We consider the interplay between magnetic skyrmions in an insulating thin film and the Dirac surface states of a 3D topological insulator (TI), coupled by proximity effect. The magnetic texture of skyrmions can lead to confinement of Dirac states at the skyrmion radius, where out of plane magnetization vanishes. This confinement can result in charging of the skyrmion texture. The presence of bound states is robust in an external magnetic field, which is needed to stabilize skyrmions. It is expected that for relevant experimental parameters skyrmions will have a few bound states that can be tuned using an external magnetic field. We argue that these charged skyrmions can be manipulated directly by an electric field, with skyrmion mobility proportional to the number of bound states at the skyrmion radius. Coupling skyrmionic thin films to a TI surface can provide a more direct and efficient way of controlling skyrmion motion in insulating materials. This provides a new dimension in the study of skyrmion manipulation.

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 dynamics of an array of spin-torque oscillators can be mapped onto a non-Hermitian Su-Schrieffer-Heeger model exhibiting topologically protected edge states. Using exact diagonalization of the linearized dynamics and numerical solutions of the nonlinear equations of motion, we find that a topological magnonic phase can be accessed by tuning the spin current injected into the array. In the topologically nontrivial regime, a single spin-torque oscillator on the edge of the array is driven into auto-oscillation and emits a microwave signal, while the bulk oscillators remain inactive. Our findings have practical utility for memory devices and spintronics neural networks relying on spin-torque oscillators as constituent units.

We observed and controlled the Brownian motion of solitons. We launched solitonic excitations in highly elongated 87 Rb BoseEinstein condensates (BECs) and showed that a dilute background of impurity atoms in a different internal state dramatically affects the soliton. With no impurities and in one dimension (1D), these solitons would have an infinite lifetime, a consequence of integrability. In our experiment, the added impurities scatter off the much larger soliton, contributing to its Brownian motion and decreasing its lifetime. We describe the soliton's diffusive behavior using a quasi-1D scattering theory of impurity atoms interacting with a soliton, giving diffusion coefficients consistent with experiment.W e studied the diffusion and decay of solitons in the highly controlled quantum environment provided by atomic Bose-Einstein condensates (BECs), where density maxima can be stabilized by attractive interactions [i.e., bright solitons (1, 2)] or, as here, where density depletions can be stabilized by repulsive interactions [i.e., dark solitons such as kink solitons (3, 4) and solitonic vortices (5)]. By contaminating these BECs with small concentrations of impurity atoms, we quantitatively studied how random processes destabilize solitons.Our BECs can be modeled by the one-dimensional (1D) Gross-Pitaevski equation (GPE): an integrable nonlinear wave equation with soliton solutions as excitations above the ground state. For a homogeneous 1D BEC of particles with mass m Rb with density ρ0, speed of sound c, and healing length ξ = / √ 2m Rb c, the dark soliton solutionsare expressed in terms of time t, axial position z , soliton velocity vs , and soliton width ξs = ξ/ 1 − (vs /c) 2 . Such dark solitons have a minimum density ρ0(vs /c) 2 and a phase jump −2 cos −1 (vs /c), both dependent on the soliton velocity vs . These behave as classical objects with a negative inertial mass ms ≈ − 4 ρ0/c, essentially the missing mass of the displaced atoms. The negative mass implies that increasing the soliton velocity reduces its kinetic energy; thus, dissipation accelerates dark solitons (6). This can be seen from the soliton equation of motionwhere −γż is the friction force and V is the confining potential due to the mean-field effects of the condensate. The random Langevin force f (t) has a white noise correlator f (t)f (t ) = 2γkBT δ(t − t ), where T is temperature and kB is Boltzmann's constant. The connection between the friction coefficient γ and f (t) derives from the same microscopic dynamics that yield the fluctuation-dissipation theorem for positive mass objects-f (t) is responsible for Brownian motion, whereas γ describes friction, but both have contributions from impurity atoms. Conventionally, the diffusion coefficient D is inversely proportional to the friction coefficient: D ∝ 1/γ. For negative mass objects, we show that the diffusion coefficient is instead proportional to the friction coefficient D ∝ γ; this reflects that friction is an antidamping force for negative mass objects. The interplay between ...

A roadmap is provided for building a quantum engineering education program to satisfy U.S. national and international workforce needs.Background: The rapidly growing quantum information science and engineering (QISE) industry will require both quantumaware and quantum-proficient engineers at the bachelor's level.Research Question: What is the best way to provide a flexible framework that can be tailored for the full academic ecosystem?Methodology: A workshop of 480 QISE researchers from across academia, government, industry, and national laboratories was convened to draw on best practices; representative authors developed this roadmap.Findings: 1) For quantum-aware engineers, design of a first quantum engineering course, accessible to all STEM students, is described; 2) for the education and training of quantumproficient engineers, both a quantum engineering minor accessible to all STEM majors, and a quantum track directly integrated into individual engineering majors are detailed, requiring only Manuscript

We propose a non-destructive means of characterizing a semiconductor wafer via measuring parameters of an induced quantum dot on the material system of interest with a separate probe chip that can also house the measurement circuitry. We show that a single wire can create the dot, determine if an electron is present, and be used to measure critical device parameters. Adding more wires enables more complicated (potentially multi-dot) systems and measurements. As one application for this concept we consider silicon metal-oxidesemiconductor and silicon/silicon-germanium quantum dot qubits relevant to quantum computing and show how to measure low-lying excited states (so-called "valley" states). This approach provides an alternative method for characterization of parameters that are critical for various semiconductor-based quantum dot devices without fabricating such devices.Semiconductor heterostructures often serve as the substrate for many solid-state devices. For quantum devices such as qubits, their quality depends crucially on the properties of these wafers. Often, these qubit characterization parameters can only be ascertained by fabricating the device and measuring it at cryogenic temperatures. Quantum dots (QDs) in silicon for quantum computing (QC) 1 are a great example. The indirect band-gap of silicon creates low-lying excited (valley) states in the QD heterostructure; if the "valley splitting" is too small, initialization, readout and even gate operation of the qubits is impeded. Optimizing the valley splitting of silicon QD qubits-in addition to other important parameters such as coherence time, charge noise, etc.-is needed for the eventual construction of quantum computers, and is limited by the design-fabrication-test cycle time.We propose a method of characterizing material properties using a separate probe chip that both creates the dot(s) and measures them. This concept was inspired by the ion trap stylus approach 2,3 where an ion qubit is trapped on a stylus-like tip that can be brought close to a material to characterize its properties, and also by the scanning nitrogen-vacancy (NV) center tip which can be used to detect magnetic fields at nanoscale for imaging or couple to spin qubits 4 . While these ideas involve putting a qubit on the scanning tip itself, our scheme uses a separate gate chip to induce a qubit in the material structure under study, then measure those material and qubit parameters of interest using the circuits on the gate chip. Indeed, scanning tunneling microscope (STM) tips have already been used to create effective dots on the surface of InAs 5,6 and, more recently, Si 7 , using tunneling to do spectroscopy. Nondestructive characterization of embedded donor atoms in a semiconductor has also been demonstrated using a scanning tip architecture 8,9 . Here, we induce the dot qubit within the material in an environment realistic to quantum computing and consider a) Electronic

The internal degrees of freedom provided by ultracold atoms give a route for realizing higher dimensional physics in systems with limited spatial dimensions. Non-spatial degrees of freedom in these systems are dubbed "synthetic dimensions". This connection is useful from an experimental standpoint but complicated by the fact that interactions alter the condensate ground state. Here we use the Gross-Pitaevskii equation to study ground state properties of a spin-1 Bose gas under the combined influence of an optical lattice, spatially varying spin-orbit coupling, and interactions at the mean-field level. The associated phases depend on the sign of the spin-dependent interaction parameter and the strength of the spin-orbit field. We find "charge" and spin density wave phases which are directly related to helical spin order in real space and affect the behavior of edge currents in the synthetic dimension. We determine the resulting phase diagram as a function of the spin-orbit coupling and spin-dependent interaction strength, considering both attractive (ferromagnetic) and repulsive (polar) spin-dependent interactions, and we provide direct comparison of our results with the non-interacting case. Our findings are applicable to current and future experiments, specifically with 87 Rb, 7 Li, 41 K, and 23 Na.

We study controllable friction in a system consisting of a dark soliton in a one-dimensional Bose-Einstein condensate coupled to a noninteracting Fermi gas. The fermions act as impurity atoms, not part of the original condensate, that scatter off of the soliton. We study semiclassical dynamics of the dark soliton, a particlelike object with negative mass, and calculate its friction coefficient. Surprisingly, it depends periodically on the ratio of interspecies (impurity-condensate) to intraspecies (condensate-condensate) interaction strengths. By tuning this ratio, one can access a regime where the friction coefficient vanishes. We develop a general theory of stochastic dynamics for negative-mass objects and find that their dynamics are drastically different from their positive-mass counterparts: they do not undergo Brownian motion. From the exact phase-space probability distribution function (i.e., in position and velocity), we find that both the trajectory and lifetime of the soliton are altered by friction, and the soliton can undergo Brownian motion only in the presence of friction and a confining potential. These results agree qualitatively with experimental observations by Aycock et al. [Proc. Natl. Acad. Sci. USA 114, 2503 (2017)] in a similar system with bosonic impurity scatterers.

Weakly measuring many-body systems and allowing for feedback in real-time can simultaneously create and measure new phenomena in quantum systems. We theoretically study the dynamics of a continuously measured two-component Bose-Einstein condensate (BEC) potentially containing a domain wall, and focus on the trade-off between usable information obtained from measurement and quantum backaction. Each weakly measured system yields a measurement record from which we extract real-time dynamics of the domain wall. We show that quantum backaction due to measurement causes two primary effects: domain wall diffusion and overall heating. The system dynamics and signal-to-noise ratio depend on the choice of measurement observable. We propose a feedback protocol to dynamically create a stable domain wall in the regime where domain walls are unstable, giving a prototype example of Hamiltonian engineering using measurement and feedback.