Leipzig Spin Resonance Colloquium

Probing the Dynamics of Interacting Spin Models with Quantum Processors

Simulating the highly non-equilibrium dynamics of complex many-particle systems remains a formidable challenge for classical computation. This presentation explores the new insights into the dynamics of interacting spin systems made possible by rapid advances in quantum processors. I will first delve into the distinct regimes of quantum dynamics, examining thermalization in isolated systems and its breakdown due to phenomena like many-body localization (MBL) and quantum many-body scars (QMBS), highlighting key recent theoretical and experimental breakthroughs. I will then discuss the use of quantum processors to simulate low-temperature phases in models of quantum magnetism, focusing on dynamics across critical points and the emergence of hydrodynamics in spin systems. The talk will conclude by outlining future research directions.

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NMR and MRI in food science: a journey from lab to real-life conditions

The quantitative characterization of molecular interactions in food matrices and of their complex transformations during, e.g., industrial processing or even human digestion, is essential for developing more nutritious and more sustainable food products. To this goal, highly versatile and robust multiscale measurement techniques are necessary, which ideally can non-invasively assess molecular-to-macroscopic dynamic structures with high chemical and spatial resolution, and can also be carried out under application-relevant conditions. However, standard laboratory techniques typically lack the required molecular and/or spatial information, and often are not easily scalable to in situ, left alone to in vivo, conditions. NMR and MRI methodologies, encompassing spectroscopy, relaxometry, imaging, and combinations thereof, successfully meet all the above requirements, and have therefore brought an important breakthrough in food science research and product development. 

In this talk, I will present an overview of past and most recent advances in translating NMR and MRI methodologies to food research studies where “real-life” conditions are mimicked. Two such recent applications will be discussed in more detail, respectively tackling industrial processing and human digestion conditions. The first application will address the quantification of dynamic structural heterogeneities and anisotropy, which develop under flow or high-moisture extrusion, by using time-domain NMR/-MRI, diffusion tensor imaging (DTI) and MRI velocimetry. The second part of the talk will focus on the use of ¹H Magnetization Transfer (MT) and CEST NMR/MRI methods for monitoring milk protein digestion both in vitro, using static and semi-dynamic models, and in vivo. Future perspectives, involving the use of advanced ultra-high sensitivity NMR/MRI systems, as well as powerful synergies with other complementary measurement modalities, will be discussed. 

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Mid-German NMR Workshop

Will be broadcasted on Zoom

Nonsecular Resonances

This talk will recapitulate the idea leading to the prediction of nonsecular resonances (NSRs) [1], cover some of the anticipated magnetic resonance phenomena and present the fast-field-cycling experiments that provided the first experimental proof of a homonuclear NSR [2]. Additionally some results of ongoing experiments on heteronuclear NSRs are discussed. NSRs are a newly identified class of magnetic resonance phenomena, the existence of which was predicted in 2012 [1].  NSRs are exemptions to two fundamental paradigms of high-field magnetic resonance of spins-1/2: (i) the secular truncation, that dipolar spin-spin-interactions are truncated to the secular terms that commute with the Zeeman Hamiltonian, and (ii) the resonance condition, that spins can only be manipulated by time-dependent magnetic fields at or near Larmor frequency Omega_0. NSRs occur for certain commensurate ratios between the frequency of the applied field and the effective Larmor precession. Under these conditions the spin system’s dynamics can be described in terms of closed trajectories on the Bloch sphere as opposed to open trajectories representing the generic case. These closed trajectories break the secular approximation for the time-averaged interaction Hamiltonian. As a consequence NSRs do not preserve Zeeman energy and lead to effects quite counterintuitive for the experienced NMR practitioner. The five homonuclear NSRs occur between ⅓ Omega_0 and 2 Omega_0 and their irradiation leads to loss of nuclear polarization, for which we have shown the first experimental proof [2] . In addition to homonuclear NSRs, a zoo of heteronuclear NSRs also covers a huge range of frequencies away from the Larmor frequencies. Heteronuclear NSRs also do not preserve Zeeman energy, and while some are dissipative similar to homonculear NSRs, others do preserve the total spin polarization. The latter ones, therefore, can drive incoherent heteronuclear polarization transfer. Notably, this transfer is driven via the irradiation at only one frequency far off either spin species' Larmor frequency, for which we show first experimental results.

[1] C. M. Kropf and B. V. Fine, Physical Review B 86, 1 (2012)

[2] M. Jurkutat et al., Physical Review B 112, L060302 (2025)

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Microstructural MRI

While magnetic resonance imaging (MRI) is indispensable for the modern medicine, its spatial resolution (of the order of a millimeter) is about three orders of magnitude coarser than the dimensions of biological cells, the fundamental scale of biology. Cells are the object of microscopy-supported histology and histopathology, which are the ultimate diagnostic methods in medicine, unfortunately mainly ex-vivo and often post-mortem. It is a great challenge to access at least some of cell properties in vivo and noninvasively. This goal inspires activities within the MRI community towards evaluating statistically averaged cell properties such as their size, spatial arrangement, membrane permeability etc. using MRI measurements of diffusion and relaxation. The core of this approach is theory of MRI signal formation in biological tissues. Theory inspires the measurement design and provides data interpretation in terms of the microscopic tissue structure. It also reveals fundamental links to other domains of physics such as transport (diffusion and current) in disordered media. In this talk, the physical concepts behind this new development will be presented with application examples in human subjects.

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