@inproceedings{RamsauerKiszkaLohmannetal., author = {Ramsauer, Ralf and Kiszka, Jan and Lohmann, Daniel and Mauerer, Wolfgang}, title = {Look Mum, no VM Exits! (Almost)}, series = {Proceedings of the 13th Annual Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT '17)}, booktitle = {Proceedings of the 13th Annual Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT '17)}, doi = {10.48550/arXiv.1705.06932}, abstract = {Multi-core CPUs are a standard component in many modern embedded systems. Their virtualisation extensions enable the isolation of services, and gain popularity to implement mixed-criticality or otherwise split systems. We present Jailhouse, a Linux-based, OS-agnostic partitioning hypervisor that uses novel architectural approaches to combine Linux, a powerful general-purpose system, with strictly isolated special-purpose components. Our design goals favour simplicity over features, establish a minimal code base, and minimise hypervisor activity. Direct assignment of hardware to guests, together with a deferred initialisation scheme, offloads any complex hardware handling and bootstrapping issues from the hypervisor to the general purpose OS. The hypervisor establishes isolated domains that directly access physical resources without the need for emulation or paravirtualisation. This retains, with negligible system overhead, Linux's feature-richness in uncritical parts, while frugal safety and real-time critical workloads execute in isolated, safe domains.}, language = {en} } @inproceedings{PichaBradaRamsaueretal., author = {Picha, Petr and Brada, Premek and Ramsauer, Ralf and Mauerer, Wolfgang}, title = {Towards Architect's Activity Detection through a Common Model for Project Pattern Analysis}, series = {First International Workshop on the Social and Organization Dimensions of Software, 5-7 April 2017, Gothenburg, Sweden}, booktitle = {First International Workshop on the Social and Organization Dimensions of Software, 5-7 April 2017, Gothenburg, Sweden}, publisher = {IEEE}, doi = {10.1109/ICSAW.2017.46}, pages = {175 -- 178}, abstract = {Software development projects leave a large amount of data in repositories of Application Lifecycle Management (ALM) tools. These data contain detailed histories of their respective projects, their results and decisions made along the way. Analysis of such data helps uncover various interesting facts about projects, e.g. their socio-technical structures and the actual (vs. purported) roles of team members. Based on experiences with tools supporting our research we are convinced that it is feasible to consolidate data from different ALM tools, tapping into the situation common in real-life projects. In this paper we report on our work towards a shared common data model and tool integration aimed at improved project analysis. We discuss how this can help in the identification of architects in the project organizational structures, their activity patterns and collaboration with other team roles.}, language = {en} } @inproceedings{RamsauerLohmannMauerer, author = {Ramsauer, Ralf and Lohmann, Daniel and Mauerer, Wolfgang}, title = {Observing Custom Software Modifications: A Quantitative Approach of Tracking the Evolution of Patch Stacks}, series = {Proceedings of the 12th International Symposium on Open Collaboration (OpenSym '16)}, booktitle = {Proceedings of the 12th International Symposium on Open Collaboration (OpenSym '16)}, editor = {Wassermann, Tony}, publisher = {ACM}, address = {New York}, doi = {10.1145/2957792.2957810}, pages = {1 -- 4}, abstract = {Modifications to open-source software (OSS) are often provided in the form of "patch stacks" -- sets of changes (patches) that modify a given body of source code. Maintaining patch stacks over extended periods of time is problematic when the underlying base project changes frequently. This necessitates a continuous and engineering-intensive adaptation of the stack. Nonetheless, long-term maintenance is an important problem for changes that are not integrated into projects, for instance when they are controversial or only of value to a limited group of users. We present and implement a methodology to systematically examine the temporal evolution of patch stacks, track non-functional properties like integrability and maintainability, and estimate the eventual economic and engineering effort required to successfully develop and maintain patch stacks. Our results provide a basis for quantitative research on patch stacks, including statistical analyses and other methods that lead to actionable advice on the construction and long-term maintenance of custom extensions to OSS.}, language = {en} } @inproceedings{HofmannRiehleKolassaetal., author = {Hofmann, Gottfried and Riehle, Dirk and Kolassa, Carsten and Mauerer, Wolfgang}, title = {A Dual Model of Open Source License Growth}, series = {Open Source Software: Quality Verification : 9th IFIP WG 2.13 International Conference, OSS 2013, Koper-Capodistria, Slovenia, June 25-28, 2013, Proceedings}, volume = {404}, booktitle = {Open Source Software: Quality Verification : 9th IFIP WG 2.13 International Conference, OSS 2013, Koper-Capodistria, Slovenia, June 25-28, 2013, Proceedings}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/978-3-642-38928-3_18}, pages = {245 -- 256}, abstract = {Every open source project needs to decide on an open source license. This decision is of high economic relevance: Just which license is the best one to help the project grow and attract a community? The most common question is: Should the project choose a restrictive (reciprocal) license or a more permissive one? As an important step towards answering this question, this paper analyses actual license choice and correlated project growth from ten years of open source projects. It provides closed analytical models and finds that around 2001 a reversal in license choice occurred from restrictive towards permissive licenses.}, language = {en} } @misc{MauererWagner, author = {Mauerer, Wolfgang and Wagner, Daniel}, title = {Cyclic Tests Unleashed: Large-Scale RT Analysis with Jitterdebugger}, series = {Open Source Summit, North America, 17.07.2019}, journal = {Open Source Summit, North America, 17.07.2019}, language = {en} } @inproceedings{Mauerer, author = {Mauerer, Wolfgang}, title = {Are any big brothers watching you, and if yes, what can they tell about Debian}, series = {DebConf18 Hsinchu, Taiwan}, booktitle = {DebConf18 Hsinchu, Taiwan}, abstract = {Debian, as a collection of software packages and components, is known to be one of the largest software projects in the history of mankind. Combined with a traceable history over many years, the artefacts created by Debian developers and users make it one of science's favourite targets to quantitatively or qualitatively understand how real-world software development works (or does not), how people collaborate, and many other other related questions. Unfortunately, while scientists make ample use of the resources and artefacts created by FLOSS and friends, the exchange of insights and ideas does not seem to extend in both directions: Developers, users and integrators are often unaware of results obtained in science. This talk will introduce the Debian community to a selection the most important results obtained by scientific (software engineering) research, with a special focus on large-scale socio-technical analysis of projects like Debian, and the possible implications and improvements these may bring to Debian development itself.}, language = {en} } @misc{MauererRamsauer, author = {Mauerer, Wolfgang and Ramsauer, Ralf}, title = {Torturing Git for Fun and Profit}, series = {Microsoft Developer Meetup Regensburg 02.04.2019}, journal = {Microsoft Developer Meetup Regensburg 02.04.2019}, abstract = {In diesem Talk blicken Prof. Dr. Wolfgang Mauerer und Ralf Ramsauer unter die Haube des verteilten Versionskontrollsystems Git. Neben einer genauen Beschreibung der Strukturen und Plumbing APIs, mit denen Git intern Commits erzeugt und verkn{\"u}pft, gehen die Vortragenden auch auf n{\"u}tzliche Features und Standards ein, welche die Kollaborition in großen Open-Source Projekten erleichtern.}, language = {en} } @article{FeldRochGaboretal., author = {Feld, Sebastian and Roch, Christoph and Gabor, Thomas and Seidel, Christian and Neukart, Florian and Galter, Isabella and Mauerer, Wolfgang and Linnhoff-Popien, Claudia}, title = {A Hybrid Solution Method for the Capacitated Vehicle Routing Problem Using a Quantum Annealer}, series = {Frontiers in ICT}, volume = {6}, journal = {Frontiers in ICT}, publisher = {Frontiers}, doi = {10.3389/fict.2019.00013}, pages = {1 -- 13}, abstract = {he Capacitated Vehicle Routing Problem (CVRP) is an NP-optimization problem (NPO) that has been of great interest for decades for both, science and industry. The CVRP is a variant of the vehicle routing problem characterized by capacity constrained vehicles. The aim is to plan tours for vehicles to supply a given number of customers as efficiently as possible. The problem is the combinatorial explosion of possible solutions, which increases superexponentially with the number of customers. Classical solutions provide good approximations to the globally optimal solution. D-Wave's quantum annealer is a machine designed to solve optimization problems. This machine uses quantum effects to speed up computation time compared to classic computers. The problem on solving the CVRP on the quantum annealer is the particular formulation of the optimization problem. For this, it has to be mapped onto a quadratic unconstrained binary optimization (QUBO) problem. Complex optimization problems such as the CVRP can be translated to smaller subproblems and thus enable a sequential solution of the partitioned problem. This work presents a quantum-classic hybrid solution method for the CVRP. It clarifies whether the implementation of such a method pays off in comparison to existing classical solution methods regarding computation time and solution quality. Several approaches to solving the CVRP are elaborated, the arising problems are discussed, and the results are evaluated in terms of solution quality and computation time.}, language = {en} } @inproceedings{RamsauerBulwahnLohmannetal., author = {Ramsauer, Ralf and Bulwahn, Lukas and Lohmann, Daniel and Mauerer, Wolfgang}, title = {The Sound of Silence : Mining Security Vulnerabilities from Secret Integration Channels in Open-Source Projects}, series = {Proceedings of the 2020 ACM SIGSAC Conference on Cloud Computing Security Workshop: 09.11.2020, virtual event}, booktitle = {Proceedings of the 2020 ACM SIGSAC Conference on Cloud Computing Security Workshop: 09.11.2020, virtual event}, editor = {Zhang, Yinqian and Sion, Radu}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {9781450380843}, doi = {10.1145/3411495.3421360}, pages = {147 -- 157}, abstract = {Public development processes are a key characteristic of open source projects. However, fixes for vulnerabilities are usually discussed privately among a small group of trusted maintainers, and integrated without prior public involvement. This is supposed to prevent early disclosure, and cope with embargo and non-disclosure agreement (NDA) rules. While regular development activities leave publicly available traces, fixes for vulnerabilities that bypass the standard process do not. We present a data-mining based approach to detect code fragments that arise from such infringements of the standard process. By systematically mapping public development artefacts to source code repositories, we can exclude regular process activities, and infer irregularities that stem from non-public integration channels. For the Linux kernel, the most crucial component of many systems, we apply our method to a period of seven months before the release of Linux 5.4. We find 29 commits that address 12 vulnerabilities. For these vulnerabilities, our approach provides a temporal advantage of 2 to 179 days to design exploits before public disclosure takes place, and fixes are rolled out. Established responsible disclosure approaches in open development processes are supposed to limit premature visibility of security vulnerabilities. However, our approach shows that, instead, they open additional possibilities to uncover such changes that thwart the very premise. We conclude by discussing implications and partial countermeasures.}, language = {en} } @inproceedings{MauererSilberhorn, author = {Mauerer, Wolfgang and Silberhorn, Christine}, title = {Numerical Analysis of Parametric Downconversion}, series = {AIP Conference Proceedings}, volume = {1110}, booktitle = {AIP Conference Proceedings}, number = {1}, publisher = {AIP Publishing}, doi = {10.1063/1.3131312}, abstract = {Parametric downconversion (PDC) is a popular technique to produce twin beams of photons that are entangled in multiple degrees of freedom. The generated states form the basis for numerous applications that require entanglement. An exact quantification of this resource is therefore essential, for instance for quantum cryptography that relies on a complete knowledge of the correlation contained in the state. While the determination of an entanglement monotone for the PDC process is only possible analytically in special cases, an exact calculation must usually be performed numerically. Recent work by Mikhailova et al. [2] analyses a certain class of PDC states for which the concurrence entanglement measure can be obtained by an analytical approximation. In this contribution, we analyse the validity of the approximation by comparison with exact numerical methods.}, language = {en} } @misc{Mauerer, author = {Mauerer, Wolfgang}, title = {OSS Community, Health and Ecosystem Research: Theory and, or Theory versus Practice?}, series = {2nd International Workshop on Software Health (SoHEAL@ICSE, Montr{\´e}al), 2019}, journal = {2nd International Workshop on Software Health (SoHEAL@ICSE, Montr{\´e}al), 2019}, language = {en} } @inproceedings{RamsauerLohmannMauerer, author = {Ramsauer, Ralf and Lohmann, Daniel and Mauerer, Wolfgang}, title = {System Software for Manufacturing Systems}, series = {Proc. First European Advances in Digital Transformation Conference, (2018)}, booktitle = {Proc. First European Advances in Digital Transformation Conference, (2018)}, language = {en} } @inproceedings{Mauerer, author = {Mauerer, Wolfgang}, title = {A Virtual Computing Platform for the Internet of Things}, series = {Embedded Linux Conference (San Diego), 2016}, booktitle = {Embedded Linux Conference (San Diego), 2016}, language = {de} } @inproceedings{WinterspergerSafiMauerer, author = {Wintersperger, Karen and Safi, Hila and Mauerer, Wolfgang}, title = {QPU-System Co-Design for Quantum HPC Accelerators?}, series = {Architecture of Computing Systems: 35th International Conference, ARCS 2022, Heilbronn, Germany, September 13-15, 2022, Proceedings}, booktitle = {Architecture of Computing Systems: 35th International Conference, ARCS 2022, Heilbronn, Germany, September 13-15, 2022, Proceedings}, publisher = {Springer}, isbn = {978-3-031-21866-8}, doi = {10.1007/978-3-031-21867-5_7}, pages = {100 -- 114}, abstract = {The use of quantum processing units (QPUs) promises speed-ups for solving computational problems, but the quantum devices currently available possess only a very limited number of qubits and suffer from considerable imperfections. One possibility to progress towards practical utility is to use a co-design approach: Problem formulation and algorithm, but also the physical QPU properties are tailored to the specific application. Since QPUs will likely be used as accelerators for classical computers, details of systemic integration into existing architectures are another lever to influence and improve the practical utility of QPUs. In this work, we investigate the influence of different parameters on the runtime of quantum programs on tailored hybrid CPU-QPU-systems. We study the influence of communication times between CPU and QPU, how adapting QPU designs influences quantum and overall execution performance, and how these factors interact. Using a simple model that allows for estimating which design choices should be subjected to optimisation for a given task, we provide an intuition to the HPC community on potentials and limitations of co-design approaches. We also discuss physical limitations for implementing the proposed changes on real quantum hardware devices.}, language = {en} } @unpublished{MurrMauerer, author = {Murr, Florian and Mauerer, Wolfgang}, title = {McFSM: Near Turing-Complete Finite-State Based Programming}, pages = {11}, abstract = {Finite state machines (FSMs) are an appealing mechanism for simple practical computations: They lend themselves to very effcient and deterministic implementation, are easy to understand, and allow for formally proving many properties of interest. Unfortunately, their computational power is deemed insuffcient for many tasks, and their usefulness has been further hampered by the state space explosion problem and other issues when na{\"i}vely trying to scale them to sizes large enough for many real-life applications. This paper expounds on theory and implementation of multiple coupled fnite state machines (McFSMs), a novel mechanism that combines benefits of FSMs with near Turing-complete, practical computing power, and that was designed from the ground up to support static analysis and reasoning. We develop an elaborate category-theoretical foundation based on non-deterministic Mealy machines, which gives a suitable algebraic description for novel ways of blending di\#erent computing models. Our experience is based on a domain specific language and an integrated development environment that can compile McFSM models to multiple target languages, applying it to use-cases based on industrial scenarios. We discuss properties and advantages of McFSMs, explain how the mechanism can interact with real-world systems and existing code without sacrificing provability, determinism or performance. We discuss how McFSMs can be used to replace and improve on commonly employed programming patterns, and show how their effcient handling of large state spaces enables them to be used as core building blocks for distributed, safety critical, and real-time systems of industrial complexity, which contributes to the longdesired goal of providing executable specifications.}, language = {en} } @inproceedings{MauererKlessingerScherzinger, author = {Mauerer, Wolfgang and Klessinger, Stefan and Scherzinger, Stefanie}, title = {Beyond the badge: reproducibility engineering as a lifetime skill}, series = {Proceedings 4th International Workshop on Software Engineering Education for the Next Generation SEENG 2022, 17 May 2022, Pittsburgh, PA, USA}, booktitle = {Proceedings 4th International Workshop on Software Engineering Education for the Next Generation SEENG 2022, 17 May 2022, Pittsburgh, PA, USA}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {9781450393362}, doi = {10.1145/3528231.3528359}, pages = {1 -- 4}, abstract = {Ascertaining reproducibility of scientific experiments is receiving increased attention across disciplines. We argue that the necessary skills are important beyond pure scientific utility, and that they should be taught as part of software engineering (SWE) education. They serve a dual purpose: Apart from acquiring the coveted badges assigned to reproducible research, reproducibility engineering is a lifetime skill for a professional industrial career in computer science. SWE curricula seem an ideal fit for conveying such capabilities, yet they require some extensions, especially given that even at flagship conferences like ICSE, only slightly more than one-third of the technical papers (at the 2021 edition) receive recognition for artefact reusability. Knowledge and capabilities in setting up engineering environments that allow for reproducing artefacts and results over decades (a standard requirement in many traditional engineering disciplines), writing semi-literate commit messages that document crucial steps of a decision-making process and that are tightly coupled with code, or sustainably taming dynamic, quickly changing software dependencies, to name a few: They all contribute to solving the scientific reproducibility crisis, and enable software engineers to build sustainable, long-term maintainable, software-intensive, industrial systems. We propose to teach these skills at the undergraduate level, on par with traditional SWE topics.}, language = {en} } @inproceedings{WinkerGroppeUotilaetal., author = {Winker, Tobias and Groppe, Sven and Uotila, Valter Johan Edvard and Yan, Zhengtong and Lu, Jiaheng and Maja, Franz and Mauerer, Wolfgang}, title = {Quantum Machine Learning: Foundation, New Techniques, and Opportunities for Database Research}, series = {SIGMOD '23, proceedings of the 2023 International Conference on Management of Data: June 18-23, 2023, Seattle, WA, USA}, booktitle = {SIGMOD '23, proceedings of the 2023 International Conference on Management of Data: June 18-23, 2023, Seattle, WA, USA}, publisher = {ACM}, address = {New York}, doi = {10.1145/3555041.3589404}, pages = {8}, abstract = {In the last few years, the field of quantum computing has experienced remarkable progress. The prototypes of quantum computers already exist and have been made available to users through cloud services (e.g., IBM Q experience, Google quantum AI, or Xanadu quantum cloud). While fault-tolerant and large-scale quantum computers are not available yet (and may not be for a long time, if ever), the potential of this new technology is undeniable. Quantum algorithms havethe proven ability to either outperform classical approaches for several tasks, or are impossible to be efficiently simulated by classical means under reasonable complexity-theoretic assumptions. Even imperfect current-day technology is speculated to exhibit computational advantages over classical systems. Recent research is using quantum computers to solve machine learning tasks. Meanwhile, the database community already successfully applied various machine learning algorithms for data management tasks, so combining the fields seems to be a promising endeavour. However, quantum machine learning is a new research field for most database researchers. In this tutorial, we provide a fundamental introduction to quantum computing and quantum machine learning and show the potential benefits and applications for database research. In addition, we demonstrate how to apply quantum machine learning to the optimization of join order problem for databases.}, language = {en} } @unpublished{ThelenSafiMauerer, author = {Thelen, Simon and Safi, Hila and Mauerer, Wolfgang}, title = {Approximating under the Influence of Quantum Noise and Compute Power}, series = {Proceedings of WIHPQC@IEEE QCE}, journal = {Proceedings of WIHPQC@IEEE QCE}, abstract = {The quantum approximate optimisation algorithm (QAOA) is at the core of many scenarios that aim to combine the power of quantum computers and classical high-performance computing appliances for combinatorial optimisation. Several obstacles challenge concrete benefits now and in the foreseeable future: Imperfections quickly degrade algorithmic performance below practical utility; overheads arising from alternating between classical and quantum primitives can counter any advantage; and the choice of parameters or algorithmic variant can substantially influence runtime and result quality. Selecting the optimal combination is a non-trivial issue, as it not only depends on user requirements, but also on details of the hardware and software stack. Appropriate automation can lift the burden of choosing optimal combinations for end-users: They should not be required to understand technicalities like differences between QAOA variants, required number of QAOA layers, or necessary measurement samples. Yet, they should receive best-possible satisfaction of their non-functional requirements, be it performance or other. We determine factors that affect solution quality and temporal behaviour of four QAOA variants using comprehensive density-matrix-based simulations targeting three widely studied optimisation problems. Our simulations consider ideal quantum computation, and a continuum of scenarios troubled by realistic imperfections. Our quantitative results, accompanied by a comprehensive reproduction package, show strong differences between QAOA variants that can be pinpointed to narrow and specific effects. We identify influential co-variables and relevant non-functional quality goals that, we argue, mark the relevant ingredients for designing appropriate software engineering abstraction mechanisms and automated tool-chains for devising quantum solutions from high-level problem specifications.}, language = {en} } @unpublished{PeriyasamyPlingeMutschleretal., author = {Periyasamy, Maniraman and Plinge, Axel and Mutschler, Christopher and Scherer, Daniel D. and Mauerer, Wolfgang}, title = {Guided-SPSA: Simultaneous Perturbation Stochastic Approximation assisted by the Parameter Shift Rule}, abstract = {The study of variational quantum algorithms (VQCs) has received significant attention from the quantum computing community in recent years. These hybrid algorithms, utilizing both classical and quantum components, are well-suited for noisy intermediate-scale quantum devices. Though estimating exact gradients using the parameter-shift rule to optimize the VQCs is realizable in NISQ devices, they do not scale well for larger problem sizes. The computational complexity, in terms of the number of circuit evaluations required for gradient estimation by the parameter-shift rule, scales linearly with the number of parameters in VQCs. On the other hand, techniques that approximate the gradients of the VQCs, such as the simultaneous perturbation stochastic approximation (SPSA), do not scale with the number of parameters but struggle with instability and often attain suboptimal solutions. In this work, we introduce a novel gradient estimation approach called Guided-SPSA, which meaningfully combines the parameter-shift rule and SPSA-based gradient approximation. The Guided-SPSA results in a 15\% to 25\% reduction in the number of circuit evaluations required during training for a similar or better optimality of the solution found compared to the parameter-shift rule. The Guided-SPSA outperforms standard SPSA in all scenarios and outperforms the parameter-shift rule in scenarios such as suboptimal initialization of the parameters. We demonstrate numerically the performance of Guided-SPSA on different paradigms of quantum machine learning, such as regression, classification, and reinforcement learning.}, language = {en} } @inproceedings{ZwingelKediliogluReitelshoeferetal., author = {Zwingel, Maximilian and Kedilioglu, Oguz and Reitelsh{\"o}fer, Sebastian and Mauerer, Wolfgang}, title = {Optimization Problems in Production and Planning: Approaches and Limitations in View of Possible Quantum Superiority}, series = {Annals of Scientific Society for Assembly, Handling and Industrial Robotics 2023}, booktitle = {Annals of Scientific Society for Assembly, Handling and Industrial Robotics 2023}, publisher = {Springer Nature}, isbn = {9783031740091}, language = {en} } @inproceedings{TrespUdluftHeinetal., author = {Tresp, Volker and Udluft, Steffen and Hein, Daniel and Hauptmann, Werner and Leib, Martin and Mutschler, Christopher and Scherer, Daniel D. and Mauerer, Wolfgang}, title = {Workshop Summary: Quantum Machine Learning}, series = {2023 IEEE International Conference on Quantum Computing and Engineering, Bellevue, WA, United States, September 17-22, 2023}, booktitle = {2023 IEEE International Conference on Quantum Computing and Engineering, Bellevue, WA, United States, September 17-22, 2023}, publisher = {IEEE}, doi = {10.1109/QCE57702.2023.10174}, language = {en} } @inproceedings{GogeisslSafiMauerer, author = {Gogeißl, Martin and Safi, Hila and Mauerer, Wolfgang}, title = {Quantum Data Encoding Patterns and their Consequences}, series = {Q-Data '24: Proceedings of the 1st Workshop on Quantum Computing and Quantum-Inspired Technology for Data-Intensive Systems and Applications, June 9 - 15, 2024, Santiago AA Chile}, booktitle = {Q-Data '24: Proceedings of the 1st Workshop on Quantum Computing and Quantum-Inspired Technology for Data-Intensive Systems and Applications, June 9 - 15, 2024, Santiago AA Chile}, publisher = {ACM}, isbn = {979-8-4007-0553-3}, doi = {10.1145/3665225.3665446}, pages = {27 -- 37}, abstract = {The use of quantum processing units (QPUs) promises speed-ups for solving computational problems, in particular for discrete optimisation. While a few groundbreaking algorithmic approaches are known that can provably outperform classical computers, we observe a scarcity of programming abstractions for constructing efficient quantum algorithms. A good fraction of the literature that addresses solving concrete problems related to database management concentrates on casting them as quadratic unconstrained binary optimisation problems (QUBOs), which can then, among others, be processed on gate-based machines (using the quantum approximate optimisation algorithm), or quantum annealers. A critical aspect that affects efficiency and scalability of either of these approaches is how classical data are loaded into qubits, respectively how problems are encoded into QUBO representation. The effectiveness of encodings is known to be of crucial importance for quantum computers, especially since the amount of available qubits is strongly limited in the era of noisy, intermediate-size quantum computers. In this paper, we present three encoding patterns, discuss their impact on scalability, and their ease of use. We consider the recreational (yet computationally challenging) Sudoku problem and its reduction to graph colouring as an illustrative example to discuss their individual benefits and disadvantages. Our aim is enable database researchers to choose an appropriate encoding scheme for their purpose without having to acquire in-depth knowledge on quantum peculiarities, thus easing the path towards applying quantum acceleration on data management systems.}, language = {en} } @unpublished{JungKrumkeSchrothetal., author = {Jung, Matthias and Krumke, Sven O. and Schroth, Christof and Lobe, Elisabeth and Mauerer, Wolfgang}, title = {QCEDA: Using Quantum Computers for EDA}, abstract = {The field of Electronic Design Automation (EDA) is crucial for microelectronics, but the increasing complexity of Integrated Circuits (ICs) poses challenges for conventional EDA: Corresponding problems are often NP-hard and are therefore in general solved by heuristics, not guaranteeing optimal solutions. Quantum computers may offer better solutions due to their potential for optimization through entanglement, superposition, and interference. Most of the works in the area of EDA and quantum computers focus on how to use EDA for building quantum circuits. However, almost no research focuses on exploiting quantum computers for solving EDA problems. Therefore, this paper investigates the feasibility and potential of quantum computing for a typical EDA optimization problem broken down to the Min-k-Union problem. The problem is mathematically transformed into a Quadratic Unconstrained Binary Optimization (QUBO) problem, which was successfully solved on an IBM quantum computer and a D-Wave quantum annealer.}, language = {en} } @incollection{Mauerer, author = {Mauerer, Wolfgang}, title = {Superoperators for Quantum Software Engineering}, series = {Quantum Software: Aspects of Theory and System Design}, booktitle = {Quantum Software: Aspects of Theory and System Design}, editor = {Exman, Iaakov and Perez-Castillo, Ricardo and Piattini, Mario and Felderer, Michael}, publisher = {Springer Nature}, issn = {978-3-031-64136-7}, doi = {10.1007/978-3-031-64136-7_3}, abstract = {As implementations of quantum computers grow in size and maturity, the question of how to program this new class of machines is attracting increasing attention in the software engineering domain. Yet, many questions from how to design expressible quantum languages augmented with formal semantics via implementing appropriate optimizing compilers to abstracting details of machine properties in software systems remain challenging. Performing research at this intersection of quantum computing and software engineering requires sufficient knowledge of the physical processes underlying quantum computations, and how to model these. In this chapter, we review a superoperator-based approach to quantum dynamics, as it can provide means that are sufficiently abstract, yet concrete enough to be useful in quantum software and systems engineering, and outline how it is used in several important applications in the field.}, language = {en} } @inproceedings{SafiWinterspergerMauerer, author = {Safi, Hila and Wintersperger, Karen and Mauerer, Wolfgang}, title = {Influence of HW-SW-Co-Design on Quantum Computing Scalability}, series = {2023 IEEE International Conference on Quantum Software (QSW), Chicago, IL, USA, 02-08 July 2023}, booktitle = {2023 IEEE International Conference on Quantum Software (QSW), Chicago, IL, USA, 02-08 July 2023}, publisher = {IEEE}, isbn = {979-8-3503-0479-4}, doi = {10.1109/QSW59989.2023.00022}, pages = {104 -- 115}, abstract = {The use of quantum processing units (QPUs) promises speed-ups for solving computational problems. Yet, current devices are limited by the number of qubits and suffer from significant imperfections, which prevents achieving quantum advantage. To step towards practical utility, one approach is to apply hardware-software co-design methods. This can involve tailoring problem formulations and algorithms to the quantum execution environment, but also entails the possibility of adapting physical properties of the QPU to specific applications. In this work, we follow the latter path, and investigate how key figures— circuit depth and gate count—required to solve four cornerstone NP-complete problems vary with tailored hardware properties. Our results reveal that achieving near-optimal performance and properties does not necessarily require optimal quantum hardware, but can be satisfied with much simpler structures that can potentially be realised for many hardware approaches.m Using statistical analysis techniques, we additionally identify an underlying general model that applies to all subject problems. This suggests that our results may be universally applicable to other algorithms and problem domains, and tailored QPUs can find utility outside their initially envisaged problem domains. The substantial possible improvements nonetheless highlight the importance of QPU tailoring to progress towards practical deployment and scalability of quantum software.}, language = {en} } @article{WinterspergerDommertEhmeretal., author = {Wintersperger, Karen and Dommert, Florian and Ehmer, Thomas and Hoursanov, Andrey and Klepsch, Johannes and Mauerer, Wolfgang and Reuber, Georg and Strohm, Thomas and Yin, Ming and Luber, Sebastian}, title = {Neutral Atom Quantum Computing Hardware: Performance and End-User Perspective}, series = {EPJ Quantum Technology}, volume = {10}, journal = {EPJ Quantum Technology}, publisher = {Springer Nature}, doi = {10.1140/epjqt/s40507-023-00190-1}, pages = {27}, abstract = {We present an industrial end-user perspective on the current state of quantum computing hardware for one specific technological approach, the neutral atom platform. Our aim is to assist developers in understanding the impact of the specific properties of these devices on the effectiveness of algorithm execution. Based on discussions with different vendors and recent literature, we discuss the performance data of the neutral atom platform. Specifically, we focus on the physical qubit architecture, which affects state preparation, qubit-to-qubit connectivity, gate fidelities, native gate instruction set, and individual qubit stability. These factors determine both the quantum-part execution time and the end-to-end wall clock time relevant for end-users, but also the ability to perform fault-tolerant quantum computation in the future. We end with an overview of which applications have been shown to be well suited for the peculiar properties of neutral atom-based quantum computers.}, language = {en} } @inproceedings{GreiweKruegerMauerer, author = {Greiwe, Felix and Kr{\"u}ger, Tom and Mauerer, Wolfgang}, title = {Effects of Imperfections on Quantum Algorithms}, series = {2023 IEEE International Conference on Quantum Software (QSW), Chicago, IL, USA, 02-08 July 2023}, booktitle = {2023 IEEE International Conference on Quantum Software (QSW), Chicago, IL, USA, 02-08 July 2023}, publisher = {IEEE}, doi = {10.1109/QSW59989.2023.00014}, pages = {31 -- 42}, abstract = {Quantum computers promise considerable speedups over classical approaches, which has raised interest from many disciplines. Since any currently available implementations suffer from noise and imperfections, achieving concrete speedups for meaningful problem sizes remains a major challenge. Yet, imperfections and noise may remain present in quantum computing for a long while. Such limitations play no role in classical software computing, and software engineers are typically not well accustomed to considering such imperfections, albeit they substantially influence core properties of software and systems. In this paper, we show how to model imperfections with an approach tailored to (quantum) software engineers. We intuitively illustrate, using numerical simulations, how imperfections influence core properties of quantum algorithms on NISQ systems, and show possible options for tailoring future NISQ machines to improve system performance in a co-design approach. Our results are obtained from a software framework that we provide in form of an easy-to-use reproduction package. It does not require computer scientists to acquire deep physical knowledge on noise, yet provide tangible and intuitively accessible means of interpreting the influence of noise on common software quality and performance indicators.}, language = {en} } @incollection{YueMauererAlietal., author = {Yue, Tao and Mauerer, Wolfgang and Ali, Shaukat and Taibi, Davide}, title = {Challenges and Opportunities in Quantum Software Architecture}, series = {Software Architecture: Research Roadmaps from the Community}, booktitle = {Software Architecture: Research Roadmaps from the Community}, isbn = {978-3-031-36847-9}, doi = {10.1007/978-3-031-36847-9_1}, pages = {1 -- 23}, abstract = {Quantum computing is a relatively new paradigm that has raised considerable interest in physics and computer science in general but has so far received little attention in software engineering and architecture. Hybrid applications that consist of both quantum and classical components require the development of appropriate quantum software architectures. However, given that quantum software engineering (QSE) in general is a new research area, quantum software architecture-a subresearch area in QSE is also understudied. The goal of this chapter is to provide a list of research challenges and opportunities for such architectures. In addition, to make the content understandable to a broader computer science audience, we provide a brief overview of quantum computing and explain the essential technical foundations.}, language = {en} } @inproceedings{SchoenbergerTrummerMauerer, author = {Sch{\"o}nberger, Manuel and Trummer, Immanuel and Mauerer, Wolfgang}, title = {Quantum Optimisation of General Join Trees}, series = {Joint Workshops at 49th International Conference on Very Large Data Bases (VLDBW'23) — International Workshop on Quantum Data Science and Management (QDSM'23), August 28 - September 1, 2023, Vancouver, Canada (CEUR Workshop Proceedings)}, booktitle = {Joint Workshops at 49th International Conference on Very Large Data Bases (VLDBW'23) — International Workshop on Quantum Data Science and Management (QDSM'23), August 28 - September 1, 2023, Vancouver, Canada (CEUR Workshop Proceedings)}, publisher = {RWTH Aachen, Sun SITE Central Europe}, address = {Aachen}, pages = {1 -- 12}, abstract = {Recent advances in the manufacture of quantum computers attract much attention over a wide range of fields, as early-stage quantum processing units (QPU) have become accessible. While contemporary quantum machines are very limited in size and capabilities, mature QPUs are speculated to eventually excel at optimisation problems. This makes them an attractive technology for database problems, many of which are based on complex optimisation problems with large solution spaces. Yet, the use of quantum approaches on database problems remains largely unexplored. In this paper, we address the long-standing join ordering problem, one of the most extensively researched database problems. Rather than running arbitrary code, QPUs require specific mathematical problem encodings. An encoding for the join ordering problem was recently proposed, allowing first small-scale queries to be optimised on quantum hardware. However, it is based on a faithful transformation of a mixed integer linear programming (MILP) formulation for JO, and inherits all limitations of the MILP method. Most strikingly, the existing encoding only considers a solution space with left-deep join trees, which tend to yield larger costs than general, bushy join trees. We propose a novel QUBO encoding for the join ordering problem. Rather than transforming existing formulations, we construct a native encoding tailored to quantum systems, which allows us to process general bushy join trees. This makes the full potential of QPUs available for solving join order optimisation problems.}, language = {en} } @inproceedings{UotilaGroppeGruenwaldetal., author = {Uotila, Valter and Groppe, Sven and Gruenwald, Le and Lu, Jiaheng and Mauerer, Wolfgang}, title = {Preface QDSM}, series = {Joint Workshops at 49th International Conference on Very Large Data Bases (VLDBW'23) — International Workshop on Quantum Data Science and Management (QDSM'23), August 28 - September 1, 2023, Vancouver, Canada (CEUR Workshop Proceedings)}, booktitle = {Joint Workshops at 49th International Conference on Very Large Data Bases (VLDBW'23) — International Workshop on Quantum Data Science and Management (QDSM'23), August 28 - September 1, 2023, Vancouver, Canada (CEUR Workshop Proceedings)}, publisher = {RWTH Aachen, Sun SITE Central Europe}, address = {Aachen}, abstract = {The first international workshop on Quantum Data Science and anagement (QDSM), co-located with VLDB 2023, is centered around addressing the possibilities of quantum computing for data science and data management. Quantum computing is a relatively new and emerging field that is believed to have huge computational potential in the future. In the QDSM workshop, we want to provide a venue for discussing and publishing novel results of applying quantum computing to hard data science and data management problems. These problems include join order optimization, designing efficient quantum feature maps, studying possibilities of solving linear programs with quantum algorithms, and divergent index tuning with quantum machine learning. Besides, we include a short and visionary survey on quantum computing for databases. Theworkshop provides a platform for active discussion on these and related topics.}, language = {en} } @inproceedings{JoblinApelHunsenetal., author = {Joblin, Mitchell and Apel, Sven and Hunsen, Claus and Mauerer, Wolfgang}, title = {Classifying Developers into Core and Peripheral: An Empirical Study on Count and Network Metrics}, series = {2017 IEEE/ACM 39th International Conference on Software Engineering (ICSE), Buenos Aires, Argentina, 20-28 May 2017}, booktitle = {2017 IEEE/ACM 39th International Conference on Software Engineering (ICSE), Buenos Aires, Argentina, 20-28 May 2017}, publisher = {IEEE}, doi = {10.1109/icse.2017.23}, pages = {164 -- 174}, abstract = {Knowledge about the roles developers play in a software project is crucial to understanding the project's collaborative dynamics. In practice, developers are often classified according to the dichotomy of core and peripheral roles. Typically, count-based operationalizations, which rely on simple counts of individual developer activities (e.g., number of commits), are used for this purpose, but there is concern regarding their validity and ability to elicit meaningful insights. To shed light on this issue, we investigate whether count-based operationalizations of developer roles produce consistent results, and we validate them with respect to developers' perceptions by surveying 166 developers. Improving over the state of the art, we propose a relational perspective on developer roles, using fine-grained developer networks modeling the organizational structure, and by examining developer roles in terms of developers' positions and stability within the developer network. In a study of 10 substantial open-source projects, we found that the primary difference between the count-based and our proposed network-based core-peripheral operationalizations is that the network-based ones agree more with developer perception than count-based ones. Furthermore, we demonstrate that a relational perspective can reveal further meaningful insights, such as that core developers exhibit high positional stability, upper positions in the hierarchy, and high levels of coordination with other core developers, which confirms assumptions of previous work.}, language = {en} } @inproceedings{JoblinMauererApeletal., author = {Joblin, Mitchell and Mauerer, Wolfgang and Apel, Sven and Siegmund, Janet and Riehle, Dirk}, title = {From Developer Networks to Verified Communities: A Fine-Grained Approach}, series = {2015 IEEE/ACM 37th IEEE International Conference on Software Engineering, 16-24 May 2015, Florence, Italy}, booktitle = {2015 IEEE/ACM 37th IEEE International Conference on Software Engineering, 16-24 May 2015, Florence, Italy}, publisher = {IEEE}, isbn = {978-1-4799-1934-5}, doi = {10.1109/icse.2015.73}, pages = {563 -- 573}, abstract = {Effective software engineering demands a coordinated effort. Unfortunately, a comprehensive view on developer coordination is rarely available to support software-engineering decisions, despite the significant implications on software quality, software architecture, and developer productivity. We present a fine-grained, verifiable, and fully automated approach to capture a view on developer coordination, based on commit information and source-code structure, mined from version-control systems. We apply methodology from network analysis and machine learning to identify developer communities automatically. Compared to previous work, our approach is fine-grained, and identifies statistically significant communities using order-statistics and a community-verification technique based on graph conductance. To demonstrate the scalability and generality of our approach, we analyze ten open-source projects with complex and active histories, written in various programming languages. By surveying 53 open-source developers from the ten projects, we validate the authenticity of inferred community structure with respect to reality. Our results indicate that developers of open-source projects form statistically significant community structures and this particular view on collaboration largely coincides with developers' perceptions of real-world collaboration.}, language = {en} } @article{JoblinApelMauerer, author = {Joblin, Mitchell and Apel, Sven and Mauerer, Wolfgang}, title = {Evolutionary trends of developer coordination: a network approach}, series = {Empirical Software Engineering}, volume = {22}, journal = {Empirical Software Engineering}, number = {4}, publisher = {Springer}, doi = {10.1007/s10664-016-9478-9}, pages = {2050 -- 2094}, abstract = {Software evolution is a fundamental process that transcends the realm of technical artifacts and permeates the entire organizational structure of a software project. By means of a longitudinal empirical study of 18 large open-source projects, we examine and discuss the evolutionary principles that govern the coordination of developers. By applying a network-analytic approach, we found that the implicit and self-organizing structure of developer coordination is ubiquitously described by non-random organizational principles that defy conventional software-engineering wisdom. In particular, we found that: (a) developers form scale-free networks, in which the majority of coordination requirements arise among an extremely small number of developers, (b) developers tend to accumulate coordination requirements with more and more developers over time, presumably limited by an upper bound, and (c) initially developers are hierarchically arranged, but over time, form a hybrid structure, in which core developers are hierarchically arranged and peripheral developers are not. Our results suggest that the organizational structure of large projects is constrained to evolve towards a state that balances the costs and benefits of developer coordination, and the mechanisms used to achieve this state depend on the project's scale.}, language = {en} } @inproceedings{FranzZuritaDiefenthaleretal., author = {Franz, Maja and Zurita, P{\´i}a and Diefenthaler, Markus and Mauerer, Wolfgang}, title = {Co-Design of Quantum Hardware and Algorithms in Nuclear and High Energy Physics}, series = {EPJ Web of Conferences}, volume = {295}, booktitle = {EPJ Web of Conferences}, publisher = {EDP Sciences}, doi = {10.1051/epjconf/202429512002}, abstract = {Quantum computing (QC) has emerged as a promising technology, and is believed to have the potential to advance nuclear and high energy physics (NHEP) by harnessing quantum mechanical phenomena to accelerate computations. In this paper, we give a brief overview of the current state of quantum computing by highlighting challenges it poses and opportunities it offers to the NHEP community. Noisy intermediate-scale quantum (NISQ) computers, while limited by imperfections and small scale, may hold promise for near-term quantum advantages when coupled with co-designed quantum algorithms and special-purpose quantum processing units (QPUs). We explore various applications in NHEP, including quantum simulation, event classification, and realtime experiment control, emphasising the potential of variational quantum circuits and related techniques. To identify current interests of the community, we perform an analysis of recent literature in NHEP related to QC.}, language = {en} } @article{MauererJoblinTamburrietal., author = {Mauerer, Wolfgang and Joblin, Mitchell and Tamburri, Damian and Paradis, Carlos and Kazman, Rick and Apel, Sven}, title = {In Search of Socio-Technical Congruence: A Large-Scale Longitudinal Study}, series = {IEEE Transactions on Software Engineering (TSE)}, volume = {48}, journal = {IEEE Transactions on Software Engineering (TSE)}, number = {8}, publisher = {IEEE}, doi = {10.1109/TSE.2021.3082074}, pages = {3159 -- 3184}, abstract = {This paper describes a large-scale empirical study investigating the relevance of socio-technical congruence over key basic software quality metrics, namely, bugs and churn. That is, we explore whether alignment or misalignment of social communication structures and technical dependencies in large software projects influences software quality. To this end, we have defined a quantitative and operational notion of socio-technical congruence, which we call /socio-technical motif congruence/ (STMC). STMC is a measure of the degree to which developers working on the same file or on two related files, need to communicate. As socio-technical congruence is a complex and multi-faceted phenomenon, the interpretability of the results is one of our main concerns, so we have employed a careful mixed-methods statistical analysis. In particular, we provide analyses with similar techniques as employed by seminal work in the field to ensure comparability of our results with the existing body of work. The major result of our study, based on an analysis of 25 large open-source projects, is that STMC is /not/ related to project quality measures---software bugs and churn---in any temporal scenario. That is, we find no statistical relationship between the alignment of developer tasks and developer communications on one hand, and project outcomes on the other hand. We conclude that, wherefore congruence does matter as literature shows, then its measurable effect lies elsewhere.}, language = {en} } @inproceedings{GabrielWittmannHackeretal., author = {Gabriel, Christian and Wittmann, Christoffer and Hacker, B. and Mauerer, Wolfgang and Huntington, E. and Sabuncu, M. and Marquardt, Christoph and Leuchs, Gerd}, title = {A high-speed secure quantum random number generator based on vacuum states}, series = {IEEE/OSA Conference on Lasers and Electro-Optics (CLEO), 06-11 May 2012, San Jose CA USA}, booktitle = {IEEE/OSA Conference on Lasers and Electro-Optics (CLEO), 06-11 May 2012, San Jose CA USA}, publisher = {Optical Society of America}, abstract = {A high-speed continuous-variable quantum random bit generator with an expected effective bit generation rate of up to 10 GBit/s is presented. The obtained bit sequences are truly random and unique, i.e. they cannot be known by an adversary.}, language = {en} } @phdthesis{Ramsauer, author = {Ramsauer, Ralf}, title = {OSS Architecture for Mixed-Criticality Systems}, publisher = {Leibniz Universit{\"a}t Hannover}, pages = {188}, abstract = {Computer-based automation in industrial appliances led to a growing number of logically dependent, but physically separated embedded control units per appliance. Many of those components are safety-critical systems, and require adherence to safety standards, which is inconsonant with the relentless demand for features in those appliances. Features lead to a growing amount of control units per appliance, and to a increasing complexity of the overall software stack, being unfavourable for safety certifications. Modern CPUs provide means to revise traditional separation of concerns design primitives: the consolidation of systems, which yields new engineering challenges that concern the entire software and system stack. Multi-core CPUs favour economic consolidation of formerly separated systems with one efficient single hardware unit. Nonetheless, the system architecture must provide means to guarantee the freedom from interference between domains of different criticality. System consolidation demands for architectural and engineering strategies to fulfil requirements (e.g., real-time or certifiability criteria) in safety-critical environments. In parallel, there is an ongoing trend to substitute ordinary proprietary base platform software components by mature OSS variants for economic and engineering reasons. There are fundamental differences of processual properties in development processes of OSS and proprietary software. OSS in safety-critical systems requires development process assessment techniques to build an evidence-based fundament for certification efforts that is based upon empirical software engineering methods. In this thesis, I will approach from both sides: the software and system engineering perspective. In the first part of this thesis, I focus on the assessment of OSS components: I develop software engineering techniques that allow to quantify characteristics of distributed OSS development processes. I show that ex-post analyses of software development processes can be used to serve as a foundation for certification efforts, as it is required for safety-critical systems. In the second part of this thesis, I present a system architecture based on OSS components that allows for consolidation of mixed-criticality systems on a single platform. Therefore, I exploit virtualisation extensions of modern CPUs to strictly isolate domains of different criticality. The proposed architecture shall eradicate any remaining hypervisor activity in order to preserve realtime capabilities of the hardware by design, while guaranteeing strict isolation across domains.}, language = {en} } @inproceedings{SchmidbauerWinterspergerLobeetal., author = {Schmidbauer, Lukas and Wintersperger, Karen and Lobe, Elisabeth and Mauerer, Wolfgang}, title = {Polynomial Reduction Methods and their Impact on QAOA Circuits}, series = {IEEE International Conference on Quantum Software (QSW), 7-13 July 2024, Shenzhen, China}, booktitle = {IEEE International Conference on Quantum Software (QSW), 7-13 July 2024, Shenzhen, China}, doi = {10.1109/QSW62656.2024.00018}, pages = {35 -- 45}, abstract = {Abstraction layers are of paramount importance in software architecture, as they shield the higher-level formulation of payload computations from lower-level details. Since quantum computing (QC) introduces many such details that are often unaccustomed to computer scientists, an obvious desideratum is to devise appropriate abstraction layers for QC. For discrete optimisation, one such abstraction is to cast problems in quadratic unconstrained binary optimisation (QUBO) form, which is amenable to a variety of quantum approaches. However, different mathematically equivalent forms can lead to different behaviour on quantum hardware, ranging from ease of mapping onto qubits to performance scalability. In this work, we show how using higher-order problem formulations (that provide better expressivity in modelling optimisation tasks than plain QUBO formulations) and their automatic transformation into QUBO form can be used to leverage such differences to prioritise between different desired non-functional properties for quantum optimisation. Based on a practically relevant use-case and a graph-theoretic analysis, we evaluate how different transformation approaches influence widely used quantum performance metrics (circuit depth, gates count, gate distribution, qubit scaling), and also consider the classical computational efforts required to perform the transformations, as they influence possibilities for achieving future quantum advantage. Furthermore, we establish more general properties and invariants of the transformation methods. Our quantitative study shows that the approach allows us to satisfy different trade-offs, and suggests various possibilities for the future construction of general-purpose abstractions and automatic generation of useful quantum circuits from high-level problem descriptions.}, language = {en} } @inproceedings{HoessParadisKazmanetal., author = {Hoess, Nicole and Paradis, Carlos and Kazman, Rick and Mauerer, Wolfgang}, title = {Does the Tool Matter? Exploring Some Causes of Threats to Validity in Mining Software Repositories}, series = {2025 IEEE International Conference on Software Analysis, Evolution and Reengineering (SANER), Montreal, QC, Canada, March, 4-7, 2025}, booktitle = {2025 IEEE International Conference on Software Analysis, Evolution and Reengineering (SANER), Montreal, QC, Canada, March, 4-7, 2025}, publisher = {IEEE}, isbn = {979-8-3315-3510-0}, doi = {10.1109/SANER64311.2025.00067}, pages = {645 -- 656}, abstract = {Software repositories are an essential source of information for software engineering research on topics such as project evolution and developer collaboration. Appropriate mining tools and analysis pipelines are therefore an indispensable precondition for many research activities. Ideally, valid results should not depend on technical details of data collection and processing. It is, however, widely acknowledged that mining pipelines are complex, with a multitude of implementation decisions made by tool authors based on their interests and assumptions. This raises the questions if (and to what extent) tools agree on their results and are interchangeable. In this study, we use two tools to extract and analyse ten large software projects, quantitatively and qualitatively comparing results and derived data to better understand this concern. We analyse discrepancies from a technical point of view, and adjust code and parametrisation to minimise replication differences. Our results indicate that despite similar trends, even simple metrics such as the numbers of commits and developers may differ by up to 500\%. We find that such substantial differences are often caused by minor technical details. We show how tool-level and data post-processing changes can overcome these issues, but find they may require considerable efforts. We summarise identified causes in our lessons learned to help researchers and practitioners avoid common pitfalls, and reflect on implementation decisions and their influence in ensuring obtained data meets explicit and implicit expectations. Our findings lead us to hypothesise that similar uncertainties exist in other analysis tools, which may limit the validity of conclusions drawn in tool-centric research.}, language = {en} } @incollection{CarbonelliFeldererJungetal., author = {Carbonelli, Cecilia and Felderer, Michael and Jung, Matthias and Lobe, Elisabeth and Lochau, Malte and Luber, Sebastian and Mauerer, Wolfgang and Ramler, Rudolf and Sch{\"a}fer, Ina and Schroth, Christoph}, title = {Challenges for Quantum Software Engineering: An Industrial Application Scenario Perspective}, series = {Quantum Software: Aspects of Theory and System Design}, booktitle = {Quantum Software: Aspects of Theory and System Design}, editor = {Exman, Iaakov and Perez-Castillo, Ricardo and Piattini, Mario and Felderer, Michael}, publisher = {Springer-Nature}, isbn = {978-3-031-64135-0}, doi = {10.1007/978-3-031-64136-7_12}, abstract = {Quantum software is becoming a key enabler for applying quantum computing to industrial use cases. This poses challenges to quantum software engineering in providing efficient and effective means to develop such software. Eventually, this must be reliably achieved in time, on budget, and in quality, using sound and well-principled engineering approaches. Given that quantum computers are based on fundamentally different principles than classical machines, this raises the question if, how, and to what extent established techniques for systematically engineering software need to be adapted. In this chapter, we analyze three paradigmatic application scenarios for quantum software engineering from an industrial perspective. The respective use cases center around (1) optimization and quantum cloud services, (2) quantum simulation, and (3) embedded quantum computing. Our aim is to provide a concise overview of the current and future applications of quantum computing in diverse industrial settings. We derive presumed challenges for quantum software engineering and thus provide research directions for this emerging field.}, language = {en} } @unpublished{AmmermannMauererSchaefer, author = {Ammermann, Joshua and Mauerer, Wolfgang and Sch{\"a}fer, Ina}, title = {Towards View-based Development of Quantum Software}, abstract = {Quantum computing is an interdisciplinary field that relies on the expertise of many different stakeholders. The views of various stakeholders on the subject of quantum computing may differ, thereby complicating communication. To address this, we propose a view-based quantum development approach based on a Single Underlying Model (SUM) and a supporting quantumIntegrated Development Environment (IDE). We highlight emerging challenges for future research.}, language = {en} } @article{Schoenberger, author = {Sch{\"o}nberger, Manuel}, title = {Applicability of Quantum Computing on Database Query Optimization}, series = {SIGMOD '22: proceedings of the 2022 International Conference on Management of Data : June 12-17, 2022, Philadelphia, PA, USA}, journal = {SIGMOD '22: proceedings of the 2022 International Conference on Management of Data : June 12-17, 2022, Philadelphia, PA, USA}, publisher = {ACM}, address = {New York, NY}, doi = {10.1145/3514221.3520257}, pages = {2512 -- 2514}, abstract = {We evaluate the applicability of quantum computing on two fundamental query optimization problems, join order optimization and multi query optimization (MQO). We analyze the problem dimensions that can be solved on current gate-based quantum systems and quantum annealers, the two currently commercially available architectures. First, we evaluate the use of gate-based systems on MQO, previously solved with quantum annealing. We show that, contrary to classical computing, a different architecture requires involved adaptations. We moreover propose a multi-step reformulation for join ordering problems to make them solvable on current quantum systems. Finally, we systematically evaluate our contributions for gate-based quantum systems and quantum annealers. Doing so, we identify the scope of current limitations, as well as the future potential of quantum computing technologies for database systems.}, language = {en} } @misc{SchoenbergerScherzingerMauerer, author = {Sch{\"o}nberger, Manuel and Scherzinger, Stefanie and Mauerer, Wolfgang}, title = {Quantum Computing for DB - Applicability on Multi Query Optimization and Join Order Optimization}, series = {Fr{\"u}hjahrstreffen Fachgruppe Datenbanken in Potsdam, 2022}, journal = {Fr{\"u}hjahrstreffen Fachgruppe Datenbanken in Potsdam, 2022}, language = {en} } @inproceedings{SchoenbergerFranzScherzingeretal., author = {Sch{\"o}nberger, Manuel and Franz, Maja and Scherzinger, Stefanie and Mauerer, Wolfgang}, title = {Peel | Pile? Cross-Framework Portability of Quantum Software}, series = {2022 IEEE 19th International Conference on Software Architecture Companion (ICSA-C), 12-15 March 2022, Honolulu, HI, USA}, booktitle = {2022 IEEE 19th International Conference on Software Architecture Companion (ICSA-C), 12-15 March 2022, Honolulu, HI, USA}, publisher = {IEEE}, doi = {10.1109/ICSA-C54293.2022.00039}, abstract = {In recent years, various vendors have made quantum software frameworks available. Yet with vendor-specific frameworks, code portability seems at risk, especially in a field where hardware and software libraries have not yet reached a consolidated state, and even foundational aspects of the technologies are still in flux. Accordingly, the development of vendor-independent quantum programming languages and frameworks is often suggested. This follows the established architectural pattern of introducing additional levels of abstraction into software stacks, thereby piling on layers of abstraction. Yet software architecture also provides seemingly less abstract alternatives, namely to focus on hardware-specific formulations of problems that peel off unnecessary layers. In this article, we quantitatively and experimentally explore these strategic alternatives, and compare popular quantum frameworks from the software implementation perspective. We find that for several specific, yet generalisable problems, the mathematical formulation of the problem to be solved is not just sufficiently abstract and serves as precise description, but is likewise concrete enough to allow for deriving framework-specific implementations with little effort. Additionally, we argue, based on analysing dozens of existing quantum codes, that porting between frameworks is actually low-effort, since the quantum- and framework-specific portions are very manageable in terms of size, commonly in the order of mere hundreds of lines of code. Given the current state-of-the-art in quantum programming practice, this leads us to argue in favour of peeling off unnecessary abstraction levels.}, language = {en} } @unpublished{SchoenbergerTrummerMauerer, author = {Sch{\"o}nberger, Manuel and Trummer, Immanuel and Mauerer, Wolfgang}, title = {Quantum-Inspired Digital Annealing for Join Ordering}, series = {Proceedings of the VLDB Endowment}, journal = {Proceedings of the VLDB Endowment}, pages = {14}, abstract = {Finding the optimal join order (JO) is one of the most important problems in query optimisation, and has been extensively considered in research and practise. As it involves huge search spaces, approximation approaches and heuristics are commonly used, which explore a reduced solution space at the cost of solution quality. To explore even large JO search spaces, we may consider special-purpose software, such as mixed-integer linear programming (MILP) solvers, which have successfully solved JO problems. However, even mature solvers cannot overcome the limitations of conventional hardware prompted by the end of Moore's law. We consider quantum-inspired digital annealing hardware, which takes inspiration from quantum processing units (QPUs). Unlike QPUs, which likely remain limited in size and reliability in the near and mid-term future, the digital annealer (DA) can solve large instances of mathematically encoded optimisation problems today. We derive a novel, native encoding for the JO problem tailored to this class of machines that substantially improves over known MILP and quantum-based encodings, and reduces encoding size over the state-of-the-art. By augmenting the computation with a novel readout method, we derive valid join orders for each solution obtained by the (probabilistically operating) DA. Most importantly and despite an extremely large solution space, our approach scales to practically relevant dimensions of around 50 relations and improves result quality over conventionally employed approaches, adding a novel alternative to solving the long-standing JO problem.}, language = {en} } @unpublished{SchmidlDengMaetal., author = {Schmidl, Sebastian and Deng, Yangshen and Ma, Pingchuan and Sch{\"o}nberger, Manuel and Mauerer, Wolfgang}, title = {Reproducibility Report for ACM SIGMOD 2023 Paper: Ready to Leap (by Co-Design)? Join Order Optimisation}, abstract = {The paper "Ready to Leap (by Co-Design)? Join Order Optimisation on Quantum Hardware" proposes the first approach to solve the problem of join order optimization on quantum hardware. The authors characterize the applicability and limitations of current state-of-the-art quantum hardware, i. e. gate-based quantum computing and quantum annealing, for join ordering and recommend key improvements to the physical hardware to reach practical utility. Based on the provided database queries and QPU system processing data, we have been able to reproduce the original paper's key insights and quantum problem characteristics reported in its experimental section. The authors provided a self-contained and fully automated reproduction package, including data (database queries, statistics, and collected QPU processing data), experiment scripts, and plotting routines that allowed the identical reconstruction of the three main figures in the paper.}, language = {en} } @misc{SchoenbergerScherzingerMauerer, author = {Sch{\"o}nberger, Manuel and Scherzinger, Stefanie and Mauerer, Wolfgang}, title = {Applicability of Quantum Computing on Database Query Optimization}, series = {Fr{\"u}hjahrstreffen Fachgruppe Datenbanken in Potsdam (Poster Presentation)}, journal = {Fr{\"u}hjahrstreffen Fachgruppe Datenbanken in Potsdam (Poster Presentation)}, language = {en} } @inproceedings{FranzWinkerGroppeetal., author = {Franz, Maja and Winker, Tobias and Groppe, Sven and Mauerer, Wolfgang}, title = {Hype or Heuristic? Quantum Reinforcement Learning for Join Order Optimisation}, series = {2024 IEEE International Conference on Quantum Computing and Engineering (QCE), 15-20 September 2024, Montreal, QC, Canada}, booktitle = {2024 IEEE International Conference on Quantum Computing and Engineering (QCE), 15-20 September 2024, Montreal, QC, Canada}, publisher = {IEEE}, doi = {10.1109/QCE60285.2024.00055}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-76877}, pages = {409 -- 420}, abstract = {Identifying optimal join orders (JOs) stands out as a key challenge in database research and engineering. Owing to the large search space, established classical methods rely on approximations and heuristics. Recent efforts have successfully explored reinforcement learning (RL) for JO. Likewise, quantum versions of RL have received considerable scientific attention. Yet, it is an open question if they can achieve sustainable, overall practical advantages with improved quantum processors. In this paper, we present a novel approach that uses quantum reinforcement learning (QRL) for JO based on a hybrid variational quantum ansatz. It is able to handle general bushy join trees instead of resorting to simpler left-deep variants as compared to approaches based on quantum(-inspired) optimisation, yet requires multiple orders of magnitudes fewer qubits, which is a scarce resource even for post-NISQ systems. Despite moderate circuit depth, the ansatz exceeds current NISQ capabilities, which requires an evaluation by numerical simulations. While QRL may not significantly outperform classical approaches in solving the JO problem with respect to result quality (albeit we see parity), we find a drastic reduction in required trainable parameters. This benefits practically relevant aspects ranging from shorter training times compared to classical RL, less involved classical optimisation passes, or better use of available training data, and fits data-stream and low-latency processing scenarios. Our comprehensive evaluation and careful discussion delivers a balanced perspective on possible practical quantum advantage, provides insights for future systemic approaches, and allows for quantitatively assessing trade-offs of quantum approaches for one of the most crucial problems of database management systems.}, language = {en} } @article{KruegerMauerer, author = {Kr{\"u}ger, Tom and Mauerer, Wolfgang}, title = {Out of the Loop: Structural Approximation of Optimisation Landscapes and non-Iterative Quantum Optimisation}, series = {Quantum}, volume = {9}, journal = {Quantum}, publisher = {Verein zur F{\"o}rderung des Open Access Publizierens in den Quantenwissenschaften}, doi = {10.22331/q-2025-11-06-1903}, pages = {32}, abstract = {The Quantum Approximate Optimisation Algorithm (QAOA) is a widely studied quantum-classical iterative heuristic for combinatorial optimisation. While QAOA targets problems in complexity class NP, the classical optimisation procedure required in every iteration is itself known to be NP-hard. Still, advantage over classical approaches is suspected for certain scenarios, but nature and origin of its computational power are not yet satisfactorily understood. By introducing means of efficiently and accurately approximating the QAOA optimisation landscape from solution space structures, we derive a new algorithmic variant of unit-depth QAOA for two-level Hamiltonians (including all problems in NP): Instead of performing an iterative quantum-classical computation for each input instance, our non-iterative method is based on a quantum circuit that is instance-independent, but problem-specific. It matches or outperforms unit-depth QAOA for key combinatorial problems, despite reduced computational effort. Our approach is based on proving a long-standing conjecture regarding instance-independent structures in QAOA. By ensuring generality, we link existing empirical observations on QAOA parameter clustering to established approaches in theoretical computer science, and provide a sound foundation for understanding the link between structural properties of solution spaces and quantum optimisation.}, language = {de} } @inproceedings{SchoenbergerTrummerMauerer, author = {Sch{\"o}nberger, Manuel and Trummer, Immanuel and Mauerer, Wolfgang}, title = {Large-Scale Multiple Query Optimisation with Incremental Quantum(-Inspired) Annealing}, series = {Proceedings of the ACM on Management of Data}, volume = {3}, booktitle = {Proceedings of the ACM on Management of Data}, number = {4}, publisher = {ACM}, doi = {10.1145/3749171}, pages = {25}, abstract = {Multiple-query optimization (MQO) seeks to reduce redundant work across query batches. While MQO offers opportunities for dramatic performance improvements, the problem is NP-hard, limiting the sizes of problems that can be solved on generic hardware. We propose to leverage specialized hardware solvers for optimization, such as Fujitsu's Digital Annealer (DA), to scale up MQO to problem sizes formerly out of reach. We present a novel incremental processing approach that combines classical computation with DA acceleration. By efficiently partitioning MQO problems into sets of partial problems, and by applying a dynamic search steering strategy that reapplies initially discarded information to incrementally process individual problems, our method overcomes capacity limitations, and scales to extremely large MQO instances (up to νm1000 queries). A thorough and comprehensive empirical evaluation finds our method substantially outperforms existing approaches. Our generalisable framework lays the ground for other database use-cases on quantum-inspired hardware, and bridges towards future quantum accelerators.}, language = {en} }