Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of Earth-based gravitational wave observatories [1, 2, 3, 4] is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometre-level sensitivity of the kilometre-scale Michelson interferometers deployed for this task. Here, we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz, critically important for several astrophysical sources, with no deterioration of performance observed at any frequency. With the injection of squeezed states, this LIGO detector demonstrated the best broadband sensitivity to gravitational waves ever achieved, with important implications for observing the gravitational-wave Universe with unprecedented sensitivity

In this article, we explore the typological distinction between primary and secondary states. We outline a methodology for exploring variability in the formation and organization of secondary states that integrates aspects of traditional neoevolutionary approaches, Marcus's "dynamic model," Blanton et al.'s "dual-processual model," and world-systems theory. We discuss the development of the Minoan and Mycenaean states of the Bronze Age Aegean and argue that they arose via different mechanisms of secondary state formation, through direct and indirect contact with neighboring societies in the Eastern Mediterranean, Near East, and Egypt. We argue that a model that measures state formation along several different theoretical dimensions encourages archaeological exploration of secondary states along varied historical trajectories, in different (pre)historic contexts.

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This article reviews recent research into the archaeological interpretation and investigation of fortifications and enclosures during the Neolithic and Bronze Age in Europe. Recent methodological, technological, and cultural developments have expanded our understanding of the temporal, spatial, and formal variability of these features on the landscape. Interpretations of this variability also have varied with different theoretical trends in the discipline. We advocate a crosscultural approach that focuses on the occurrence of enclosures and fortifications over the long term at the continental scale. Such a macroscalar approach complements interpretive frameworks at the regional and microregional scales. The geographic and temporal distribution of these features indicates that social institutions associated with principles of segmentation and substitutability became formalized and tethered to the landscape during the Neolithic.

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