PhD student doing research in quantum foundations. Supervisor: Rob Spekkens

Talks by David Schmid

The Stabilizer Subtheory Has a Unique Noncontextual Model

David Schmid Perimeter Institute for Theoretical Physics

We give a complete characterization of the (non)classicality of all stabilizer subtheories. First, we prove that there is a unique nonnegative and diagram-preserving quasiprobability representation of the stabilizer subtheory in all odd dimensions, namely Gross’s discrete Wigner function. This representation is equivalent to Spekkens’ epistemically restricted toy theory, which is consequently singled out as the unique noncontextual ontological model for the stabilizer subtheory.

Causal-Inferential theories: Realism revisited

David Schmid Perimeter Institute for Theoretical Physics

Using a process-theoretic formalism, we introduce the notion of a causal-inferential theory: a triple consisting of a theory of causal influences, a theory of inferences (of both the Boolean and Bayesian varieties), and a specification of how these interact. Recasting the notions of operational and realist theories in this mold clarifies what a realist account of an experiment offers beyond an operational account.

Why standard entanglement theory is inappropriate for the study of Bell scenarios

David Schmid Perimeter Institute for Theoretical Physics

A standard approach to quantifying resources is to determine which operations on the resources are freely available and to deduce the ordering relation among the resources that these operations induce. If the resource of interest is the nonclassicality of the correlations embodied in a quantum state, that is, entanglement, then it is typically presumed that the appropriate choice of free operations is local operations and classical communication (LOCC).

Unscrambling the Omelette of Causation and Inference in Operational and Ontological Theories

David Schmid Perimeter Institute for Theoretical Physics
I will discuss how the standard frameworks for operational theories involve a scrambling of causal and inferential concepts. I will then present a new framework for operational theories which separates out the inferential and the causal aspects of a given physical theory. Generalized probabilistic theories and operational probabilistic theories are recovered within our framework when one ignores some of these distinctions.