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Full-Text Articles in Physics
Feedback Induced Magnetic Phases In Binary Bose-Einstein Condensates, Hilary M. Hurst, Shangjie Guo, I. B. Spielman
Feedback Induced Magnetic Phases In Binary Bose-Einstein Condensates, Hilary M. Hurst, Shangjie Guo, I. B. Spielman
Faculty Research, Scholarly, and Creative Activity
Weak measurement in tandem with real-time feedback control is a new route toward engineering novel non-equilibrium quantum matter. Here we develop a theoretical toolbox for quantum feedback control of multicomponent Bose-Einstein condensates (BECs) using backaction-limited weak measurements in conjunction with spatially resolved feedback. Feedback in the form of a single-particle potential can introduce effective interactions that enter into the stochastic equation governing system dynamics. The effective interactions are tunable and can be made analogous to Feshbach resonances -- spin-independent and spin-dependent -- but without changing atomic scattering parameters. Feedback cooling prevents runaway heating due to measurement backaction and we present …
Non-Hermitian Topology Of One-Dimensional Spin-Torque Oscillator Arrays, Benedetta Flebus, Rembert A. Duine, Hilary M. Hurst
Non-Hermitian Topology Of One-Dimensional Spin-Torque Oscillator Arrays, Benedetta Flebus, Rembert A. Duine, Hilary M. Hurst
Faculty Research, Scholarly, and Creative Activity
Magnetic systems have been extensively studied both from a fundamental physics perspective and as building blocks for a variety of applications. Their topological properties, in particular those of excitations, remain relatively unexplored due to their inherently dissipative nature. The recent introduction of non-Hermitian topological classifications opens up new opportunities for engineering topological phases in dissipative systems. Here, we propose a magnonic realization of a non-Hermitian topological system. A crucial ingredient of our proposal is the injection of spin current into the magnetic system, which alters and can even change the sign of terms describing dissipation. We show that the magnetic …
Quantum Control With Spinor Bose-Einstein Condensates, Hilary M. Hurst
Quantum Control With Spinor Bose-Einstein Condensates, Hilary M. Hurst
Faculty Research, Scholarly, and Creative Activity
Understanding and controlling many-body quantum systems in noisy environments is paramount to developing robust quantum technologies. An external environment can be thought of as a measurement reservoir which extracts information about the quantum system. Cold atoms are well suited to examine system-environment interaction via weak (i.e. minimally destructive) measurement techniques, wherein the measurement probe acts as the environment and also provides a noisy record of system dynamics. The measurement record can then be used in a feedback scheme, opening the door to real time control of quantum gases. In this talk I discuss our theoretical proposal to use weak measurement …
Electron-Induced Massive Dynamics Of Magnetic Domain Walls, Hilary M. Hurst, Victor Galitski, Tero T. Heikkilä
Electron-Induced Massive Dynamics Of Magnetic Domain Walls, Hilary M. Hurst, Victor Galitski, Tero T. Heikkilä
Faculty Research, Scholarly, and Creative Activity
We study the dynamics of domain walls (DWs) in a metallic, ferromagnetic nanowire. We develop a Keldysh collective coordinate technique to describe the effect of conduction electrons on rigid magnetic structures. The effective Lagrangian and Langevin equations of motion for a DW are derived. The DW dynamics is described by two collective degrees of freedom: position and tilt-angle. The coupled Langevin equations therefore involve two correlated noise sources, leading to a generalized fluctuation-dissipation theorem (FDT). The DW response kernel due to electrons contains two parts: one related to dissipation via FDT, and another `inertial' part. We prove that the latter …