Theoretische Physik (Bruder)Head of Research Unit Prof. Dr.Christoph BruderOverviewMembersPublicationsProjects & CollaborationsProjects & Collaborations OverviewMembersPublicationsProjects & Collaborations Projects & Collaborations 16 foundShow per page10 10 20 50 Quantum synchronization and quantum phase transitions in arrays of nano- and optomechanical systems Research Project | 1 Project MembersWe will explore novel aspects of quantum synchronization in networks of self-sustained oscillators. This includes even-odd effects in the number of levels of the synchronization nodes and the dependence on network topology (number of neighbors and interaction range). Another interesting direction that we will study is frustration effects and possible links to frustrated quantum spin systems. Furthermore, we will investigate symmetry-breaking pattern formation in synchronization networks Using unsupervised machine-learning schemes, we will investigate phase diagrams of models that exhibit synchronization or other types of long-range order. We will also explore neural network architectures that involve physical insights and recent innovations in machine learning to compute steady states of driven dissipative quantum systems. Single organelle size sorting by a nanofluidic device Research Project | 3 Project MembersReduction of the number and size of mitochondria in dopaminergic neurons of the central nerve system is the hallmark of neurodegenerative Parkinson's disease. We here propose to establish a method to quantify the number and size of mitochondrial organelles, to provide a direct diagnostic tool for Parkinson's disease. The proposed single-organelle size sorter is shown in the figure (not to scale). Nanochannels with a variable height are realized in PDMS, using gray scale lithography and bonded on a glass slide. A single cell is lysed with osmotic pressure and the solution is introduced into a nanochannel via capillary forces. The bioparticles are sterically trapped at different locations, thus static size sorting is achieved. The width of the channels is sufficiently large to avoid clogging so that the particles reach their steric trapping position. Size distribution and density of certain bioparticles are evaluated under an optical microscope. Quantum coherence, quantum statistics, and superconductivity in mesoscopic systems Research Project | 1 Project MembersA. Quantum coherence and statistics of mesoscopic system We will explore novel nano- and optomechanical setups and their applications (phononic structures, combined photonic and phononic crystals, quantum dots embedded in nanowires, and trapped ions). We will propose and analyze new transport experiments with ultracold atoms, e.g. addressing the question of the phase dependence of heat transport. We will analyze models that illustrate how system-mediated detector-detector interactions will determine the measured operator order in a quantum correlation measurement. B. Mesoscopic superconductivity We will investigate a quantum realization of the Kuramoto model in a one-dimensional Josephson array. Using a tight-binding approach we will explore the influence of magnetic disorder on the disorder-induced 2D topological insulator state, the so-called topological Anderson insulator. Lastly, we will investigate the possibility to use superconducting transmon qubits as an implementation of driven anharmonic self-oscillators. This would lead to applications in the study of dissipative quantum phase transitions. A3EDPI - Applicability of 3D Electron Diffraction in the Pharmaceutical Industry Research Project | 3 Project MembersNo Description available Generic Helical Liquids in 2D Topological Insulators: Transport Properties and Applications Research Project | 1 Project MembersThis research proposal focuses on the investigation of electronic transport properties ofmetallic helical edge states of two-dimensional topological insulators. The objectives canbe divided into two major parts.The first part is devoted to the investigation of fundamental properties of the helical liquids.In a recent paper [Schmidt et al., Phys. Rev. Lett. 108, 156402 (2012)], we introduced theconcept of a generic helical liquid (GHL). This is the most general model of a time-reversalinvariant helical liquid without axial spin symmetry. This symmetry is usually broken inexperimental realizations, and we showed that its absence changes the transport propertiessignificantly. In the first part of this project, we will investigate transport properties ofinteracting GHLs in the presence of disorder, the effect of a weak breaking of time-reversalsymmetry, and we will develop proposals on how to measure the spin structure of the helicaledge states.The second part focuses on nanostructured geometries of two-dimensional topologicalinsulators which can be realized in experiments and allow a more detailed characterizationof the properties of GHLs. In particular, we shall examine antidots, which are coupled bytunnelling to the edges of the sample. We shall use a combination of numerical and analytictechniques to determine the current through such an antidot. We expect it to display adistinctive interference pattern which is unique to GHLs. Moreover, we shall investigate therole of the charging energy on the antidot and the possible emergence of the Kondo effect. NCCR QSIT: Quantum Sensing Research Project | 7 Project MembersThe readout of quantum states is part of any quantum information proces- sor and the question of a quantum measurement is a central one in quantum mechanics. In Project 1 we focus on quantum sensing - that is the development of well characterized quantum systems that will be used to probe either ultra-weak classical fields or complex quantum systems. Single qubits or oscillators designed and perfected to have ultra-long coherence times can be extremely sensitive to small electric or magnetic fields. QSIT researchers will use cutting-edge nano-technology to fully exploit the power of systems such as nano-mechanical oscil lators or nitrogen-vacancy (NV) centers in diamond, to engineer ultimate "quantum meters". NCCR QSIT: Quantum Simulation Research Project | 1 Project MembersProject 4 focuses on the realization of quantum simulators. While the ultimate goal is the physical realization of condensed-matter models that can- not be solved using classical computers the realization of topological states using ultra-cold bosonic or fermionic atoms will also be pursued. Quantum coherence, quantum statistics, and superconductivity Research Project | 3 Project MembersThe physics of mesoscopic quantum systems, i.e., electronic structures in the nanometer range, is one of the most active research areas of condensed-matter physics. These systems allow us to study fundamental physics questions, and their understanding is necessary for possible future electronic device applications. The goal of our research is to exploit and analyze quantum effects in such circuits, e.g. novel excitations like Majorana quasiparticles. These particles have been predicted but not yet been found in particle physics. Another interesting field that we work on is generalized quantum measurements and quantum model systems that can be used to test the foundations and limits of quantum mechanics. In particular, our group (about 3 PhD students and 3 Postdocs) plans to study the interplay of electric currents through nanostructures with mechanical degrees of freedom (nanomechanics). We are also interested in fluctuation and noise phenomena: electrical currents are not exactly constant but fluctuate, and these fluctuations contain a great deal of information about the quantum nature of the electrons that carry the current. We will also investigate ultracold atoms which can be used to study quantum coherence and quantum many-body phenomena. Finally, we study macroscopic quantum phenomena like superconductivity. Cooling, Amplification, and Lasing in the reversed dissipation regime of cavity Research Project | 2 Project MembersP { margin-bottom: 0.08in; direction: ltr; color: rgb(0, 0, 0); widows: 2; orphans: 2; }P.western { } Cavity optomechanical phenomena, e.g. cooling, amplification or optomechanically-induced transparency, emerge due a stark imbalance between the dissipation rates of the optical and mechanical degrees of freedom. However, it has been an unquestioned assumption that the mechanical damping rate is much smaller than optical dissipation rate. Our goal is to investigate the regime of reversed dissipation hierarchy where the mechanical damping rate is much larger than the optical line width. We will show that this regime can be exploited for cooling and amplifying microwave signals and leads to novel lasing phenomena. The project will be carried out in close collaboration with the group of Tobias Kippenberg, in particular between Andreas Nunnenkamp (Basel) and Vivishek Sudhir (EPFL). Quantum information processing with superconducting qubits and molecular magnets Research Project | 1 Project MembersThe laws of Physics constrain the task of information processing. The possibility to control matter and light in their quantum states opens up the possibility to investigate how the laws of quantum physics can alter the paradigm of computation and possibly lead to exponential increase in computational efficiency for certain problems. This project aims at furthering our understanding of one very promising architecture for quantum information processing, namely superconducting circuits composed of Josephson junctions and microwave oscillators. In particular we propose to investigate the possibilities to engineer quantum logic operations based on utilizing a geometric phase effect discovered in the early 80's. We also propose to explore possibilities to implement non-linear oscillators with superconducting circuits in a recently demonstrated regime of ultra-strong dispersive coupling between light and matter. Finally, as part of this project we plan to explore the coherence properties of molecular magnet systems coupled to the magnetic field of microwave resonators. 12 12 OverviewMembersPublicationsProjects & Collaborations
Projects & Collaborations 16 foundShow per page10 10 20 50 Quantum synchronization and quantum phase transitions in arrays of nano- and optomechanical systems Research Project | 1 Project MembersWe will explore novel aspects of quantum synchronization in networks of self-sustained oscillators. This includes even-odd effects in the number of levels of the synchronization nodes and the dependence on network topology (number of neighbors and interaction range). Another interesting direction that we will study is frustration effects and possible links to frustrated quantum spin systems. Furthermore, we will investigate symmetry-breaking pattern formation in synchronization networks Using unsupervised machine-learning schemes, we will investigate phase diagrams of models that exhibit synchronization or other types of long-range order. We will also explore neural network architectures that involve physical insights and recent innovations in machine learning to compute steady states of driven dissipative quantum systems. Single organelle size sorting by a nanofluidic device Research Project | 3 Project MembersReduction of the number and size of mitochondria in dopaminergic neurons of the central nerve system is the hallmark of neurodegenerative Parkinson's disease. We here propose to establish a method to quantify the number and size of mitochondrial organelles, to provide a direct diagnostic tool for Parkinson's disease. The proposed single-organelle size sorter is shown in the figure (not to scale). Nanochannels with a variable height are realized in PDMS, using gray scale lithography and bonded on a glass slide. A single cell is lysed with osmotic pressure and the solution is introduced into a nanochannel via capillary forces. The bioparticles are sterically trapped at different locations, thus static size sorting is achieved. The width of the channels is sufficiently large to avoid clogging so that the particles reach their steric trapping position. Size distribution and density of certain bioparticles are evaluated under an optical microscope. Quantum coherence, quantum statistics, and superconductivity in mesoscopic systems Research Project | 1 Project MembersA. Quantum coherence and statistics of mesoscopic system We will explore novel nano- and optomechanical setups and their applications (phononic structures, combined photonic and phononic crystals, quantum dots embedded in nanowires, and trapped ions). We will propose and analyze new transport experiments with ultracold atoms, e.g. addressing the question of the phase dependence of heat transport. We will analyze models that illustrate how system-mediated detector-detector interactions will determine the measured operator order in a quantum correlation measurement. B. Mesoscopic superconductivity We will investigate a quantum realization of the Kuramoto model in a one-dimensional Josephson array. Using a tight-binding approach we will explore the influence of magnetic disorder on the disorder-induced 2D topological insulator state, the so-called topological Anderson insulator. Lastly, we will investigate the possibility to use superconducting transmon qubits as an implementation of driven anharmonic self-oscillators. This would lead to applications in the study of dissipative quantum phase transitions. A3EDPI - Applicability of 3D Electron Diffraction in the Pharmaceutical Industry Research Project | 3 Project MembersNo Description available Generic Helical Liquids in 2D Topological Insulators: Transport Properties and Applications Research Project | 1 Project MembersThis research proposal focuses on the investigation of electronic transport properties ofmetallic helical edge states of two-dimensional topological insulators. The objectives canbe divided into two major parts.The first part is devoted to the investigation of fundamental properties of the helical liquids.In a recent paper [Schmidt et al., Phys. Rev. Lett. 108, 156402 (2012)], we introduced theconcept of a generic helical liquid (GHL). This is the most general model of a time-reversalinvariant helical liquid without axial spin symmetry. This symmetry is usually broken inexperimental realizations, and we showed that its absence changes the transport propertiessignificantly. In the first part of this project, we will investigate transport properties ofinteracting GHLs in the presence of disorder, the effect of a weak breaking of time-reversalsymmetry, and we will develop proposals on how to measure the spin structure of the helicaledge states.The second part focuses on nanostructured geometries of two-dimensional topologicalinsulators which can be realized in experiments and allow a more detailed characterizationof the properties of GHLs. In particular, we shall examine antidots, which are coupled bytunnelling to the edges of the sample. We shall use a combination of numerical and analytictechniques to determine the current through such an antidot. We expect it to display adistinctive interference pattern which is unique to GHLs. Moreover, we shall investigate therole of the charging energy on the antidot and the possible emergence of the Kondo effect. NCCR QSIT: Quantum Sensing Research Project | 7 Project MembersThe readout of quantum states is part of any quantum information proces- sor and the question of a quantum measurement is a central one in quantum mechanics. In Project 1 we focus on quantum sensing - that is the development of well characterized quantum systems that will be used to probe either ultra-weak classical fields or complex quantum systems. Single qubits or oscillators designed and perfected to have ultra-long coherence times can be extremely sensitive to small electric or magnetic fields. QSIT researchers will use cutting-edge nano-technology to fully exploit the power of systems such as nano-mechanical oscil lators or nitrogen-vacancy (NV) centers in diamond, to engineer ultimate "quantum meters". NCCR QSIT: Quantum Simulation Research Project | 1 Project MembersProject 4 focuses on the realization of quantum simulators. While the ultimate goal is the physical realization of condensed-matter models that can- not be solved using classical computers the realization of topological states using ultra-cold bosonic or fermionic atoms will also be pursued. Quantum coherence, quantum statistics, and superconductivity Research Project | 3 Project MembersThe physics of mesoscopic quantum systems, i.e., electronic structures in the nanometer range, is one of the most active research areas of condensed-matter physics. These systems allow us to study fundamental physics questions, and their understanding is necessary for possible future electronic device applications. The goal of our research is to exploit and analyze quantum effects in such circuits, e.g. novel excitations like Majorana quasiparticles. These particles have been predicted but not yet been found in particle physics. Another interesting field that we work on is generalized quantum measurements and quantum model systems that can be used to test the foundations and limits of quantum mechanics. In particular, our group (about 3 PhD students and 3 Postdocs) plans to study the interplay of electric currents through nanostructures with mechanical degrees of freedom (nanomechanics). We are also interested in fluctuation and noise phenomena: electrical currents are not exactly constant but fluctuate, and these fluctuations contain a great deal of information about the quantum nature of the electrons that carry the current. We will also investigate ultracold atoms which can be used to study quantum coherence and quantum many-body phenomena. Finally, we study macroscopic quantum phenomena like superconductivity. Cooling, Amplification, and Lasing in the reversed dissipation regime of cavity Research Project | 2 Project MembersP { margin-bottom: 0.08in; direction: ltr; color: rgb(0, 0, 0); widows: 2; orphans: 2; }P.western { } Cavity optomechanical phenomena, e.g. cooling, amplification or optomechanically-induced transparency, emerge due a stark imbalance between the dissipation rates of the optical and mechanical degrees of freedom. However, it has been an unquestioned assumption that the mechanical damping rate is much smaller than optical dissipation rate. Our goal is to investigate the regime of reversed dissipation hierarchy where the mechanical damping rate is much larger than the optical line width. We will show that this regime can be exploited for cooling and amplifying microwave signals and leads to novel lasing phenomena. The project will be carried out in close collaboration with the group of Tobias Kippenberg, in particular between Andreas Nunnenkamp (Basel) and Vivishek Sudhir (EPFL). Quantum information processing with superconducting qubits and molecular magnets Research Project | 1 Project MembersThe laws of Physics constrain the task of information processing. The possibility to control matter and light in their quantum states opens up the possibility to investigate how the laws of quantum physics can alter the paradigm of computation and possibly lead to exponential increase in computational efficiency for certain problems. This project aims at furthering our understanding of one very promising architecture for quantum information processing, namely superconducting circuits composed of Josephson junctions and microwave oscillators. In particular we propose to investigate the possibilities to engineer quantum logic operations based on utilizing a geometric phase effect discovered in the early 80's. We also propose to explore possibilities to implement non-linear oscillators with superconducting circuits in a recently demonstrated regime of ultra-strong dispersive coupling between light and matter. Finally, as part of this project we plan to explore the coherence properties of molecular magnet systems coupled to the magnetic field of microwave resonators. 12 12
Quantum synchronization and quantum phase transitions in arrays of nano- and optomechanical systems Research Project | 1 Project MembersWe will explore novel aspects of quantum synchronization in networks of self-sustained oscillators. This includes even-odd effects in the number of levels of the synchronization nodes and the dependence on network topology (number of neighbors and interaction range). Another interesting direction that we will study is frustration effects and possible links to frustrated quantum spin systems. Furthermore, we will investigate symmetry-breaking pattern formation in synchronization networks Using unsupervised machine-learning schemes, we will investigate phase diagrams of models that exhibit synchronization or other types of long-range order. We will also explore neural network architectures that involve physical insights and recent innovations in machine learning to compute steady states of driven dissipative quantum systems.
Single organelle size sorting by a nanofluidic device Research Project | 3 Project MembersReduction of the number and size of mitochondria in dopaminergic neurons of the central nerve system is the hallmark of neurodegenerative Parkinson's disease. We here propose to establish a method to quantify the number and size of mitochondrial organelles, to provide a direct diagnostic tool for Parkinson's disease. The proposed single-organelle size sorter is shown in the figure (not to scale). Nanochannels with a variable height are realized in PDMS, using gray scale lithography and bonded on a glass slide. A single cell is lysed with osmotic pressure and the solution is introduced into a nanochannel via capillary forces. The bioparticles are sterically trapped at different locations, thus static size sorting is achieved. The width of the channels is sufficiently large to avoid clogging so that the particles reach their steric trapping position. Size distribution and density of certain bioparticles are evaluated under an optical microscope.
Quantum coherence, quantum statistics, and superconductivity in mesoscopic systems Research Project | 1 Project MembersA. Quantum coherence and statistics of mesoscopic system We will explore novel nano- and optomechanical setups and their applications (phononic structures, combined photonic and phononic crystals, quantum dots embedded in nanowires, and trapped ions). We will propose and analyze new transport experiments with ultracold atoms, e.g. addressing the question of the phase dependence of heat transport. We will analyze models that illustrate how system-mediated detector-detector interactions will determine the measured operator order in a quantum correlation measurement. B. Mesoscopic superconductivity We will investigate a quantum realization of the Kuramoto model in a one-dimensional Josephson array. Using a tight-binding approach we will explore the influence of magnetic disorder on the disorder-induced 2D topological insulator state, the so-called topological Anderson insulator. Lastly, we will investigate the possibility to use superconducting transmon qubits as an implementation of driven anharmonic self-oscillators. This would lead to applications in the study of dissipative quantum phase transitions.
A3EDPI - Applicability of 3D Electron Diffraction in the Pharmaceutical Industry Research Project | 3 Project MembersNo Description available
Generic Helical Liquids in 2D Topological Insulators: Transport Properties and Applications Research Project | 1 Project MembersThis research proposal focuses on the investigation of electronic transport properties ofmetallic helical edge states of two-dimensional topological insulators. The objectives canbe divided into two major parts.The first part is devoted to the investigation of fundamental properties of the helical liquids.In a recent paper [Schmidt et al., Phys. Rev. Lett. 108, 156402 (2012)], we introduced theconcept of a generic helical liquid (GHL). This is the most general model of a time-reversalinvariant helical liquid without axial spin symmetry. This symmetry is usually broken inexperimental realizations, and we showed that its absence changes the transport propertiessignificantly. In the first part of this project, we will investigate transport properties ofinteracting GHLs in the presence of disorder, the effect of a weak breaking of time-reversalsymmetry, and we will develop proposals on how to measure the spin structure of the helicaledge states.The second part focuses on nanostructured geometries of two-dimensional topologicalinsulators which can be realized in experiments and allow a more detailed characterizationof the properties of GHLs. In particular, we shall examine antidots, which are coupled bytunnelling to the edges of the sample. We shall use a combination of numerical and analytictechniques to determine the current through such an antidot. We expect it to display adistinctive interference pattern which is unique to GHLs. Moreover, we shall investigate therole of the charging energy on the antidot and the possible emergence of the Kondo effect.
NCCR QSIT: Quantum Sensing Research Project | 7 Project MembersThe readout of quantum states is part of any quantum information proces- sor and the question of a quantum measurement is a central one in quantum mechanics. In Project 1 we focus on quantum sensing - that is the development of well characterized quantum systems that will be used to probe either ultra-weak classical fields or complex quantum systems. Single qubits or oscillators designed and perfected to have ultra-long coherence times can be extremely sensitive to small electric or magnetic fields. QSIT researchers will use cutting-edge nano-technology to fully exploit the power of systems such as nano-mechanical oscil lators or nitrogen-vacancy (NV) centers in diamond, to engineer ultimate "quantum meters".
NCCR QSIT: Quantum Simulation Research Project | 1 Project MembersProject 4 focuses on the realization of quantum simulators. While the ultimate goal is the physical realization of condensed-matter models that can- not be solved using classical computers the realization of topological states using ultra-cold bosonic or fermionic atoms will also be pursued.
Quantum coherence, quantum statistics, and superconductivity Research Project | 3 Project MembersThe physics of mesoscopic quantum systems, i.e., electronic structures in the nanometer range, is one of the most active research areas of condensed-matter physics. These systems allow us to study fundamental physics questions, and their understanding is necessary for possible future electronic device applications. The goal of our research is to exploit and analyze quantum effects in such circuits, e.g. novel excitations like Majorana quasiparticles. These particles have been predicted but not yet been found in particle physics. Another interesting field that we work on is generalized quantum measurements and quantum model systems that can be used to test the foundations and limits of quantum mechanics. In particular, our group (about 3 PhD students and 3 Postdocs) plans to study the interplay of electric currents through nanostructures with mechanical degrees of freedom (nanomechanics). We are also interested in fluctuation and noise phenomena: electrical currents are not exactly constant but fluctuate, and these fluctuations contain a great deal of information about the quantum nature of the electrons that carry the current. We will also investigate ultracold atoms which can be used to study quantum coherence and quantum many-body phenomena. Finally, we study macroscopic quantum phenomena like superconductivity.
Cooling, Amplification, and Lasing in the reversed dissipation regime of cavity Research Project | 2 Project MembersP { margin-bottom: 0.08in; direction: ltr; color: rgb(0, 0, 0); widows: 2; orphans: 2; }P.western { } Cavity optomechanical phenomena, e.g. cooling, amplification or optomechanically-induced transparency, emerge due a stark imbalance between the dissipation rates of the optical and mechanical degrees of freedom. However, it has been an unquestioned assumption that the mechanical damping rate is much smaller than optical dissipation rate. Our goal is to investigate the regime of reversed dissipation hierarchy where the mechanical damping rate is much larger than the optical line width. We will show that this regime can be exploited for cooling and amplifying microwave signals and leads to novel lasing phenomena. The project will be carried out in close collaboration with the group of Tobias Kippenberg, in particular between Andreas Nunnenkamp (Basel) and Vivishek Sudhir (EPFL).
Quantum information processing with superconducting qubits and molecular magnets Research Project | 1 Project MembersThe laws of Physics constrain the task of information processing. The possibility to control matter and light in their quantum states opens up the possibility to investigate how the laws of quantum physics can alter the paradigm of computation and possibly lead to exponential increase in computational efficiency for certain problems. This project aims at furthering our understanding of one very promising architecture for quantum information processing, namely superconducting circuits composed of Josephson junctions and microwave oscillators. In particular we propose to investigate the possibilities to engineer quantum logic operations based on utilizing a geometric phase effect discovered in the early 80's. We also propose to explore possibilities to implement non-linear oscillators with superconducting circuits in a recently demonstrated regime of ultra-strong dispersive coupling between light and matter. Finally, as part of this project we plan to explore the coherence properties of molecular magnet systems coupled to the magnetic field of microwave resonators.
