Strong Zero Modes in Integrable Quantum Circuits.

It is a classic result that certain interacting integrable spin chains host robust edge modes known as strong zero modes (SZMs). In this Letter, we extend this result to the Floquet setting of local quantum circuits, focusing on a prototypical model providing an integrable Trotterization for the evolution of the XXZ Heisenberg spin chain. By exploiting the algebraic structures of integrability, we show that an exact SZM operator can be constructed for these integrable quantum circuits in certain regions of parameter space. Our construction, which recovers a well-known result by Paul Fendley in the continuous-time limit, relies on a set of commuting transfer matrices known from integrability, and allows us to easily prove important properties of the SZM, including normalizabilty. Our approach is different from previous methods and could be of independent interest even in the Hamiltonian setting. Our predictions, which are corroborated by numerical simulations of infinite-temperature autocorrelation functions, are potentially interesting for implementations of the XXZ quantum circuit on available quantum platforms.

Lifetime of Almost Strong Edge-Mode Operators in One-Dimensional, Interacting, Symmetry Protected Topological Phases.

Almost strong edge-mode operators arising at the boundaries of certain interacting one-dimensional symmetry protected topological phases with Z_{2} symmetry have infinite temperature lifetimes that are nonperturbatively long in the integrability breaking terms, making them promising as bits for quantum information processing. We extract the lifetime of these edge-mode operators for small system sizes as well as in the thermodynamic limit. For the latter, a Lanczos scheme is employed to map the operator dynamics to a one-dimensional tight-binding model of a single particle in Krylov space. We find this model to be that of a spatially inhomogeneous Su-Schrieffer-Heeger model with a hopping amplitude that increases away from the boundary, and a dimerization that decreases away from the boundary. We associate this dimerized or staggered structure with the existence of the almost strong mode. Thus, the short time dynamics of the almost strong mode is that of the edge mode of the Su-Schrieffer-Heeger model, while the long time dynamics involves decay due to tunneling out of that mode, followed by chaotic operator spreading. We also show that competing scattering processes can lead to interference effects that can significantly enhance the lifetime.

Circumferential Partial-Thickness Burn Caused by Mobile Telephone Charger: A Case Report.

Many children and adolescents have access to portable electronic devices. Although not always the case, these devices are often charged at nighttime, especially while being used in bed. There are increasing media reports of electric current injury from the portable electronic devices' charging cables, particularly with equipment that is available for lower cost from generic manufacturers. A 19-year-old woman presented to the pediatric emergency department after a burn from her generic iPhone charger. She was lying in bed wearing a chain necklace, with the charger underneath her pillow and plugged into an electrical outlet, when she felt a sudden burning sensation and severe pain around her neck. She was found to have a circumferential partial-thickness burn. She underwent computed tomographic angiogram, whose result was unremarkable. The wound was debrided, and she was then discharged home. She likely sustained an electrical injury from the charger as it came in contact with her necklace, causing a burn. Several companies have investigated the difference in quality and safety of generic versus Apple-brand chargers and have found that the majority of the generic chargers fail basic safety testing, making them a higher risk for electrical injury. As a result of this case, patients and families should be educated about safe use of these devices, especially while they are charging.

Model Predictions for Time-Resolved Transport Measurements Made near the Superfluid Critical Points of Cold Atoms and K_{3}C_{60} Films.

Recent advances in ultrafast measurement in cold atoms, as well as pump-probe spectroscopy of K_{3}C_{60} films, have opened the possibility of rapidly quenching systems of interacting fermions to, and across, a finite temperature superfluid transition. However, determining that a transient state has approached a second-order critical point is difficult, as standard equilibrium techniques are inapplicable. We show that the approach to the superfluid critical point in a transient state may be detected via time-resolved transport measurements, such as the optical conductivity. We leverage the fact that quenching to the vicinity of the critical point produces a highly time dependent density of superfluid fluctuations, which affect the conductivity in two ways. First, by inelastic scattering between the fermions and the fluctuations, and second by direct conduction through the fluctuations, with the latter providing a lower resistance current carrying channel. The competition between these two effects leads to nonmonotonic behavior in the time-resolved optical conductivity, providing a signature of the critical transient state.

Central Charge of Periodically Driven Critical Kitaev Chains.

Periodically driven Kitaev chains show a rich phase diagram as the amplitude and frequency of the drive is varied, with topological phase transitions separating regions with different number of Majorana zero and π modes. We explore whether the critical point separating different phases of the periodically driven chain may be characterized by a universal central charge. We affirmatively answer this question by studying the entanglement entropy (EE) numerically and analytically for the lowest entangled many particle eigenstate at arbitrary nonstroboscopic and stroboscopic times. We find that the EE at the critical point scales logarithmically with a time-independent central charge, and that the Floquet micromotion gives only subleading corrections to the EE. This result also generalizes to multicritical points where the EE is found to have a central charge that is the sum of the central charges of the intersecting critical lines.

Reduced Na⁺ current density underlies impaired propagation in the diabetic rabbit ventricle.

Diabetes is associated with an increased risk of sudden cardiac death, but the underlying mechanisms remain unclear. Our goal was to investigate changes occurring in the action potential duration (APD) and conduction velocity (CV) in the diabetic rabbit ventricle, and delineate the principal ionic determinants. A rabbit model of alloxan-induced diabetes was utilized. Optical imaging was used to record electrical activity in isolated Langendorff-perfused hearts in normo-, hypo- and hyper-kalemia ([K(+)]o=4, 2, 12 mM respectively). Patch clamp experiments were conducted to record Na(+) current (I(Na)) in isolated ventricular myocytes. The mRNA/protein expression levels for Nav1.5 (the α-subunit of I(Na)) and connexin-43 (Cx43), as well as fibrosis levels were examined. Computer simulations were performed to interpret experimental data. We found that the APD was not different, but the CV was significantly reduced in diabetic hearts in normo-, hypo-, and, hyper-kalemic conditions (13%, 17% and 33% reduction in diabetic vs. control, respectively). The cell capacitance (Cm) was increased (by ~14%), and the density of INa was reduced by ~32% in diabetic compared to control hearts, but the other biophysical properties of I(Na) were unaltered. The mRNA/protein expression levels for Cx43 were unaltered. For Nav1.5, the mRNA expression was not changed, and though the protein level tended to be less in diabetic hearts, this reduction was not statistically significant. Staining showed no difference in fibrosis levels between the control and diabetic ventricles. Computer simulations showed that the reduced magnitude of I(Na) was a key determinant of impaired propagation in the diabetic ventricle, which may have important implications for arrhythmogenesis.

Transient orthogonality catastrophe in a time-dependent nonequilibrium environment.

We study the response of a highly excited time-dependent quantum many-body state to a sudden local perturbation, a sort of orthogonality catastrophe problem in a transient nonequilibrium environment. To this extent we consider, as a key quantity, the overlap between time-dependent wave functions, which we write in terms of a novel two-time correlator generalizing the standard Loschmidt echo. We discuss its physical meaning, general properties, and its connection with experimentally measurable quantities probed through nonequilibrium Ramsey interferometry schemes. Then we present explicit calculations for a one-dimensional interacting Fermi system brought out of equilibrium by a sudden change of the interaction, and perturbed by the switching on of a local static potential. We show that different scattering processes give rise to remarkably different behaviors at long times, quite opposite from the equilibrium situation. In particular, while the forward scattering contribution retains its power-law structure even in the presence of a large nonequilibrium perturbation, with an exponent that is strongly affected by the transient nature of the bath, the backscattering term is a source of nonlinearity which generates an exponential decay in time of the Loschmidt Echo, reminiscent of an effective thermal behavior.

Quench dynamics of one-dimensional interacting bosons in a disordered potential: elastic dephasing and critical speeding-up of thermalization.

The dynamics of interacting bosons in one dimension following the sudden switching on of a weak disordered potential is investigated. On time scales before quasiparticles scatter (prethermalized regime), the dephasing from random elastic forward scattering causes all correlations to decay exponentially fast, but the system remains far from thermal equilibrium. For longer times, the combined effect of disorder and interactions gives rise to inelastic scattering and to thermalization. A novel quantum kinetic equation accounting for both disorder and interactions is employed to study the dynamics. Thermalization turns out to be most effective close to the superfluid-Bose-glass critical point where nonlinearities become more and more important. The numerically obtained thermalization times are found to agree well with analytic estimates.

Telemedicine in paediatric emergency care: A systematic review.

INTRODUCTION: The impact of telemedicine on the access and quality of paediatric emergency care remains largely unexplored because most studies to date are focused on adult emergency care. We performed a systematic review of the literature to determine if telemedicine is effective in improving quality of paediatric emergency care with regards to access, process measures of care, appropriate disposition, patient-centred outcomes and cost-related outcomes. METHODS: We developed a systematic review protocol in accordance with PRISMA (Preferred Reporting Items for Systematic Review) guidelines. We included studies that evaluated the impact of synchronous and asynchronous forms of telemedicine on patient outcomes and process measures in the paediatric emergency care setting. Inclusion criteria were study setting, study design, intervention type, age, outcome measures, publication year and language. RESULTS: Overall, 1.9% (28/1434) studies met study inclusion and exclusion criteria. These studies revealed that telemedicine increased accuracy of patient assessment in the pre-clinical setting, improved time-to disposition, guided referring emergency department (ED) physicians in performing appropriate life-saving procedures and led to cost savings when compared to regular care. Studies focused on telepsychiatry demonstrated decreased length of stay (LOS), transfer rates and improved patient satisfaction scores. DISCUSSION: Our comprehensive review revealed that telemedicine enhances paediatric emergency care, enhances therapeutic decision-making and improves diagnostic accuracy, and reduces costs. Specifically, telemedicine has its most significant impact on LOS, access to specialized care, cost savings and patient satisfaction. However, there was a relative lack of randomized control trials, and more studies are needed to substantiate its impact on morbidity and mortality.

Time evolution and dynamical phase transitions at a critical time in a system of one-dimensional bosons after a quantum quench.

A renormalization group approach is used to show that a one-dimensional system of bosons subject to a lattice quench exhibits a finite-time dynamical phase transition where an order parameter within a light cone increases as a nonanalytic function of time after a critical time. Such a transition is also found for a simultaneous lattice and interaction quench where the effective scaling dimension of the lattice becomes time dependent, crucially affecting the time evolution of the system. Explicit results are presented for the time evolution of the boson interaction parameter and the order parameter for the dynamical transition as well as for more general quenches.