Dipole-Coupled Defect Pairs as Deterministic Entangled Photon Pair Sources

Scalable quantum systems require deterministic entangled photon pair sources. Here, we demonstrate a scheme that uses a dipole-coupled defect pair to deterministically emit polarization-entangled photon pairs. Based on this scheme, we predict spectroscopic signatures and quantify the entanglement with physically realizable system parameters. We describe how the Bell state fidelity and efficiency can be optimized by precisely tuning transition frequencies. A defect-based entangled photon pair source would offer numerous advantages including flexible on-chip photonic integration and tunable emission properties via external fields, electromagnetic environments, and defect selection.Comment: 8 pages, 4 figures and 2 table

Decentralized Exchange and Factor Payments: A Multiple-Matching Approach

The emergence of fiat money is studied in an environment in which exchange is organized around trading posts where many producers and shoppers are matched in a dynamic monopolistically competitive framework. Each household consumes a bundle of commodities and has a preference for consumption variety. Within this multiple matching structure we determine the endogenous organization of exchange between firms and shoppers and the means of factor payment (remuneration) as well as the price at which these trades occur. Although each household contacts many sellers, the specialization of tastes implies that the variety of the consumption basket under barter mediated exchange is sparser than that obtained under monetary exchange. We verify that the endogenous linkage of factor payments with the medium of exchange can lead to a monetary equilibrium outcome where only fiat money trades for goods, an ex-ante feature of cash-in-advance models. We also examine the long-run effects of money growth on the equilibrium pattern of exchange. A primary finding, consistent with documented hyperinflationary episodes, is that a sufficiently rapid expansion of money supply and inflation leads to the gradual emergence of barter. Under these circumstances sellers will accept both goods and cash payments whereas workers receive part of their remuneration in goods.Variety Preference, Search, Trading Post, Monetary vs. Barter Equilibrium

A semi-empirical representation of the temporal variation of total greenhouse gas levels expressed as equivalent levels of carbon dioxide

Abstract and PDF report are also available on the MIT Joint Program on the Science and Policy of Global Change website (http://globalchange.mit.edu/).In order to examine the underlying longer-term trends in greenhouse gases, that are driven for example by anthropogenic emissions or climate change, it is useful to remove the recurring effects of natural cycles and oscillations on the sources and/or sinks of those gases that have strong biological (e.g., CO2, CH4, N2O) and/or photochemical (e.g. CH4) influences on their global atmospheric cycles. We use global observations to calculate monthly estimates of greenhouse gas levels expressed as CO2 equivalents, and then fit these estimates to a semi-empirical model that includes the natural seasonal, QBO, and ENSO variations, as well as a second order polynomial expressing longer-term variations. We find that this model provides a reasonably accurate fit to the observation-based monthly data. We also show that this semiempirical model has some predictive capability; that is it can be used to provide a reasonably reliable estimate of CO2 equivalents at the current time using validated observations that lag real time by a few to several months.This study received support from the MIT Joint Program on the Science and Policy of Global Change, which is funded by a consortium of government, industry and foundation sponsors

Inflation and economic activity in a multiple matching model of money

This paper investigates the relationship between money growth, inflation, and productive activity in a general equilibrium model where search frictions motivate the transactions role of money. The use of a multiple matching technique, where search frictions are captured by limited consumption variety, allows us to study price determination in a search-theoretic environment with divisible money and goods. We find that in such a setting, a positive feedback between work and shopping effort decisions create a channel by which inflation can positively influence real activity. This feature also creates the possibility of multiple steady state equilibria. We also analyze the impact of inflation on capital accumulation, the role search frictions play in determining the extent to which inflation distorts relative prices, and the effect of money growth on firm entry on trade friction. In doing so, we demonstrate that a multiple matching model of money is amendable to study a wide range of traditional issues in monetary theory.Inflation (Finance) ; Money ; Econometric models

Aspects of Floquet Bands and Topological Phase Transitions in a Continuously Driven Superlattice

Recently the creation of novel topological states of matter by a periodic driving field has attracted great attention. To motivate further experimental and theoretical studies, we investigate interesting aspects of Floquet bands and topological phase transitions in a continuously driven Harper model. In such a continuously driven system with an odd number of Floquet bands, the bands are found to have nonzero Chern numbers in general and topological phase transitions take place as we tune various system parameters, such as the amplitude or the period of the driving field. The nontrivial Floquet band topology results in a quantized transport of Wannier states in the lattice space. For certain parameter choices, very flat yet topologically nontrivial Floquet bands may also emerge, a feature that is potentially useful for the simulation of physics of strongly correlated systems. Some cases with an even number of Floquet bands may also have intriguing Dirac cones in the spectrum. Under open boundary conditions, anomalous counter-propagating chiral edge modes and degenerate zero modes are also found as the system parameters are tuned. These results should be of experimental interest because a continuously driven system is easier to realize than a periodically kicked system.Comment: 29 pages, 9 figures. Comments are welcom

Privacy Management and Optimal Pricing in People-Centric Sensing

With the emerging sensing technologies such as mobile crowdsensing and Internet of Things (IoT), people-centric data can be efficiently collected and used for analytics and optimization purposes. This data is typically required to develop and render people-centric services. In this paper, we address the privacy implication, optimal pricing, and bundling of people-centric services. We first define the inverse correlation between the service quality and privacy level from data analytics perspectives. We then present the profit maximization models of selling standalone, complementary, and substitute services. Specifically, the closed-form solutions of the optimal privacy level and subscription fee are derived to maximize the gross profit of service providers. For interrelated people-centric services, we show that cooperation by service bundling of complementary services is profitable compared to the separate sales but detrimental for substitutes. We also show that the market value of a service bundle is correlated with the degree of contingency between the interrelated services. Finally, we incorporate the profit sharing models from game theory for dividing the bundling profit among the cooperative service providers.Comment: 16 page

nu444 is a novel allele of pkc-1 in C. elegans

Here, we report nu444 as a novel allele of the gene pkc-1 that encodes the protein kinase C-1 in C. elegans. The nu444 allele was originally isolated from a forward genetic screen for mutants that suppressed the “Hic” (Hypersensitivity to Inhibitors of Cholinesterase) phenotype of dgk-1(nu62) mutants, which had increased acetylcholine release at the neuromuscular junction (Sieburth et al., 2007). In this screen, several genes that are important for neuropeptide secretion were recovered, including pkc-1(nu448) (Sieburth et al., 2007) and ric-7(nu447) (Hao et al., 2012). Sanger sequencing of the exons and exon-intron junctions of the pkc-1 locus revealed that nu444 had a nonsense mutation (C to T, in the coding strand of pkc-1, with left flanking sequence: 5’-GGATGAATATCATATAGGAAAGACG-3’ and right flanking sequence: 5’- AAGTTCGGCCCAAGACTAATGAACC-3’) in an early exon that is only present in pkc1a and pkc-1c isoforms (Fig.1). Thus, pkc-1(nu444) allele is probably a null allele for both pkc-1a (Q53stop) and pkc-1c (Q109stop), but presumably does not affect pkc-1b.

Health Condition Monitoring of Induction Motors

Induction motors (IMs) are commonly used in various industrial applications. A spectrum synch (SS) technique is proposed in this chapter for early IM defect detection using electric current signals; fault detection in this work will focus on defects in rolling element bearings and rotor bars, which together account for more than half of IM imperfections. In bearing fault detection, the proposed SS technique will highlight the peakedness of the fault frequency components distributed over several fault related local bands. These bands are synchronized to form a fault information spectrum to accentuate fault features. A central kurtosis indicator is proposed to extract representative features from the fault information spectrum and formulate a fault index for incipient IM fault diagnosis. The effectiveness of the developed SS technique is tested on IMs with broken rotor bars and with damaged bearings