Roman-Pascal Riwar
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View article: Frustrated Frustration of Arrays with Four-Terminal Nb-Pt-Nb Josephson Junctions
Frustrated Frustration of Arrays with Four-Terminal Nb-Pt-Nb Josephson Junctions Open
We study the frustration pattern of a square lattice with fabricated Nb-Pt-Nb four-terminal Josephson junctions. The four-terminal geometry gives rise to a checkerboard pattern of alternating fluxes f, f′ piercing the plaquettes, which sta…
View article: Consistent quantum treatments of non-convex kinetic energies
Consistent quantum treatments of non-convex kinetic energies Open
The task of finding a consistent relationship between a quantum Hamiltonian and a classical Lagrangian is of utmost importance for basic, but ubiquitous techniques like canonical quantization and path integrals. Nonconvex kinetic energies …
View article: Emulating moiré materials with quasiperiodic circuit quantum electrodynamics
Emulating moiré materials with quasiperiodic circuit quantum electrodynamics Open
Topological band structures interfering with moiré superstructures give rise to a plethora of emergent phenomena, which are pivotal for correlated insulating and superconducting states of twisttronics materials. While quasiperiodicity was …
View article: Of gyrators and anyons
Of gyrators and anyons Open
In recent years there have emerged various ideas to create and control topological excitations in superconducting devices. Notably, nontrivial Chern bands were predicted to exist in conventional multiterminal Josephson junctions, but the C…
View article: Interplay between evanescent scattering modes and finite dispersion in superconducting junctions
Interplay between evanescent scattering modes and finite dispersion in superconducting junctions Open
Superconducting junctions are essential building blocks for quantum hardware, and their fundamental behaviour remains a highly active research field. The behaviour of generic junctions is conveniently described by Beenakker's determinant f…
View article: On-demand analog space-time in superconducting networks: grey holes, dynamical instability and exceptional points
On-demand analog space-time in superconducting networks: grey holes, dynamical instability and exceptional points Open
There has been considerable effort to mimic analog black holes and wormholes in solid state systems. Lattice realizations in particular present specific challenges. One of those is that event horizons in general have both white and black h…
View article: Limitations of Caldeira-Leggett model for description of phase transitions in superconducting circuits
Limitations of Caldeira-Leggett model for description of phase transitions in superconducting circuits Open
The inherent complexity of system-bath interactions often requires making critical approximations, which we here show to have a radical influence on the renormalization group flow and the resulting phase diagram. Specifically, for the Cald…
View article: Compact description of quantum phase slip junctions
Compact description of quantum phase slip junctions Open
Quantum circuit theory is a powerful tool to describe superconducting circuits. In its language, quantum phase slips (QPSs) are considered to be the exact dual to the Josephson effect. This duality renders the integration of QPS junctions …
View article: Quasiperiodic circuit quantum electrodynamics
Quasiperiodic circuit quantum electrodynamics Open
Superconducting circuits are an extremely versatile platform to realize quantum information hardware and to emulate topological materials. We here show how a simple arrangement of capacitors and conventional superconductor-insulator-superc…
View article: Emulating moiré materials with quasiperiodic circuit quantum electrodynamics
Emulating moiré materials with quasiperiodic circuit quantum electrodynamics Open
Topological bandstructures interfering with moiré superstructures give rise to a plethora of emergent phenomena, which are pivotal for correlated insulating and superconducting states of twisttronics materials. While quasiperiodicity was u…
View article: Time-dependent driving and topological protection in the fractional Josephson effect
Time-dependent driving and topological protection in the fractional Josephson effect Open
The control of any type of quantum hardware invariably necessitates time-dependent driving. If the basis depends on the control parameter, the presence of a time-dependent control field yields an extra term in the Schrödinger equation that…
View article: Discrete control of capacitance in quantum circuits
Discrete control of capacitance in quantum circuits Open
Precise in-situ control of system parameters is indispensable for all quantum hardware applications. The capacitance in a circuit, however, is usually a simple consequence of electrostatics, and thus quite literally cast in stone. We here …
View article: Quasiperiodic circuit quantum electrodynamics
Quasiperiodic circuit quantum electrodynamics Open
Superconducting circuits are an extremely versatile platform to realize quantum information hardware, and, as was recently realized, to emulate topological materials, such as three-dimensional Weyl semimetals or two-dimensional Chern insul…
View article: Compact description of quantum phase slip junctions
Compact description of quantum phase slip junctions Open
Quantum circuit theory is a powerful and ever-evolving tool to predict the dynamics of superconducting circuits. In its language, quantum phase slips (QPSs) are famously considered to be the exact dual to the Josephson effect. However, thi…
View article: Quasiperiodic circuit quantum electrodynamics
Quasiperiodic circuit quantum electrodynamics Open
Superconducting circuits are an extremely versatile platform to realize quantum information hardware and to emulate topological materials. We here show how a simple arrangement of capacitors and conventional superconductor-insulator-superc…
View article: Electromotive force in driven topological quantum circuits
Electromotive force in driven topological quantum circuits Open
Time-dependent control of superconducting quantum circuits is a prerequisite for building scalable quantum hardware. The quantum description of these circuits is complicated due to the electromotive force (emf) induced by time-varying magn…
View article: Compact description of quantum phase slip junctions
Compact description of quantum phase slip junctions Open
Quantum circuit theory is a powerful and ever-evolving tool to predict the dynamics of superconducting circuits. In its language, quantum phase slips (QPSs) are famously considered to be the exact dual to the Josephson effect. However, thi…
View article: Fractional Josephson effect versus fractional charge in superconducting-normal metal hybrid circuits
Fractional Josephson effect versus fractional charge in superconducting-normal metal hybrid circuits Open
Fractionally charged excitations play a central role in condensed matter physics, and can be probed in different ways. If transport occurs via dissipation-less supercurrents, they manifest as a fractional Josephson effect, whereas in dissi…
View article: Circuit quantization with time-dependent magnetic fields for realistic geometries
Circuit quantization with time-dependent magnetic fields for realistic geometries Open
Quantum circuit theory has become a powerful and indispensable tool to predict the dynamics of superconducting circuits. Surprisingly however, the question of how to properly account for a time-dependent driving via external magnetic field…
View article: Cooper-pair transistor as a minimal topological quantum circuit
Cooper-pair transistor as a minimal topological quantum circuit Open
The outlook of protected quantum computing spurred enormous progress in the\nsearch for topological materials, sustaining a continued race to find the most\nexperimentally feasible platform. Here, we show that one of the simplest\nquantum …
View article: Charge quantization and detector resolution
Charge quantization and detector resolution Open
Charge quantization, or the absence thereof, is a central theme in quantum circuit theory, with dramatic consequences for the predicted circuit dynamics. Very recently, the question of whether or not charge should actually be described as …
View article: Report on 2012.13012v3
Report on 2012.13012v3 Open
Charge quantization, or the absence thereof, is a central theme in quantum circuit theory, with dramatic consequences for the predicted circuit dynamics.Very recently, the question of whether or not charge should actually be described as q…
View article: Circuit quantization with time-dependent magnetic fields for realistic geometries
Circuit quantization with time-dependent magnetic fields for realistic geometries Open
Quantum circuit theory has become a powerful and indispensable tool to predict the dynamics of superconducting circuits. Surprisingly however, the question of how to properly account for a time-dependent driving via external magnetic field…
View article: Report on 2012.13012v3
Report on 2012.13012v3 Open
Charge quantization, or the absence thereof, is a central theme in quantum circuit theory, with dramatic consequences for the predicted circuit dynamics.Very recently, the question of whether or not charge should actually be described as q…
View article: A "minimal" topological quantum circuit
A "minimal" topological quantum circuit Open
The outlook of protected quantum computing spurred enormous progress in the search for topological materials, sustaining a continued race to find the most experimentally feasible platform. Here, we show that one of the simplest quantum cir…
View article: Fractional charges in conventional sequential electron tunneling
Fractional charges in conventional sequential electron tunneling Open
The notion of fractional charges was up until now reserved for quasiparticle\nexcitations emerging in strongly correlated quantum systems, such as Laughlin\nstates in the fractional quantum Hall effect, Luttinger quasiparticles, or\nparafe…
View article: Efficient quasiparticle traps with low dissipation through gap engineering
Efficient quasiparticle traps with low dissipation through gap engineering Open
Quasiparticles represent an intrinsic source of perturbation for superconducting qubits, leading to both dissipation of the qubit energy and dephasing. Recently, it has been shown that normal-metal traps may efficiently reduce the quasipar…
View article: Dissipation by normal-metal traps in transmon qubits
Dissipation by normal-metal traps in transmon qubits Open
Quasiparticles are an intrinsic source of relaxation and decoherence for\nsuperconducting qubits. Recent works have shown that normal-metal traps may be\nused to evacuate quasiparticles, and potentially improve the qubit life time.\nHere, …
View article: Optimal Configurations for Normal-Metal Traps in Transmon Qubits
Optimal Configurations for Normal-Metal Traps in Transmon Qubits Open
Controlling quasiparticle dynamics can improve the performance of superconducting devices. For example, it has been demonstrated effective in increasing the lifetime and stability of superconducting qubits. In this work, we study how to op…
View article: Topological transconductance quantization in a four-terminal Josephson junction
Topological transconductance quantization in a four-terminal Josephson junction Open
Recently we predicted that the Andreev bound-state spectrum of four-terminal Josephson junctions may possess topologically protected zero-energy Weyl singularities, which manifest themselves in a quantized transconductance in units of 4e2/…