VCQ Colloquium Summer Semester 2024
All talks of this semester will be held at the Helmut Rauch Lecture Hall at Atominstitut, Stadionallee 2, 1020 Wien
> 17:00 Get-together with drinks and snacks!
> 17:30 VCQ Student talk
> 17:45 VCQ Colloquium Talk
Schedule
Bethe-Peierls approximation in the era of quantum computers
Tensor networks have been foundational tools in our understanding of many-body physics of one-dimensional systems. In this talk I will discuss efforts to move away from one-dimensional tensor networks towards networks of arbitrary structures. I will discuss how well established tools from statistical mechanics have propelled recent algorithmic advances and how these tools have been employed to efficiently simulate recent large scale quantum computations.
Many-body physics with ultracold gases of atoms and molecules
Understanding emergent behaviors in strongly interacting quantum systems is a frontier area of condensed matter physics. However, simulations of quantum many-body systems on classical computers are not scalable beyond a few dozen particles. This motivates the development of quantum simulators, highly controllable analog quantum computers specifically designed to study certain types of problems in condensed matter physics. I will present an overview of quantum simulation with ultracold gases of atoms and molecules, discussing examples relevant for understanding phenomena that occur in real materials, and others that explore completely novel regimes inaccessible in the solid-state. In particular, I will focus on advances enabled by the introduction of microscopy techniques that probe ultracold gases at the single-particle level and reveal the rich quantum correlations present in these systems.
Coherent Effects in Biological Processes: A Case Study in the Dynamics and Response of Open Quantum Systems
The inquiry into non-trivial quantum effects in biological systems has persisted since the inception of quantum mechanics. Recent experiments utilizing non linear ultrafast spectroscopy of molecular aggregates have reignited this discussion. In this seminar, we will delve into recent research conducted within our group aimed at characterizing the possible origin and nature of coherent oscillations observed in the spectral response of pigment protein complexes (PPCs). These complexes serve as the fundamental components in light-induced reactions, crucial for processes ranging from photosynthesis to vision.
We will explore the methodologies employed, which span from quantum master equations to tensor network simulations, to dissect the intricacies of PPC dynamics. This examination will highlight the significant challenges in establishing a quantitative connection between the experimental spectral response and underlying theoretical models. Furthermore, we will investigate the application of resource theories, rooted in the formalism of quantum information theory, to offer a complementary perspective on this enduring debate.
Photonic quantum technologies: from unravelling quantum foundations to advancing quantum integration and developing applications in quantum networks and computing
I will explore various facets of photonic quantum systems and their application in photonic quantum technologies. Firstly, I will discuss quantum interference, a key element in photonic quantum technologies. I will highlight how the distinguishability and mixedness of quantum states influence the interference of multiple single photons – and demonstrate novel schemes for generating multipartite entangled quantum states. I will then address photonic quantum computing, specifically focusing on the building blocks of photonic quantum computers. This includes the generation of resource states essential for photonic quantum computing. I will then shift to photonic quantum networks, covering both their hardware aspects and showcasing quantum-network applications that extend beyond bi-partite quantum communication. Lastly, I will outline how photonic integration facilitates the scalability of these systems and discuss the associated challenges.
Quantum correlations in the phase space
Quantum physics is currently being leveraged to push forward information science and various technologies. Key questions remain unanswered, however, about what is possible under quantum theory, and how classical limits can be surpassed. In our work, we focus on the strategy of characterizing physical systems in phase space. In this talk, I will examine the boundary between quantum and classical mechanics in the phase space. I will present new, mathematically rigorous methods for practical applications of phase space-based theory that shed light on the distinction between the classical and quantum realms, and enable quantum state characterization. For instance, we will demonstrate effects that go beyond classical correlations using a theory that is experimentally accessible. We will also showcase cutting-edge techniques to differentiate between classical and quantum phenomena in quantum optics experiments, introducing concepts such as nonclassicality, quasiprobabilities, and phase space inequalities, while exploring the evolution of complex correlated systems.