Frank Pollmann
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View article: Non-Universality from Conserved Superoperators in Unitary Circuits
Non-Universality from Conserved Superoperators in Unitary Circuits Open
An important result in the theory of quantum control is the "universality" of $2$-local unitary gates, i.e. the fact that any global unitary evolution of a system of $L$ qudits can be implemented by composition of $2$-local unitary gates. …
View article: Non-Universality from Conserved Superoperators in Unitary Circuits
Non-Universality from Conserved Superoperators in Unitary Circuits Open
An important result in the theory of quantum control is the "universality" of $2$-local unitary gates, i.e. the fact that any global unitary evolution of a system of $L$ qudits can be implemented by composition of $2$-local unitary gates. …
View article: Unconventional spin dynamics and supersolid excitations in the triangular-lattice XXZ model
Unconventional spin dynamics and supersolid excitations in the triangular-lattice XXZ model Open
Motivated by recent experiments, we investigate the spin- 1 2 XXZ model on the triangular lattice with strong Ising anisotropy, combining large-scale numerical simulations and analytical methods to uncover unconventional spin dynamics …
View article: Simulating Topological Order on Quantum Processors
Simulating Topological Order on Quantum Processors Open
It is an ongoing quest to realize topologically ordered quantum states on different platforms including condensed matter systems, quantum simulators and digital quantum processors. Unlike conventional states characterized by their local or…
View article: Recipe for local simulation of strongly correlated fermionic matter on quantum computers: The two-dimensional Fermi-Hubbard model
Recipe for local simulation of strongly correlated fermionic matter on quantum computers: The two-dimensional Fermi-Hubbard model Open
The simulation of quantum many-body systems, relevant for quantum chemistry and condensed matter physics, is one of the most promising applications of near-term quantum computers before fault-tolerance. However, since the vast majority of …
View article: Anisotropic spin ice on a breathing pyrochlore lattice
Anisotropic spin ice on a breathing pyrochlore lattice Open
Spin ice systems represent a prime example of constrained spin systems and exhibit rich low-energy physics. In this study, we explore how introducing a tunable anisotropic spin coupling to the conventional Ising spin ice Hamiltonian on the…
View article: Dynamics in the presence of local symmetry-breaking impurities
Dynamics in the presence of local symmetry-breaking impurities Open
Continuous symmetries lead to universal slow relaxation of correlation functions in quantum many-body systems. In this work, we study how local symmetry-breaking impurities affect the dynamics of these correlation functions using Brownian …
View article: Alternating and Gaussian Fermionic Isometric Tensor Network States
Alternating and Gaussian Fermionic Isometric Tensor Network States Open
Isometric tensor networks in two dimensions enable efficient and accurate study of quantum many-body states, yet the effect of the isometric restriction on the represented quantum states is not fully understood. We address this question in…
View article: Quantum phase transitions between symmetry-enriched fracton phases
Quantum phase transitions between symmetry-enriched fracton phases Open
Topologically ordered phases exhibit further complexity in the presence of global symmetries: Their anyonic excitations may exhibit different transformation patterns under these symmetries, leading to a classification in terms of symmetry-…
View article: Genuine Topological Anderson Insulator from Impurity Induced Chirality Reversal
Genuine Topological Anderson Insulator from Impurity Induced Chirality Reversal Open
We investigate a model of Dirac fermions with mass impurities that open a global topological gap even in the dilute limit. Surprisingly, we find that the chirality of this mass term, i.e., the sign of the Chern number, can be reversed by t…
View article: Probing non-equilibrium topological order on a quantum processor
Probing non-equilibrium topological order on a quantum processor Open
Out-of-equilibrium phases in many-body systems constitute a new paradigm in quantum matter—they exhibit dynamical properties that may otherwise be forbidden by equilibrium thermodynamics. Among these non-equilibrium phases are periodically…
View article: Typical machine learning datasets as low-depth quantum circuits
Typical machine learning datasets as low-depth quantum circuits Open
Quantum machine learning (QML) is an emerging field that investigates the capabilities of quantum computers for learning tasks. While QML models can theoretically offer advantages such as exponential speed-ups, challenges in data loading a…
View article: Disentangling strategies and entanglement transitions in unitary circuit games with matchgates
Disentangling strategies and entanglement transitions in unitary circuit games with matchgates Open
In unitary circuit games, two competing parties, an "entangler" and a "disentangler", can induce an entanglement phase transition in a quantum many-body system. The transition occurs at a certain rate at which the disentangler acts. We ana…
View article: Tensor-Network Study of the Roughening Transition in a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mi mathvariant="normal">D</mml:mi></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="double-struck">Z</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> Lattice Gauge Theory with Matter
Tensor-Network Study of the Roughening Transition in a Lattice Gauge Theory with Matter Open
Within the confined phase of (2+1)D lattice gauge theories a roughening transition arises between a weakly confined regime with floppy string excitations and a strongly confined regime with stiff string excitations. In this Letter, we use …
View article: Entanglement Holography in Quantum Phases via Twisted Rényi-N Correlators
Entanglement Holography in Quantum Phases via Twisted Rényi-N Correlators Open
We introduce a holographic framework for the entanglement Hamiltonian in symmetry-protected topological (SPT) phases with area-law entanglement, whose reduced density matrix $ρ\propto e^{-H_e}$ can be treated as a lower-dimensional mixed s…
View article: Quantum Entrepreneurship Lab: Training a Future Workforce for the Quantum Industry
Quantum Entrepreneurship Lab: Training a Future Workforce for the Quantum Industry Open
The Quantum Entrepreneurship Lab (QEL) is a one-semester, project-based course at the Technical University of Munich (TUM), designed to bridge the gap between academic research and industrial application in the quantum sector. As part of t…
View article: Typical Machine Learning Datasets as Low-Depth Quantum Circuits
Typical Machine Learning Datasets as Low-Depth Quantum Circuits Open
Quantum machine learning (QML) is an emerging field that investigates the capabilities of quantum computers for learning tasks. While QML models can theoretically offer advantages such as exponential speed-ups, challenges in data loading a…
View article: Anisotropic Spin Ice on a Breathing Pyrochlore Lattice
Anisotropic Spin Ice on a Breathing Pyrochlore Lattice Open
Spin ice systems represent a prime example of constrained spin systems and exhibit rich low-energy physics. In this study, we explore how introducing a tunable anisotropic spin coupling to the conventional Ising spin ice Hamiltonian on the…
View article: Emergent Fracton Hydrodynamics of Ultracold Atoms in Partially Filled Landau Levels
Emergent Fracton Hydrodynamics of Ultracold Atoms in Partially Filled Landau Levels Open
The realization of synthetic gauge fields for charge neutral ultracold atoms and the simulation of quantum Hall physics have witnessed remarkable experimental progress. Here, we establish key signatures of fractional quantum Hall systems i…
View article: Digital quantum magnetism at the frontier of classical simulations
Digital quantum magnetism at the frontier of classical simulations Open
The utility of near-term quantum computers for simulating realistic quantum systems hinges on the stability of digital quantum matter--realized when discrete quantum gates approximate continuous time evolution--and whether it can be mainta…
View article: Tensor-Network Study of the Roughening Transition in (2 + 1)D lattice gauge theories
Tensor-Network Study of the Roughening Transition in (2 + 1)D lattice gauge theories Open
Within the confined phase of (2+1)D lattice gauge theories a roughening transition arises between a weakly confined regime with floppy string excitations and a strongly confined regime with stiff string excitations. In this work, we use an…
View article: Highly Entangled Stationary States from Strong Symmetries
Highly Entangled Stationary States from Strong Symmetries Open
We find that the presence of strong non-Abelian symmetries can lead to highly entangled stationary states even for unital quantum channels. We derive exact expressions for the bipartite logarithmic negativity, Rényi negativities, and opera…
View article: Information-theoretic principle of emergent 1-form symmetries
Information-theoretic principle of emergent 1-form symmetries Open
Higher-form symmetries act on sub-dimensional spatial manifolds of a quantum system. They can emerge as an exact symmetry at low energies even when they are explicitly broken at the microscopic level, making them difficult to characterize.…
View article: Alternating and Gaussian fermionic Isometric Tensor Network States
Alternating and Gaussian fermionic Isometric Tensor Network States Open
Isometric tensor networks in two dimensions enable efficient and accurate study of quantum many-body states, yet the effect of the isometric restriction on the represented quantum states is not fully understood. We address this question in…
View article: Quantum Phase Transitions between Symmetry-Enriched Fracton Phases
Quantum Phase Transitions between Symmetry-Enriched Fracton Phases Open
Topologically ordered phases exhibit further complexity in the presence of global symmetries: Their anyonic excitations may exhibit different transformation patterns under these symmetries, leading to a classification in terms of symmetry-…
View article: Probing non-equilibrium topological order on a quantum processor
Probing non-equilibrium topological order on a quantum processor Open
Out-of-equilibrium phases in many-body systems constitute a new paradigm in quantum matter - they exhibit dynamical properties that may otherwise be forbidden by equilibrium thermodynamics. Among these non-equilibrium phases are periodical…
View article: Fractonic critical point proximate to a higher-order topological insulator: A Coupled wire approach
Fractonic critical point proximate to a higher-order topological insulator: A Coupled wire approach Open
We propose an unconventional topological quantum phase transition between a higher-order topological insulator (HOTI) and a featureless Mott insulator, both sharing the same symmetry patterns. Our approach constructs an effective theory fo…
View article: Entanglement Properties of Gauge Theories from Higher-Form Symmetries
Entanglement Properties of Gauge Theories from Higher-Form Symmetries Open
We explore the relationship between higher-form symmetries and entanglement properties in lattice gauge theories with discrete gauge groups, which can exhibit both topologically ordered phases and higher-form symmetry-protected topological…
View article: Simulating two-dimensional topological quantum phase transitions on a digital quantum computer
Simulating two-dimensional topological quantum phase transitions on a digital quantum computer Open
Efficient preparation of many-body ground states is key to harnessing the power of quantum computers in studying quantum many-body systems. In this work, we propose a simple method to design exact linear-depth parameterized quantum circuit…