Efficient parallelization of tensor network contraction for simulating quantum computation

We develop an algorithmic framework for contracting tensor networks and demonstrate its power by classically simulating quantum computation of sizes previously deemed out of reach. Our main contribution, index slicing, is a method that efficiently parallelizes the contraction by breaking it down into much smaller and identically structured subtasks, which can then be executed in parallel without dependencies. We benchmark our algorithm on a class of random quantum circuits, achieving greater than 105 times acceleration over the original estimate of the simulation cost. We then demonstrate applications of the simulation framework for aiding the development of quantum algorithms and quantum error correction. As tensor networks are widely used in computational science, our simulation framework may find further applications.

A new geography of civil war: a machine learning approach to measuring the zones of armed conflicts

Where do armed conflicts occur? In applied studies, we may take ad hoc approaches to answer this question. In some regression studies, for instance, a single conflict event can cause an entire province to be classified as a conflict zone. In this paper, I fill this void of knowledge by developing a machine learning method that is less dependent on the areal-unit assumptions and can flexibly estimate conflict zones. I apply the method to a conflict event dataset and create a new dataset of conflict zones. A replication of Daskin and Pringle (2018, Nature 553, 328–332) with the new dataset indicates that the effect of civil war on mammal populations is much smaller than the original estimate.

Response to Comment on “Insulator-metal transition in dense fluid deuterium”

In their comment, Desjarlais et al. claim that a small temperature drop occurs after isentropic compression of fluid deuterium through the first-order insulator-metal transition. We show that their calculations do not correspond to the experimental thermodynamic path, and that thermodynamic integrations with parameters from first-principles calculations produce results in agreement with our original estimate of the temperature drop.

Minimax Shrunken Technique for Estimate Burr X Distribution Shape Parameter

The present paper concern with minimax shrinkage estimator technique in order to estimate Burr X distribution shape parameter, when prior information about the real shape obtainable as original estimate while known scale parameter. Derivation for Bias Ratio, Mean squared error and the Relative Efficiency equations. Numerical results and conclusions for the expressions mentioned above were displayed. Comparisons for proposed estimator with most recent works were made.

Two Phase Annular Flow Approximation Using 1-D Flow Equations Coupled With a Drift Flux Model for Concurrent Flow in Vertical or Near Vertical Channels

Annular flow is a flow regime of two-phase gas-liquid flow dominated by high gas flowrate moving through the center of the pipe (gas core). In this paper we have developed and studied an innovative phenomenological model which combines the Zuber & Findlay’s Drift Flux Model’s weighted mean value approach [1] with the 1-D flow approximation equations. The flow is described in terms of a distribution parameter and an averaged local velocity difference between the phases across the pipe cross-section. The average void fraction is calculated as a function of the ratio of weighted mean gas velocity to the weighted mean liquid velocity (Slip ratio) and the drift flux velocity. The void fraction thus estimated is then applied to the 1-D continuity, momentum and energy equations. The equations are solved simultaneously to obtain the pressure gradient. Lastly, we obtain the liquid film thickness using the triangular hydrodynamic relationship between the liquid flow rate, pressure gradient and the liquid film thickness. The thickness of layer obtained, is then used to verify the original estimate of the void fraction. An iterative procedure is used to match the original estimate to the final value. The results from this study were validated against PipeSIM© software and two field measurements conducted on a wet-gas field in Brazil. As opposed to conventional drift flux models which are based on four simultaneous equations, this model relies on three, thereby significantly reducing the computational resources necessary and is more accurate as we account for variable velocities and void fractions across the pipe cross-section.

Angolan economy set for further tightening

Significance The Fund now expects economic growth to flat-line this year against the 2.5% growth forecast made just six months ago; inflation is now expected to reach 45.0% by year-end compared with the previously projected rate of 19.2%; and public debt could rise to 77.7% from the original estimate of 70.1%. If the government resumes negotiations on the EFF -- possible after elections in August -- it could face a more severe adjustment than originally envisaged and a harder landing for the economy. Impacts Maintaining a low budget oil price to shore up reserves could become untenable given likely revenue shortfalls in 2017. Negotiating favourable terms for up to 4.5 billion dollars in available IMF funds will be more difficult than earlier this year. The government may resort to more administrative measures to try stabilise the economy after introducing price controls to curb inflation.

Unclothed firewalls

We have previously argued that fluctuations of the Hawking emission rate can cause a black hole event horizon to fluctuate inside the location of a putative firewall, rendering the firewall naked. This assumes that the firewall is located near where the horizon would be expected based on the past evolution of the spacetime. Here, we expand our previous results by defining two new estimates for where the firewall might be that have more smooth temporal behavior than our original estimate. Our results continue to contradict the usual assumption that the firewall should not be observable except by infalling observers. This casts doubt about the idea that firewalls are the ‘most conservative’ solution to the information loss paradox.

New Viewpoints about Pseudo Measurements Method in Equality-Constrained State Estimation

We discuss the pseudo measurement method which is one of the main approaches to equality-constrained state estimation for a dynamic system. We demonstrate by the fundamental theory of Kalman filtering that reviewing the equality constraint as a pseudo measurement seems questionable. The main reason is that the additional pseudo measurement is actually a constant here which cannot help to estimate the state. More specifically, when the states in an unconstrained dynamic system model have already satisfied the equality constraint, the extra constraint is obviously not necessary. When the true equality-constrained states do not satisfy the unconstrained dynamic process equation, the effect of pseudo measurement is projecting the estimate which is not optimal onto the constraint set. However, since the performance of a projected estimate is also certainly influenced by its original estimate, we show through a numerical example that the pseudo measurement method is not always a good choice, especially when the process equation mismatch is large.

Re-evaluation of the age model for North Atlantic Ocean Site 982 – arguments for a return to the original chronology

Recently, the veracity of the published chronology for the Pliocene section of North Atlantic Ocean Drilling Program Site 982 was called into question. Here, we examine the robustness of the original age model as well as the proposed age model revision. The proposed revision is predicated on an apparent misidentification of the depth to the Gauss–Matuyama (G/M) polarity chronozone reversal boundary (2.581 Ma) based on preliminary shipboard paleomagnetic data, and offers a new chronology that includes a hiatus between ~3.2 and 3 Ma. However, an even more accurate shore-based, u-channel-derived polarity chronozone stratigraphy for the past ~2.7 Ma supports the shipboard composite stratigraphy and demonstrates that the original estimate of the depth of the G/M reversal in the Site 982 record is correct. Thus, the main justification forwarded to support the revised chronology no longer exists. We demonstrate that the proposed revision results in a pronounced anomaly in sedimentation rates proximal to the proposed hiatus, erroneous assignment of marine-isotope stages in the Site 982 Pliocene benthic stable oxygen isotope stratigraphy, and a markedly worse correlation of proxy records between this site and other regional paleoclimate data. We conclude that the original chronology for Site 982 is a far more accurate age model than that which arises from the published revision. We strongly recommend the use of the original chronology for all future work at Site 982.