Recursos de colección

Caltech Authors (160.010 recursos)

Repository of works by Caltech published authors.

Type = Report or Paper

Mostrando recursos 1 - 20 de 2.695

  1. Are Early Stage Investors Biased Against Women?

    Ewens, Michael; Townsend, Richard R.
    We examine whether male investors are biased against female entrepreneurs. To do so, we use a proprietary dataset from AngelList covering fundraising startups. We find that female founders are less successful with male investors compared to observably similar male founders. In contrast, the same female founders are more successful than male founders with female investors. The results do not appear to be driven by differences across founder gender in startup quality, sector focus, or risk. Given that investors are predominately male, our results suggest that an increase in female investors is likely necessary to support an increase in female entrepreneurship.

  2. Are Early Stage Investors Biased Against Women?

    Ewens, Michael; Townsend, Richard R.
    We examine whether male investors are biased against female entrepreneurs. To do so, we use a proprietary dataset from AngelList covering fundraising startups. We find that female founders are less successful with male investors compared to observably similar male founders. In contrast, the same female founders are more successful than male founders with female investors. The results do not appear to be driven by differences across founder gender in startup quality, sector focus, or risk. Given that investors are predominately male, our results suggest that an increase in female investors is likely necessary to support an increase in female entrepreneurship.

  3. The Polarization of American Politics

    Poole, Keith T.; Rosenthal, Howard
    Elected officials in the United States appear to represent relatively extreme support coalitions rather than the interests of middle-of-the-road voters. This contention is supported by analysis of variance of liberal-conservative positions in the United States Senate from 1959 to 1980. Within both the Democratic and the Republican parties, there is considerable variation in liberal-conservative positions, but two senators from the same state and party tend to be very similar. In contrast, two senators from the same state but from different parties are highly dissimilar, suggesting that each party represents an extreme support coalition in the state. Moreover, the distribution of...

  4. Quantum efficiency enhancement by photon recycling with backscatter evasion

    Nagano, Koji; Perreca, Antonio; Arai, Koji; Adhikari, Rana X.
    The non-unity quantum efficiency (QE) in photodiodes (PD) causes deterioration of signal quality in quantum optical experiments due to photocurrent loss as well as the introduction of vacuum fluctuations into the measurement. In this article, we report that the QE enhancement of a PD was demonstrated by recycling the reflected photons. The effective external QE for an InGaAs PD was increased by 2-6% over a wide range of incident angles. Moreover, we confirmed that this technique does not increase backscattered light when the recycled beam is properly misaligned.

  5. Generalized surface codes and packing of logical qubits

    Delfosse, Nicolas; Iyer, Pavithran; Poulin, David
    We consider a notion of relative homology (and cohomology) for surfaces with two types of boundaries. Using this tool, we study a generalization of Kitaev's code based on surfaces with mixed boundaries. This construction includes both Bravyi and Kitaev's and Freedman and Meyer's extension of Kitaev's toric code. We argue that our generalization offers a denser storage of quantum information. In a planar architecture, we obtain a three-fold overhead reduction over the standard architecture consisting of a punctured square lattice.

  6. A linear-time benchmarking tool for generalized surface codes

    Delfosse, Nicolas; Iyer, Pavithran; Poulin, David
    Quantum information processors need to be protected against errors and faults. One of the most widely considered fault-tolerant architecture is based on surface codes. While the general principles of these codes are well understood and basic code properties such as minimum distance and rate are easy to characterize, a code's average performance depends on the detailed geometric layout of the qubits. To date, optimizing a surface code architecture and comparing different geometric layouts relies on costly numerical simulations. Here, we propose a benchmarking algorithm for simulating the performance of surface codes, and generalizations thereof, that runs in linear time. We implemented...

  7. Linear-Time Maximum Likelihood Decoding of Surface Codes over the Quantum Erasure Channel

    Delfosse, Nicolas; Zémor, Gilles
    Surface codes are among the best candidates to ensure the fault-tolerance of a quantum computer. In order to avoid the accumulation of errors during a computation, it is crucial to have at our disposal a fast decoding algorithm to quickly identify and correct errors as soon as they occur. We propose a linear-time maximum likelihood decoder for surface codes over the quantum erasure channel. This decoding algorithm for dealing with qubit loss is optimal both in terms of performance and speed.

  8. The quasiprobability behind the out-of-time-ordered correlator

    Yunger Halpern, Nicole; Swingle, Brian; Dressel, Justin
    Two topics, evolving rapidly in separate fields, were combined recently: The out-of-time-ordered correlator (OTOC) signals quantum-information scrambling in many-body systems. The Kirkwood-Dirac (KD) quasiprobability represents operators in quantum optics. The OTOC was shown to equal a moment of a summed quasiprobability. That quasiprobability, we argue, is an extension of the KD distribution. We explore the quasiprobability's structure from experimental, numerical, and theoretical perspectives. First, we simplify and analyze Yunger Halpern's weak-measurement and interference protocols for measuring the OTOC and its quasiprobability. We decrease, exponentially in system size, the number of trials required to infer the OTOC from weak measurements. We also construct...

  9. Test for a large amount of entanglement, using few measurements

    Chao, Rui; Reichardt, Ben W.; Sutherland, Chris; Vidick, Thomas
    Bell-inequality violations establish that two systems share some quantum entanglement. We give a simple test to certify that two systems share an asymptotically large amount of entanglement, n EPR states. The test is efficient: unlike earlier tests that play many games, in sequence or in parallel, our test requires only one or two CHSH games. One system is directed to play a CHSH game on a random specified qubit i, and the other is told to play games on qubits {i,j}, without knowing which index is i. The test is robust: a success probability within delta of optimal guarantees distance O(n^{5/2} sqrt{delta})...

  10. Land Rents and Agricultural Productivity: The Paris Basin, 1450-1789

    Hoffman, Philip T.
    Using evidence from a sample of over 800 leases, this paper examines the productivity of farming in the Paris Basin between 1450 and 1789. Existing evidence about productivity is unreliable, the paper argues, and the leases provide historians with a new and valuable source for the study of productivity and economic growth. Much of the paper is devoted to a defense of the method employed with the leases, which point to spurts of spectacular growth on local farms but also stunning setbacks during times of war and increased taxation. The paper concludes with analysis of the causes of economic growth...

  11. Land Rents and Agricultural Productivity: The Paris Basin, 1450-1789

    Hoffman, Philip T.
    Using evidence from a sample of over 800 leases, this paper examines the productivity of farming in the Paris Basin between 1450 and 1789. Existing evidence about productivity is unreliable, the paper argues, and the leases provide historians with a new and valuable source for the study of productivity and economic growth. Much of the paper is devoted to a defense of the method employed with the leases, which point to spurts of spectacular growth on local farms but also stunning setbacks during times of war and increased taxation. The paper concludes with analysis of the causes of economic growth...

  12. An Analysis of Linear Induction Motors for Propulsion and Suspension of Magnetically Levitated Vehicles

    Yang, Fang-Chou
    A four-layer single-sided LIM used for propulsion and suspension of magnetically levitated vehicles is studied. The track is assumed to be made of conductors with uniaxial μ and σ. A general analysis allows us to exclude unsuitable geometries. The machine performance is given for the promising geometries. A possible way of computing the effective μ and σ for a composite track is sketched. From the analysis of an extremely simplified geometry, the conditions for the validity of the effective μ and σ concept are given. Finally, a three-dimensional correction is introduced.

  13. An Analysis of Linear Induction Motors for Propulsion and Suspension of Magnetically Levitated Vehicles

    Yang, Fang-Chou
    A four-layer single-sided LIM used for propulsion and suspension of magnetically levitated vehicles is studied. The track is assumed to be made of conductors with uniaxial μ and σ. A general analysis allows us to exclude unsuitable geometries. The machine performance is given for the promising geometries. A possible way of computing the effective μ and σ for a composite track is sketched. From the analysis of an extremely simplified geometry, the conditions for the validity of the effective μ and σ concept are given. Finally, a three-dimensional correction is introduced.

  14. An Analysis of Linear Induction Motors for Propulsion and Suspension of Magnetically Levitated Vehicles

    Yang, Fang-Chou
    A four-layer single-sided LIM used for propulsion and suspension of magnetically levitated vehicles is studied. The track is assumed to be made of conductors with uniaxial μ and σ. A general analysis allows us to exclude unsuitable geometries. The machine performance is given for the promising geometries. A possible way of computing the effective μ and σ for a composite track is sketched. From the analysis of an extremely simplified geometry, the conditions for the validity of the effective μ and σ concept are given. Finally, a three-dimensional correction is introduced.

  15. Vertigo: Comparing Structural Models of Imperfect Behavior in Experimental Games

    El-Gamal, Mahmoud; Palfrey, Thomas R.
    This paper investigates learning in games with one-sided incomplete information using laboratory data from a game which we call the game of Vertigo. The predicted Bayes-Nash equilibrium behavior of the agents in this type of game generates overly strong restrictions on the data, including the zero likelihood problem: certain actions should never be observed. To circumvent statistical problems, and to allow for deviations from perfectly rational behavior, we introduce the possibility of players making errors when choosing their actions. We compare two competing models depending on whether players take the errors in actions into consideration when formulating their strategies. We...

  16. Matrix Product Representation of Locality Preserving Unitaries

    Sahinoğlu, M. Burak; Shukla, Sujeet K.; Bi, Feng; Chen, Xie
    The matrix product representation provides a useful formalism to study not only entangled states, but also entangled operators in one dimension. In this paper, we focus on unitary transformations and show that matrix product operators that are unitary provides a necessary and sufficient representation of 1D unitaries that preserve locality. That is, we show that matrix product operators that are unitary are guaranteed to preserve locality by mapping local operators to local operators while at the same time all locality preserving unitaries can be represented in a matrix product way. Moreover, we show that the matrix product representation gives a straight-forward...

  17. EPA's New Emissions Trading Mechanism: A Laboratory Evaluation

    Cason, Timothy N.; Plott, Charles R.
    The EPA has designed a new call auction institution for trading allowances to emit sulfur dioxide. This paper reports twelve laboratory markets that investigate trader behavior in this new institution and evaluate its performance relative to the more commonly observed uniform price call market. We find that the uniform price call market (1) is more efficient, (2) induces more truthful revelation of underlying values and costs, (3) provides more accurate price information, and (4) is more responsive to and recovers more quickly from changes in underlying market conditions. All of these differences result from the intense strategic manipulation incentives of the EPA auction. Under -the EPA auction...

  18. Ambiguity Made Precise: A Comparative Foundation

    Ghirardato, Paolo; Marinacci, Massimo
    The theory of subjective expected utility (SEU) has been recently extended to allow ambiguity to matter for choice. We propose a notion of absolute ambiguity aversion by building on a notion of comparative ambiguity aversion. We characterize it for a preference model which encompasses some of the most popular models in the literature. We next build on these ideas to provide a definition of unambiguous act and event, and show the characterization of the latter. As an illustration, we consider the classical Ellsberg 3-color urn problem and find that the notions developed in the paper provide intuitive answers.

  19. Markets for Contracts: Experiments Exploring the Compatibility of Games and Markets for Games

    Plott, Charles R.; Williamson, Dean V.
    The research presented here explores the relationship between games and the economic environment in which the game might be embedded. In particular, the focus is on a market institution in which agents buy and sell rights to participate in a follow-on stage of strategic interaction. Many instruments found in markets, such as insurance contracts and warranties, have that property and motivate the study. The central question posed is how the game and the market, two different types of processes, interact. Traditionally two sets of theory are applied to each of the separate processes: one relates to price formation in the...

  20. On the Behavioral Foundations of the Law of Supply and Demand: Human Convergence and Robot Randomness

    Brewer, Paul J.; Huang, Maria; Nelson, Brad; Plott, Charles R.
    In a seminal series of papers, Gode and Sunder [1993, b, 1996] have explored the relationship between limited rationality, market institutions and the general equilibration of markets to the competitive equilibrium. Their fundamental discovery is that within the classical double auction market institution only the weakest elements of rationality need to be present for markets to exhibit high allocative efficiency and price convergence. While Gode and Sunder place more emphasis on allocative efficiency than on price convergence, the apparent price convergence increases the agreement between their simulation results and observed price convergence in single isolated periods of double auction markets...

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