Program

Note that there may still be some minor last-minute changes to the program. Titles and abstracts can be found below.
The list of posters can be downloaded here. If you are a poster presenter, please let us know as soon as possible if you spot a mistake, if you would like to cancel your participation, or if you have any other comments.

All times are Central European Summer Time (CEST), the local time zone of Vienna.
Location (unless specified otherwise): Christian Doppler lecture hall, Boltzmanngasse 5, 3rd floor, room 3355.

	Monday, Sept. 23	Tuesday, Sept. 24	Wednesday, Sept. 25	Thursday, Sept. 26	Friday, Sept. 27
8:45 – 9:00	Coffee + welcome	Coffee + welcome	Coffee + welcome	Coffee + welcome	Meet & Greet
9:00 – 9:50	Welcome address by Reinhold Bertlmann	Talk by Mariami Gachechiladze	Talk by Flavio del Santo	Talk by Costantino Budroni	9:00 – 9:10: Opening Words (Univ.-Prof. Dr. Manuela Baccarini, Vice Rector for Research, University of Vienna; Univ.-Prof. Dr. Ulrike Diebold, Vice President, Austrian Academy of Sciences) 9:10 – 9:30: 20 Years of IQOQI: presentation by Markus Aspelmeyer
9:50 – 10:40	Talk by Stefan Wolf	Talk by Philippe Grangier	Talk by Matt Leifer	Talk by Eleni Diamanti	9:30 – 10:00: A glimpse of the future: presentations by IQOQI Junior Groups Peter Asenbaum, Marios Christodoulou, Esteban Castro-Ruiz
10:40 – 11:30	Talk by Victoria Wright	Talk by Sandu Popescu	Talk by Lluis Masanes	Talk by Chris Fuchs	10:00 – 11:00: Talk by Anton Zeilinger 11:00 – 11:30: Reception
11:30 – 13:30	Lunch Break	Lunch Break	Lunch Break	Lunch Break	Lunch Break (on Friday, lunch will be available at the conference venue)
13:30 – 14:20	Talk by Harald Weinfurter	Online talk by Flaminia Giacomini	Talk by Philipp Höhn	Talk by Marissa Giustina	Talk by Valerio Scarani
14:20 – 15:10	Talk by Nikolai Miklin	Online talk by V. Vilasini	Talk by Antoine Tilloy	Talk by Nicolas Gisin	Talk by Marek Zukowski
15:10 – 15:40	Coffee Break	Coffee Break	Coffee Break	Coffee Break	Coffee Break
15:40 – 16:30	Talk by David Schmid	Talk by John Selby	Talk by Sally Shrapnel	Talk by Antonio Acín	Časlav Brukner, Eric Cavalcanti, Renato Renner: Paul Ehrenfest Award Talk
16:30 – 17:20	Flash Talks for Poster Session 1	Talk by Beatrix Hiesmayr	Talk by Xiaosong Ma	Flash Talks for Poster Session 2
17:20 – 18:00		Talk by Philip Goyal (-18:10)
18:00 – 20:30	Poster Session 1 (IQOQI Seminar Room & Erwin Schrödinger lecture hall)		Conference Dinner (Schübel-Auer)	Poster Session 2 (IQOQI Seminar Room & Erwin Schrödinger lecture hall)
20:30 – …			Conference Dinner

Titles and abstracts (to be completed)

• Antonio Acín: News from the device-independent scenario
  The talk reviews some recent results on Bell nonlocality and device-independent quantum information protocols. We first introduce the convex combination attack on device-independent quantum key distribution (DIQKD) and use it to (i) prove that Bell nonlocality in not sufficient for the security of standard DIQKD protocols, and (ii) quantify the possible benefits of using qudits for DIQKD. Then, we discuss novel quantum optical schemes for Bell nonlocality detection and DIQKD photonic implementations.
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• Costantino Budroni: Quantum memory and quantum correlations in time
  We present recent progress on the investigation of temporal correlations, namely, sequences of outputs from repeated measurements on physical systems. We identify scenarios where quantum systems outperform classical ones and investigate the associated limits using numerical methods. We observe that the key resource for generating these correlations is the memory encoded within the internal states of the physical system. Our results contradict the common belief that entanglement-breaking channels represent classical memory: a qudit passing through such a channel cannot be simulated by a classical system of the same size.
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• Eleni Diamanti: Experimental quantum certification of channels and states
  Developing robust and practically relevant certification tools for quantum resources is a fundamental task in quantum information as it determines how much trust can be placed in those resources. One would also like to make as minimal assumptions as possible on the functioning of the certification setup itself, in a so-called device-independent (DI) setting. Often, this is only possible when considering large, identically and independently distributed (IID) samples, which weakens the DI claim and makes experimental implementations challenging. We show two cases where we have crafted theoretical protocols enabling in practice the certification of a quantum channel and of a multipartite entangled state, in the non-IID regime and considering losses and errors, based on high-fidelity polarization-entangled Bell pair and GHZ states, respectively.
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• Christopher A. Fuchs: QBist Ontology Descending a Staircase, No. 2
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• Mariami Gachechiladze: Implications of the Generalized Information Causality Principle
  Nonlocality is a fundamental property of quantum mechanics and a potent tool for quantum information processing.  However, since the works of Tsirelson, we know that the amount of nonlocality produced in quantum mechanical experiments is limited. Since then, a few physical principles have aimed at deriving the predictions of quantum mechanics on the type of correlations observed in the Bell experiment. In this talk, we will focus on the nontrivial communication complexity and the information causality principles. As the first step, we generalize the latter principle to the distributed computation scenario. Then we show that in any theory that collapses the communication complexity, the generalized information causality principle is violated. Finally, we apply the generalized information causality statement to various distributed functions, resulting in novel bounds on the set of quantum correlations.
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• Flaminia Giacomini: Quantum effects in gravity from a delocalised quantum source
  Understanding the fundamental nature of gravity at the interface with quantum theory is a major open question in theoretical physics. Recently, the study of gravitating quantum systems, for instance a massive quantum system prepared in a quantum superposition of positions and sourcing a gravitational field, has attracted a lot of attention: experiments are working towards realising such a scenario in the laboratory, and measuring the gravitational field associated to a quantum source is expected to give some information about quantum aspects of gravity. However, there are still open questions concerning the precise conclusions that these experiments could draw on the nature of gravity, such as whether experiments in this regime will be able to test more than the Newtonian part of the gravitational field. In my talk, I will present a new result, where a delocalised quantum source gives rise to effects that cannot be reproduced using the Newton potential nor as a limit of classical General Relativity. These effects can in principle be measured by performing an interference experiment, and are independent of graviton emission. Identifying stronger quantum aspects of gravity than those reproducible with the Newton potential is crucial to prove the nonclassicality of the gravitational field and to plan a new generation of experiments testing quantum aspects of gravity in a broader sense than what proposed so far.
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• Nicolas Gisin: Signaling?
  According to John Bell “something is going on behind the scene”. Let’s gain intuition from Bohmian mechanics, more precisely naïve – or natural – Bohmian mechanics (N-BM) which assumes that position measurements merely reveal the hidden positions of Bohmian particles. I show that N-BM, while solving the measurement problem, allows for signaling. Instead of concluding that N-BM is wrong (and thus that BM does not solve the measurement problem), let’s take Bell seriously and study the consequences, both experimentally and theoretically, of signaling as an explanation of Bell inequality violations, beyond BM. At the end, I argue that we, the community, did not yet finish our job: more experiments are needed to test possible faster than light communication.
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• Marissa Giustina: The physicality of information and the information of physicality
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• Philip Goyal: Reconstructive Insights into Identical Particle Statistics and Entanglement
  Identical quantum particles exhibit extraordinary behaviour described by an amalgam of distinct rules, many of which have a heuristic quality.  I argue that answers to many of the outstanding questions concerning the nature and behaviour of identical particles, such as their entanglement, is presently inhibited by the lack of an unambiguous formulation of these rules.  In this talk, I outline the operational reconstruction of the core rules for handling identical particles, which removes these ambiguities.  I then show how a careful examination of the interplay between persistence and reidentifiability in classical and quantum systems enables one to clearly understand why these rules are needed in the first place (specifically why such rules are not needed either for identical classical particles or for non-identical quantum particles).  Next, I propose a metaphysical understanding of the nature of identical particles as so-called “potential parts”, which is directly inspired by this key postulate.  Finally, in light of the reconstructed and freshly-interpreted rules, I offer some reflections on an open question of great recent interest, namely whether (and if so how) one can legitimately speak about—and formalize—the entanglement of identical particles.
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• Philippe Grangier: Contextual unification of classical and quantum physics
  Following an article by John von Neumann on infinite tensor products, we develop the idea that the usual formalism of quantum mechanics, associated with unitary equivalence of representations, stops working when countable infinities of particles (or degrees of freedom) are encountered. This is because the dimension of the corresponding Hilbert space becomes uncountably infinite, leading to the loss of unitary equivalence, and to sectorization. By interpreting physically this mathematical fact, we show that it provides a natural way to describe the “Heisenberg cut”, as well as a unified mathematical model including both quantum and classical physics, appearing as required incommensurable facets in the description of nature.
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• Beatrix Hiesmayr: The matter-antimatter difference and Bell’s inequality
  John Bell, a particle physicist at CERN, has shaken the foundations of quantum theory.  This lecture shows that Bell’s inequality can also be tested in high-energy systems. In particular, the difference between a world of matter and a world of antimatter can be exploited to violate Bell’s inequality, so that, curiously, you don’t get a secure key if you measure the particle content, whereas it works if you measure the antiparticle content.
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• Philipp Höhn: Subsystem relativity
  I will discuss the notion of subsystems in the context of internal quantum reference frames. The key observation is subsystem relativity, and I will summarize some of its implications for topics ranging from entanglement, over quantum thermodynamics to gravitational algebras and entropies.
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• Matt Leifer: What is nonclassical about quantum interference?
  Last time I spoke at the Vienna Quantum Foundations Conference, I explained how several quantum interference phenomena that are Traditionally Regarded as Problematic (TRAP) can be reproduced in a simple classical model.  This time, I will explain why some more subtle aspects of quantum interference are not possible in a Spekkens noncontextual theory.  This provides a more rigorous and compelling demonstration of their nonclassicality.  The phenomena I will discuss are:
  – The precise form of the visibility/which-path tradeoff in a Mach-Zehnder Interferometer.
  – The probability of freezing the state in the quantum Zeno effect.
  The former result goes via a proof that the simplest kind of uncertainty relation for a qubit cannot be reproduced in a noncontextual model.  The latter result is relevant to quantum interference because the quantum Zeno effect is used to boost the probability of success in the Elitzur-Vaidman bomb tester.  Our result implies that if we do not allow false positives then it is not possible to asymptotically reduce the probability of false negatives or of the bomb blowing up to zero in a noncontextual theory via this method. The first result is based on L. Catani et. al., Phys. Rev. Lett. 129, 240401 (2022) and L. Catani et. al., Phys. Rev. A 108, 022207 (2023).
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• Xiaosong Ma: Multiphoton non-local quantum interference controlled by an undetected photon
  Quantum technology employs the ‘spooky’ phenomena of quantum physics such as superposition, randomness and entanglement to process information in a novel way. Quantum optics provides a promising path for both delivering quantum-enhanced technologies and exploring fundamental physics. In this talk, I will introduce our recent work on multiphoton non-local quantum interference controlled by an undetected photon, in which we demonstrate multiphoton non-local quantum interference that does not require entanglement of any intrinsic properties of the photons. With the intrinsic indistinguishability in the generation process of photons, we realize four-photon frustrated quantum interference. This allows us to observe the noteworthy difference to quantum entanglement: We control the non-local multipartite quantum interference with a photon that we never detect.
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• Lluis Masanes: Holography in unitary circuits and toy quantum gravity
  We introduce a spin-chain with dynamics consisting of a unitary circuit with discrete conformal symmetry. This model is holographically dual to a toy theory of quantum gravity in 2+1 dimensions, where certain tensor-network states correspond to classical discrete geometries. Unlike previous approaches, like holographic codes, these tensor networks and geometries evolve in time, reproducing some general relativity phenomana. Also, these states satisfy the Ryu-Takayanagi correspondence between entanglement and geometry, but they provide much more, they contain a complete description of the bulk, including the interior of black holes, a feature that is not so transparent in standard AdS/CFT.
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• Nikolai Miklin: Classical certification of memory-bounded quantum computers
  We develop an efficient method for certifying single-qubit quantum gates in a black-box scenario, assuming only the dimension of the quantum system is known. The method is based on testing the outcomes of exact quantum computations on a single qubit, with no auxiliary systems required. We prove that the method’s sample complexity grows inverse linearly with respect to the average gate infidelity for the certification of a relevant single-qubit gate, which experimentally corresponds to a pi/2-pulse. Furthermore, we show that the proposed method can be used to certify a gate set universal for single-qubit quantum computation. Our approach takes a first step in bridging the gap between strong notions of certification from self-testing and practically highly relevant approaches from quantum system characterization.
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• Flavio del Santo: Which features of quantum physics are (not) fundamentally quantum?
  What is fundamentally quantum? I will argue that most of the features, problems, and paradoxes – such as the measurement problem, the Wigner’s friend paradox and its proposed solutions, single particle nonlocality, and no-cloning – allegedly attributed to quantum physics have a clear classical analogue if one is to interpret classical physics as fundamentally indeterministic. What really characterizes quantum physics boils down only to phenomena that involve ℏ, i.e., incompatible observables. On the contrary, attributing a genuine quantum nature to phenomena that can be explained without invoking ℏ is part of a persistent folklore that should now be set aside.
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• Valerio Scarani: Non-classicality witnesses from precessing dynamics
  In this talk I shall review the work done in the past few years, inspired by a previously unnoticed observation by Tsirelson [https://arxiv.org/abs/quant-ph/0611147]. He noticed that the non-classicality of some states of a single harmonic oscillator can be certified by measuring only one observable (say, position) at one among a set of suitable times. This is somewhat surprising, as it is common knowledge that the evolution of a harmonic oscillator is identical to the classical one in the Heisenberg representation. Tsirelson’s observation was first extended to single finite-dimensional systems [https://arxiv.org/abs/2204.10498], and I shall present the results of a forthcoming experimental realisation. It was then adapted to detect entanglement: for continuous variables, it gives one of the few entanglement witness that is free from false positives [https://arxiv.org/abs/2210.10357]; for discrete variables, it gives the first witness that detects GHZ entanglement using only measurements of the total angular momentum [https://arxiv.org/abs/2311.00806]. The task being operational, it can be framed in the language of generalized probabilistic theories: contrary to what happens for Bell-type correlations, for this task quantum physics achieves the maximum score [https://arxiv.org/abs/2401.16147]. I shall report on a modification of the protocol that detects a different class of states [https://arxiv.org/abs/2405.17966], and on an improved rigorous upper bound for the score achievable with Tsirelson’s original protocol. And of course, I won’t omit mentioning related work by other groups [https://arxiv.org/abs/2209.00725, https://arxiv.org/abs/2309.00021].
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• John Selby: Rethinking Realism
  In this talk, I will present a new interpretational programme aimed at resolving the many no-go theorems (such as the now 60 year old Bell’s theorem) which impede our ability to provide a satisfactory realist account of quantum theory. Central to this research programme is the idea that the lesson to take from these no-go theorems is not that we should reject realism per se, but just that it needs a little rehabilitation. The goal is that if we suitably redefine our notion of what constitutes a realist explanation, then we will still be able to hold on to our cherished principles, including locality and noncontextuality. There is a great deal of work to be done to reach this goal, but we (David Schmid, Rob Spekkens, and I) took a substantial first step towards it in arXiv:2009.03297. In this work we develop a categorical framework for formulating theories of nature, which (unlike standard operational approaches) clearly separates out the ontological from the epistemological aspects of the theory. By doing so, we are able to provide a set of criteria which we believe any such theory must meet in order to be deemed realist. None of these criteria are manifestly in conflict with quantum theory, and so we find ourselves on the path towards a new form of quantum realism.
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• Sally Shrapnel: Quantum algorithms for classical causality
  While humans are pretty good at identifying causes and effects, machines are currently less so. While deep learning and generative machine learning models have taken centre stage in the industrial application of automated learning, it is nonetheless well known that these techniques fail to capture causal concepts, leading to significant performance vulnerabilities. To address these short-comings, computer scientists are taking ideas from causal inference, a field traditionally limited to small data sets of low dimension, and injecting modern machine learning elements to create new algorithms that can benefit from the best of both worlds. These hybrid classical approaches provide new opportunity to search for potential quantum advantage. In this talk I will present a family of non-parametric classical causal estimators and consider whether quantizing these algorithms might provide some advantage for classical causal inference.
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• Antoine Tilloy: Quantum-classical dynamics as measurement based feedback
  It is possible to couple quantum and classical variables consistently (i.e. without paradoxes like faster than light signalling) provided one accepts a certain amount of stochasticity. This is useful, for example, if one wants to entertain the possibility that spacetime is fundamentally classical. These hybrid dynamics are not trivial (like meanfield) but they are nothing fancy either, and one way to construct them is via “measurement and feedback”. I will explain how this is concretely done, and how the construction gives some intuition about the type of physics one can expect. I’ll also try to mention some of the challenges in applying this formalism to gravity.
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• Harald Weinfurter: Everyday Loophole-Free
  Originating from Bell experiments, device independent QKD could be demonstrated. I will describe the current status of the experiments, and what is still necessary for the grand goal of realizing quantum networks, where DI-QKD, and thus loophole-free Bell experiments become the standard applications.
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• Stefan Wolf: From Bell to Boltzmann (via Coiteux-Roy)
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• Victoria Wright: Non-locality, generalised contextuality and Schrödinger–GHJW
  I will discuss a couple of advances in the connection between two fundamental phenomena of quantum theory: Bell non-locality and generalised contextuality. In a previous work, we demonstrated how the two-party non-locality of quantum theory could be exactly characterised by quantum contextuality. A key result for this connection is known as the Schrödinger–GHJW theorem. Consider a set of ensembles of quantum states that all mix to the same density operator. The theorem states that there exists a fixed entangled state such that one can prepare one half of system in any desired ensemble from the set by performing a well-chosen measurement on the other half of the system. Firstly, I will present an extension of this result showing that ensembles that mix to close but not identical density operators can be similarly remotely prepared when one is allowed to post-select on the outcome of the preparing measurement. The closeness of the density operators is then found the give a tight bound on the success probability of the remote preparation. This result connects Bell scenarios with no-click events to a broadened type of contextuality experiment. Secondly, a recent work [arXiv:2408.06711] on compiled non-local games proved an alternative characterisation of the set of quantum commuting correlations. I will present a consequence of this characterisation and our previous results which shows that there are statistics in single system generalised contextuality experiments that are compatible with an algebraic quantum field theoretic description of the universe but not with a non-relativistic quantum theoretic one.
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• Marek Zukowski: Against (unitary) interpretation (of quantum mechanics): removing the metaphysical load
  Physics is a science. Thus a statement can be treated as its “law” only if it agrees with our experience of the World/Nature (this includes our experiments). Statements which are fundamentally untestable are hypotheses which belong to metaphysics. Such are all interpretations of quantum mechanics, which attribute to its mathematical tools meanings that are beyond (experimentally) observable events, while not affecting quantum  predictions  of these events. We show  that  “unitary quantum mechanics”, which according to its followers leads to some paradoxes, is an interpretation of quantum mechanics, based on hypotheses that are untestable. The (operational) quantum mechanics, which is the one tested in every quantum experiment is free of these paradoxes. The root of “unitary” vs. operational discrepancy is that the latter treats  the measurement process as irreversible, and in different  answers to the question of what is described by the state vector.
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