2023Activity reportProjectTeamQURIOSITY
RNSR: 202324386L Research center Inria Saclay Centre at Institut Polytechnique de Paris
 In partnership with:Institut Polytechnique de Paris
 Team name: Quantum Information Processing and Communication
 In collaboration with:Laboratoire Traitement et Communication de l'Information
 Domain:Algorithmics, Programming, Software and Architecture
 Theme:Algorithmics, Computer Algebra and Cryptology
Keywords
Computer Science and Digital Science
 A3.4. Machine learning and statistics
 A4.2. Correcting codes
 A4.3. Cryptography
 A4.3.4. Quantum Cryptography
 A4.6. Authentication
 A5.9. Signal processing
 A6.1.2. Stochastic Modeling
 A6.5. Mathematical modeling for physical sciences
 A7.1. Algorithms
 A7.1.4. Quantum algorithms
Other Research Topics and Application Domains
 B5.11. Quantum systems
 B6.2. Network technologies
 B9.1. Education
 B9.10. Privacy
1 Team members, visitors, external collaborators
Research Scientist
 Cambyse Rouze [INRIA, ISFP, from Sep 2023]
Faculty Members
 Romain Alléaume [Team leader, Télécom Paris  IP Paris, Professor, HDR]
 Peter Brown [Télécom Paris, Associate Professor]
 Augustin Vanrietvelde [Télécom Paris, Associate Professor]
PostDoctoral Fellow
 Thomas Van Himbeeck [Telecom Paris]
PhD Students
 Jan Kochanowski [IP Paris, from Nov 2023]
 Francesco Mazzoncini [Telecom Paris]
 Tristan Nemoz [Telecom Paris]
 Thomas Pousset [Télécom Paris]
 Guillaume Ricard [Telecom Paris]
 Pierre Enguerrand Verdier [Orange, CIFRE]
Interns and Apprentices
 Ali Almasi [IP Paris, from Sep 2023, PhD Track student]
 Evdokia Gneusheva [École Polytechnique, Intern, until Mar 2023]
Administrative Assistant
 Natalia Alves [Inria]
External Collaborators
 Pablo Arrighi [Université ParisSaclay, Team Leader, Inria Team QuACS, HDR]
 Roger Colbeck [University of York, Professor, University of York, HDR]
 Nicolas Fabre [Telecom Paris]
 Omar Fawzi [Inria, Team Leader of QInfo at ENS Lyon, HDR]
 Sylvain Gigan [Ecole Normale Supérieure, HDR]
 Yves Jaouën [Telecom Paris, HDR]
 Robert König [Technical University Münich, Professor, HDR]
 David Peres Garcia [ Universidad Complutense de Madrid , Professor, HDR]
 Cambyse Rouze [Technical University Münich, from Apr 2023 until Aug 2023]
 Daniel Stilck França [Inria, Inria Research Scientist at QInfo, ENS Lyon]
 Simone Warzel [Technical University Münich, Professor, HDR]
 Mirjam Weilenmann [University of Geneva]
2 Overall objectives
Quriosity's ambition is to extend the application horizon of quantum information science by addressing novel questions positioned at the intersection between theoretical research in quantum information and the engineering of quantum devices, with a focus on approaches combining digital and quantum photonics technologies.
The overarching goal of the projectteam will be to push forward our ability to harness and exploit highdimensional complex quantum systems for quantum information processing and quantum communications purposes.
Leveraging a dual approach combining fundamental research in quantum information with quantum photonics expertise, Quriosity will strive to take advantage of and develop strong synergies with the unique quantum ecosystem of Saclay and to pursue objectives that have the potential to bring radical advances to several application domains of quantum technologies, ranging from cryptography to computing:
 Design quantumenhanced cryptographic hardware, leveraging concepts based on computational hardness and quantum information.
 Conceive and engineer photonicbased processors and systems capable of achieving quantum advantage in computation or communication tasks.
 Develop efficient quantum information processing schemes implementable on nearterm hardware and advance the theoretical framework to understand the fundamental limits of noisy quantum information processing.
3 Research program
The research program that we aim to lead in the Quriosity projectteam intends to embrace a relatively wide area of theoretical questions, ranging from quantum cryptography, that we ambition to combine with complexitybased schemes and establish as a framework to enhance hardware security, to the mathematical foundations of quantum information and quantum computing. Conversely, we also intend to develop research capable of leveraging photonics and digital information processing technologies to design systems capable of producing highdimensional and controllable quantum states of light in order to push forward the frontiers of quantum information processing advantage.
3.1 Research axis 1: Quantum cryptography complexity and hardware frontiers
This axis aims to identify and solve frontier research topics in quantum cryptography, from two main perspectives. First by exploring the interplay between security models  including computational ones  and theoretical quantum cryptography, allowing to build protocols with stronger security properties and lesser resource requirements. Second by laying a special emphasis on interplay between quantum cryptography and hardware security, with the need to develop extended techniques for quantum cryptographic hardware security certification, but also the idea to strengthen hardware security and its resilience to information leakage by resorting to quantum cryptographic constructions.
3.1.1 Everlasting security from a quantumcomputational hybrid model
We proposed in 2015 a security model that we later coined a Quantum Computational Timelock (QCT) security model. It consists in assuming that computationally secure encryption may only be broken after time much longer than the coherence time of quantum memories available at the time of protocol execution. The QCT security model opens the possibility to propose new quantum cryptographic constructions and in particular to make use of encoding and security proof techniques that strongly depart from “traditional” quantum conjugate coding that is a central ingredient in most quantum cryptographic protocols.
The QCT security model opens towards a rich variety of fascinating questions, that we have certainly not all identified. In the coming years we intend to push forward the theoretical analysis of several of these questions, that relate to the computational frontiers of quantum cryptography. One ongoing direction consists in studying key agreement constructions whose security can be reduced to distributed computational problems that exhibit an exponential separation in terms of quantum or classical communication complexity.
As an alternative way to build secure protocols in the QCT model, we also intend to investigate pseudorandom quantum states, which can be seen as a computational variant of a $t$design, i.e. an ensemble of quantum states characterized by the fact that $t$ copies of one sampled state are statistically indistinguishable from $t$ copies of a states picked uniformly at random. Interestingly, construction of pseudorandom states can be based on quantumsecure oneway functions, and therefore from the first assumption. This line of work will also allow us to consider realistic and pratical constructions of quantum cryptographic schemes based on computational and /or quantumhardware security assumptions. We also intend to study constructions for quantum physically uncloneable functions qPUFs and their aplication.
3.1.2 Deviceindependent cryptography
Deviceindependent cryptography allows one to perform quantum cryptography with reduced or even no trust assumptions on the quantum hardware. It remains a challenge experimentally and pushing the performance (in terms of key rate, or trust reduction) of deviceindependent cryptography defines an active research frontier for quatum cryptography. Recent implementations of DIQKD147, 57, 57 have shown that whilst it is now feasible, it has a relatively low rate and can only be executed over a short distance. By improving the theoretical methods for analyzing various protocols and security proofs and by improving the protocol design we can look to boost the rates of these protocols and push them towards a more viable technology. Examples of such improvements include protocol design modifications 51, 40 and improved methods to calculate rates 28, 29, 50. Our goals are to develop better designed protocols and security proofs (assessing their performance in experiments) and to investigate the fundamental limitations of DI protocol rates Overall pushing the practicality of DI forwards and improving our understanding of its limitations.
As a complementary line of research we will also investigate prospects of semideviceindependent protocols as a viable nearterm alternative to deviceindependent security. Proposed protocols rely on assumptions of system energy 49, dimension bounds and bounded distrust 52 amongst others. We will investigate alternative assumptions and derive resulting protocols to be analyzed and subsequently implemented. We will also apply the semideviceindependent framework to the problem of hardware verification, designing tests to establish that the hardware is functioning correctly whilst placing limited trust on the components.
3.1.3 Quantumenhanced leakageresilience
We will also investigate some questions placed at the intersection between classical hardware security and quantum cryptography, namely how to prove the security of a cryptographic protocols when implemented using hardware, such as processors or storage, that may leak some of the securitysensitive information.
We intend to tackle leakageresilience cryptography from a new viewpoint, that will consist in integrating quantum cryptographic constructions as a base layer within cryptographic systems, in order to obtain security guarantees even in presence of information leakage with strictly weaker assumptions than existing classical leakageresilience protocols. We will first consider simple cryptographic protocols such as OneTimePad encryption or authentication protocols relying on Physically Uncloneable Functions PUFs. We intend for example to investigate how the use of hybrid classicalquantum cryptographic hardware, comprising quantum channels to interconnect processors or secure storage sites, can lead to cryptographic protocols with provable security under some realistic information leakage models.
3.1.4 Realworld quantum cryptography
40 year of quantum cryptography (QC) have lead to major theoretical and technological advances, with fundamental impact on the field of information security. Market adoption however remains limited, with major challenges that practical QC still needs to be overcome in order to become widely used in realworld applications. We identify in particular two main challenges: 1) cryptographic advantage, namely the design of protocols for which the use of QC in combination with classical cryptography gives a competitive edge over classical cryptography only; 2) security certification of quantum cryptographic implementations. Quriosity intends to actively contribute to lift these barriers and to foster the development of realworld quantum cryptography and in particular to the uptake of a French and European industry. The development of a QC industry is indeed becoming an important topic, with strategic investments from leading scientific countries (China, Korea, Japan, UK, etc. ) including also notably the EU27 supporthing the EuroQCI initiative. On the other hand, the adoption of quantum cryptography for realworld application remains often considered with skepticism by representatives of the cybersecurity community, stressing the dire need of crossdisciplinary vision combining bestinclass classical and quantum cryptography expertise.
Regarding cryptographic advantage, our conviction is that one should not aim at constructions where quantum cryptography would just functionally replace classical cryptography, but on the other hand to identify applications where the use of QC combined with postquantum cryptography (PQC) can present strict security gain over PQC alone.
Regarding security certification, it has become a central challenge in particular in the context of the EuroQCI initiative aiming at developing a panEuropean quantum communication infrastructure, together with an industry, in the next 10 years It constitutes a complex task, requiring the collaboration of experts from different fields. In future years, we intend to tackle this question from different angles: on the theory side, we intend to propose a shift in the security objective towards everlasting security, and demonstrate how this can make the security certification of key establishment based on QKD combined with ephemeral postquantum cryptography primitives much more tractable. On the system engineering side and in resonance with Section 3.2, we intend to identify and close implementation security gaps in modern CVQKD systems relying on digital signal processing, notably the complex interplay between calibration procedure and finitesize security, but also between Nyquist pulse shaping and leakage.
3.2 Research axis 2: Multimode photonic systems for quantum information processing and communications
Building a quantum processor that we could use to solve realworld problems with practical benefits might constitute one of the most burning scientific and technological challenges of the beginning of the 21st century. Very interestingly, recent results indicate that quantum optical circuits constitute a very promising approach for quantum information processing, in particularly highdimensional linear optics systems, which can form a (weaker) nonuniversal quantum computing platform, and yet efficiently perform tasks intractable for a classical computer, such as Boson Sampling 17.
We will actively investigate new theoretical questions related to quantum information processing with highdimensional photonic system, and their interplay with technology and experiments.
3.2.1 Quantum coherent communications and digital signal processing
Quantum Key Distribution (QKD) systems are among the most advanced quantum communications technologies available today. QKD therefore provides an ideal platform to test novel system designs and validate quantum communication technology over real networks Leveraging essential features of modern optical communication systems, and in particular high sampling rates and digital signal processing 43, quantum coherent communications systems constitute a recent and promising route towards highrates, highly integrated and costeffective quantum communication systems. They rely on two central ingredients: Spectrally efficient modulation formats and coherent detection, exploiting phase and intensity information and able to operate a very high rates (> GHz) even with shotnoise limited receivers.  Digital signal processing that takes advantage of the high sampling rates to digitally evaluate and compensate many impairments of the communications such as optical carrier phase noise or polarization mode dispersion, using dedicated algorithms.
In collaboration with Prof. Yves Jaouen from the GTO team of Telecom Paris,and working on a stateoftheart experimental platform, Quriosity has designed and demonstrated for the first time DSPenhanced quantum communications, with noise control performances that allow to successfully run QKD over metropolitan distances while being jointly deployed over classical coherent optical link 21. We have also filed a patent about this general concept and our inventive system design.
In the future, we then aim to leverage digital signal processing and machine learning (ML) techniques to characterize and mitigate noise in order to push further our ability to operate quantum communications over existing optical fibers, in coexistence with classical signals.
As a complementary line of research, we intend to theoretically study multimode quantum coherent communications using multimode shaping of the local oscillator, taking inspiration from 30. We also intend to explore the possibility to rely on CV multimode encoding as a way to experimentally implement new quantum cryptographic constructions in the hybrid quantum computational security models introduced in Section 3.1.
3.2.2 Quantum information processing with a programmable frequency processor
In collaboration with the teams of Nadia Belabas and Pascale Senellart at C2N and in the context of the ParisQCI project, we study how to combine highdimensional photonic gates in the frequency domain, to efficiently synthesize highdimensional unitary transformations. Leveraging on the possibility to parallelize singlequbit unitaries, that we have recently analyzed 5 we intend to study how such systems could be leveraged for optical quantum information processing, and in particular for quantum metrology. In the future, we will also investigate how to scale the platform to perform information processing with highdimensional quantum states, opening the possibility to achieve quantum computational advantage, but also implementation routes for the hybrid quantumcomputational cryptographic protocols in the QCT model, studied in Section 3.1
3.2.3 Quantum information processing using multimode programmable linear circuits
In collaboration with the team of Sylvain Gigan at ENS Ulm, and in the context of Francesco Mazzoncini's PhD that we cosupervise, we aim to use a multimode programmable linear circuit, built around a multimode fiber (cf. Figure 2) to perform some fundamental tests and demonstrations of quantum communication advantage, related to fundamental problems such as the Vector in a Subspace 48.
The prospects of this work are very promising: first they could lead to the first experimental demonstration of a exponential communication complexity gap between oneway quantum communication and twoway classical communications and may also open towards the possibility for experimentally robust Bell inequality violations 45, with applications for quantum cryptography and also in quantum computing.
3.3 Research axis 3: Mathematical foundations of quantum information
Quantum information and computation are built upon the mathematical frameworks of functional analysis and information theory. Developing our understanding of the mathematical underpinnings of these theories can in turn lead to new insights and applications. At Quriosity, one of our aims is to explore quantum information theory through the lens of the underlying mathematics. In a nutshell, we will parallelly develop new analytic and numerical tools for the study of quantum entropic quantities and complex quantum systems made of spin or bosonic degrees of freedom. We will in turn consider these systems to design new, physically motivated models of noiserobust quantum computing.
3.3.1 Convex relaxations of quantum optimization problems
Convex optimization concerns the optimization of convex functions over convex sets. This family of optimization problems has several particularly nice properties, including the guarantee of global optima, which makes them particularly appealing from both the perspective of the mathematics and the applications. They are widely applicable to many domains of science but in particular they arise rather naturally in the context of quantum theory as many of the relevant objects (states, channels and measurements) form convex sets.
We will aim to develop and apply techniques in convex optimization theory to problems within quantum information and quantum computing. Recent examples of our work in this area include 28, 29 where we developed semidefinite programming relaxations for entropic optimization problems relevant to device independent cryptography. Continuing this line of research we aim to extend these techniques to other entropic quantities beyond the relative entropy, for instance to the Petz and sandwiched families of Rényi divergences. We also have the ambitious goal of understanding and characterizing what classes of functions, relevant in the context of quantum theory, are amenable to such semidefinite programming approximations. In other words, what optimization problems in quantum information theory and quantum computing can we approximate?
A wellknown example concerns strengthenings of the monotonicity of the relative entropy under the action of a quantum channel or a Markovian evolution known as strong data processing and modified logarithmic Sobolev inequalities. These fundamental inequalities are known to be hard to prove analytically, even for simple random walks on $n$cycles, and convex relaxation techniques were recently successfully used to approximate them 37. We are currently collaborating with Omar Fawzi and Daniel Stilck França from QINFO to adapt these numerical tools to the quantum realm. In the future, we will consider extending these tools to the infinite dimensional bosonic setting in order to approach longstanding conjectures such as the entropy photon number inequality 39. This research direction will complement analytic approaches presented in Section 3.3.2.
3.3.2 Fundamental properties of entropies
Entropies are fundamental quantities in quantum information theory, obtaining operational meanings in terms of rates of various tasks 36. By improving our understanding of these quantities, we can in turn gain new insights into the various applications in which they appear.
For example, new chain rules for Rényi entropies 35 led to a versatile framework for cryptographic security proofs 20. The result, known as the entropy accumulation theorem, effectively gives sufficient conditions under which the entropy of a large system can be accurately described by the entropy of its individual systems. At QURIOSITY we aim to understand under which conditions does entropy accumulate in this manner? By understanding the minimal requirements for entropy to accumulate we can understand the minimal requirements under which a randomness based cryptographic protocol functions securely. Moreover, we aim to investigate the connection between the entropy accumulation theorem and the related works of the quantum probability estimation framework 56. This is an alternative method to break large entropies down into smaller quantities and reports several advantages over the entropy accumulation theorem. Understanding how advantages from one technique can be transferred to the other will lead to much stronger theoretical results and would have immediate applications to improve security proofs and rates of cryptographic protocols, leading to more practical technologies.
Other types of decompositions of entropic quantities of interacting complex systems into smaller components involving marginals over subsystems include generalizations of the famous strong subadditivity of the relative entropy known as approximate tensorstability of the relative entropy. These are at the core of most successful methods for finding the speed of convergence of Gibbs sampling algorithms based on the modified logarithmic Sobolev inequality. In previous work, we successfully extended these notions to the quantum realm 38 and applied them to problems in network quantum information theory 25, 33 and open complex quantum systems 31, 22. Extensions and refinements of these concepts will lead to new breakthroughs in both fields (see Sections 3.3.3 and 3.3.4).
3.3.3 Complexity and entanglement properties of quantum Gibbs states
A complexity theoretical definition of the quantum phase of a state $\psi $ consists in taking the vicinity of states which are reachable from $\psi $ after applying a local evolution during a short period of time. A topologically ordered phase has the property that the time required to reach it starting from a trivial (i.e. product) state scales extensively with the system size. In other words, topological order can be described in terms of circuit depth lower bounds. The classification of quantum phases of matter is by now a very wellestablished field with farreaching applications e.g. to the construction of good quantum errorcorrecting codes exploiting the properties of topologically ordered phases. However, a more realistic description of a quantum mechanical system is in terms of a finite temperature Gibbs state describing its thermal equilibrium with a large environment. Despite their practical relevance, until recently Gibbs states were primarily studied by mathematical physicists, and many fundamental questions regarding their use in quantum information processing remain open. We propose to investigate the complexity of quantum Gibbs states through the scope of their finite temperature phase transitions. Additionally to its fundamental value, this research direction will undoubtedly lead to several important practical applications, as described in section 3.3.4.
In the setting of classical Gibbs measures, analogous questions have been intensively studied from the perspective of Markov chain Monte Carlo algorithms (MCMC). On regular lattices, the analysis of the speed of convergence of MCMC for lattice spin systems is by now wellunderstood through the study of correlations at equilibrium. The generalization to general interaction graphs is still a very active field of research in theoretical computer science, probability theory and mathematical physics 32. The problem becomes even harder in the quantum regime, where purely quantum mechanical effects, e.g. longrange entanglement, may cause the quantum Markov chain to slow down in an unpredicted manner. For the important case of commuting interactions, which include most hitherto studied Hamiltonians for the purpose of quantum errorcorrection, and for physical dynamics generated by the weak coupling of the system with a large environment (Davies dynamics), general results were obtained through spectral methods. However the latter are not powerful enough to distinguish evolutions generating topologically ordered states from rapidly mixing ones. Instead, more involved techniques, e.g. entropic inequalities, are needed. In 24, 31, 23, 22, we were able to prove rapid mixing by extending one of the most successful classical approaches to prove rapid mixing based on the modified logarithmic Sobolev inequality and the approximate tensorstability of the relative entropy (cf Section 3.3.2). Extending this novel powerful approach, we plan to conduct a systematic joint study of mixing times and thermal stability of topological quantum order in low lattice dimensions. We will conduct this research in collaboration with Daniel Stilck França from QINFO with whom we coauthored 31. We also see a clear connection with the research focus of Daniel Malz who was recently recruited as a junior professor at Inria Saclay, the mathematical and theoretical condensed matter physicists at CPhT, as well as the team PEIPS at CMAP (X).
3.3.4 Mathematical analysis of quantum memories
In parallel to the previous research plan, we will conduct a mathematical analysis on the storage of quantum information and the concept of selfcorrection in complex quantum systems. Early work on the storage time of candidates of selfcorrecting quantum memories relied on the connection to the energy barrier of the system, that is the energy the system must reach for a logical error to occur, via an empirical principle called the Arrhenius law. More recently, the energy barrier was rigorously related to spectral properties of the evolution, whereas some nogo theorems showed the impossibility of an exact mathematical formulation of the Arrhenius law. Here instead, we plan to relate the memory lifetime of a device directly to properties of its thermal equilibrium state. We currently work on this research direction in the setting of lattice spin systems with Anthony Leverrier and Ivan Bardet from the team COSMIQ through the development of spectral methods, and plan to extend our framework to lattices with bosonic degrees of freedom in the near future. We also plan to initiate a dialogue with JeanRené Chazottes from CPhT (X) on refinements of our techniques using concentration and entropic inequalities which already proved their usefulness in the study of hitting times of classical Markov chains and their metastability. One of our long–term goals is to find systems with thermally stable entanglement, both stable against thermal fluctuations and robust against local perturbations. Such a theoretical result would be of very high practical interest since experimental implementations are inevitably subject to noise and errors.
3.3.5 Tomography of complex quantum systems
As the size of quantum devices continues to increase beyond what can be easily simulated classically, new challenges have appeared concerning the robust and efficient characterization of their states. This often necessitates the preparation and destructive measurement of exponentially many copies of the quantum system, as well as the storage of measurement outcomes in a classical memory. Recently, new methods of tomography have been proposed which precisely leverage this important simplification to develop efficient state learning algorithms. One highly relevant development in this direction is that of classical shadows 41, 42. In we propose a better solution by combining classical shadows with new insights from the emerging field of quantum optimal transport. Our current first step only applies to topologically trivial quantum states such as hightemperature Gibbs states or outputs of shallow quantum circuits, and more effort is needed to adapt and generalize our algorithm to nontrivial phases. We envision three new major contributions: First, we will develop constrained versions of concentration inequalities in order to develop efficient tomography algorithms of complex quantum states, assuming the prior knowledge of their phase. This line of research is original even in the classical setting where works on constrained entropic inequalities only very recently appeared in the literature. The expertise of JeanRené Chazottes from CPhT (X) will prove crucial to the success of this project. Second, we will extend the framework of shadow tomography to CV quantum systems. The main difficulties here are twofold: first, CV systems are infinitedimensional in nature, and hence some physical constraints need to be imposed on the states that one can hope to learn, such as their energy. Moreover, the set of measurements (homodyne/heterodyne) available in photonic experiments further limits the type of observables that one can hope to predict. In order to ensure the wide applicability of the method and test the resulting algorithm, we will rely on the already established interactions of IQA with the groups of experimentalists at IP Paris and Saclay, and initiate a fruitful dialogue with startup like Quandela and Pasqal. In the future, we will use these methods to devise hardwareoriented noiselearning algorithms for manybody systems. For this, we plan to get in touch with the experts on statistical learning among IP Paris, and in particular at LIX.
3.3.6 Formal tools for higherorder quantum computation
The theoretical study of quantum computation and its advantages has, in the past decade, opened to a new perspective: higherorder quantum computation, i.e. the way in which one can transform blackbox quantum gates by inserting them into computation architectures. This is useful to study the ways in which one can query subroutines in quantum computation, a pratice that is bound to become ubiquitous, for example in delegated quantum computing. The study of higherorder quantum computation has already led to promising as well as disconcerting results, such as about the difficulty of formally defining a quantum version of the computational `if' clause 19, or the fact that one might be able to query two unknown gates in a `superposed order of application', using a computation architecture called the quantum switch 34. Using the latter leads to computational advantages for certain tasks 18. However, the mathematical study of higherorder quantum processes quickly encounters thorny formal issues related to their nontrivial compositional structure.
Overcoming these issues would require the development of a specific and robust type system, stipulating which inputs a given higherorder quantum process admits and which output it produces. Despite recent advances 44, currently available type systems are not detailed enough to provide a fully compositional view of higherorder quantum computation. Our work thus focuses on refining them, through the encoding of sectorial structure, i.e. information about how quantum channels behave with respect to certain directsum decompositions of their input and output spaces, using the recently developed framework of routed quantum circuits 53, 54. Progress in this direction will pave the way to computer manipulation of complex higherorder processes, for instance to numerically optimise the advantage they yield.
3.3.7 Causal structure in quantum theory
Many of the peculiarities of quantum theory can be tracked down to it not matching our classical notion of causal structure 55; this leads to the question of how one could develop a quantum notion of causal structure, on which some progress has been achieved recently 26. Exploring quantum theory from a causal perspective yields potential progress in understanding its structure and potential applications, in particular for the aforementioned higherorder quantum processes, whose performances are directly connected to their causal structure. In that regard, a particularly important conjecture to prove is that of causal decompositions46, which puts forward a tentative equivalence between a unitary channel's causal structure (operational data about which of its inputs can affect which of its outputs) and its compositional structure (mathematical data about how it can be written as the composition of subchannels). If such a conjecture (which has not been proven yet in the general case) were to be true, it would yield a remarkable mathematical lever on the relationship between the operational and formal sides of quantum theory. We investigate this conjecture mathematically with the aim to prove it in more and more general cases; this involves abstract mathematical methods employing C* algebras. More generally, we explore how the latter might provide a useful formal basis for considerations of causality in a quantum context.
4 Application domains
Quriosity positions its activity at the  fruitfull  frontier between theoretical research in quantum computer science and mathematics, and quantum technology engineering and applications.
We in particular believe that useful quantum inventions and technologies are going to emerge from the current investments in quantum information sciences and technologies, much before large scale (and error corrected) quantum computers can be built.
Our research programs opens in particular towards such perspective, on different aspects:
 The development of more efficient and higher security quantum cryptographic protocols.
 The ability to leverage quantum cryptography principles and tecnnologies to strengthen hardware security.
 The design of costeffective quantum communications systems that can tightly integrated into modern communication infrastructures, making them widely deployable.
 The design of better quantum memories and therefore larger quantum computer as well as quantum networks.
5 Social and environmental responsibility
5.1 Footprint of research activities
Quriosity members are individually, and collectively making efforts to reduce their carbon footprint, in particular by taking the plane much less than before the Covid period. Augustin Vanrietvelde and Peter Brown will moreover act as carbon footprint delegates for Quriosity, and report to a working group at LTCI level, whose objective will be to increase the global awareness on carbon footprint, and steer the discussions to help decide on collective regulatory measures.
5.2 Impact of research results
Scientific publication
Quriosity aims at publishing highimpact papers in high profile journals such as Nature, Science, Physical Review, Quantum, IEEE Transactions on Information Theory, as well as top conferences in our field such as QIP, QCrypt, TQC as well as Crypto, EuroCrypt, CHES.
Innovation
Telecom Paris currently holds 5 granted patents: 3 on hybrid quantum computational cryptography (axis 3.1) and 2 on quantum coherent communications (axis 3.2). We plan to patent technological innovations, including foundamental proposals for which we see a clear implementation route and possible exploitation paths.
Teaching
Quriosity intends to play a vigorous role in the training of the future generation of quantum engineers and researchers. IQA and Romain Alléaume have been at the forefront of such development by opening the Quantum Engineering M2 Program in 2017. At Saclay level, and in collaboration notably with the QuACs Inria team but also with active Saclay quantum industry, we have the midterm ambition to launch a master program on quantum computer science and engineering.
6 Highlights of the year
6.1 Five papers selected at QIP 2024
After less than a year of existence Quriosity has obtained oustanding results at QIP 2024 in terms of selected contributions, with 4 members of Quriosity that are coauthors of 5 accepted papers:
 Thomas van Himbeeck and Peter Brown. A tight and general finitesize security proof for quantum key distribution.
 Jan Kochanowski, Alvaro Alhambra, Ángela Capel and Cambyse Rouzé. Spectral gap implies rapid mixing for commuting Hamiltonians
 Robert König and Cambyse Rouzé. Limitations of local update recovery in stabilizerGKP codes: a quantum optimal transport approach.
 Emilio Onorati, Cambyse Rouzé, Daniel Stilck Franca and James Watson. Efficient learning of ground and thermal states within phases of matter.
 Emilio Onorati, Cambyse Rouzé, Daniel Stilck França and James Watson. Provably Efficient Learning of Phases of Matter
6.2 Awards and Grants
Starting Packages
Cambyse Rouzé, Mirjam Weilenmann and Augustin Vanrietvelde have each been awarded a starting package in the context of the ANR ExcellenceS Program, on the STEP2 project sucessfully presented by IP Paris.
Best Poster Award
Tristan Nemoz has been granted the Best Poster Award (category Information Communication Electronics) at IP PAris PhD Day, on December 10 2023.
6.3 Quantum Hardware Security Workshop
The 2day workshop held at University of Edinburgh on Novepber 2324 and organized between Quriosity (Romain Alléaume, Peter Brown, Francesco Mazzoncini, Tristan Nemoz) and the team of Elham Kashefi at Quantum Software Lab (Elham Kashefi, Mina Doosti, Myrto Arapinis, Yao Ma, Abbas Poshtvan, Chrirag Wadhwa) has been extremly fruitful both scientifically and in the quality and friendlyness of the exchanges. We can see strong convergence, and possible synergies and collaborations, between our visions of the role that Quantum Cryptography can play in Hardware Security, as also expressed in 3.1 )
7 New results
7.1 Research axis 1: Quantum cryptography complexity and hardware frontiers
7.1.1 Prove the security of hybrid quantumcomputational cryptographic protocols by a reduction to a quantum to classical communication complexity gap
Participants: Romain Alléaume, Peter Brown, Francesco Mazzoncini.
In 11, we introduce an explicit construction for a key distribution protocol in the Quantum Computational Timelock (QCT) security model, where one assumes that computationally secure encryption may only be broken after a time much longer than the coherence time of available quantum memories. Taking advantage of the QCT assumptions, we build a key distribution protocol called HMQCT from the Hidden Matching problem for which there exists an exponential gap in oneway communication complexity between classical and quantum strategies. We establish that the security of HMQCT against arbitrary i.i.d. attacks can be reduced to the difficulty of solving the underlying Hidden Matching problem with classical information. Legitimate users, on the other hand, can use quantum communication, which gives them the possibility of sending multiple copies of the same quantum state while retaining an information advantage. This leads to an everlasting secure key distribution scheme over n bosonic modes. Such a level of security is unattainable with purely classical techniques. Remarkably, the scheme remains secure with up to $\frac{\sqrt{n}}{log\left(n\right)}$ input photons for each channel use, extending the functionalities and potentially outperforming QKD rates by several orders of magnitudes.
7.1.2 New selftesting constructions for deviceindependent cryptography
Participants: Lewis Wooltorton, Peter Brown, Roger Colbeck.
In 16, 15 we developed new constructions to certify properties of quantum systems using Belltests. In 16 we provide a method to stitch together bipartite Bellinequalties to construct useful multipartite Bellinequalities. We show that these new inequalities inherit certain selftesting prop erties of the original inequalities and we use this to produce protocols that achieve maximal deviceindependent randomness generation. In 15 we explore the complicated relationship between nonlocality and secretkey, showing that perfect secret keyrates can be achieved in deviceindependent quantum key distribution protocols with correlations that are arbitrarily close to classical. This involves developing a compact expression of a parameterized Bellinequality that represents all possible selftests of the maximally entangled state
7.1.3 Tight finitesize security proof for quantum key distribution protocols
Participants: Thomas Van Himbeeck, Peter Brown.
We have developed a new security proof framework for standard quantum keydistribution (QKD) protocols. The framework is: (i) generic, applying to all possible round based QKD protocols; (ii) tight, providing keyrates that are optimal for any given finite number of rounds up to leading order correction and (iii) computable, we develop convex optimization methods to compute the keyrates. This is achieved in part through the development of new entropic quantities that enable tight accounting of finitesize corrections. We expect the work to have significant impact on the future development of QKD protocols and security proofs.
7.2 Research axis 2: Multimode photonic systems for quantum information processing and communications
7.2.1 Quantum Coherent Communication and Digital Signal Processing
Participants: Romain Alléaume, Gjuillaume Ricard, Nicolas Fabre, Thomas Pousset, Yves Jaouën.
Building up on 21, we are performing a systematic analysis and model of excess noise in a quantum coherent communication channel, jointly operated with a classical coherent channel, taking into account the effect of digital signal processing. We are moreover validating our results with digital simulation along with experimental system demonstration. We are moreover studying how KramersKrönig coherent detection can be used in quantum communications.
7.2.2 Parallelizable Synthesis of Arbitrary SingleQubit Gates with Linear Optics and TimeFrequency Encoding
Participants: Romain Alléaume, Guillaume Ricard, Antoine Henry, Nadia Belabas.
In 5, we propose novel methods for the exact synthesis of singlequbit unitaries with high success probability and gate fidelity, considering both timebin and frequencybin encodings. The proposed schemes are experimentally implementable with a spectral linearoptical quantum computation (S LOQC) platform, composed of electrooptic phase modulators and phaseonly programmable filters (pulse shapers). We further investigate the parallelization of arbitrary singlequbit gates over multiple qubits with a compact experimental setup, both for spectral and temporal encodings. Our analysis positions spectral SLOQC as a promising platform to conduct massively parallel single qubit operations, with potential applications to quantum metrology and quantum tomography.
7.2.3 Limitations of GKPLDPC concatenated codes
Participants: Robert König, Cambyse Rouze.
In 10, we established an analytic upper bound on the faulttolerance threshold for concatenated GKPstabilizer codes with local update recovery. Our bound applies to noise channels that are tensor products of onemode beamsplitters with arbitrary environment states, capturing, in particular, photon loss occurring independently in each mode. It shows that for loss rates above a threshold given explicitly as a function of the locality of the recovery maps, encoded information is lost at an exponential rate.
7.3 Research axis 3: Mathematical foundations of quantum information
7.3.1 HigherOrder quantum computation
Participants: Augustin Vanrietvelde, Octave Mestoudjian.
We are developing finegrained type systems for the certification of quantum computation architectures, in particular those involving quantum control (quantum versions of the "if" clause) and indefinite causal order (application of operations in a superposed order).
7.3.2 Causal models in quantum theory
Participants: Augustin Vanrietvelde, Pablo Arrighi, Octave Mestoudjian.
We are investigating the relationship (and in particular the potential equivalence) between the causal structure of quantum dynamics and their compositional structure. We are finishing a proof (to be published soon) that there is an equivalence between the two in the case of local dynamics over a 1D array of quantum systems, at any range.
7.3.3 Learning complex quantum states
Participants: Marco Fanizza, Niklas Galke, Josep Lumbreras, Cambyse Rouzé, Andreas Winter, Emilio Onorati, Daniel Stilck França, James D Watson, Tim Möbus, Andreas Bluhm, Matthia C Caro, Abert H Werner, Cambyse Rouzé.
In 12, 12, 13, 27, we have developed robust, sample and computationally efficient quantum algorithms for tomography and learning of states and noise on manybody discrete and continuous variables quantum systems, including thermal and ground states of spin and Bosonic Hamiltonians, finitely correlated states, and Pauli noise channels with unknown underlying local structure.
7.3.4 Complexity of quantum Gibbs states
Participants: Ivan Bardet, Ángela Capel, Li Gao, Angelo Lucia, David PeresGarcía, Cambyse Rouzé, Jan Kochanowski, Alvaro Alhambra, Paul Gondolf.
We have kept on working on the complexity of Gibbs sampling algorithms and its applications to the stability of quantum simulation and the characterization of selfcorrecting quantum memories 22, 23. In particular, we have extended our previous result on the rapid mixing of Gibbs samplers from 2local to klocal interacting systems (the article is being finalized). In particular, we resolved an old open problem, namely whether the existence of a dissipative gap implies rapid mixing of the thermalization process. As regards to applications to quantum memories, our result implies that the entire class of quantum double models (including the 2D Toric code) reaches thermal equilibrium in logarithmic time, while the previous best thermalization time scaled linearly with the system size.
7.3.5 Improved quantum algorithm design from polynomial optimization
Participants: Thomas Van Himbeeck, Peter Brown.
A recently developed quantum algorithm known as the Quantum Singular Value Transform (QSVT) was shown to encompass the standard quantum algorithms, Shor/Grover etc., as special cases. Using the fact that the QSVT provides a correspondence between polynomials and certain families of quantum circuits, we develop methods to optimize these circuits (and hence the resulting algorithms) in terms of polynomial optimization and its resulting SDP relaxations. We also show to scale up these optimizations to largescale circuits, demonstrating its usefulness at scales necessary for quantum advantage.
8 Bilateral contracts and grants with industry
8.1 Bilateral contracts with industry
Orange Innvovation
Participants: Romain Alléaume, Yves Jaouën, Guillaume Ricard, PierreEnguerrand Verdier.
 CIFRE with Orange Innovation (Chatillon) on Discrete Variable Quantum Key Distribution and Time Multiplexing, PhD Student: PierreEnguerrand Verdier.
 CIFRE with Orange Innovation (Lannion) on Continous Variable Quantum Key Distribution and Wavelenght Division Multiplexing, PhD student: Marco Andersohn.
8.2 Grants with industry
Paris Region PhD Grant, collaboration with Quandela
Doctoral project of Guillaume Ricard, on Quatum Coherent Communications and Digital Signal Processing, Funded by Paris funded by Paris Region (region Ilede France) in the context of the Paris Region PhD call, with a planned collaboration with Quandela on noise mitigation in optical coherent quantum communications.
9 Partnerships and cooperations
9.1 European initiatives
9.1.1 Horizon Europe
Quantum Secure Network Partnership
Participants: Romain Alléaume, Peter Brown, Tristan Nemoz, Francesco Mazzoncini, Guillaume Ricard, Thomas Van Himbeeck, Thomas Pousset, Nicolas Fabre, Yves Jaouën.

Partner Institutions:
The Quantum Secure Networks Partnership (QSNP) aims at creating a sustainable European ecosystem in quantum cryptography and communication. Its 42 partners are worldleading academic groups, research and technology organizations (RTOs), quantum component and system spinoffs, cybersecurity providers, integrators, and telecommunication operators. The Partnership thus has the expertise in all technology development phases, from new designs to field deployment, making it ideal to carry out the future Specific Grant Agreement (SGA) projects.
 ICFOThe Institute of Photonic Sciences, Spain, (Coordinator)
 Centre National de la Recherche Scientifique, France
 Institut Polytechnique de Paris, France
 Technical University of Denmark, Denmark
 Universidad Politécnica de Madrid, Spain
 FriedrichAlexander University ErlangenNuremberg, Germany
 QuTech, at the Technical University Delft, Netherlands
 Università di Padova, Italy
 AIT Austrian Institute of Technology, Austria
 Palacky University Olomouc, Czech Rep.
 Instituto Superior Técnico, Portugal
 Universidade de Vigo, Spain
 Katholieke Universiteit Leuven, Belgium
 Universität Wien, Austria
 Université libre de Bruxelles, Belgium
 University of Warsaw, Poland
 University of Malta, Malta
 Institute of Communications and Computer Systems, Greece
 Universität Paderborn, Germany
 Inria Cosmiq team, France
 National and Kapodistrian University of Athens (NKUA),Greece
 Instituto De Telecomunicacoes, Portugal
 Politecnico di Bari, Italy,
 Fraunhofer HeinrichHertzInstitut, Germany
 Commissariat à l’Energie Atomique et aux Energies Alternatives, France
 Technische Universiteit Eindhoven, Netherland
 Interuniversity Microelectronics Centre, Belgium
 University College Cork, Ireland
 QuSide, Spain
 LuxQuanta, Spain
 Micro Photon Devices, Italy
 ThinkQuantum, Italy
 VPIphotonics GmbH, Germany
 Alea Quantum Technologies ApS, Denmark
 Q*Bird, Nertherlands
 Cryptonext Security, France
 Nokia Bell Labs, France
 Nextworks, Italy
 Deutsche Telekom, Germany
 Telefónica, Spain
 TIM S.p.A, Italy
 Orange SA,France

Contract ID:
HORIZONCL42022QUANTUM04SGA

Information on the Contract:
Special Grant Agreement in the context of a Federated Grant Agreement related to the Quantum Communications Pillar of the European Quantum Technology Flagship.

Duration:
March 2023 – August 2026

Description:
The Quantum Secure Networks Partnership (QSNP) is structured around three main Science and Technology (ST) pillars. The first two pillars, “Next Generation Protocols” and “Integration”, focus on frontier research and innovation led mostly by academic partners and RTOs. The third ST pillar “Use cases and Applications” aims at expanding the industrial and economic impact of QSN technologies and is mostly driven by companies. In order to achieve the specific objectives within each pillar and ensure that knowhow transfer and synergy between them are coherent and effective, QSNP has established ST activities corresponding to the three main layers of the technology value chain, “Components and Systems”, “Networks” and “Cryptography and Security”. Future SGA projects will be able to efficiently rely on this framework, in such a way that the ultimate objective of developing quantum communication technology for critical European infrastructures, such as EuroQCI, and private information and communication market sectors, will be achieved. QSNP will contribute to achieving European sovereignty in quantum technology for cybersecurity. At the same time, it will generate significant economic benefits to the whole society, including training a new generation of scientists and engineers, and the creation of hightech jobs in the rapidly growing quantum industry.

Role of Quriosity:
Quriosity has important participations on Quantum Coherent Communications System Design (WP2), Theory of Quantum Cryptography and in particular on DeviceIndependent Quantum Crypography (WP3), Hybrid QuantumComputational Cryptography (WP4 and WP6).
 Romain Alléaume leads one of the 3 pillars of the project, devoted to Integration (at hardware, middleware and cryptographic applications levels) and is member of the Executive Board of QSNP
 Romain Alléaume leads WP6 on Quantum and Classical Cryptography Integration.
 Romain Alléaume leads IP Paris contribution to WP4 on Quantum Cryptographic Protocols beyond QKD.
 Peter Brown leads IP Paris contribution to WP3 on DeviceIndependent QKD and QRNG.
 Several teams from IP Paris participates to the project: Quriosity, GTO, C2 at Telecom Paris and GRACE at LIX/Ecole Polytechnique.
9.1.2 Digital Europe
FranceQCI
Participants: Romain Alléaume, Peter Brown, Tristan Nemoz, Francesco Mazzoncini, Guillaume Ricard, Thomas Van Himbeeck.

Partner Institutions:
 Orange SA,France (Coordinator)
 InstitutMinesTelecom (IMT), France
 Airbus Defense and Space, France
 Thales SIX, France
 CryptoNext Security, France
 CNRS, France
 Thales Alenia Space, France
 CNRS Université Cote d'Azur, France
 Sorbonne Université, France
 WeLinQ SAS, France
 VeriQloud, France
 Direction des Services de la Navigation Aérienne, DSNA, France

Contract ID:
Project: 101091675 — FranceQCI — DIGITAL2021QCI01

Information on the Contract:
Call DIGITAL2021QCI01DEPLOYNATIONAL, Topic 1 from the Digital Europe Call on Quantum Communication Infrastructures.

Duration:
January 2023 – June 2025

Description:
The objective of the project is to test use cases of quantum communication technologies and to deploy advanced national quantum systems with existing communication networks in support of national QCI initiatives.

Role of Quriosity:
Quriosity, represented as IMT, contributes to network design and deployment (WP2), to security studies (WP3), and leads the activity on training (WP7) by coordinating the first executive education training offfer (in France) on quantum communication and cryptography, in collaboration with Sorbonne University and Orange Innovation.
9.1.3 Other european programs/initiatives
PETRUS
Participants: Romain Alléaume.

Partner Institutions:
 Deutsche Telekom
 Airbus Defense and Space, France
 Thales SIX, France
 Austrian Institute of Technology, AIT, Austria

Contract ID:
DIGITAL2021QCI01 Digital European Program under grant agreement no. PETRUS 101091719.

Information on the Contract:
PETRUS is the Coordination and Support Action for the national Quantum Communication Infrastructures.

Duration:
July 2023 – December 2025

Description:
The European Quantum Communication Infrastructure (EuroQCI)is to be rolled out in the EU Member States over the coming years. PETRUS supports the Digital Europe Program projects that aim to form the basis for a European industrial ecosystem for secure quantum technologies. PETRUS brings together former consortium leaders of the most relevant studies and projects on EuroQCI, bundles their experience and expertise and includes top experts from industry and the academic quantum community.

Role of Quriosity:
Romain Alléaume acts as Scientific Expert for the project.
9.2 National initiatives
PEPR QCommTestbed
Participants: Romain Alléaume, Peter Brown, Nicolas Fabre, Yves Jaouën, Tristan Nemoz, Thomas Pousset, Thomas Van Himbeeck.

Partner Institutions:
 InstitutMinesTelecom (IMT), France
 CNRS Université Cote d'Azur, France
 Sorbonne Université, France
 CEA Leti, France
 C2N, France
 Université ParisCité, France

Contract ID:
PC 4.3 « QCommTestbed » (Quantum communication testbeds)

Duration:
01/07/2022 – 30/06/2027

Description:
The objective of the QcommTestbed project is to lay the foundations for fiber optic and freespace quantum networks on a regional and longerterm national scale, making it possible to connect systems including quantum elements (transmitters and receivers, processors, sensors) via repeater nodes. The project also aims to make decisive advances in the TRL of quantum communication systems, and also in their security evaluation and testing, to pave the way for their wider adoption and ubiquituous deployment.

Role of Quriosity:
 Demonstration of ITS secure communication over a single fiber, based on joint CVQKD and classical communication integration.
 Performance and Cost of LongTerm Secure Storage based on CVQKD
 Vulnerability analysis of a QKD (VAN) system. Definition of an evaluation methodology (based on the Common Criteria.
 Experimental Demonstration of Mulimode Frequencyencoded Key Distribution in the QCT model
9.3 Regional initiatives
ParisRegionQCI
Participants: Romain Alléaume, Francesco Mazzoncini, Thomas Van Himbeeck.

Partner Institutions:
 Orange SA,France (Coordinator)
 LTCI, Telecom Paris, France
 Thales SIX, France
 Thales Research and Technology (TRT), France
 CryptoNext Security, France
 CNRS, France
 LIP6, Sorbonne Université, France
 VeriQloud, France
 NOKIA Bell Labs, France
 Kets Quantum, UK
 Laboratoire Charles Fabry, France

Information on the Contract:
Project funded as a SIRTEQ Synergy action, funded by Paris Region

Duration:
January 2021 – Dec 2023

Description:
The ParisRegionQCI project revolves around the development and operation of a fiber network quantum in Paris Region (ÎledeFrance ). The creation of such a network is envisaged as part of the project H2020 “OpenQKD”, which is a precursor of the “European Quantum Communication Infrastructure”, EuroQCI, planned as part of the next framework program of the European Commission, and which will include terrestrial and space segments.

Role of Quriosity:
Quriosity, as part of Telecom Paris has been to contributes to network design and deployment, and to lead the security study, with a focus on the security advantage that could (or could not) be achieved using QKD, in different cryptographic constructions aiming to ensure secure communication security services.
10 Dissemination
10.1 Promoting scientific activities
10.1.1 Scientific events: organisation
Member of the organizing committees
 Romain Alléaume member of the organization committee of the LTCI Research Day, Nov 24 2023.
 Romain Alléaume coorganized the Quantum Hardware Security Workshop at Edinburgh, with the Quantum Software Lab, 2223 November 2023.
10.1.2 Scientific events: selection
Member of the conference program committees
 Romain Alléaume TPC of TPC IEEE ICC'23  SAC11 QCIT Track
 Cambyse Rouzé TPC of QIP 2024
Reviewer
 Romain Alléaume for TQC (subreviewer)
10.1.3 Journal
Reviewer  reviewing activities
 Romain Alléaume for Science Advances
10.1.4 Invited talks
 Peter Brown , Tight finitesize security proof of QKD, 5th edition of security of QKD workshop, IQC Waterloo, Canada. (September 2023).
 Peter Brown , On the computation of deviceindependent quantities, 5th edition of security of QKD workshop, IQC Waterloo, Canada. (September 2023).
 Peter Brown , Tight finitesize security proof of QKD, Workshop on Gaussian and nonGaussian Quantum Correlations, Copenhagen Denmark (November 2023).
 Romain Alléaume , Quantum Secure Network Partnership Integration Pillar, CLP Days, ICFO, Barcelona (25 Mai 2023).
 Romain Alléaume , Slow Information, Workshop On Quantum Ecology, Leyzin Switzerland (July 2023).
10.1.5 Leadership within the scientific community
 Romain Alléaume is one of the 3 Pillar Leaders, WP6 Leader and a member of the Executive Board of the Quantum Secure Network Partnership Flagship Project.
10.1.6 Scientific expertise
 Romain Alléaume , Member of the Alliance Quantum Evaluation Committee, at NSERC, in charge of scientific evaluation of Canada Quantum Grants Applications (4 sessions per year).
 Romain Alléaume , Member of the Evaluation Committee attributing the Plan Quantique PHD Grants, for the Paris Centre for Quantum Technologies (Sorbonne University, March 14 2023).
 Romain Alléaume , Member of the Evaluation Committee for IP Paris PhD Track in Qauntum Science and Technology, February, 14 2023.
 Romain Alléaume , Member of the Evaluation Committee for the admission of Polytecniciens, at Telecom Paris (double degree)
 Romain Alléaume , Member of the recruitement committee for the position at Ecole Polytechnique, Professor Monge in Quantum Computing, May 17, 2023
 Romain Alléaume , Member of the recruitement committee for the Assistant/Associate Professor position in Quantum Computing and Quantum Information Procesing at Telecom Paris, May 9, 2023
10.1.7 Research administration
 Romain Alléaume , Member of Comité Directeur of the Network and Computer Science Departement of Telecom Paris (Infres), acting as Infres Research Delegate, (2023)..
 Romain Alléaume , Deputy director of Laboratoire de Traitement and Communication de l'Information LTCI and member of LTCI board (bureau) (2023).
 Romain Alléaume , Member of Conseil Scientifique du LTCI (2023).
 Romain Alléaume , Member of Conseil du LTCI (2021).
 Romain Alléaume , Member of IP Paris IDIA Department bureau, (2023).
 Romain Alléaume , Member of the Committee in charge of supervising STEP2 program (ANR ExcellenceS program) funding allocation in Foundation of Computer Science (including Quantum Computer Science).
 Romain Alléaume is (2020–) an executive committee member of the Quantum center of Saclay. The center coordinates the French strategy for quantum technologies at the scale of Univ. ParisSaclay and Institut Polytechnique de Paris.
10.2 Teaching  Supervision  Juries
All teaching durations are given in hetd = "heures équivalent TD".
10.2.1 Teaching
L3 courses, at Telecom Paris
 Romain Alléaume is teaching in PHY101: Introduction to Quantum Technologies. Courses: 9 hetd $\sim $110 students, TD: 27 hetd $\sim $25 students.
 Peter Brown , Francesco Mazzoncini, Tristan Nemoz, Thomas Van Himbeeck, Programming a real quantum computer, 6+6+6+6 hetd, 9 students.
M1 courses at Telecom Paris
 Peter Brown , Continuous Optimization and Numerical Analysis, $\sim $30 students, 24 hetd.
 Peter Brown and Romain Alléaume , Introduction to quantum information and quantum computing, $\sim $25 students, 13.5 + 18 hetd.
M2 courses in the Quantum Engineering Program at Telecom Paris, (in collaboration with ARTeQ, ENS ParisSaclay)
 Romain Alléaume coordinates (2017) the Quantum Engineering Program, a Access PhD Program (M2 level) on Quantum Maths and TCS, and Quantum Technologies, that is currently held in collaboration with ARTeQ (ENS ParisSaclay) and M2 QDCS (Université ParisSaclay).
 Peter Brown and Romain Alléaume , Quantum information tutorials, $\sim $10 students, M2 QEng, 6+6 hetd.
 Peter Brown and Romain Alléaume , Quantum information and quantum cryptography, M2 QEng Telecom Paris and ARTeQ, $\sim $30 students, 27+22.5 hetd.
 Cambyse Rouzé has started a new Quantum Computing course for the students of QEng and ARTeQ.
 This course on the exploration of nearterm quantum advantage delves into contemporary advancements in the theory of quantum computing and quantum information processing. It covers a spectrum of topics, ranging from demonstrating quantum advantage in sampling tasks with a specific focus on BosonSampling experiments, to exploring variational quantum algorithms tailored for solving constrained satisfaction problems and their interplay with adiabatic quantum algorithms. Additionally, participants were introduced to quantum state tomography, with the study of cuttingedge shadow tomography algorithms.
 Taught 16 hetd, for $\sim $30 students
Teaching in other contexts and programs
 Romain Alléaume taught a short course on Quantum Cryptography Theory in the M1 Quantum Technologies atCentraleSupélec 4,5 hetd, to $\sim $25 students.
 Peter Brown gave an Invited lecture at Padova QCOMMS summer school (May 2023) on Deviceindependent quantum key distribution.
 Thomas Van Himbeeck gave an Invited lecture at Padova QCOMMS summer school (May 2023) on Finitesize effects in quantum key distribution.
10.2.2 Supervision
PhD Supervisions
 Tristan Nemoz, Computational models in quantum cryptography (Romain Alléaume and Peter Brown ), (2022)
 Tristan Le Roy Deloison, Deviceindependent Quantum Key Distribution (Omar Fawzi [QINFO] and Peter Brown ), (2023)
 Guillaume Ricard, Quantum Coherent Communications and Digital Signal Processing, (Romain Alléaume and Yves Jaouën), (2021)
 Francesco Mazzoncini, Communications quantiques multimodes et cryptographie hybride, (Romain Alléaume and Sylvain Gigan [ENS Paris]), (2020).
 PierreEnguerrand Verdier, Cryptographie quantique à variables discrètes : caractérisation de systèmes, déploiement opérationnel sur réseaux télécom et applications, (Thomas Rivera [Orange] and Romain Alléaume ), (2022).
 Thomas Pousset, Protocoles de communications quantiques en variables tempsfréquence, (Nicolas Fabre and Romain Alléaume ), (2023).
 Octave Mestoudjian, La notion de soussystème en informatique quantique, (Pablo Arrighi (équipe Inria Quacs) and Augustin Vanrietvelde ), (2023).
 Jan Kochanowski, Analytic and algorithmic approaches on strong data processing in complex quantum systems, (Omar Fawzi [QINFO] and Cambyse Rouzé ), (2023)
Master, PhD Track and L3 Students supervisions
 Rola Saidi, Evaluating crosstalk on quantum computers, QEng PRIM M2 project, (Peter Brown ).
 Kriss Lady Stephanie Gutierrez Anco, Rényi intrinsic randomness, QEng PRIM M2 project, (Peter Brown ).
 Tristan Philippe, Ressource theory of quantum antecents to LWE, QEng PRIM M2 project, (Romain Alléaume ).
 Thomas Vinet, Distinguishing unitary gates using controlization, QEng PRIM M2 project, (Augustin Vanrietvelde )
 Idris Delsol, Quantum error correction using Cat Qubits, QEng PRIM M2 project, (Cambyse Rouzé)
 Ali Almasi, Positive but not completely positive maps, M1 PhD Track research project, (Peter Brown )
 Timothé Bramas, Programming a LDPCbased Error Correction stack for CVQKD, ENSTA M1 research internship, (Romain Alléaume )
 Evdokia Gneusheva, Secret keyrates vs. entanglement, Polytechnique Bachelor L3 research internship, (Peter Brown )
10.2.3 Juries
PhD juries
(Apart from our own students PhD juries)
 Romain Alléaume , Rapporteur for the PhD Defense of Yao Ma, Quantum Hardware Security and Nearterm Applications December 4 2023, Sorbonne University.
 Peter Brown , Examinator for the PhD Defense of Xavier Valcarce, Device independent certification: quantum resources and quantum key distribution, Université Paris Saclay, May 17 2023.
10.3 Popularization
10.3.1 Articles and contents
 Romain Alléaume , Peter Brown, Cambyse Rouzé contributed to the writing of a wide audience presentation article of Quriosity, for the Inria website.
 Romain Alléaume was interviewed by Isabelle Mauriac, for Telecom Paris Ideas, on the scaling of quantum advantage, leading to short video and a podcast .
10.3.2 Interventions
 Romain Alléaume gave a talk "Nouvelles Quantiques de Télécom Paris", and participated to an invited panel at the Prix des Technologlies Numériques, October 17, 2023.
 Romain Alléaume gave a presentation to a delegation from University of Hannover, on Quantum Research activites at Quriosity, on March 12, 2023.
 Romain Alléaume gave an invited talk, on Quriosity, at Telecom Paris Journées Partenaires Entreprises, on March 16, 2023;
 Romain Alléaume gave a talk on Quantum Computing to MEDEF Essonne, at ENSParis Saclay, on October 20, 2023.
11 Scientific production
11.1 Major publications
 1 miscHybrid Quantum Cryptography from Communication Complexity.November 2023HAL
 2 articleLimitations of variational quantum algorithms: a quantum optimal transport approach.PRX Quantum4January 2023, 010309HALDOI
 3 miscDeviceindependent quantum key distribution with arbitrarily small nonlocality.September 2023HAL
11.2 Publications of the year
International journals
 4 articleCoarse Ricci curvature of quantum channels.Journal of Functional AnalysisJanuary 2024, 110336HALDOI
 5 articleParallelizable Synthesis of Arbitrary SingleQubit Gates with Linear Optics and TimeFrequency Encoding.Physical Review A1076June 2023, 062610HALDOIback to textback to text
 6 articleQuantum Differential Privacy: An Information Theory Perspective.IEEE Transactions on Information Theory699September 2023, 57715787HALDOI
 7 articleLimitations of variational quantum algorithms: a quantum optimal transport approach.PRX Quantum4January 2023, 010309HALDOI
Reports & preprints
 8 miscInformationtheoretic generalization bounds for learning from quantum data.November 2023HAL
 9 miscLearning finitely correlated states: stability of the spectral reconstruction.2023HAL
 10 miscLimitations of local update recovery in stabilizerGKP codes: a quantum optimal transport approach.2023HALDOIback to text
 11 miscHybrid Quantum Cryptography from Communication Complexity.November 2023HALback to text
 12 miscProvably Efficient Learning of Phases of Matter via Dissipative Evolutions.November 2023HALDOIback to textback to text
 13 miscEfficient learning of the structure and parameters of local Pauli noise channels.2023HALDOIback to text
 14 miscSemidefinite programming relaxations for quantum correlations.2023HAL
 15 miscDeviceindependent quantum key distribution with arbitrarily small nonlocality.September 2023HALback to textback to text
 16 miscExpanding bipartite Bell inequalities for maximum multipartite randomness.August 2023HALback to textback to text
11.3 Cited publications
 17 inproceedingsThe computational complexity of linear optics.Proceedings of the fortythird annual ACM symposium on Theory of computing2011, 333342back to text
 18 articleComputational advantage from quantumcontrolled ordering of gates.Physical review letters113252014, 250402DOIback to text
 19 articleQuantum circuits cannot control unknown operations.New Journal of Physics1692014, 093026DOIback to text
 20 articlePractical deviceindependent quantum cryptography via entropy accumulation.Nature communications912018, 459back to text
 21 articleSymbiotic joint operation of quantum and classical coherent communications.arXiv preprint arXiv:2202.069422022back to textback to text
 22 articleEntropy decay for Davies semigroups of a one dimensional quantum lattice.arXiv preprint arXiv:2112.006012021back to textback to textback to text
 23 articleRapid thermalization of spin chain commuting Hamiltonians.arXiv preprint arXiv:2112.005932021back to textback to text
 24 articleApproximate Tensorization of the Relative Entropy for Noncommuting Conditional Expectations.Annales Henri Poincaré2312021, 101140back to text
 25 articleGroup Transference Techniques for the Estimation of the Decoherence Times and Capacities of Quantum Markov Semigroups.IEEE Transactions on Information Theory6752021, 28782909DOIback to text
 26 articleQuantum causal models.DOIback to text
 27 articleClassical shadow tomography for continuous variables quantum systems.arXiv preprint arXiv:2211.075782022back to text
 28 articleComputing conditional entropies for quantum correlations.Nature communications1212021, 112back to textback to text
 29 articleDeviceindependent lower bounds on the conditional von Neumann entropy.arXiv preprint arXiv:2106.136922021back to textback to text
 30 articleMultimode entanglement in reconfigurable graph states using optical frequency combs.Nature communications812017, 19back to text
 31 articleThe modified logarithmic Sobolev inequality for quantum spin systems: classical and commuting nearest neighbour interactions, (QIP talk, presented at ICMP).arXiv:2009.118172020back to textback to textback to text
 32 inproceedingsOptimal Mixing of Glauber Dynamics: Entropy Factorization via HighDimensional Expansion.Proceedings of the 53rd Annual ACM SIGACT Symposium on Theory of ComputingSTOC 2021New York, NY, USAVirtual, ItalyAssociation for Computing Machinery2021, 1537?1550URL: https://doi.org/10.1145/3406325.3451035DOIback to text
 33 articleStrong Converse Bounds in Quantum Network Information Theory.IEEE Transactions on Information Theory6742021, 22692292DOIback to text
 34 articleQuantum computations without definite causal structure.Physical Review A8822013, 022318DOIback to text
 35 articleEntropy accumulation.Communications in Mathematical Physics3792020, 147back to text
 36 articleThe Entropy Zoo.https://phfaist.com/entropyzooback to text
 37 articleSumofSquares proofs of logarithmic Sobolev inequalities on finite Markov chains.arXiv preprint arXiv:2101.049882021back to text
 38 articleComplete Entropic Inequalities for Quantum Markov Chains.Archive for Rational Mechanics and Analysis2451may 2022, 183238URL: https://doi.org/10.1007%2Fs00205022017851DOIback to text
 39 inproceedingsThe Entropy PhotonNumber Inequality and its consequences.2008 Information Theory and Applications Workshop2008, 128130DOIback to text
 40 articleFidelity Bounds for DeviceIndependent Advantage Distillation.arXiv preprint arXiv:2105.032132021back to text
 41 articlePredicting many properties of a quantum system from very few measurements.Nature Physics1610June 2020, 10501057URL: https://doi.org/10.1038/s4156702009327DOIback to text
 42 articleProvably efficient machine learning for quantum manybody problems.arXiv preprint arXiv:2106.126272021back to text
 43 articleFundamentals of Coherent Optical Fiber Communications.in Journal of Lightwave Technology vol. 34, N¬∞12016back to text
 44 articleA categorical semantics for causal structure.Logical Methods in Computer ScienceVolume 15, Issue 32019DOIback to text
 45 articleRobust Bell inequalities from communication complexity.Quantum22018, 72back to text
 46 articleCausal and compositional structure of unitary transformations.Quantum52021, 511DOIback to text
 47 articleDeviceindependent quantum key distribution.arXiv preprint arXiv:2109.146002021back to text
 48 inproceedingsQuantum oneway communication can be exponentially stronger than classical communication.Proceedings of the fortythird annual ACM symposium on Theory of computing2011, 3140back to text
 49 articleSelftesting quantum randomnumber generator based on an energy bound.Physical Review A10062019, 062338back to text
 50 articleComputing secure key rates for quantum cryptography with untrusted devices.npj Quantum Information712021, 16back to text
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