970,327 research outputs found
A quantum causal discovery algorithm
Finding a causal model for a set of classical variables is now a
well-established task---but what about the quantum equivalent? Even the notion
of a quantum causal model is controversial. Here, we present a causal discovery
algorithm for quantum systems. The input to the algorithm is a process matrix
describing correlations between quantum events. Its output consists of
different levels of information about the underlying causal model. Our
algorithm determines whether the process is causally ordered by grouping the
events into causally-ordered non-signaling sets. It detects if all relevant
common causes are included in the process, which we label Markovian, or
alternatively if some causal relations are mediated through some external
memory. For a Markovian process, it outputs a causal model, namely the causal
relations and the corresponding mechanisms, represented as quantum states and
channels. Our algorithm provides a first step towards more general methods for
quantum causal discovery.Comment: 11 pages, 10 figures, revised to match published versio
Causal Set Dynamics: A Toy Model
We construct a quantum measure on the power set of non-cyclic oriented graphs
of N points, drawing inspiration from 1-dimensional directed percolation.
Quantum interference patterns lead to properties which do not appear to have
any analogue in classical percolation. Most notably, instead of the single
phase transition of classical percolation, the quantum model displays two
distinct crossover points. Between these two points, spacetime questions such
as "does the network percolate" have no definite or probabilistic answer.Comment: 28 pages incl. 5 figure
A time series causal model
Cause-effect relations are central in economic analysis. Uncovering empirical cause-effect relations is one of the main research activities of empirical economics. In this paper we develop a time series casual model to explore casual relations among economic time series. The time series causal model is grounded on the theory of inferred causation that is a probabilistic and graph-theoretic approach to causality featured with automated learning algorithms. Applying our model we are able to infer cause-effect relations that are implied by the observed time series data. The empirically inferred causal relations can then be used to test economic theoretical hypotheses, to provide evidence for formulation of theoretical hypotheses, and to carry out policy analysis. Time series causal models are closely related to the popular vector autoregressive (VAR) models in time series analysis. They can be viewed as restricted structural VAR models identified by the inferred causal relations.Inferred Causation, Automated Learning, VAR, Granger Causality, Wage-Price Spiral
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