Testing foundations of quantum mechanics with photons

The foundational ideas of quantum mechanics continue to give rise to counterintuitive theories and physical effects that are in conflict with a classical description of Nature. Experiments with light at the single photon level have historically been at the forefront of tests of fundamental quantum theory and new developments in photonics engineering continue to enable new experiments. Here we review recent photonic experiments to test two foundational themes in quantum mechanics: wave-particle duality, central to recent complementarity and delayed-choice experiments; and Bell nonlocality where recent theoretical and technological advances have allowed all controversial loopholes to be separately addressed in different photonics experiments.Comment: 10 pages, 5 figures, published as a Nature Physics Insight review articl

On what I do not understand (and have something to say): Part I

This is a non-standard paper, containing some problems in set theory I have in various degrees been interested in. Sometimes with a discussion on what I have to say; sometimes, of what makes them interesting to me, sometimes the problems are presented with a discussion of how I have tried to solve them, and sometimes with failed tries, anecdote and opinion. So the discussion is quite personal, in other words, egocentric and somewhat accidental. As we discuss many problems, history and side references are erratic, usually kept at a minimum (``see ... '' means: see the references there and possibly the paper itself). The base were lectures in Rutgers Fall'97 and reflect my knowledge then. The other half, concentrating on model theory, will subsequently appear

The Third Trick

We prove a result, similar to the ones known as Ishihara's First and Second Trick, for sequences of functions

THE INDETERMINATE PRESENT: AN ESSAY ON QUANTUM MECHANICS AND THE OPEN FUTURE

The dissertation is a defense of the following conditional claim: if there are objective collapses of the wavefunction, then the future is genuinely open. Although this is no radically new idea, the strategy I shall use to defend it is a new one. It proceeds in two main steps. First, building upon the recent literature on metaphysical indeterminacy in quantum mechanics, I argue for the view that systems in superposition have be interpreted as objectively indeterminate state of affairs. Second, I propose an alternative way to think of openness, according to which the future is open as of t, if and only if there is an indeterminate state of affair S at t, and S becomes determinate at t\u2019 (with t\u2019 later than t). To argue for the second step, I will give an analysis of the objective collapses of the wavefunction as the becoming determinate of previously indeterminate systems. Furthermore, in developing my arguments, I will also make some remarks concerning the ontology of objective collapse interpretations of quantum mechanics, the issue of whether metaphysical indeterminacy can be at some derivate level of reality, and the possibility of the openness of the future being an emergent phenomenon

Rho-associated kinase 1 in health and disease: vital roles in apoptotic blebbing, efferocytosis, and cancer

Rho-associated kinase 1 (ROCK1) is a serine/threonine kinase important for the regulation of the cellular cytoskeleton through the induction of actin stress fibres and acto-myosin contractility. The cleavage and subsequent activation of ROCK1 by caspase 3 during apoptosis is believed to cause many morphological phenomena associated with programmed cell death such as dynamic membrane blebbing. I now formally prove the necessity of ROCK1 cleavage for apoptotic blebbing by knocking-in a caspase cleavage resistant mutant of ROCK1 in a genetically modified model. In addition, animals homozygous for non-cleavable ROCK1 demonstrate a phenotype consistent with auto-immune disease suggesting that apoptotic blebbing is important to mediate rapid efferocytosis, which is a rapid phagocytic clearance of the cellular corpse, and thus maintain self-tolerance. Furthermore, apoptotic blebbing is important for the clearance of apoptotic cells and I demonstrate a novel mechanism for ROCK to mediate the release of factors participating in macrophage migration to dying cells. ROCK induced apoptotic blebs and bodies lose membrane integrity prior to secondary necrosis and leak intracellular material. Using quantitative mass spectrometry I identified numerous proteins that were previously unrecognized to be released during apoptosis. The release of protein was found to be impaired following ROCK antagonism with Y27632 which underscores the importance of ROCK activity in apoptotic protein release. One of these proteins, gelsolin, was released following caspase cleavage and encourages macrophage motility towards apoptotic cells. Finally, I now demonstrate that the three nonsynonymous somatic mutations in the ROCK1 gene identified in the Cancer Genome Project lead to elevated kinase activity and drive actin cytoskeleton rearrangements that promote increased motility and decreased adhesion, characteristics of cancer progression. Mapping of the kinase-interacting regions of the carboxy-terminus combined with structural modeling provides insight into how these mutations likely affect the regulation of ROCK1. Consistent with the frequency of ROCK1 mutations in human cancer, these results support the conclusion that there is selective pressure for the ROCK1 gene to acquire ‘driver’ mutations that result in kinase activation