Quantum phase transitions of light

Recently, condensed matter and atomic experiments have reached a length-scale and temperature regime where new quantum collective phenomena emerge. Finding such physics in systems of photons, however, is problematic, as photons typically do not interact with each other and can be created or destroyed at will. Here, we introduce a physical system of photons that exhibits strongly correlated dynamics on a meso-scale. By adding photons to a two-dimensional array of coupled optical cavities each containing a single two-level atom in the photon-blockade regime, we form dressed states, or polaritons, that are both long-lived and strongly interacting. Our zero temperature results predict that this photonic system will undergo a characteristic Mott insulator (excitations localised on each site) to superfluid (excitations delocalised across the lattice) quantum phase transition. Each cavity's impressive photon out-coupling potential may lead to actual devices based on these quantum many-body effects, as well as observable, tunable quantum simulators. We explicitly show that such phenomena may be observable in micro-machined diamond containing nitrogen-vacancy colour centres and superconducting microwave strip-line resonators.Comment: 11 pages, 5 figures (2 in colour

Achieved availability importance measure for enhancing reliability-centered maintenance decisions

An effective defense strategy requires aircraft, among other weapons systems, to be available and ready for use when circumstances deem necessary. This article offers a set of importance measures to identify the critical components in a system from their influence on system-achieved availability, a common Department of Defense availability calculation that is a ratio of mean time between maintenance and total system time, including mean maintenance time. With these measures, more effective maintenance plans, including inspection and supply inventory, can focus on those components that more significantly impact achieved availability. A decision-making formulation results from these component importance measures, and an example based on a US Air Force system illustrates the modeling contributions.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline