In order to develop a resource theory of nonlocality one must first isolate that essential physical property which underlies Bell inequality violation. We propose nonclassicality of a causal common cause as that property, which implies local operations and shared randomness (LOSR) as the choice of free operations. In this talk I’ll explore a myriad after happy conceptual clarifications that follow from electing to quantify nonlocality via LOSR. Highlights include the resolution of anomalies between nonlocality and entanglement, a linear program formulation for assessing convertibility between nonsignalling boxes, conceptual cleanup regarding self-testing, and a causally-motivated definition of multipartiteness relative to LOSR. The latter connects this work to foundational quantum (and GPT) causal inference problems in the notorious triangle scenario.
Based primarily on the recently updated Understanding the interplay of entanglement and nonlocality: motivating and developing a new branch of entanglement theory, as well as the new No Bipartite-Nonlocal Causal Theory Can Explain Nature’s Correlations, and Quantifying Bell: the Resource Theory of Nonclassicality of Common-Cause Boxes.
Authors: William F. Braasch Jr. and William K. Wootters
Abstract: In a 2016 paper, Rob Spekkens presented an “epistemically restricted classical theory” based on discrete phase space. The theory has many features in common with quantum theory, but it cannot imitate quantum theory perfectly because it is noncontextual.
Here we start with a theory like the one Spekkens proposed, but we add a crucial ingredient in order to recover quantum theory itself for a certain class of systems. The extra ingredient is to consider all the possible classical accounts of a given experiment, and to combine the predictions of these accounts by the following rule: the nonrandom part of the quantum prediction is given by the sum of the nonrandom parts of the classical predictions.
If only limited control over a multiparticle quantum system is available, a viable method to characterize correlations is to perform random measurements and consider the moments of the resulting probability distribution. We present ystematic ethods to analyze the different forms of entanglement with these moments in an optimized manner. First, we find the optimal criteria for different forms of multiparticle entanglement in three-qubit systems using the second moments of andomized measurements. Second, for higher-dimensional two-particle systems and higher moments, we provide criteria that are able to characterize various examples of bound entangled states, showing that detection of such states is possible in this framework. Finally, we analyze the resources needed for a statistically significant test
Because “quantum” was not complex enough, in this talk I will introduce you to “post-quantum”. We will discuss how current non-classical phenomena, such as those observed in Bell and Steering scenarios, have room to accommodate possible physical theories we have yet to grasp. I will also introduce you to mathematical frameworks to explore toy physical theories (which may supersede quantum) and manifestations of post-quantum phenomena. The aim is to provide you with sufficient context so you can pursue your desired journey into quantum foundations.
Random Access Code (RAC) is a protocol in which some information is encoded into a system by sender and the receiver attempts to decode part of it. It so happens that quantum systems have an advantage over the classical in the terms of probability to decode the information correctly. In this talk I will present a whole zoo of different RAC variants. They have very different properties and applications ranging from practical information processing problems like quantum key distribution to foundations of physics to pure mathematics. I’ll discuss these applications.
Physics and its philosophy are full of puzzles related to the first-person perspective of observers: Wigner’s friend, the Boltzmann brain problem, Parfit’s teletransportation paradox and many others. In my talk, I argue that there are basically only two options: first, deliberately declare those problems as outside the scope of science. Second, explore an alternative approach to the foundations of physics in which not an “external world”, but a mathematical notion of “mind” is primary. I show how such an approach can be rigorously formulated, how it reproduces our usual picture of the world to excellent approximation, and how it can solve the aforementioned problems and more in one stroke.