Molecular effects in low energy muon transfer from muonic hydrogen to oxygen

Dimitar Bakalov, INRNE, Bulgarian Academy of Sciences

An efficient computational model of the kinetics of processes involving muonic hydrogen atoms in gaseous mixture of hydrogen and oxygen is developed and analyzed. The model is applied in the description of the FAMU collaboration experiment for the measurement of the hyperfine splitting in muonic hydrogen and the Zemach radius of the proton. We determined the cross section of muon transfer to oxygen in low energy collisions from the available experimental data. The results are obtained in a model-independent way with account of the oxygen molecule structure. Building on an earlier work, the results highlight the role of the molecular effects and significantly improve the agreement with recent advanced theoretical calculations of the muon transfer rate.

Random matrix theoretic approach to multi-point observable correlation functions

Yoana Chorbadzhiyska, Sofia U

In this work we analytically derive the time dependence of multi-point observable correlation functions in quantum systems with chaotic eigenstates, with the highest order function of interest being the out-of-time-order correlator (OTOC). We find in each case that dynamical contributions are related to a simple function, related to the Fourier transform of coarse-grained wave-functions. We compare the predicted dynamics to exact numerical experiments in a spin chain, for various physical observables. We comment on implications towards the emergence of Markovianity in closed quantum systems.

Locally Optimal Disentangling of Generic Quantum States

Ludvik Cigna, LMU

Controlling entanglement is pivotal for the advancement of quantum technologies. In this context, disentangling algorithms have attracted significant attention due to their potential to address challenges in quantum state preparation, compression, complexity estimation, and quantum control. In our work, we introduce a unified and mathematically rigorous framework for disentangling based on local measurements, which is particularly suitable for current NISQ devices. This framework provides a generalization to multi-qubit disentangling and offers practical speed-ups compared to previous heuristic approaches, building on a recent solution to the relaxed quantum marginal problem. We further analyze the convergence behavior and the evolving structure of states during the algorithm.

Experimental determination of the energy dependence of the rate of the muon transfer from muonic hydrogen to carbon

Petar Danev, INRNE – BAS

The FAMU collaboration has recently conducted measurements of the ensemble-averaged muon transfer rate from hydrogen to carbon, ΛHC (T ), over the temperature range 197-300 K. Based on these experimental results, we extract the muon transfer rate, λHC ( E), as a function of the center-of-mass kinetic energy of collisions between methane molecules and muonic hydrogen. A qualitative comparison of λHC ( E) and its oxygen counterpart λHO ( E) – crucial for determining the hyperfine splitting of the ground state of muonic hydrogen – is also presented.

We acknowledge the support of Bulgarian National Science Fund Grant No. KP-06-N58/5.

Two-dimensional Schrödinger operators with non-local δ-shell interactions

Lukas Heriban, FNSPE CTU in Prague

We present a family of self-adjoint realizations of the Laplacian in L2 (ℝ2) with novel non-local transmission conditions imposed along a closed bi-Lipschitz curve Σ. These conditions allow for jumps in both the Dirichlet traces and the Wirtinger derivatives of functions across Σ. Using a generalized boundary triple approach, we show that all such realizations can be parametrized by compact self-adjoint operators in L2 (ℝ2; ℂ2).

While the essential spectrum remains stable and equal to [ 0 ,+∞) for all parameter choices, the discrete spectrum displays rich behavior. In many cases it is finite, but we also identify classes of parameters—particularly those resembling non-local oblique transmission conditions—for which the discrete spectrum is infinite and accumulates at −∞.

Asymptotic spectra of block Toeplitz matrices

Lars Koekenbier, FAU Erlangen-Nürnberg

The asymptotic spectra of non-Hermitian block Toeplitz matrices are determined in terms of transfer matrices. This approach also allows one to deal with perturbations. In particular, new results are obtained for perturbations that close the boundary. Moreover, one can detect topological zero modes for chiral Hamiltonians and this gives rise to a new gap condition.

Wave particle duality: de Broglie waves

Carlos Lopez, Spain

The wave particle duality is one of the less intuitive properties of Quantum Mechanics. Under some experimental circumstances, when corpuscular systems can follow two alternative paths which later on rejoin and superpose, some wave like interference happens. If, in a second part of the experiment, one of the paths is blocked the wave like behaviour disappears. The most celebrated experiment is the two slit experiment with electrons. A careful physical analysis of the experiment follows.

1)In the second part of the experiment, when one slit is blocked, there is a change of final state of the

electrons, the interference pattern does not appear.

2)The only additional element in the experimental set up is the blocking system.

3)The blocking system must be the origin of a different interaction in the physical process.

4)We can infer that electrons arriving to the final screen have gone through the open slit.

5)There is always a spatial separation between the particle and the bloc\-king system.

6)Some other system must intermediate in an indirect interaction between electrons and the blocking system.

This is probably a distributed field, which we can denote de Broglie wave. The existence of this new physical system offers a rational explanation of the wave particle duality. De Broglie waves modify the trajectories (geodesics?) of the electrons. A simple mathematical (toy) model, extension of General Relativity, is presented. If we add to the action of General Relativity a harmonic oscillator, the dynamical equations include new energy momentum terms associated to the additional field, and the associated wave equation is dependent on the space time metric. In this model the interaction between electrons and de Broglie waves is mediated by gravity. We can compute the scalar curvature (signature (-,+,+,+)) and we find both positive and negative terms associated to the new field, which therefore represent both dark energy and dark matter. It would be very interesting if there was a connection between a quantum phenomenon, wave particle duality, and a cosmological phenomenon, dark energy.

Anomalous diffusion in Bose-Hubbard chains: from superdiffusion to no transport

Dragan Marković, FAU Erlangen-Nürnberg

We consider Bose-Hubbard systems in one dimension in the limit of the number of bosons going to infinity. This system has a rich dynamical picture which can be accessed both analytically and numerically. The prime result of this study is anomalous diffusion, i.e. how second moments of the number of bosons evolve with time. The exponents are "quantized", and appear as: n, 2n or 4n. We discuss that this is a result of the symmetry of the Bose-Hubbard Hamiltonian: 2n and 4n appear as a result of specific geometry of the system and specific geometry of initial conditions and exponent n appears as an additional result of the Truncated Wigner Approach (TWA), which we explore in detail. As a final touch, we propose another operator describing this system, which surprisingly exudes no transport.

Thermal coherence of the Heisenberg model with Dzyaloshinsky–Moriya interactions in an inhomogenous external field

Manikandan Parthasarathy, RKM Vivekananda College, India

The quantum coherence of the two-site XYZ model with Dzyaloshinsky–Moriya(DM) interactions in an external inhomogenous magnetic field is studied. The DM interaction, the magnetic field and the measurement basis can be along different directions, and we examine the quantum coherence at finite temperature. With respect to the spin–spin interaction parameter, we find that the quantum coherence decreases when the direction of measurement basis is the same as that of the spin–spin interaction. When the spin–lattice interaction is varied, the coherence always increases irrespective of the relation between its direction and the measurement basis. Similar analysis of quantum coherence based on the variation of the external inhomogenous magnetic field is also carried out, where we find that the coherence decreases when the direction of the measurement basis is the same as that of the external field.

Resonances in quantum graphs

Jan Pekař, Nuclear Physics Institute, Czech Academy of Sciences

One of the common techniques for finding resonances in a quantum mechanical system is to confine it in the box of a finite length and then vary its spectrum with respect to the box's length. As the resonance wave function is mainly concentrated in the interaction region, resonance energies are much less influenced by such variation and are visible in the spectrum. Inspired by the rigorous proof of this technique in 1D, we prove it for a general quantum graph and illustrate our results with some examples.

Mean-Field limit of the Bose-Hubbard Model in High Dimension

Denis Périce, Constructor U Bremen

The Bose-Hubbard model effectively describes bosons on a lattice with on-site interactions and nearest-neighbour hopping, serving as a foundational framework for understanding strong particle interactions and the superfluid to Mott-insulator transition. In the physics literature, the mean field theory for this model is known to provide qualitatively accurate results in three or more dimensions. This poster will present a result that establishes the validity of the mean-field approximation for bosonic quantum systems in high dimensions. Unlike the conventional many-body mean-field limit, the high-dimensional mean-field theory exhibits a phase transition and remains compatible with strongly interacting particles.

Efficiently Computable Limits on EPR Pair Generation in Quantum Broadcast Channels

Corlie (Hjalmar) Rall, TUM

We investigate the quantum capacity of a general noisy quantum broadcast channel between three parties from the perspective of channel coding. The most general code in this scenario is a tripartite operation constrained to be causal by no-signalling conditions,but otherwise permitting assistance. We find simple semidefinite programs for bounding the one-shot sum-capacity of the assisted quantum broadcast channel, with positive partial transpose and/or mutual no-signalling constraints. We then establish a hierarchy of semidefinite programming converse bounds for the quantum capacity of quantum broadcast channels. Our bound recovers and strengthens existing results when restricted to the special case of the point-to-point channel.

Completeness stability of quantum measurement

Rakesh Saini, Macquarie U

We introduce a resource monotone, the completeness stability, to quantify the quality of quantum measurements within a resource-theoretic framework. By viewing a quantum measurement as a frame, the minimum eigenvalue of a frame operator emerges as a significant monotone. It captures bounds on estimation errors and the numerical stability of inverting the frame operator to calculate the optimal dual for state reconstruction. Maximizing this monotone identifies a well-characterized class of quantum measurements forming weighted complex projective 2-designs, which includes well-known examples such as SIC-POVMs. Our results provide a principled framework for comparing and optimizing quantum measurements for practical applications.

Efimov Effect in Mixed Dimensions

Marvin Schulz, Karlsruhe Institute of Technology

The Efimov effect, predicted by V. Efimov in 1970, describes how three particles with short-range interactions in 3D can form infinitely many bound states, even if no two-particle subsystems are bound. This occurs only when at least two subsystems are near binding. Recent progress in ultracold gas experiments has renewed interest in this effect in mixed-dimensional systems. We studied zero-energy resonances in two-dimensional Schrödinger operators and disproved the effect in a system of three particles on three distinct lines, contradicting earlier predictions. Our result highlights a rare mismatch between physics intuition and rigorous analysis. We also present other mixed-dimensional configurations of interest for future study.

UniqueNESS: Graph Theory Approach to the Uniqueness of Non-Equilibrium Stationary States of the Lindblad Master Equation

Martin Ulrich Seltmann, Niels Bohr Institute, Copenhagen

The dimensionality of kernels for Lindbladian superoperators is of physical interest in various scenarios out of equilibrium, for example in mean-field methods for driven-dissipative spin lattice models that give rise to phase diagrams with a multitude of non-equilibrium stationary states in specific parameter regions. We show that known criteria established in the literature for unique fixpoints of the Lindblad master equation can be better treated in a graph-theoretic framework via a focus on the connectivity of directed graphs associated to the Hamiltonian and jump operators.

Entanglement entropy of non-interacting massless Dirac fermions in dimension one

Wolfgang Spitzer, FernUniversität in Hagen

We present a novel proof of a formula of Casini and Huerta for the entanglement entropy of the ground state of non-interacting massless Dirac fermions in dimension one localized to (a union of) intervals and generalize it to the case of Rényi entropies and to equilibrium states at positive temperature.

Derivation of the Effective Dynamics for the Bose Polaron

Siegfried Spruck, Karlsruhe Institute of Technology

We consider the dynamics of a dense quantum gas consisting of N bosons evolving in ℝ3 in the presence of an impurity particle in the mean-field scaling with initially high density ρ and large volume Λ of the gas. In the initial state of the system almost all bosons are in the Bose-Einstein condensate, with a few excitations. For this system we derive from the microscopic dynamics in the limit of large densities and volumes the effective description by a quantum field theory modelled by the Bogoliubov-Fröhlich Hamiltonian which describes a quasi-particle, the Bose polaron.

Heat Transport in Solvable Quantum Systems

Swathi, Indian Institute Of Technology, Palakkad

We study solvable models of heat transport between two quantum systems initially prepared at different temperatures and coupled via weak interactions at time t=0. Our primary observable is the heat current, whose time evolution we analyze to understand both the transient response and the long-time behavior. We show that simple toy models—including those inspired by Random Matrix Theory (RMT) and conformal two-point functions—capture key qualitative features of energy transport, such as transient peaks and the formation of non-equilibrium steady states (NESS). For these models, we derive exact expressions for the heat current and thermal conductivity, characterizing both early-time dynamics and the steady state. We further demonstrate that these features arise naturally in specific limits of the double-scaled SYK (DSSYK) model. The Sachdev-Ye-Kitaev (SYK) model, describing a system of randomly interacting fermions in one dimension, is a solvable quantum mechanical model that exhibits strong correlations and quantum chaos. The DSSYK model is a controlled double-scaling limit of the SYK model that allows analytic control across a wide range of energy scales, including regimes beyond the low-energy conformal limit. A key appeal of the DSSYK model in this context is its ability to interpolate between distinct transport regimes, offering a unified framework to understand how the features of simpler models emerge and how they transition as the temperature or coupling is varied. We identify a characteristic timescale τs, referred to as the scrambling scale. The system is well described by the conformal model for t ≪τs, and by the RMT model for t ≫τs. In this sense, DSSYK realizes a renormalization group (RG) flow from a UV regime governed by conformal dynamics to an IR regime characterized by random matrix-like behavior.

Entanglement with a mode observable via a tunable interaction with a qubit

Malgorzata Strzalka, FZU - Institute of Physics of the Czech Academy of Sciences

We propose a qubit-environment entanglement (QEE) detection scheme for time dependent pure dephasing. We study entanglement for a transmon qubit interacting with an environment of microwave cavity photons. Previously developed detection schemes are based on operations performed only on the qubit [1]. They could not be used in the studied scenario because of inherent symmetries in the Hamiltonian. We show that it is possible to override this problem by using different Hamiltonias in the preparation and measurement stages. We use the possibility of tuning of the coupling to detect entanglement. We previously studied the evolution of QEE for the system [2] and now we present how to detect it. The scheme can be used for other systems, where decoherence is predominantly pure dephasing.

[1] M. Strzałka and K. Roszak, Phys. Rev. A 104, 042411 (2021).

[2] M. Strzałka, R. Filip, and K. Roszak, Phys. Rev. A 109, 032412 (2024).

Universal entanglement distillation

Salvatore Tirone, QuSoft, U Amsterdam

We introduce a theoretical protocol for entanglement distillation from classically unknown bipartite quantum states. By performing LOCC-based quantum tomography followed by tailored distillation, we achieve entanglement extraction with bounded error. Our method reveals a trade-off between estimation accuracy and distillation rate, enabling practical entanglement processing under limited state knowledge. The proposed LOCC tomography scheme may also be of independent interest.

Grover's search that can distinguish between different solutions

Hristo Tonchev, INRNE -BAS

Here we present a new modification of Grover's algorithm that can distinguish between different solutions. We use various analytical, semi-analytical and numerical methods in order to analyze the proposed modification and compare it with various well-known modifications of Grover's algorithm. A discussion is also presented regarding the possible applications and future research perspectives of this modification.

We acknowledge the support of Bulgarian National Science Fund Grant No. KP-06-N58/5.

Geometric Phases of an electron subjected to a rotating magnetic field

Juan Carlos Vega, Instituto Politécnico Nacional

In this work, we compute the Berry phase and its generalization, the Aharonov-Anandan phase, for a spin-½ system (an electron) in the presence of a rotating magnetic field. The Hamiltonian of this system is derived, and the theoretical foundations of the geometric phases are reviewed to compute both quantities. Finally, the adiabatic limit of the Aharonov-Anandan phase is analyzed, demonstrating that it reproduces the well-known result of the Berry phase.

Pitch talks: 

The poster session will open with 2-minute Pitch Talks from each poster presenter in Lecture Theatre 1. Please prepare a single presentation page as a PDF, which we will project on the screen in the lecture theatre to accompany your pitch talk.

Send this presentation to us at: qmath@cit.tum.de with the subject header & file name: “Pitch Talk – YOUR NAME” by August 28th at the latest. 

Poster Session:

After the Pitch Talks the posters will be on display in the foyer and you are requested to stand with your poster for discussion with interested participants. 

The posters will be reviewed by our scientific panel and prizes awarded from Springer for the best submissions. 

Format: 

The poster should be DIN A0 size (841 x 1189 mm).

Poster printing: 

If you are unable to bring your poster with you, e.g due to overseas travel, please note that there is no option to print posters at the Garching Research campus or in Garching town. 

We can print posters for you in advance via the printing services of the TUM Electrical Engineering Department. Please consult their website for all relevant information on the format of the files required: https://www.fs.ei.tum.de/en/services/posterdruck/

As we need time for printing and delivery, please submit your poster to us at  qmath@cit.tum.de by Friday, August 22nd to guarantee delivery in time for the conference. Please state in the subject header & file name: “QMATH Poster – YOUR NAME”.

Should you require last minute printing after the deadline, or wish to collect the poster personally on-site in central Munich, then please email the printing department yourself: poster@fs.ei.tum.de

Alternatively you can print at the „Printy“ store in central Munich: https://printy.de/en/homepage-english-2/