How the Car Won the Road: The Surrender of Atlanta\u27s City Streets, 1920-1929

In 1899, Atlantans saw their city streets as multi-purpose open spaces, freely available to all persons and transit modes. By 1929, that understanding had changed. Streets became automobile conduits to rapidly and efficiently move motor vehicles around town. Other modes of transportation had disappeared or been marginalized. New government regulations tightly controlled or banished other street users and uses. Vast amounts of municipal space became the domain of automobiles, losing the democratic values which public roads formerly represented. This study will demonstrate that during the 1920s, Atlanta’s powerful elites brought about this transformation of society’s comprehension of the meaning and function of a city street. Seeing the automobile as the essential tool for city expansion, this pro-growth coalition directly intervened in state and municipal government to enact laws favoring motor vehicles. They sought and won the allocation of public funds to build the physical infrastructure and legislative superstructure to facilitate the presence of cars on city streets. The print media marketed the changed definition of street space, and promoted the automobile as a status symbol and a way to escape the always-contentious, multi-racial streetcars. Realtors and investors urged better roads for automobile access to their burgeoning suburban developments. While the transformative process took root and sprouted between 1900 and 1919, the twenties witnessed the bulk of the efforts of the growth alliance to remake Atlanta’s city streets. No longer a luxury vehicle for the very rich, by 1920, the car had emerged as a necessity for all but the poorest citizens. Utilizing modern marketing methods and innovative business strategies, automakers helped emplace a national culture of consumption. Advertisements urged Atlantans to go into debt to purchase the latest models, while the local government struggled to cope with traffic gridlock and outrageous numbers of auto-related fatalities. Blaming streetcars for the congestion, business and civic leaders also increasingly faulted pedestrians and children for their own injuries and deaths—they should not have strayed onto streets which no longer belonged to everyone. By 1929, Atlanta’s leadership had surrendered the city streets to the automobile; the car had “won” the road

Critical fluctuations in an optical parametric oscillator: when light behaves like magnetism

We study the nondegenerate optical parametric oscillator in a planar interferometer near threshold, where critical phenomena are expected. These phenomena are associated with nonequilibrium quantum dynamics that are known to lead to quadrature entanglement and squeezing in the oscillator field modes. We obtain a universal form for the equation describing this system, which allows a comparison with other phase transitions. We find that the unsqueezed quadratures of this system correspond to a two-dimensional XY-type model with a tricritical Lifshitz point. This leaves open the possibility of a controlled experimental investigation into this unusual class of statistical models. We evaluate the correlations of the unsqueezed quadrature using both an exact numerical simulation and a Gaussian approximation, and obtain an accurate numerical calculation of the non-Gaussian correlations.Comment: Title changed. New figures adde

Probabilistic quantum phase-space simulation of Bell violations and their dynamical evolution

Quantum simulations of Bell inequality violations are numerically obtained using probabilistic phase space methods, namely the positive P-representation. In this approach the moments of quantum observables are evaluated as moments of variables that have values outside the normal eigenvalue range. There is thus a parallel with quantum weak measurements and weak values. Nevertheless, the representation is exactly equivalent to quantum mechanics. A number of states violating Bell inequalities are sampled, demonstrating that these quantum paradoxes can be treated with probabilistic methods. We treat quantum dynamics by simulating the time evolution of the Bell state formed via parametric down-conversion, and discuss multi-mode generalizations

Quantum probabilistic sampling of multipartite 60-qubit Bell inequality violations

We show that violation of genuine multipartite Bell inequalities can be obtained with sampled, probabilistic phase space methods. These genuine Bell violations cannot be replicated if any part of the system is described by a local hidden variable theory. The Bell violations are simulated probabilistically using quantum phase-space representations. We treat mesoscopically large Greenberger-Horne-Zeilinger (GHZ) states having up to 60 qubits, using both a multipartite SU(2) Q-representation and the positive P-representation. Surprisingly, we find that sampling with phase-space distributions can be exponentially faster than experiment. This is due to the classical parallelism inherent in the simulation of quantum measurements using phase-space methods. Our probabilistic sampling method predicts a contradiction with local realism of "Schr\"odinger-cat" states that can be realized as a GHZ spin state, either in ion traps or with photonic qubits. We also present a quantum simulation of the observed super-decoherence of the ion-trap "cat" state, using a phenomenological noise model

Probabilistic simulation of mesoscopic "Schr\"odinger cat" states

We carry out probabilistic phase-space sampling of mesoscopic Schr\"odinger cat quantum states, demonstrating multipartite Bell violations for up to 60 qubits. We use states similar to those generated in photonic and ion-trap experiments. These results show that mesoscopic quantum superpositions are directly accessible to probabilistic sampling, and we analyze the properties of sampling errors. We also demonstrate dynamical simulation of super-decoherence in ion traps. Our computer simulations can be either exponentially faster or slower than experiment, depending on the correlations measured