Lídia del Rio

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del Rio

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Lídia

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0000-0002-2445-2701

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Publications 1 - 8 of 8

Multi-agent paradoxes beyond quantum theory
Vilasini, Venkatesh; Nurgalieva, Nuriya; del Rio, Lídia (2019)
New Journal of Physics
Which theories lead to a contradiction between simple reasoning principles and modelling observers' memories as physical systems? Frauchiger and Renner have shown that this is the case for quantum theory (Frauchiger and Renner 2018 Nat. Commun. 9 3711). Here we generalize the conditions of the Frauchiger–Renner result so that they can be applied to arbitrary physical theories, and in particular to those expressed as generalized probabilistic theories (GPTs) (Hardy 2001 arXiv:quant-ph/0101012; Barrett 2007 Phys. Rev. A 75 032304). We then apply them to a particular GPT, box world, and find a deterministic contradiction in the case where agents may share a PR box (Popescu and Rohrlich 1994 Found. Phys. 24 379–85), which is stronger than the quantum paradox, in that it does not rely on post-selection. Obtaining an inconsistency for the framework of GPTs broadens the landscape of theories which are affected by the application of classical rules of reasoning to physical agents. In addition, we model how observers' memories may evolve in box world, in a way consistent with Barrett's criteria for allowed operations (Barrett 2007 Phys. Rev. A 75 032304; Gross et al 2010 Phys. Rev. Lett. 104 080402).
Toys can’t play: physical agents in Spekkens’ theory
Hausmann, Ladina; Nurgalieva, Nuriya; del Rio, Lídia (2023)
New Journal of Physics
Information is physical (Landauer 1961 IBM J. Res. Dev. 5 183-91), and for a physical theory to be universal, it should model observers as physical systems, with concrete memories where they store the information acquired through experiments and reasoning. Here we address these issues in Spekkens’ toy theory (Spekkens 2005 Phys. Rev. A 71 052108), a non-contextual epistemically restricted model that partially mimics the behaviour of quantum mechanics. We propose a way to model physical implementations of agents, memories, measurements, conditional actions and information processing. We find that the actions of toy agents are severely limited: although there are non-orthogonal states in the theory, there is no way for physical agents to consciously prepare them. Their memories are also constrained: agents cannot forget in which of two arbitrary states a system is. Finally, we formalize the process of making inferences about other agents’ experiments and model multi-agent experiments like Wigner’s friend. Unlike quantum theory (Nurgalieva and del Rio Lidia 2019 Electron. Proc. Theor. Comput. Sci. 287 267-97; Fraser et al 2020 Fitch’s knowability axioms are incompatible with quantum theory arXiv:2009.00321; Frauchiger and Renner 2018 Nat. Commun. 9 3711; Nurgalieva and Renner 2021 Contemp. Phys. 61 1-24; Brukner 2018 Entropy 20 350) or box world (Vilasini et al 2019 New J. Phys. 21 113028), in toy theory there are no inconsistencies when physical agents reason about each other’s knowledge.
Quantum Epistemology and Constructivism
Fraser, Patrick; Nurgalieva, Nuriya; del Rio, Lídia (2023)
Journal of Philosophical Logic
Constructivist epistemology posits that all truths are knowable. One might ask to what extent constructivism is compatible with naturalized epistemology and knowledge obtained from inference-making using successful scientific theories. If quantum theory correctly describes the structure of the physical world, and if quantum theoretic inferences about which measurement outcomes will be observed with unit probability count as knowledge, we demonstrate that constructivism cannot be upheld. Our derivation is compatible with both intuitionistic and quantum propositional logic. This result is implied by the Frauchiger-Renner theorem, though it is of independent importance as well.
Thought experiments in a quantum computer
Nurgalieva, Nuriya; Mathis, Simon; del Rio, Lídia; et al. (2022)
arXiv
We introduce a software package that allows users to design and run simulations of thought experiments in quantum theory. In particular, it covers cases where several reasoning agents are modelled as quantum systems, such as Wigner's friend experiment. Users can customize the protocol of the experiment, the inner workings of agents (including a quantum circuit that models their reasoning process), the abstract logical system used (which may or not allow agents to combine premises and make inferences about each other's reasoning), and the interpretation of quantum theory used by different agents. Our open-source software is written in a quantum programming language, ProjectQ, and runs on classical or quantum hardware. As an example, we model the Frauchiger-Renner extended Wigner's friend thought experiment, where agents are allowed to measure each other's physical memories, and make inferences about each other's reasoning.
A consolidating review of Spekkens’ toy theory
Hausmann, Ladina; Nurgalieva, Nuriya; del Rio, Lídia (2021)
arXiv
In order to better understand a complex theory like quantum mechanics, it is sometimes useful to take a step back and create alternative theories, with more intuitive foundations, and examine which features of quantum mechanics can be reproduced by such a foil theory. A prominent example is Spekkens' toy theory, which is based off a simple premise: "What if we took a common classical theory and added the uncertainty principle as a postulate?" In other words, the theory imposes an epistemic restriction on our knowledge about a physical system: only half of the variables can ever be known to an observer. Like good science fiction, from this simple principle a rich behaviour emerges, most notoriously when we compose several systems. The toy theory emulates some aspects of quantum non-locality, although crucially it is still a non-contextual model. In this pedagogical review we consolidate different approaches to Spekkens' toy theory, including the stabilizer formalism and the generalization to arbitrary dimensions, completing them with new results where necessary. In particular, we introduce a general characterization of measurements, superpositions and entanglement in the toy theory.
Reply to: Quantum mechanical rules for observed observers and the consistency of quantum theory
del Rio, Lídia; Renner, Renato (2024)
Nature Communications
Thermodynamic optimization of quantum algorithms: On-the-go erasure of qubit registers
Meier, Florian; del Rio, Lídia (2022)
Physical Review A
We consider two bottlenecks in quantum computing: limited memory size and noise caused by heat dissipation. Trying to optimize both, we investigate "on-the-go erasure"of quantum registers that are no longer needed for a given algorithm: freeing up auxiliary qubits as they stop being useful would facilitate the parallelization of computations. We study the minimal thermodynamic cost of erasure in these scenarios, applying results on the Landauer erasure of entangled quantum registers. For the class of algorithms solving the Abelian hidden subgroup problem, we find optimal on-the-go erasure protocols. We conclude that there is a trade-off: if we have enough partial information about a problem to build efficient on-the-go erasure, we can use it to instead simplify the algorithm, so that fewer qubits are needed to run the computation in the first place. We provide explicit protocols for these two approaches.
Discovering physical concepts with neural networks
Iten, Raban; Metger, Tony; Wilming, Henrik; et al. (2018)

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