Quantum and Linear-Optical Computation group @INL
@QLOC_INL
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QLOC research group at @INLnano. We work on foundations of quantum computation, photonic QC, and quantum software engineering. @[email protected]
Braga, Portugal
Joined June 2022
New @QLOC_INL preprint! Wagner Balthazar, @efgalvao and colleagues from Bristol describe a Feynman path technique for simulation of boson sampling - including open-source code. @phoqusing @INLnano
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Newest @QLOC_INL PhD! Rafael Wagner passed his PhD viva at Univ. Minho today with flying colours. Multiple papers and collaborations, deep foundational insights and even experiments, this thesis has it all. Congrats Rafael! @INLnano @foqacia_org
Rafael Wagner is the newest PhD in the group! 5 papers reported in the thesis, 14 others (and counting) on related topics. Congrats Rafael, please keep up the enthusiasm and good work! It was a pleasure to co-supervise your project together with Rui and Mikhail.
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Here's a poster with the programme:
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The Univ. of Minho will celebrate the International Year of Quantum Science and Technology with a meeting on Nov. 3rd. Specialists discussing the theme include Filipa Peres and Rafael Wagner, graduates from our group. Register for free:
docs.google.com
Ano Internacional da Ciência e Tecnologia Quântica “The Second Quantum Revolution: fundamental science and new technologies” 3 de novembro de 2025 10h00-17h00 Universidade do Minho, Auditório B2,...
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And this paper on the characterization of which complex values unitary invariants can take has been published in PRA! Congrats to the authors. @INLnano
journals.aps.org
Bargmann invariants, also known as multivariate traces of quantum states $\mathrm{Tr}({\ensuremath{\rho}}_{1}{\ensuremath{\rho}}_{2}\ensuremath{\cdots}{\ensuremath{\rho}}_{n})$, are unitary invariant...
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New preprint out! By @efgalvao and collaborators from UFF in Brazil. They measure overlaps of classical states of a light beam featuring fractional OAM states. They use overlap inequalities to witness dimension and coherence in this classical setting.
arxiv.org
We characterize sets of fractional orbital angular momentum (OAM) modes of a light beam using unitary-invariant properties encoded by two-mode overlaps. Using basis-independent coherence and...
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New @QLOC_INL preprint! Rafael Wagner and collaborators from Gdansk and Waterloo extend the framework of generalized probabilistic theories to describe general complex-valued quasiprobability representations. Congrats!
arxiv.org
Quasiprobability representations are well-established tools in quantum information science, with applications ranging from the classical simulability of quantum computation to quantum process...
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New QLOC group paper published by Alexandra Ramôa and Luís Paulo Santos. They develop a new algorithm for amplitude estimation, with advantage in noisy scenarios, and accompanying open-source software. Congrats!
quantum-journal.org
Alexandra Ramôa and Luis Paulo Santos, Quantum 9, 1856 (2025). We present BAE, a problem-tailored and noise-aware Bayesian algorithm for quantum amplitude estimation. In a fault tolerant scenario,...
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New @QLOC_INL paper out! Leonardo Novo (INL) and Michael Jabbour (Brussels) look at the complexity of CV states in linear-optical devices, describing how it increases when nonlinear gates are introduced. Congrats! @phoqusing
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New @QLOC_INL paper out! Rafael Wagner and collaborators show that a Wigner's friend argument can be made having contextuality rather than nonlocality at its core, extending our understanding of the measurement problem. Congrats Rafael!
journals.aps.org
Extended Wigner's friend no-go theorems provide a modern lens for investigating the measurement problem, by making precise the challenges that arise when one attempts to model agents as dynamical...
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@QLOC_INL members presented their research this week at the IX Paraty Quantum Information Workshop in Brazil. Sara Franco (pictured), Wagner Balthazar, Pedro Azado, and @efgalvao presented talks and posters. Sea, sun, and quantum! https://t.co/xeI7bewTcy
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New preprint by Alexandra Ramôa, Luís Paulo Santos, and Akihito Soeda. They propose a novel Hamiltonian learning algorithm with reliable performance against other low cost methods, especially in the presence of decoherence. Congrats! @EPIQUEquantum
arxiv.org
A two-level quantum system evolving under a time-independent Hamiltonian produces oscillatory measurement probabilities. The estimation of the associated frequency is a cornerstone problem in...
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New @QLOC_INL paper published! This is a study on the role of contextuality in a Wigner's friend scenario, designed to study the measurement problem in quantum mechanics. Joint work of Laurens Walleghem, Rafael Wagner, and colleagues from Canada. Congrats!
quantum-journal.org
Laurens Walleghem, Yìlè Yīng, Rafael Wagner, and David Schmid, Quantum 9, 1819 (2025). The Local Friendliness argument is an extended Wigner's friend no-go theorem that provides strong constraints on...
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New @QLOC_INL preprint! We show processes featuring indefinite causal order (switches) can be used to measure and use unitary invariants for applications. Congrats Pedro Azado, Rafael Wagner, @ruisb and @efgalvao! @foqacia_org @INLnano
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New @QLOC_INL paper out! We use a tunable interferometer to do variationally learn near-optimal quantum cloning machines. Collaboration with @FabioSciarrino's group, @fastgroup_ifn, Mina Doosti, Sebastià Nicolau.
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New @QLOC_INL group preprint! Rafael Wagner, together with Li (South China U.) and Zhang (Hangzhou Dianzi U.) investigate the characterization of quantum imaginarity using Bargmann invariants. Congrats Rafael! https://t.co/flGlJobasw
arxiv.org
Traditionally, the characterization of quantum resources has focused on individual quantum states. Recent literature, however, has increasingly explored the characterization of resources in...
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New @QLOC_INL preprint! Alexandra Ramôa, Gilberto Cunha, André Sequeira, Michael de Oliveira and Luís Soares Barbosa propose a Bayesian quantum-enhanced reinforcement learning algorithm, showing the potential for quantum advantage. Congrats! @INLnano
arxiv.org
Reinforcement learning (RL) provides a principled framework for decision-making in partially observable environments, which can be modeled as Markov decision processes and compactly represented...
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And this work has now appeared in print in Quantum Science and Technology. Congrats Anita, Benoît, Leonardo and colleagues from Twente! @INLnano @EPIQUEquantum
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New @QLOC_INL paper published in Linear Algebra and Applications! It describes how the quantum theory of photonic indistinguishability is linked to counter-examples to mathematical conjectures on permanents. Congrats Leonardo, Benoît and colleagues!
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@INLnano @foqacia_org And this work has now been published in Quantum: https://t.co/KL7km4cup0 Congrats Leonardo!
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