Lennart Binkowski (Leibniz Universität Hannover)
Watch on YouTube: https://youtu.be/PsalMyGxxlE

Quantum algorithmic design is tedious, especially when compared to how classical programmers formulate their algorithms. Quantum programmers are often forced to reason directly in terms of low-level quantum gates rather than high-level abstractions. This is mainly due to the premature status of quantum hardware, considering that every gate has to be haggled over, whereas classical hardware is more forgiving. In the long run, however, we expect quantum computers to become powerful enough to reliably execute some of the textbook quantum routines such as Grover's or Shor's algorithm, a regime for which Preskill recently coined the term megaquop machine. It is for this regime that we require more abstraction tools, leaving the gate-wise formulation of quantum algorithms behind, a task for programming languages. In this talk, I introduce CQ, a high-level imperative hybrid programming language for integer-based programs. CQ inherits its core syntax from C, but dispenses with classical low-level control in favour of a joint abstraction of classical and quantum variables. We will, step by step, formulate Grover's algorithm in CQ and compare the result with what other high-level frameworks like Qiskit and Q# have to offer.

Ruben Campos Delgado (Leibniz Universität Hannover)
Watch on YouTube: https://youtu.be/Ls2lfk9vD_Y

Nonlinear modifications of quantum theory are considered potential candidates for a final theory of quantum gravity, with the intuitive argument that since Einstein field equations are nonlinear, quantum gravity should be nonlinear as well. Contextuality is a fundamental concept which captures the idea that measurements in quantum theory cannot be considered as revealing pre-existing values of a specific classical hidden variable. In this talk, I will discuss both concepts and show how one can use contextuality to rule out nonlinear modifications of quantum mechanics, and hence restrict the spectrum of potential candidates.

Thomas Cope (IQM)
Watch on YouTube: https://youtu.be/NhjvK8yIAko

Quantum supremacy experiments have attracted a great deal of attention in the last few years. These have consisted of drawing random samples from families of circuits understood to be difficult to sample from classically. A natural question to ask of these experiments is, do they have any purpose beyond simply demonstrating something quantum?

In this talk, I discuss IQM's approach to answer that question, and the challenges involved with dealing with such circuits.

Polina Feldmann (University of British Columbia)
Watch on YouTube: https://youtu.be/5hMuRdkkjL4

Quantum machine learning (QML) leverages quantum computing for classical inference, furnishes the processing of quantum data with machine-learning methods, and provides quantum algorithms adapted to noisy devices. Typically, QML proposals are framed in terms of the circuit model of quantum computation. The alternative measurement-based quantum computing (MBQC) paradigm can exhibit lower circuit depths, is naturally compatible with classical co-processing of mid-circuit measurements, and offers a promising avenue towards error correction. Despite significant progress on MBQC devices, QML in terms of MBQC has been hardly explored. We propose the multiple-triangle ansatz (MuTA), a universal quantum neural network assembled from MBQC neurons featuring bias engineering, monotonic expressivity, tunable entanglement, and scalable training. We numerically demonstrate that MuTA can learn a universal set of gates in the presence of noise, a quantum-state classifier, as well as a quantum instrument, and classify classical data using a quantum kernel tailored to MuTA. Finally, we incorporate hardware constraints imposed by photonic Gottesman-Kitaev-Preskill qubits. Our framework lays the foundation for versatile quantum neural networks native to MBQC, allowing to explore MBQC-specific algorithmic advantages and QML on MBQC devices.

Thierry Kaldenbach (Deutsches Zentrum für Luft- und Raumfahrt)

We present efficient quantum circuits for fermionic excitation operators tailored for ion trap quantum computers exhibiting the Mølmer-Sørensen (MS) gate. Such operators commonly arise in the study of static and dynamic properties in electronic structure problems using Unitary Coupled Cluster theory or Trotterized time evolution. We detail how the global MS interaction naturally suits the non-local structure of fermionic excitation operators under the Jordan-Wigner mapping and simultaneously provides optimal parallelism in their circuit decompositions. Compared to previous schemes on ion traps, our approach reduces the number of MS gates by factors of 2-, and 4, for single-, and double excitations, respectively. This improvement promises significant speedups and error reductions.

Andreea-Iulia Lefterovici (Leibniz Universität Hannover)
Watch on YouTube: https://youtu.be/C04gunR26nw

Hybrid benchmarking is an alternative way to asymptotic worst-case analysis, gauging the performance of a fault tolerant quantum hardware platform for solving real-world instances of optimisation problem. The overall strategy is to evaluate how a quantum algorithm would perform under idealised assumptions and to identify the ranges where a quantum algorithm could potentially be useful. In this talk, I'll present a methodology that goes beyond the asymptotic scaling for assessing the potential performance of a quantum algorithms in ideal conditions.

Celeste Torkzaban (Leibniz Universität Hannover)

We are part of Quantum Valley Lower Saxony, and project members of the BMFTI-funded ATIQ, MIQRO, and QuMIC projects. In our group, we develop trap designs, trap fabrication methods, and have set up three new cryogenic experiments here at the Leibniz Universität Hannover. We work with Beryllium and Calcium ion qubits, and I will share our developments in trap design and trap fabrication methods, and then provide a detailed overview into our cryostat design, discuss our approach to microwave-based gates, and share our near-term plans for scaling up the number of trapped-ion qubits. 

Henrik Wilming (Leibniz Universität Hannover)
Watch on YouTube: https://youtu.be/hBKq1KTOr_M

Just as phase transitions, some properties of entanglement in many-body systems only emerge sharply in the thermodynamic limit. I will discuss recent results providing operational distinctions for different ways of being infinitely entangled in the context of quantum information theory, quantum many-body physics and quantum field theory. A striking example is the ability of quantum fields and critical many-body systems to "embezzle" entanglement.

Ramona Wolf (Universität Siegen)
Watch on YouTube: https://youtu.be/yan00Y_og-Q

Demonstrating the security of a (quantum) information-processing protocol is already a significant challenge. In realistic settings, however, such protocols rarely operate in isolation; they are typically embedded within larger communication networks that integrate both classical and quantum components. While it may appear straightforward to conclude that the composition of individually secure protocols remains secure as a whole, experience shows that subtle and often unexpected vulnerabilities can emerge. These issues are closely tied to the chosen security definitions and to implicit assumptions made during the design and analysis of protocols. In this talk, I will highlight several concrete examples of security pitfalls that arise when combining protocols and discuss approaches for achieving robust composable security in complex quantum-classical networks.