-depth interview study heightened her sensitivity to “borderline illegitimate” data. The term illegitimate data usually refers to the data collected during a covert study, whereas “legitimate” data are collected during an overt study. Hence, data collected during any nonconsented period(s) of an overt study lie on the borderline of illegitimacy and legitimacy, and constitute what the author calls borderline illegitimate data. Such data need legitimization before use. The borderline illegitimate data were collected during the pre- and postinterview stages of her study as they explained how medical and ethnic cultures and sensitivity to racism as a topic combined to create sample recruitment difficulties of the study. The author later legitimized them by sharing them with the participants, guaranteeing anonymity, and asking their permission to use them
Countermodels from Sequent Calculi in Multi-Modal Logics
No full textA novel countermodel-producing decision procedure that applies to several multi-modal logics, both intuitionistic and classical, is presented. Based on backwards search in labeled sequent calculi, the procedure employs a novel termination condition and countermodel construction. Using the procedure, it is argued that multi-modal variants of several classical and intuitionistic logics including K, T, K4, S4 and their combinations with D are decidable and have the finite model property. At least in the intuitionistic multi-modal case, the decidability results are new. It is further shown that the countermodels produced by the procedure, starting from a set of hypotheses and no goals, characterize the atomic formulas provable from the hypotheses. © 2012 IEEE
The Leggett-Garg inequality and Page-Wootters mechanism
No full textViolation of the Leggett-Garg inequality (LGI) implies quantum phenomena. In this light we establish that Moreva et al.'s (Phys. Rev. A, 89 (2014) 052122) experiment demonstrating Page-Wootters' mechanism (Pag
Relationship between Vitamin D and Insulin Resistance in Polycystic Ovary Syndrome Women
No full textHow to cite this article
Garg R, Malhotra J, Singh S, Singh R, Kokila BT, Agrawal P. Relationship between Vitamin D and Insulin Resistance in Polycystic Ovary Syndrome Women. J South Asian Feder Obst Gynae 2017;9(3):211-215.</jats:p
Learning Generalized Depth Three Arithmetic Circuits in the Non-Degenerate Case
No full textConsider a homogeneous degree d polynomial f = T₁ + ⋯ + T_s, T_i = g_i(_{i,1}, …, _{i, m}) where g_i’s are homogeneous m-variate degree d polynomials and _{i,j}’s are linear polynomials in n variables. We design a (randomized) learning algorithm that given black-box access to f, computes black-boxes for the T_i’s. The running time of the algorithm is poly(n, m, d, s) and the algorithm works under some non-degeneracy conditions on the linear forms and the g_i’s, and some additional technical assumptions n ≥ (md)², s ≤ n^{d/4}. The non-degeneracy conditions on _{i,j}’s constitute non-membership in a variety, and hence are satisfied when the coefficients of _{i,j}’s are chosen uniformly and randomly from a large enough set. The conditions on g_i’s are satisfied for random polynomials and also for natural polynomials common in the study of arithmetic complexity like determinant, permanent, elementary symmetric polynomial, iterated matrix multiplication. A particularly appealing algorithmic corollary is the following: Given black-box access to an f = Det_r(L^(1)) + … + Det_r(L^(s)), where L^(k) = (_{i,j}^(k))_{i,j} with _{i,j}^(k)’s being linear forms in n variables chosen randomly, there is an algorithm which in time poly(n, r) outputs matrices (M^(k))_k of linear forms s.t. there exists a permutation π: [s] → [s] with Det_r(M^(k)) = Det_r(L^(π(k))).
Our work follows the works [Neeraj Kayal and Chandan Saha, 2019; Garg et al., 2020] which use lower bound methods in arithmetic complexity to design average case learning algorithms. It also vastly generalizes the result in [Neeraj Kayal and Chandan Saha, 2019] about learning depth three circuits, which is a special case where each g_i is just a monomial. At the core of our algorithm is the partial derivative method which can be used to prove lower bounds for generalized depth three circuits. To apply the general framework in [Neeraj Kayal and Chandan Saha, 2019; Garg et al., 2020], we need to establish that the non-degeneracy conditions arising out of applying the framework with the partial derivative method are satisfied in the random case. We develop simple but general and powerful tools to establish this, which might be useful in designing average case learning algorithms for other arithmetic circuit models
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