Relativistic Quantum Information Forum - Recent Topics https://rqi-cost.org/community/ Relativistic Quantum Information Discussion Board en-US Thu, 30 Apr 2026 05:24:15 +0000 wpForo 60 Questions from the conference Observers and Causality in Quantum Gravity - 2026 https://rqi-cost.org/community/time-causality-and-memory-in-quantum-physics-wg3/questions-from-the-conference-observers-and-causality-in-quantum-gravity-2026/ Sat, 25 Apr 2026 14:15:38 +0000 At the recent conference Observers and Causality in Quantum Gravity, In Bratislava, there have been several interesting discussions on notions such as events, observers, reference frame, causality, as understood in different fields and by different people. We invite everyone from the RQI community to contribute to and extend this discussion here on the Forum. You can start by filling this survey.

]]> Fabio Costa https://rqi-cost.org/community/time-causality-and-memory-in-quantum-physics-wg3/questions-from-the-conference-observers-and-causality-in-quantum-gravity-2026/ Past WG2 seminars (video recording + slides) https://rqi-cost.org/community/gravitational-quantum-physics-and-metrology-wg2/past-wg2-seminars-video-recording-slides/ Thu, 23 Apr 2026 10:19:54 +0000 This thread will collect detailed information about past seminars, including links to the video recording and the presentation slides when available.

]]> Albert Roura https://rqi-cost.org/community/gravitational-quantum-physics-and-metrology-wg2/past-wg2-seminars-video-recording-slides/ Upcoming WG2 Online Seminars https://rqi-cost.org/community/gravitational-quantum-physics-and-metrology-wg2/upcoming-wg2-online-seminars/ Thu, 23 Apr 2026 08:59:44 +0000 Updates about the upcoming online seminars of the Working Group 2.

]]> navdeeparya https://rqi-cost.org/community/gravitational-quantum-physics-and-metrology-wg2/upcoming-wg2-online-seminars/ Conceptual Foundations of QFT Workshop, Vienna, 1-3 June 2026 https://rqi-cost.org/community/event-1/conceptual-foundations-of-qft-workshop-vienna-1-3-june-2026-2/ Mon, 02 Feb 2026 13:17:26 +0000 Registration is now open until February 28 

https://www.iqoqi-vienna.at/news-events/conceptual-foundations-of-qft

]]> Maria Papageorgiou https://rqi-cost.org/community/event-1/conceptual-foundations-of-qft-workshop-vienna-1-3-june-2026-2/ Multi-time quantum process tomography on a superconducting qubit https://rqi-cost.org/community/publication-1-2/multi-time-quantum-process-tomography-on-a-superconducting-qubit/ Thu, 22 Jan 2026 00:25:26 +0000 Current quantum technologies are at the cusp of becoming useful, but still face formidable obstacles such as noise. Noise severely limits the ability to scale quantum devices to the point that they would offer an advantage over classical devices. To understand the sources of noise it is necessary to fully characterise the quantum processes occurring across many time steps; only this would reveal any time-correlated noise called non-Markovian. Previous efforts have attempted such a characterisation but obtained only a limited reconstruction of such multi-time processes. In this work, we fully characterise a multi-time quantum process on superconducting hardware using in-house and cloud-based quantum processors. We achieve this by employing sequential measure-and-prepare operations combined with post-processing. Employing a recently developed formalism for multi-time processes, we detect general multi-time correlated noise. We also detect quantum correlated noise which demonstrates that part of the noise originates from quantum sources, such as physically nearby qubits on the chip.

Multi-Time Quantum Process Tomography On A Superconducting Qubit, Christina Giarmatzi, Tyler Jones, Alexei Gilchrist, Prasanna Pakkiam, Arkady Fedorov, Fabio Costa, Quantum 9, 1952 (2025). https://quantum-journal.org/papers/q-2025-12-18-1952/

]]> Christina_giarmatzi https://rqi-cost.org/community/publication-1-2/multi-time-quantum-process-tomography-on-a-superconducting-qubit/ Conceptual Foundations of QFT Workshop, Vienna, 1-3 June 2026 https://rqi-cost.org/community/qft-aspects-of-quantum-information-wg1/conceptual-foundations-of-qft-workshop-vienna-1-3-june-2026/ Mon, 19 Jan 2026 16:37:59 +0000 Interdisciplinary workshop on the foundations of QFT uniting philosophical, historical, and mathematical perspectives of relativistic quantum physics.

link: https://www.iqoqi-vienna.at/de/news-events/conceptual-foundations-of-qft

]]> Maria Papageorgiou https://rqi-cost.org/community/qft-aspects-of-quantum-information-wg1/conceptual-foundations-of-qft-workshop-vienna-1-3-june-2026/ Causalworlds 2026: The 3rd International Conference on Quantum, Classical, and Relativistic Causality https://rqi-cost.org/community/topic-1/causalworlds-2026-the-3rd-international-conference-on-quantum-classical-and-relativistic-causality/ Wed, 10 Dec 2025 13:18:52 +0000 Dear everyone,

We are pleased to announce the following conference which might be of interest to the RQI community and the RQI COST Action, and we welcome  submissions for contributed talks and posters. 

Hope to see many of you there!

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Causalworlds 2026 - First Call for Papers

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Causalworlds 2026: The 3rd International Conference on Quantum, Classical, and Relativistic Causality

Grenoble, France, June 22-26, 2026

https://causalworlds2026.inria.fr

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Presentation and scope

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Understanding causality is foundational to science and has wide-ranging applications, yet there are several distinct notions of causation. Recently, there have been important developments on the role of causality in quantum physics, relativistic physics and their interplay. These have unearthed a plethora of deep and fascinating questions regarding the nature of causation in physical theories, emergence of space-time structure and how relativistic principles can shape the landscape of quantum information processing. At the same time, causal reasoning is central in classical statistics, and has become a crucial tool in machine learning, with applications ranging from big data to healthcare. The interface between classical and quantum causality has also been crucial for identifying when and how quantum theory can surpass classical models in information processing. Causalworlds aims to bring together researchers from different areas of physics, computer science, mathematics and philosophy working on such questions related to causality, both from fundamental and applied perspectives, to provide a venue for cross-pollination of ideas and techniques across these disciplines and consolidate efforts towards a more unified understanding of causation.

The scope of the conference includes (but is not limited to): 

* Quantum and classical causal inference and causal models

* The role of causal structure in information processing

* Indefinite causality and quantum reference frames

* Cyclic causality and time symmetry

* Causality in quantum field theory and quantum gravity

* Experiments in causality and applications

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Important Dates

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* Paper submission deadline: Feb 20, 2026 (AoE)

* Paper notification: Late March, 2026

* Conference: June 22-26, 2026

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Submission Guidelines

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We invite submissions of papers for talk and/or posters. Submissions for a talk will automatically be considered for a poster if not accepted for a talk.

* Talk: Submission will consist of a 3 page (excluding references) extended abstract, together with a link to the full paper (published or preprint) or a draft of the manuscript if not yet publicly available.

* Poster: Submission will consist of a short plaintext abstract. Work in progress is welcome.

Submissions will be considered via EasyChair: https://easychair.org/conferences?conf=cw2026

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Invited Speakers

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To be announced shortly.

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Organising Committee

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* Alastair Abbott (Inria)

* Cyril Branciard (Institut Néel)

* Mehdi Mhalla (LIG)

* Kuntal Sengupta (Institut Néel)

* V. Vilasini (Inria)

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PC Chairs

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* Alastair Abbott (Inria)

* Elie Wolfe (Perimeter Institute)

The programme committee will be announced shortly.

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Causalworlds Steering Committee

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* Hlér Kristjánsson (Université de Montréal & Mila)

* V. Vilasini (Inria)

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Previous editions:

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* Causalworlds 2024 at Perimeter Institute for Theoretical Physics, Canada (https://events.perimeterinstitute.ca/event/69/)
-Link to talk recordings of Causalworlds 2024: https://pirsa.org/c24018
-Link to an article about Causalworlds 2024: https://perimeterinstitute.ca/news/causation-rules-our-lives-how-does-it-work-quantum-realm

* Causalworlds 2022 at ETH Zürich, Switzerland (https://causalworlds.ethz.ch/)
-Link to talk recordings of Causalworlds 2022: https://www.youtube.com/@CausalWorlds

]]> Vilasini https://rqi-cost.org/community/topic-1/causalworlds-2026-the-3rd-international-conference-on-quantum-classical-and-relativistic-causality/ Operational Models of Temperature Superpositions https://rqi-cost.org/community/publication-1-2/operational-models-of-temperature-superpositions/ Mon, 08 Dec 2025 05:15:59 +0000 Dear colleagues, I'd like to draw your attention to our recent publication, which touches on topics relevant to the RQI community. Please find the abstract below: 

An interacting quantum system and thermal bath can reach thermal equilibrium, resulting in the system and bath acquiring the same temperature. But how does a delocalized quantum system thermalize with a bath whose local temperature varies as, for example, in the Tolman effect? Here, we formulate two scenarios in which the notion of a “superposition of temperatures” may arise: first, a probe interaction with two different baths dependent on the state of another quantum system (a control); and second, a probe interaction with a single bath whose purified state is a superposition of states that each correspond to different temperatures. We show that the two scenarios are fundamentally different and can be operationally distinguished. Moreover, we show that the final probe state is sensitive to the specific realization of the thermalizing channels, and that our results hold for partial and prethermalization cases. Our models may be applied to scenarios involving joint quantum and relativistic phenomena, and explain some recent results found in quantum interference of relativistic probes thermalizing with Unruh or Hawking radiation.

]]> CarolynWood https://rqi-cost.org/community/publication-1-2/operational-models-of-temperature-superpositions/ How to acknowledge the COST action https://rqi-cost.org/community/topic-1/how-to-acknowledge-the-cost-action/ Wed, 26 Nov 2025 17:22:51 +0000 We would like to encourage you to acknowledge the Action in relevant publications that have benefited from those activities. Such acknowledgements are important for any future assessment of the Action's impact.

Please, acknowledge the Action in publications that

1. benefited from  Action activities  (online seminars, conferences/workshops, forum interactions and so on);

2. were initiated/inspired during Action activities;

3. involve international collaboration fostered or facilitated by the Action;

4. are outputs of STSMs;

5. are entirely outputs of COST activities (review articles for the WGs, write-up of an invited talk in a COST conference, lecture notes in Action schools, and so on).



For cases 1-3, you can write:

``The authors have benefited from the activities of COST Action CA23115: Relativistic Quantum Information, funded  by COST (European Cooperation in Science and Technology)."

 possibly with an additional phrase explaining the type of benefit.


For case 4, please acknowledge the STSM as a grant, e.g., you may write:

``This work was supported by an a STSM Grant from COST Action CA23115: Relativistic Quantum Information, funded by COST (European Cooperation in Science and Technology).".

For case 5, please write:

``This work is supported from COST Action CA23115: Relativistic Quantum Information, funded by COST (European Cooperation in Science and Technology).".


Writing the number CA23115 is the most important component of the acknowledgement, as this is the keyword that will be searched.

In some cases, you might want to include the Action as a citation in your document (in papers,  research proposals, and so on). I suggest the following

COST Action ``Relativistic Quantum Information'' (CA23115). URL: https://rqi-cost.org 

 

]]> Charis Anastopoulos https://rqi-cost.org/community/topic-1/how-to-acknowledge-the-cost-action/ Quantum signatures of proper time in optical ion clocks https://rqi-cost.org/community/gravitational-quantum-physics-and-metrology-wg2/quantum-signatures-of-proper-time-in-optical-ion-clocks/ Thu, 06 Nov 2025 03:38:08 +0000 Hello all,

I recently gave a seminar for WG2 on our recent preprint “Quantum signatures of proper time in optical ion clocks,” written in collaboration with Gabriel Sorci, Dietrich Leibfried, Christian Sanner, and Igor Pikovski . Dennis suggested I start a discussion on this work; feel free to contribute in the replies, I will be glad to discuss further. 

In our paper, we show that optical ion clocks can be used to probe quantum signatures of proper time that cannot be explained by a semiclassical description (e.g. one in which the clock’s evolution occurs with respect to a fixed external parameter). We derive observable signatures in optical ion clocks that require a “quantisation” of proper time through dependence on the momentum operator, tau = tau(p-hat^2). We show that by preparing initial squeezed motional states of the clock, the interferometric visibility of the internal states (i.e. “the clock”) observably reduces, an effect that results from entanglement between the internal and external degrees of freedom of the clock. We also show that this quantum treatment of proper time leads to anomalous excitation of the clock’s motion when initially prepared in its ground state, leading to a new frequency shift dubbed “quantum second-order Doppler shift”.

Albert raised some good questions following the seminar, and the discussion can be viewed on the recording of the seminar on the RQI-Cost YouTube page. One question was whether state-engineering the ground and excited states of the clock to follow the same trajectory can “mitigate” the visibility loss effect. 

https://arxiv.org/abs/2509.09573

 

 

]]> Joshua Foo https://rqi-cost.org/community/gravitational-quantum-physics-and-metrology-wg2/quantum-signatures-of-proper-time-in-optical-ion-clocks/