125 research outputs found
Discovering Quantum Causal Models (final)
No full textCosta and Shrapnel [2016] have recently proposed an interventionist theory of quantum causation. The formalism generalises the classical methods of Pearl [2000] and allows for the discovery of quantum causal structure via localised interventions. Classical causal structure is presented as a special case of this more general framework. I introduce the account and consider whether this formalism provides a causal explanation for the Bell correlations
Shrapnel
No full textPlease note: creative writing theses are permanently embargoed in OpenBU. No public access is forecasted for these. To request private access, please click on the lock icon and filled out the appropriate web form.Anyone who tries to tell a conventional story about an unconventional war is a damned liar. Shrapnel is an experimental novel structurally designed to reflect the distance, despair, and rage felt by a veteran of the wars in Iraq and Afghanistan.
The author of this work, Andrew M. Swanson, is a veteran of Kosovo, Afghanistan, and Iraq, and has served in the prestigious 173rd and 82nd Airborne as an infantry paratrooper between 2000 and 2006
Quantum causal explanation: or, why birds fly south
No full textIt is widely held that it is difficult, if not impossible, to apply causal theory to the domain of quantum mechanics. However, there are several recent scientific explanations that appeal crucially to quantum processes, and which are most naturally construed as causal explanations. They come from two relatively new fields: quantum biology and quantum technology. We focus on two examples, the explanation for the optical interferometer LIGO and the explanation for the avian magneto-compass. We analyse the explanation for the avian magneto-compass from the perspective of Woodward's interventionist theory and provide a causal model. Furthermore, we show how worries expressed by Woodward about quantum causation are circumvented in these cases, concluding that these kinds of explanations are most naturally construed as causal
Discovering Quantum Causal Models
No full textI present an Interventionist account of quantum causation, based on the process matrix formalism of Oreshkov, Costa and Brukner (2012), and Costa (2015). The formalism generalises the classical methods of Pearl (2000), and allows for the discovery of quantum causal structure. I show that classical causal structure emerges in certain situations as a special case. I emphasise the crucial role causal discovery plays, in order to distinguish this approach from other recent alternatives
Causation does not explain contextuality
No full textRealist interpretations of quantum mechanics presuppose the existence of elements of reality that are independent of the actions used to reveal them. Such a view is challenged by several no-go theorems that show quantum correlations cannot be explained by non-contextual ontological models, where physical properties are assumed to exist prior to and independently of the act of measurement. However, all such contextuality proofs assume a traditional notion of causal structure, where causal influence flows from past to future according to ordinary dynamical laws. This leaves open the question of whether the apparent contextuality of quantum mechanics is simply the signature of some exotic causal structure, where the future might affect the past or distant systems might get correlated due to non-local constraints. Here we show that quantum predictions require a deeper form of contextuality: even allowing for arbitrary causal structure, no model can explain quantum correlations from non-contextual ontological properties of the world, be they initial states, dynamical laws, or global constraints
Classical and quantum causal interventions
No full textCharacterising causal structure is an activity that is ubiquitous across the sciences. Causal models are representational devices that can be used as oracles for future interventions, to predict how values of some variables will change in response to interventions on others. Recent work has generalised concepts from this field to situations involving quantum systems, resulting in a new notion of quantum causal structure. A key concept in both the classical and quantum context is that of an intervention. Interventions are the controlled operations required to identify causal structure and ultimately the feature that endows causal models with empirical meaning. Although interventions are a crucial feature of both the classical and quantum causal modelling frameworks, to date there has been no discussion of their physical basis. In this paper, we consider interventions from a physical perspective and show that, in both the classical and quantum case, they are constrained by the thermodynamics of measurement and feedback in open systems. We demonstrate that the perfect "atomic" or "surgical" interventions characterised by Pearl's famous do-calculus are physically impossible, and this is the case for both classical and quantum systems
Quantum causal modelling
No full textCausal modelling provides a powerful set of tools for identifying causal structure from observed correlations. It is well known that such techniques fail for quantum systems, unless one introduces 'spooky' hidden mechanisms. Whether one can produce a genuinely quantum framework in order to discover causal structure remains an open question. Here we introduce a new framework for quantum causal modelling that allows for the discovery of causal structure. We define quantum analogues for core features of classical causal modelling techniques, including the causal Markov condition and faithfulness. Based on the process matrix formalism, this framework naturally extends to generalised structures with indefinite causal order
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