Stefano Gogioso
Dr Stefano Gogioso
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Stefano Gogioso is a mathematician and computer scientist, focusing on the foundations of quantum theory and the creation of quantum software.
He obtained his doctorate in the Oxford Quantum Group, under the supervision of Bob Coecke, developing pictorial ways to talk about quantum particles and their peculiar behaviour. Since then, he's been working on ways to make the quantum world more accessible to the general public, efforts which culminated in the recent release of "Quantum in Pictures: A New Way to Understand the Quantum World".
He is a Departmental Lecturer at the University of Oxford, teaching applied courses on Quantum Computing to Master's students and professionals from a variety of backgrounds:
 Quantum Software for MSc/MFoCS students
 Quantum Computing for Software Engineering students
 Quantum Computing for Continued Education
 Bespoke Quantum Computing courses for organisations
He cofounded the startup Hashberg, where he directs the development of highlevel quantum programming tools. He is actively engaged in fundamental research, focusing on the connection between quantum systems and the structure of spacetime. He serves as a Mentor for the AI stream of CDLOxford.
Summary of Publications and Presentations
Stefano Gogioso and Nicola Pinzani
arXiv:2206.08911
In this work, presented at QPL 2022, we provide a unified operational framework for the study of causality, nonlocality and contextuality, in a fully deviceindependent and theoryindependent setting. Our investigation proceeds from two complementary fronts: a topological one, using tools from sheaf theory, and a geometric one, based on polytopes and linear programming. From the topological perspective, we understand experimental outcome probabilities as bundles of compatible contextual data over certain topological spaces, encoding causality constraints. From the geometric perspective, we understand the same experimental outcome probabilities as points in highdimensional causal polytopes, which we explicitly construct and fully characterise. Our work is a significant extension of both the established AbramskyBrandenburger framework for contextuality and the current body of work on indefinite causality. We provide definitions of causal fraction and causal separability for empirical models relative to a broad class of causal constraints: this allows us to construct and characterise novel examples which explicitly connect causal inseparability to nonlocality and contextuality. In particular, we clearly demonstrate the existence of "causal contextuality", a phenomenon where causal structure is explicitly correlated to the classical inputs and outputs of local instruments, so that contextuality of the associated empirical model directly implies causal inseparability.
Stefano Gogioso and Richie Yeung
arXiv:2206.11839
To appear in Electronic Proceedings of Theoretical Computer Science (EPTCS)
In this work, presented at QPL 2022, we introduce a topologyaware optimisation technique for circuits of mixed ZX phase gadgets, based on conjugation by CX gates and simulated annealing.
Razin A. Shaikh and Stefano Gogioso
arXiv:2205.00466
In this work, presented at ACT 2022, we introduce a novel compositional description of Feynman diagrams, with a welldefined interpretation as morphisms in a daggercompact category. Our chosen setting is suitable for infinitedimensional diagrammatic reasoning, generalising the ZX calculus and other algebraic gadgets familiar to the categorical quantum theory community. The Feynman diagrams we define look very similar to their traditional counterparts, but are more general: instead of depicting scattering amplitudes, they embody the linear maps from which the amplitudes themselves are computed, for any given initial and final particle states. This shift in perspective reflects into a formal transition from the syntactic, graphtheoretic compositionality of traditional Feynman diagrams to a semantic, categoricaldiagrammatic compositionality. Because we work in a concrete categorical setting  powered by nonstandard analysis  we are able to take direct advantage of complex additive structure in our description. This makes it possible to derive a particularly compelling characterisation for the sequential composition of categorical Feynman diagrams, which automatically results in the superposition of all possible graphtheoretic combinations of the individual diagrams themselves.
Konstantinos Meichanetzidis, Stefano Gogioso, Giovanni De Felice, Nicolò Chiappori, Alexis Toumi and Bob Coecke
arXiv:2005.04147
Electronic Proceedings in Theoretical Computer Science (EPTCS) doi:10.4204/EPTCS.340.11
In this work, presented at QPL 2020 (as well as ACT 2020 and other workshops), we describe a fullstack pipeline for natural language processing on nearterm quantum computers, aka QNLP. The language modelling framework we employ is that of compositional distributional semantics (DisCoCat), which extends and complements the compositional structure of pregroup grammars. Within this model, the grammatical reduction of a sentence is interpreted as a diagram, encoding a specific interaction of words according to the grammar. It is this interaction which, together with a specific choice of word embedding, realises the meaning (or "semantics") of a sentence. Building on the formal quantumlike nature of such interactions, we present a method for mapping DisCoCat diagrams to quantum circuits. Our methodology is compatible both with NISQ devices and with established Quantum Machine Learning techniques, paving the way to nearterm applications of quantum technology to natural language processing.
Nicola Pinzani and Stefano Gogioso
arXiv:2003.13306
Electronic Proceedings in Theoretical Computer Science (EPTCS) doi:10.4204/EPTCS.340.13
In this work, presented at QPL 2020, we give rigorous operational meaning to superposition of causal orders. This fits within a recent effort to understand how the standard operational perspective on quantum theory could be extended to include indefinite causality. The mainstream view, that of "process matrices", takes a topdown approach to the problem, considering all causal correlations that are compatible with local quantum experiments. Conversely, we pursue a bottomup approach, investigating how the concept of indefiniteness emerges from specific characteristics of generic operational theories. Specifically, we pin down the operational phenomenology of the notion of nonclassical (e.g. "coherent") control, which we then use to formalise a theoryindependent notion of control (e.g. "superposition") of causal orders. To validate our framework, we show how salient examples from the literature can be captured in our framework.
Stefano Gogioso, Maria E Stasinou and Bob Coecke
arXiv:2003.13271
Frontiers in Physics doi:10.3389/fphy.2021.534265
In this work, under review for publication in a journal, we present a compositional algebraic framework to describe the evolution of quantum fields in discretised spacetimes. We show how familiar notions from Relativity and quantum causality can be recovered in a purely ordertheoretic way from the causal order of events in spacetime, with no direct mention of analysis or topology. We formulate theoryindependent notions of fields over causal orders in a compositional, functorial way. We draw a strong connection to Algebraic Quantum Field Theory (AQFT), using a sheaftheoretical approach in our definition of spaces of states over regions of spacetime. We introduce notions of symmetry and cellular automata, which we show to subsume existing definitions of Quantum Cellular Automata (QCA) from previous literature. Given the extreme flexibility of our constructions, we propose that our framework be used as the starting point for new developments in AQFT, QCA and more generally Quantum Field Theory. .
Nicola Pinzani, Stefano Gogioso and Bob Coecke
arXiv:1902.00032
To appear in the Proceedings of the 34th Annual ACM/IEEE Symposium on Logic in Computer Science (LICS'19)
In this work, presented at LICS 2019, we introduce a general categorical framework to reason about quantum theory and other process theories living in spacetimes where Closed Timelike Curves (CTCs) are available, allowing resources to travel back in time and provide computational speedups. This work fits within a broader research program on quantum causal structure, aimed at understanding the interaction of quantum theory with relativistic causality and its impact on quantum computation, communication and cryptography.
In this talk we discuss the use of visual languages in quantum theory and quantum computing, advocating for the broader adoption of compositional and visual programming languages in computer science.
Stefano Gogioso and Fabrizio Romano Genovese
arXiv:1805.12087
Electronic Proceedings in Theoretical Computer Science (EPTCS) doi:10.4204/EPTCS.287.9
In this work, presented at QPL 2018, we use tools from nonstandard analysis to formulate the building blocks of quantum field theory within the framework of categorical quantum mechanics. This formulation opens the way to the application of categorical methods from classical and quantum computer science to the study of quantum fields and particle physics. This work fits within a broader research program on quantum causal structure, aimed at understanding the interaction of quantum theory with relativistic causality and its impact on quantum computation, communication and cryptography.
Stefano Gogioso
arXiv:1709.09772
Thesis submitted for the degree of Doctor of Philosophy (DPhil) at the University of Oxford
Leibniz International Proceedings in Informatics (LIPIcs) doi:10.4230/LIPIcs.CALCO.2019.16
In this thesis, we use strong complementarity to introduce dynamics and symmetries within the framework of CQM, which we also extend to infinitedimensional Hilbert spaces: these were longmissing features, which open the way to a wealth of new applications. The coherent treatment presented in this work also provides a variety of novel insights into the dynamics and symmetries of quantum systems: examples include the extremely simple characterisation of symmetryobservable duality, the connection of strong complementarity with the Weyl Canonical Commutation Relations, the generalisations of Feynman's clock construction, the existence of time observables and the emergence of quantum clocks. Furthermore, we show that strong complementarity is a key resource for quantum algorithms and protocols. We provide the first fully diagrammatic, theoryindependent proof of correctness for the quantum algorithm solving the Hidden Subgroup Problem, and show that strong complementarity is the feature providing the quantum advantage. In quantum foundations, we use strong complementarity to derive the exact conditions relating nonlocality to the structure of phase groups, within the context of Mermintype nonlocality arguments. Our nonlocality results find further application to quantum cryptography, where we use them to define a quantumclassical secret sharing scheme with provable deviceindependent security guarantees.
Stefano Gogioso and William Zeng
arXiv:1702.01772
Logical Methods in Computer Science (LMCS), Volume 15, Issue 2 (April 26, 2019) lmcs:5402
In this work, published in LMCS, we broadly generalise Mermintype arguments on GHZ states, and we provide exact grouptheoretic conditions for nonlocality to be achieved. Our results find direct application in quantum foundations, where they yield a new hierarchy of quantumrealisable AllvsNothing arguments, as well as in quantum cryptography, where they provide deviceindependent security guarantees for a broad family of hybrid quantumclassical secret sharing protocols.
Stefano Gogioso and Aleks Kissinger
arXiv:1701.08669
Accepted for publication in Quantum
Presentation at Categories Logic and Physics Scotland, Edinburgh May 2016, available here
In this work, accepted for publication in Quantum, we provide the first fully diagrammatic proof of correctness for the abelian HSP protocol, showing that strongly complementary observables are the key ingredient to its success. The abelian Hidden Subgroup Problem (HSP) is extremely general, and many problems with known quantum exponential speedup (such as integers factorisation, the discrete logarithm and Simon's problem) can be seen as specific instances of it. The traditional presentation of the quantum protocol for the abelian HSP is lowlevel, and relies heavily on the the interplay between classical group theory and complex vector spaces. Instead, we give a highlevel diagrammatic presentation which showcases the quantum structures truly at play.
Biography
Oxford University   Departmental Lecturer   2019  Present 
Kellogg College   Fellow   2021  Present 
Hashberg Ltd   Director   2019  Present 
Oriel College   College Lecturer   2016  2021 
Oxford University   Postdoctoral Researcher   2017  2019 
Oxford University   DPhil in Computer Science   2013  2017 
Cambridge University   MASt in Mathematics (Part III)   2012  2013 
Cambridge University   BA in Mathematics (Tripos)   2009  2012 
ISICT Consortium   ICT and Management   2006  2009 
University of Genova   MSc in Computer Science   2009  2009 
University of Genova   BSc in Computer Science   2006  2009 
Selected Publications

Quantum Natural Language Processing on Near−Term Quantum Computers
Konstantinos Meichanetzidis‚ Stefano Gogioso‚ Giovanni De Felice‚ Nicolò Chiappori‚ Alexis Toumi and Bob Coecke
2020.
Details about Quantum Natural Language Processing on Near−Term Quantum Computers  BibTeX data for Quantum Natural Language Processing on Near−Term Quantum Computers  Link to Quantum Natural Language Processing on Near−Term Quantum Computers

Categorical Semantics for Time Travel
Nicola Pinzani‚ Stefano Gogioso and Bob Coecke
In LICS 2019. 2019.
Details about Categorical Semantics for Time Travel  BibTeX data for Categorical Semantics for Time Travel

A Diagrammatic Approach to Quantum Dynamics
Stefano Gogioso
In CALCO 2019. 2019.
Details about A Diagrammatic Approach to Quantum Dynamics  BibTeX data for A Diagrammatic Approach to Quantum Dynamics