Publications
For a complete list, please visit Google Scholar.
Systematic Construction of Time-Dependent Hamiltonians for Microwave-Driven Josephson Circuits
Yao Lu, Tianpu Zhao, André Vallières, Kevin C. Smith, Daniel Weiss, Xinyuan You, Yaxing Zhang, Suhas Ganjam, Aniket Maiti, John W.O. Garmon, Shantanu Mundhada, Ziwen Huang, Ian Mondragon-Shem, S.M. Girvin, Jens Koch, Robert J. Schoelkopf
We present a systematic framework for constructing time-dependent Hamiltonians of microwave-driven Josephson circuits, enabling accurate modeling and design of parametrically driven superconducting quantum processors.
Exceeding the Parametric Drive Strength Threshold in Nonlinear Circuits
Mingkang Xia, Cristóbal Lledó, Matthew Capocci, Jacob Repicky, Benjamin D’Anjou, Ian Mondragon-Shem, Ryan Kaufman, Jens Koch, Alexandre Blais, Michael Hatridge
We demonstrate that a nonlinear coupler undergoes ionization under strong parametric driving, leading to a breakdown of coherent control. Through experiments and numerical simulations, we associate this behavior with drive-induced chaotic dynamics, characterized using the instantaneous Floquet spectrum.
Robust Topological Invariants of Topological Crystalline Phases in the Presence of Impurities
Ian Mondragon-Shem, Taylor L. Hughes
We show that robust basis-independent topological invariants can be generically constructed for topological crystalline phases using projected symmetry operators. The real-space topological markers are exponentially localized to the fixed points of the spatial symmetry, protecting them against impurities.
Local Imaging of Diamagnetism in Proximity-Coupled Niobium Nanoisland Arrays on Gold Thin Films
Logan Bishop-Van Horn, Irene P. Zhang, Emily N. Waite, Ian Mondragon-Shem, Scott Jensen, Junseok Oh, Tom Lippman, Malcolm Durkin, Taylor L. Hughes, Nadya Mason, Kathryn A. Moler, Ilya Sochnikov
We study the effect of engineered disorder on the local magnetic response of proximity-coupled superconducting island arrays by comparing scanning SQUID susceptibility measurements to a junction network model.
Computer-Aided Quantization and Numerical Analysis of Superconducting Circuits
Sai Pavan Chitta, Tianpu Zhao, Ziwen Huang, Ian Mondragon-Shem, Jens Koch
We present work utilizing symbolic computer algebra and numerical diagonalization routines versatile enough to tackle a variety of superconducting circuits. Results are accessible through a newly released module of the scqubits package.
Fate of Quantum Many-Body Scars in the Presence of Disorder
Ian Mondragon-Shem, Maxim G. Vavilov, Ivar Martin
We study the stability of quantum many-body scars against disorder in the PXP model of Rydberg atoms. Scarred eigenstates persist at weak disorder but are eventually destroyed at strong disorder.
Imaging and Controlling Vortex Dynamics in Mesoscopic Superconductor–Normal-Metal–Superconductor Arrays
Tyler R. Naibert, Hryhoriy Polshyn, Rita Garrido-Menacho, Malcolm Durkin, Brian Wolin, Victor Chua, Ian Mondragon-Shem, Taylor L. Hughes, Nadya Mason, Raffi Budakian
We use a scanning probe technique to study vortex dynamics in superconducting systems by leveraging the resonant behavior of a magnetic-tipped cantilever, obtaining spatial patterns that encode the vortex energy landscape.
Quantized Frequency-Domain Polarization of Driven Phases of Matter
Ian Mondragon-Shem, Ivar Martin, A. Alexandradinata, Meng Cheng
We study signatures of drive-induced phases on the Floquet lattice. The average position of Floquet eigenstates along the frequency axis can be written in terms of a non-adiabatic Berry phase, which we interpret as frequency-domain polarization. Whenever this polarization is quantized to a nontrivial value, the phase cannot be continuously connected to a time-independent state.
Dissipative Vortex Dynamics in Superconducting Arrays
Malcolm Durkin, Ian Mondragon-Shem, Taylor L. Hughes, Nadya Mason
We perform current-voltage measurements on low resistance superconductor-normal-superconductor arrays in finite magnetic fields, finding that the behavior can be explained by a history-dependent dissipative force.
Many-Body Mobility Edge due to Symmetry-Constrained Dynamics and Strong Interactions
Ian Mondragon-Shem, Arijeet Pal, Taylor L. Hughes, Chris R. Laumann
We provide numerical evidence combined with an analytical understanding of the many-body mobility edge for the strongly anisotropic spin-1/2 XXZ model in a random magnetic field.
Entanglement of a 3D Generalization of the Kitaev Model on the Diamond Lattice
Ian Mondragon-Shem, Taylor L. Hughes
We study the entanglement properties of a three-dimensional generalization of the Kitaev honeycomb model on the diamond lattice, characterizing topological and gapless phases using entanglement entropy and the entanglement spectrum.
Signatures of Metal-Insulator and Topological Phase Transitions in the Entanglement of One-Dimensional Disordered Fermions
Ian Mondragon-Shem, Taylor L. Hughes
We study one-dimensional disordered fermions undergoing metal-insulator or topological phase transitions, developing entanglement tools that reveal metallic states and show clear signatures of localization transitions even with interactions.
Topological Criticality in the Chiral-Symmetric AIII Class at Strong Disorder
Ian Mondragon-Shem, Juntao Song, Taylor L. Hughes, Emil Prodan
We derive a covariant real-space formula for the winding number and show it remains quantized even when the bulk spectrum is completely localized. An abrupt change to a trivial value marks a critical point where the localization length diverges.
Characterizing Disordered Fermion Systems Using the Momentum-Space Entanglement Spectrum
Ian Mondragon-Shem, Mayukh Nilay Khan, Taylor L. Hughes
We propose the momentum-space entanglement spectrum as a means of characterizing disordered models, showing that localization in one dimension can be characterized by the momentum space entanglement between left and right movers.
Unconventional Bose-Einstein Condensations from Spin-Orbit Coupling
Congjun Wu, Ian Mondragon-Shem, Xiang-Fa Zhou
We find that multi-component bosons with spin-orbit coupling provide an unconventional type of BEC where the condensate spontaneously generates a half-quantum vortex combined with skyrmion-type spin texture, breaking time-reversal symmetry.
Efficient Calculation of Coulomb Matrix Elements for Bilayers of Confined Charge Carriers with Arbitrary Spatial Separation
Ian Mondragon-Shem, Boris A. Rodríguez, Francisco Eugenio López Giraldo
Coulomb Correlations of a Few Body System of Spatially Separated Charges
Ian Mondragon-Shem, Boris A. Rodríguez, Francisco Eugenio López Giraldo
Hartree-Fock and Hartree-Fock-Bogoliubov study of a few body system of spatially separated charge carriers. We compute the correlation energy and discuss how it can determine the formation of indirect excitons relevant to Bose-Einstein condensation.