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Congenital heart disease (CHD) and cardiomyopathies represent the two most important causes of paediatric heart failure (HF) in developed countries. We made a review of the literature on pathophysiology and clinical presentation of paediatric HF in children with CHD. Two main pathophysiologic models can be identified: the 'over-circulation failure', characterised by signs and symptoms of congestion or hypoperfusion, due respectively to volume or pressure overload, and the 'pump failure'. CONCLUSIONS: The comprehension of the HF pathophysiology in paediatric patients with CHD is of paramount importance for the optimal management and for addressing the best therapeutic choices.

A large ongoing research effort focuses on Variational Quantum Algorithms (VQAs), representing leading candidates to achieve computational speed-ups on current quantum devices. The scalability of VQAs to a large number of qubits, beyond the simulation capabilities of classical computers, is still debated. Two major hurdles are the proliferation of low-quality variational local minima, and the exponential vanishing of gradients in the cost function landscape, a phenomenon referred to as barren plateaus. Here we show that by employing iterative search schemes one can effectively prepare the ground state of paradigmatic quantum many-body models, circumventing also the barren plateau phenomenon. This is accomplished by leveraging the transferability to larger system sizes of iterative solutions, displaying an intrinsic smoothness of the variational parameters, a result that does not extend to other solutions found via random-start local optimization. Our scheme could be directly tested on near-term quantum devices, running a refinement optimization in a favorable local landscape with non-vanishing gradients., 5 + 9 pages, 4 + 12 figures, comments are welcome

The cyclic sudden switching of a magnetic impurity from Kondo to a non-Kondo state and back was recently shown to involve an important dissipation of the order of several $k_BT_K$ per cycle. The possibility to reveal this and other electronic processes through nanomechanical dissipation by e.g., ultrasensitive Atomic Force Microscope (AFM) tools currently represents an unusual and interesting form of spectroscopy. Here we explore the dependence on the switching time of the expected dissipation, a quantity whose magnitude is physically expected to drop from maximum to zero between sudden and slow switching, respectively. By applying a recently established matrix-product-state based time-dependent variational algorithm to the magnetic field-induced Kondo switching in an Anderson model of the magnetic impurity, we find that dissipation requires switching within the Kondo time scale $\hbar(k_B T_K)^{-1}$ or faster. While such a fast switching seems problematic for current AFM setups, the challenge is open for future means to detect this dissipation by time-dependent magnetic fields, electrostatic impurity level shift, or hybridization switching.

AIM To report on the feasibility, efficacy and long-term outcome of transcatheter closure of fenestrated Atrial Septal Aneurysm (ASA). METHODS Between April 2000 and May 2020, 568 patients with fenestrated ASA underwent transcatheter closure at two large-volume Pediatric Cardiology and GUCH Units (Naples and Massa, Italy). Procedural indications were cardiac volume overload in 223 patients (39%) or prophylaxis of paradoxical embolization in 345 patients (61%). Patients' median age and weight were 42 years (range 19-52) and 66 kg (range 54-79), respectively. One-hundred and thirty-nine patients (25%) were younger than 18 years. RESULTS Single fenestration was found in 311 patients (55%) (Group 1), whereas 257 patients (45%) had multifenestrated ASA (Group 2). The procedure was successful in all but seven patients (1.2%). In Group 1, closure was achieved with a single device. In Group 2, one device was used in 168 patients (67%), two devices in 74 patients (28%), three devices in 12 patients (5%), and four devices in 1 patient (0.3%). The early complication rate was 3%, without any difference according to anatomy or patient's age. At discharge, complete shunt closure was higher in Group 1 (92% vs. 72%, P

Unilateral posterior crossbite is a type of malocclusion that involves morpho-functional characteristics of masticatory muscle, such as the masseter: electrophysiological data have shown that the affected side works less than the contralateral muscle, which shows a normal or increased activity, probably in order to compensate for the affected side. The aim of present work was to measure the diameter and the cross-sectional area of ipsilateral and contralateral muscle fibers to verify if hypertrophy and/or hypotrophy take place in this malocclusion. We used immunofluorescence pictures to measure, using ImageJ software, the diameter and the cross-sectional area of fibers from control and crossbite groups, after that, the data were processed to perform statistical analyses. Results show that the fiber diameters of contralateral muscle are larger than the diameters of ipsilateral and control fibers, and that this difference is statistically significant. No statistically significant difference was found between the fiber diameters of the ipsilateral and control muscles. All these data suggest that, during unilateral posterior crossbite, morphological changes take place in the contralateral masseter muscle, which undergoes hypertrophy, probably to compensate for the low activity of the affected muscle.

We study the dynamics of the quenched Anderson model at finite temperature using matrix product states (MPSs). Exploiting a chain mapping for the electron bath, we investigate the entanglement structure in the MPS for various orderings of the two chains, which emerge from the thermofield transformation employed to deal with nonzero temperature. We show that merging both chains can significantly lower the entanglement at finite temperatures as compared to an intuitive nearest-neighbor implementation of the Hamiltonian. Analyzing the population of the free bath modes—possible when simulating the full dynamics of impurity plus bath—we find clear signatures of the Kondo effect in the quench dynamics.

We propose an efficient algorithm to numerically solve Anderson impurity problems using matrix product states. By introducing a modified chain mapping we obtain significantly lower entanglement, as compared to all previous attempts, while keeping the short-range nature of the couplings. Our approach naturally extends to finite temperatures, with applications to dynamical mean field theory, non-equilibrium dynamics and quantum transport., Comment: (6+8) pages, (4+9) figures

We show that the quantum approximate optimization algorithm (QAOA) can construct, with polynomially scaling resources, the ground state of the fully connected $p$-spin Ising ferromagnet, a problem that notoriously poses severe difficulties to a vanilla quantum annealing (QA) approach due to the exponentially small gaps encountered at first-order phase transition for $p\ensuremath{\ge}3$. For a target ground state at arbitrary transverse field, we find that an appropriate QAOA parameter initialization is necessary to achieve good performance of the algorithm when the number of variational parameters $2P$ is much smaller than the system size $N$ because of the large number of suboptimal local minima. Instead, when $P$ exceeds a critical value ${P}_{N}^{*}\ensuremath{\propto}N$, the structure of the parameter space simplifies, as all minima become degenerate. This allows achieving the ground state with perfect fidelity with a number of parameters scaling extensively with $N$ and with resources scaling polynomially with $N$.

We investigate the effect of dissipation from a thermal environment on topological pumping in the periodically-driven Rice-Mele model. We report that dissipation can improve the robustness of pumping quantisation in a regime of finite driving frequencies. Specifically, in this regime, a low-temperature dissipative dynamics can lead to a pumped charge that is much closer to the Thouless quantised value, compared to a coherent evolution. We understand this effect in the Floquet framework: dissipation increases the population of a Floquet band which shows a topological winding, where pumping is essentially quantised. This finding is a step towards understanding a potentially very useful resource to exploit in experiments, where dissipation effects are unavoidable. We consider small couplings with the environment and we use a Bloch-Redfield quantum master equation approach for our numerics: Comparing these results with an exact MPS numerical treatment we find that the quantum master equation works very well also at low temperature, a quite remarkable fact., 21 pages, 8 figures

We propose a reinforcement learning (RL) scheme for feedback quantum control within the quan-tum approximate optimization algorithm (QAOA). QAOA requires a variational minimization for states constructed by applying a sequence of unitary operators, depending on parameters living ina highly dimensional space. We reformulate such a minimum search as a learning task, where a RL agent chooses the control parameters for the unitaries, given partial information on the system. We show that our RL scheme finds a policy converging to the optimal adiabatic solution for QAOA found by Mbeng et al. arXiv:1906.08948 for the translationally invariant quantum Ising chain. In presence of disorder, we show that our RL scheme allows the training part to be performed on small samples, and transferred successfully on larger systems., 4 pages, 3 figures

We present a study of the digitized quantum annealing protocol proposed by R. Barends et al. [Nature (London) 534, 222 (2016)]. Our analysis, performed on the benchmark case of a transverse Ising chain problem, shows that the algorithm has a well-defined optimal working point for the annealing time ${\ensuremath{\tau}}_{\mathrm{P}}^{\mathrm{opt}}$, scaling as ${\ensuremath{\tau}}_{\mathrm{P}}^{\mathrm{opt}}\ensuremath{\sim}\mathrm{P}$, where $\mathrm{P}$ is the number of digital Trotter steps, beyond which the residual energy error shoots up toward the value characteristic of the maximally disordered state. We present an analytical analysis for the translationally invariant transverse Ising chain case, but our numerical evidence suggests that this scenario is more general, surviving, for instance, the presence of disorder.

We revisit here the Kibble-Zurek mechanism for superfluid bosons slowly driven across the transition towards the Mott-insulating phase. By means of a combination of the Time-Dependent Variational Principle and a Tree-Tensor Network, we characterize the current flowing during annealing in a ring-shaped one-dimensional Bose-Hubbard model with artificial classical gauge field on up to 32 lattice sites. We find that the superfluid current shows, after an initial decrease, persistent oscillations which survive even when the system is well inside the Mott insulating phase. We demonstrate that the amplitude of such oscillations is connected to the residual energy, characterizing the creation of defects while crossing the quantum critical point, while their frequency matches the spectral gap in the Mott insulating phase. Our predictions can be verified in future atomtronics experiments with neutral atoms in ring shaped traps. We believe that the proposed setup provides an interesting but simple platform to study the non-equilibrium quantum dynamics of persistent currents experimentally., 11 pages, 10 figures

Summary A 61 years-old patient with post-ischemic severe congestive heart failure (NYHA class III-IV) due to left ventricular pseudo-aneurysm and functional mitral valve regurgitation refractory to medical therapy was successfully treated by trans-catheter occlusion of the aneurismal sac with an Amplatzer Septal Occluder device and implantation of multiple MitraClips. After the procedure, his clinical conditions dramatically improved to NYHA class I.

We discuss and qualify the connection between two separate phenomena in the physics of nanoscale friction, general in nature and relevant to experiments. The first is thermally assisted lubricity (TAL), i.e., the low-velocity regime where a nanosized dry slider exhibits a viscouslike friction despite corrugations that would otherwise imply hard stick--slip friction. The second is the occurrence of negative dissipated work (NDW) events in sampling the work probability distribution. The abundance, or scarcity due to insufficient sampling, of these NDW events implies experimental fulfillment or violation of the celebrated Jarzynski equality (JE) of nonequilibrium statistical mechanics. We show, both analytically and in simulations of the one-dimensional point slider Prandtl-Tomlinson model, that a general crossover can be individuated as the total frictional work per cycle crosses ${k}_{B}T$. Below such crossover, the TAL regime holds, the dissipation is essentially linear, and the numerical validation for the JE is feasible (i.e., does not require an exponentially large sampling size). Above it, the dissipation profile departs from linearity and gains its hard stick--slip features, and the mandatory sampling for the JE becomes exponentially large. In addition, we derive a parameter-free formula expressing the linear velocity coefficient of viscous friction, correcting previous empirically parameterized expressions. With due caution, the connection between friction and work tails can be extended beyond a single degree of freedom to more complex sliders, thus inviting realistic crosscheck experiments. Of importance for experimental nanofriction will be the search for NDW tails in the sliding behavior of trapped cold ions, and alternatively checking for TAL in the sliding pattern of dragged colloid monolayers as well as in forced protein unwinding.

We show that a hierarchy of topological phases in one dimension—a topological Devil’s staircase—can emerge at fractional filling fractions in interacting systems, whose single-particle band structure describes a topological or a crystalline topological insulator. Focusing on a specific example in the BDI class, we present a field-theoretical argument based on bosonization that indicates how the system, as a function of the filling fraction, hosts a series of density waves. Subsequently, based on a numerical investigation of the low-lying energy spectrum, Wilczek–Zee phases, and entanglement spectra, we show that they are symmetry protected topological phases. In sharp contrast to the non-interacting limit, these topological density waves do not follow the bulk-edge correspondence, as their edge modes are gapped. We then discuss how these results are immediately applicable to models in the AIII class, and to crystalline topological insulators protected by inversion symmetry. Our findings are immediately relevant to cold atom experiments with alkaline-earth atoms in optical lattices, where the band structure properties we exploit have been recently realized.

Simulated quantum annealing (SQA) is a classical computational strategy that emulates a quantum annealing (QA) dynamics through a path-integral Monte Carlo whose parameters are changed during the simulation. Here we apply SQA to the one-dimensional transverse field Ising chain, where previous works have shown that, in the presence of disorder, a coherent QA provides a quadratic speedup with respect to classical simulated annealing, with a density of Kibble-Zurek defects decaying as ${\ensuremath{\rho}}_{\mathrm{KZ}}^{\mathrm{QA}}\ensuremath{\sim}{({log}_{10}\ensuremath{\tau})}^{\ensuremath{-}2}$ as opposed to ${\ensuremath{\rho}}_{\mathrm{KZ}}^{\mathrm{SA}}\ensuremath{\sim}{({log}_{10}\ensuremath{\tau})}^{\ensuremath{-}1}, \ensuremath{\tau}$ being the total annealing time, while for the ordered case both give the same power law ${\ensuremath{\rho}}_{\mathrm{KZ}}^{\mathrm{QA}}\ensuremath{\approx}{\ensuremath{\rho}}_{\mathrm{KZ}}^{\mathrm{SA}}\ensuremath{\sim}{\ensuremath{\tau}}^{\ensuremath{-}1/2}$. We show that the dynamics of SQA, while correctly capturing the Kibble-Zurek scaling ${\ensuremath{\tau}}^{\ensuremath{-}1/2}$ for the ordered case, is unable to reproduce the QA dynamics in the disordered case at intermediate $\ensuremath{\tau}$. We analyze and discuss several issues related to the choice of the Monte Carlo moves (local or global in space), the time-continuum limit needed to eliminate the Trotter-discretization error, and the long autocorrelation times shown by a local-in-space Monte Carlo dynamics for large disordered samples.

Recent model simulations discovered unexpected non-monotonic features in the wear-free dry phononic friction as a function of the sliding speed. Here we demonstrate that a rather straight- forward application of linear-response theory, appropriate in a regime of weak slider-substrate in- teraction, predicts frictional one-phonon singularities which imply a non-trivial dependence of the dynamical friction force on the slider speed and/or coupling to the substrate. The explicit formula which we derive reproduces very accurately the classical atomistic simulations when available. By modifying the slider-substrate interaction the analytical understanding obtained provides a practical means to tailor and control the speed dependence of friction with substantial freedom.

One of the major complications of radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF) is pulmonary vein stenosis (PVS). The natural history of PVS, especially when it involves more than one vein, leads to severe and irreversible pulmonary hypertension with end-stage right heart failure that can require, in extreme cases, even heart-lung transplantation. We report the case of a young patient who underwent RFCA for a single lasting episode of AF and developed PVS years later. He was treated with ballon venoplasty followed by stent implantation in left pulmonary vein because of PVS relief. This reported case emphasizes the need of an adequate indication for RFCA for AF, considering the benefit-risk ratio especially in young patients with normal cardiac function.

Revealing phase transitions of solids through mechanical anomalies in the friction of nanotips sliding on their surfaces is an unconventional and instructive tool for continuous transitions, unexplored for first-order ones. Owing to slow nucleation, first-order structural transformations generally do not occur at the precise crossing of free energies, but hysteretically, near the spinodal temperatures where, below and above the thermodynamic transition temperature, one or the other metastable free energy branches terminates. The spinodal transformation, a collective one-shot event with no heat capacity anomaly, is easy to trigger by a weak external perturbations. Here we propose that even the gossamer mechanical action of an AFM tip may locally act as a surface trigger, narrowly preempting the spontaneous spinodal transformation, and making it observable as a nanofrictional anomaly. Confirming this expectation, the CCDW-NCCDW first-order transition of the important layer compound 1T-TaS$_2$ is shown to provide a demonstration of this effect., 8 pages, 5 figures

We investigate the use of variational wave-functions that mimic stochastic recurrent neural networks, specifically, unrestricted Boltzmann machines, as guiding functions in projective quantum Monte Carlo (PQMC) simulations of quantum spin models. As a preliminary step, we investigate the accuracy of such unrestricted neural network states as variational Ans\"atze for the ground state of the ferromagnetic quantum Ising chain. We find that by optimizing just three variational parameters, independently on the system size, accurate ground-state energies are obtained, comparable to those previously obtained using restricted Boltzmann machines with few variational parameters per spin. Chiefly, we show that if one uses optimized unrestricted neural network states as guiding functions for importance sampling the efficiency of the PQMC algorithms is greatly enhanced, drastically reducing the most relevant systematic bias, namely that due to the finite random-walker population. The scaling of the computational cost with the system size changes from the exponential scaling characteristic of PQMC simulations performed without importance sampling, to a polynomial scaling, even at the ferromagnetic quantum critical point. The important role of the protocol chosen to sample hidden-spins configurations, in particular at the critical point, is analyzed. We discuss the implications of these findings for what concerns the problem of simulating adiabatic quantum optimization using stochastic algorithms on classical computers., Comment: 10 pages, 6 figures

Transcatheter closure of arterial duct (AD) remains challenging in low-weight patients and using Amplatzer Duct Occluder devices is still considered off-label in infants < 6kg. This study aimed to report a large, single-center experience of percutaneous AD closure in infants < 6kg as well as to compare the most frequently used devices, Amplatzer Duct Occluder type I (ADO I) and Amplatzer Duct Occluder type II Additional Sizes devices (ADO II-AS) (St. Jude Medical Corp, St. Paul, MN, USA). From March 2000 to March 2017, among the 762 patients submitted to percutaneous closure of AD at our Institution, 33 were infants < 6kg (age 4.8 ± 2.1months; weight 5.0 ± 0.9kg). Fourteen patients (45%) underwent ADO I (Group I) and 19 patients ADO II-AS (Group II) device implantation. AD diameter was 2.6 ± 0.8 (range 1.5–4.0) mm resulting in QP/QS of 2.6 ± 0.0.9 (range 1.1–4.5). Successful device deployment was achieved in all patients without procedural morbidity or mortality. Procedural and fluoroscopy times were not significantly different between the groups. However, total X-ray absorbed dose was significantly higher in Group I (121 ± 69 vs 29 ± 16mGy/cm2, p < 0.01). Immediate, 24h, and mid-term (46 ± 37 months, median 39) complete occlusion were recorded in 72.7, 90.9, and 97% of patients, respectively without significant difference between the groups. In conclusion, transcatheter closure of AD with Amplatzer Duct Occluder devices is feasible, safe, and effective also in infants less than 6kg, without significant difference between the most commonly used devices, namely, ADO I and ADO II-AS.

The quantum motion of nuclei, generally ignored in the physics of sliding friction, can affect in an important manner the frictional dissipation of a light particle forced to slide in an optical lattice. The density matrix-calculated evolution of the quantum version of the basic Prandtl-Tomlinson model, describing the dragging by an external force of a point particle in a periodic potential, shows that purely classical friction predictions can be very wrong. The strongest quantum effect occurs not for weak but for strong periodic potentials, where barriers are high but energy levels in each well are discrete, and resonant Rabi or Landau-Zener tunneling to states in the nearest well can preempt classical stick-slip with nonnegligible efficiency, depending on the forcing speed. The resulting permeation of otherwise unsurmountable barriers is predicted to cause quantum lubricity, a phenomenon which we expect should be observable in the recently implemented sliding cold ion experiments. © 2018 National Academy of Sciences. All rights reserved.

We study Thouless pumping out of the adiabatic limit. Our findings show that despite its topological nature, this phenomenon is not generically robust to nonadiabatic effects. Indeed, we find that the Floquet diagonal ensemble value of the pumped charge shows a deviation from the topologically quantized limit which is quadratic in the driving frequency for a sudden switch on of the driving. This is reflected also in the charge pumped in a single period, which shows a nonanalytic behavior on top of an overall quadratic decrease. Exponentially small corrections are recovered only with a careful tailoring of the driving protocol. We also discuss thermal effects and the experimental feasibility of observing such a deviation. © 2018 American Physical Society.

We study the effect of a thermal environment on the quantum annealing dynamics of a transverse-field Ising chain. The environment is modeled as a single Ohmic bath of quantum harmonic oscillators weakly interacting with the total transverse magnetization of the chain in a translationally invariant manner. We show that the density of defects generated at the end of the annealing process displays a minimum as a function of the annealing time, the so-called optimal working point, only in rather special regions of the bath temperature and coupling strength plane. We discuss the relevance of our results for current and future experimental implementations with quantum annealing hardware. © 2018 American Physical Society.

We study the robustness of the quantization of the Hall conductivity in the Harper-Hofstadter model towards the details of the protocol with which a longitudinal uniform driving force $F_x(t)$ is turned on. In the vector potential gauge, through Peierls substitution, this involves the switching-on of complex time-dependent hopping amplitudes $\mathrm{e}^{-\frac{i}{\hbar}\mathcal{A}_x(t)}$ in the $\hat{\mathbf{x}}$-direction such that $\partial_t \mathcal{A}_x(t)=F_x(t)$. The switching-on can be sudden, $F_x(t)=\theta(t) F$, where $F$ is the steady driving force, or more generally smooth $F_x(t)=f(t/t_{0}) F$, where $f(t/t_{0})$ is such that $f(0)=0$ and $f(1)=1$. We investigate how the time-averaged (steady-state) particle current density $j_y$ in the $\hat{\mathbf{y}}$-direction deviates from the quantized value $j_y \, h/F = n$ due to the finite value of $F$ and the details of the switching-on protocol. Exploiting the time-periodicity of the Hamiltonian $\hat{H}(t)$, we use Floquet techniques to study this problem. In this picture the (Kubo) linear response $F\to 0$ regime corresponds to the adiabatic limit for $\hat{H}(t)$. In the case of a sudden quench $j_y \, h/F$ shows $F^2$ corrections to the perfectly quantized limit. When the switching-on is smooth, the result depends on the switch-on time $t_{0}$: for a fixed $t_{0}$ we observe a crossover force $F^*$ between a quadratic regime for $FF^*$. The crossover $F^*$ decreases as $t_{0}$ increases, eventually recovering the topological robustness. These effects are in principle amenable to experimental tests in optical lattice cold atomic systems with synthetic gauge fields., Comment: 13 pages, 11 figures

In simple ferromagnetic quantum Ising models characterized by an effective double-well energy landscape the characteristic tunneling time of path-integral Monte Carlo (PIMC) simulations has been shown to scale as the incoherent quantum-tunneling time, i.e., as $1/\Delta^2$, where $\Delta$ is the tunneling gap. Since incoherent quantum tunneling is employed by quantum annealers (QAs) to solve optimization problems, this result suggests there is no quantum advantage in using QAs w.r.t. quantum Monte Carlo (QMC) simulations. A counterexample is the recently introduced shamrock model, where topological obstructions cause an exponential slowdown of the PIMC tunneling dynamics with respect to incoherent quantum tunneling, leaving the door open for potential quantum speedup, even for stoquastic models. In this work, we investigate the tunneling time of projective QMC simulations based on the diffusion Monte Carlo (DMC) algorithm without guiding functions, showing that it scales as $1/\Delta$, i.e., even more favorably than the incoherent quantum-tunneling time, both in a simple ferromagnetic system and in the more challenging shamrock model. However a careful comparison between the DMC ground-state energies and the exact solution available for the transverse-field Ising chain points at an exponential scaling of the computational cost required to keep a fixed relative error as the system size increases., Comment: 9 pages, 7 figures

We compare the performance of quantum annealing (QA, through Schr\"odinger dynamics) and simulated annealing (SA, through a classical master equation) on the $p$-spin infinite range ferromagnetic Ising model, by slowly driving the system across its equilibrium, quantum or classical, phase transition. When the phase transition is second-order ($p=2$, the familiar two-spin Ising interaction) SA shows a remarkable exponential speed-up over QA. For a first-order phase transition ($p \ge 3$, i.e., with multi-spin Ising interactions), in contrast, the classical annealing dynamics appears to remain stuck in the disordered phase, while we have clear evidence that QA shows a residual energy which decreases towards $0$ when the total annealing time $\tau$ increases, albeit in a rather slow (logarithmic) fashion. This is one of the rare examples where a limited quantum speedup, a speedup by QA over SA, has been shown to exist by direct solutions of the Schr\"odinger and master equations in combination with a non-equilibrium Landau-Zener analysis. We also analyse the imaginary-time QA dynamics of the model, finding a $1/\tau^2$ behaviour for all finite values of $p$, as predicted by the adiabatic theorem of quantum mechanics. The Grover-search limit $p({\rm odd})=\infty$ is also discussed., Comment: Submitted to PRA

We study the approach to the adiabatic limit in periodically driven systems. Specifically focusing on a spin-1/2 in a magnetic field we find that, when the parameters of the Hamiltonian lead to a quasi-degeneracy in the Floquet spectrum, the evolution is not adiabatic even if the frequency of the field is much smaller than the spectral gap of the Hamiltonian. We argue that this is a general phenomenon of periodically driven systems. Although an explanation based on a perturbation theory in $\omega_0$ cannot be given, because of the singularity of the zero frequency limit, we are able to describe this phenomenon by means of a mapping to an extended Hilbert space, in terms of resonances of an effective two-band Wannier-Stark ladder. Remarkably, the phenomenon survives in the presence of dissipation towards an environment and can be therefore easily experimentally observed., Comment: 14 pages, 5 figures, version published in Journal of Statistical Mechanics

We introduce and study the adiabatic dynamics of free-fermion models subject to a local Lindblad bath and in the presence of a time-dependent Hamiltonian. The merit of these models is that they can be solved exactly, and will help us to study the interplay between nonadiabatic transitions and dissipation in many-body quantum systems. After the adiabatic evolution, we evaluate the excess energy (the average value of the Hamiltonian) as a measure of the deviation from reaching the final target ground state. We compute the excess energy in a variety of different situations, where the nature of the bath and the Hamiltonian is modified. We find robust evidence of the fact that an optimal working time for the quantum annealing protocol emerges as a result of the competition between the nonadiabatic effects and the dissipative processes. We compare these results with the matrix-product-operator simulations of an Ising system and show that the phenomenology we found also applies for this more realistic case., publishedVersion

We revisit the issue of thermally assisted quantum annealing by a detailed study of the dissipative Landau-Zener problem in presence of a Caldeira-Leggett bath of harmonic oscillators, using both a weak-coupling quantum master equation and a quasi-adiabatic path-integral approach. Building on the known zero-temperature exact results (Wubs et al., PRL 97, 200404 (2006)), we show that a finite temperature bath can have a beneficial effect on the ground-state probability only if it couples also to a spin-direction that is transverse with respect to the driving field, while no improvement is obtained for the more commonly studied purely longitudinal coupling. In particular, we also highlight that, for a transverse coupling, raising the bath temperature further improves the ground-state probability in the fast-driving regime. We discuss the relevance of these findings for the current quantum-annealing flux qubit chips., Comment: 10 pages, 6 figures

We investigate theoretically the possibility to observe dynamical mode locking, in the form of Shapiro steps, when a time-periodic potential or force modulation is applied to a two-dimensional (2D) lattice of colloidal particles that are dragged by an external force over an optically generated periodic potential. Here we present realistic molecular dynamics simulations of a 2D experimental setup, where the colloid sliding is realized through the motion of soliton lines between locally commensurate patches or domains, and where the Shapiro steps are predicted and analyzed. Interestingly, the jump between one step and the next is seen to correspond to a fixed number of colloids jumping from one patch to the next, across the soliton line boundary, during each AC cycle. In addition to ordinary "integer" steps, coinciding here with the synchronous rigid advancement of the whole colloid monolayer, our main prediction is the existence of additional smaller "subharmonic" steps due to localized solitonic regions of incommensurate layers executing synchronized slips, while the majority of the colloids remains pinned to a potential minimum. The current availability and wide parameter tunability of colloid monolayers makes these predictions potentially easy to access in an experimentally rich 2D geometrical configuration.

Non-equilibrium molecular dynamics simulations, of crucial importance in sliding friction, are hampered by arbitrariness and uncertainties in the removal of the frictionally generated Joule heat. Building upon general pre-existing formulation, we implement a fully microscopic dissipation approach which, based on a parameter-free, non-Markovian, stochastic dynamics, absorbs Joule heat equivalently to a semi-infinite solid, and harmonic substrate. As a test case, we investigate the stick-slip friction of a slider over a two-dimensional Lennard-Jones solid, comparing our virtually exact frictional results with approximate ones from commonly adopted dissipation schemes. Remarkably, the exact results can be closely reproduced by a standard Langevin dissipation scheme, once its parameters are determined according to a general and self-standing variational procedure.

Summary: In a longitudinal study one healthy man aged 26 yrs underwent semen collections and blood samplings at monthly interval from January to December 1985. The ejaculated samples were analyzed for sperm density, motility, relative proportion of early (ab) and late (cd) spermatids, concentrations of Fructose, L-Carnitine and Transferrin. In a transverse study, 248 serially independent samplings were performed of normal men, 28.9 ± 7.5 yrs old, consulting for infertility from January 1981 to December 1983. The Cosinor method was employed for searching on circannual rhythms of the studied parameters. The longitudinal study did not detect circannual rhythms of the considered seminal parameters nor of the studied hormones. However, peaks, significantly above the mean values throughout the year (p < 0.005), were observed of Cortisol, PRL, FSH, LH, Testosterone, Fructose and L-Carnitine levels. Young spermatids and sperm motility showed significant (p < 0.001) acrophases between June and July; an acrophase was also evident for late spermatids but shifted by six months, between December and January. Mesors and amplitudes were respectively: 28 ± 1.5 and 9.6 ± 43 (mean ± SE) for motility; 33.4 ± 1.6 and 9.9 ±5 for early spermatids; 46.6 ±1.9 and 13 ± 6.2 for late spermatids. Zusammenfassung: Jahreszeitliche Schwankungen der reproduktiven Funktionen von Mannern Korrelation von Hormonen und hormonabhangigen Parametern In einer Longitudinalstudie eines 26jahrigen gesunden Mannes wur-den in monatlichen Intervallen von Januar bis Dezember 1985 Ejakulate und Blutproben gewonnen. Die Ejakulate wurden auf Spermatozoendichte, -motilitat, relativen Anteil von fruhen und spaten Spermatiden und Fruktose-, L-Carnitin- und Transferrinkonzentration unter-sucht. In einer transversalen Studie wurden 248 unabhangige Serienuntersuchungen von nor-malen Mannern durchgefuhrt. Die Manner waren durchschnittlich 28,9 ±7,5 Jahre alt und wurden in dem Zeitraum von Januar 1981 bis Dezember 1983 wegen Infertilitat unter-sucht. Um jahreszeitliche Schwankungen der untersuchten Parameter herauszufinden, wur-de die Methode nach Cosinor angewandt. Die Longitudinalstudie ergab keine jahreszeitlichen Schwankungen fur die Spermio-grammparameter und die untersuchten Hormone. Es wurden jedoch uber das ganze Jahr verteilt, signifikant uber den Normalwerten liegende Spitzenwerte (p < 0,005) fur Corti-sol, PRL, FSH, LH, Testosteron, Fruktose und L-Carnitin gefunden. Fur die fruhen Spermatiden und die Spermatozoenmotilitat ergaben sich signifikante (p < 0,001) Phasen mit Spitzenwerten zwischen Juni und Juli; ahnliche Phasen waren fur die spaten Spermatiden allerdings um 6 Monate verschoben zwischen Dezember und Ja-nuar erkennbar. Die Messungen bzw. Amplituden im einzelnen ergaben: 28 ± 1,5 und 9,6 ± 4,3 (Mittel ± SE) fur die Motilitat; 33,4 ± 1,6 und 9,9 ± 5 fur die fruhen Spermatiden; 46,6 ±1,9 und 13 ± 6,2 fur die spaten Spermatiden.

Summary: We have investigated on eventual relationships existing in men between plasma levels of 17-a-OH-Progesterone (17-a-OH-P) and, plasma levels of Testosterone (T) and on the modifications of these relationships after stimulation of the testicles by HCG (Human Chorionic Gonadotropin). An inverse correlation exists between basal plasma levels of the two steroids and their Δ max (%max increase 96 h after the injection of 5000 I.U. of hCG): r = -06, p 0.01. This suggests that the enzymatic steps of the Δ -4 steroidogenic pathway are rate-limiting for the synthesis of T. The Δ max of the two-steroids are also inversely correlated with the circulating levels of LH (Luteinizing Hormone) (r = -05, -06; p < 0.01) suggesting that the rate-limiting activity of the Δ 4 pathway is under endogenous LH control. A desensitized state of this pathway can be expected in presence of high circulating levels of LH. Similarly to LH also the FSH plasma levels, an index of function of the seminiferous tubules, are inversely correlated with the 17-a-OH-P and T Δ max (r = -0.4, -05; p 0.005) indicating close relationships between tubular and interstitial functions. In men with idiopathic oligozoospermia and high circulating levels of FSH we have found increased 17-a-OH-P/T ratios after hCG. Zusammenfassung: Es wurde eine Untersuchung durchgefuhrt hinsichtlich moglicher Beziehungen zwischen den Plasmawerten von 17-a-OH-Progesteron, den Plasmawerten fur Testosteron und den Modifikationen dieser Beziehungen nach Stimulation der Hoden mit hCG. Danach besteht eine inverse Korrelation zwischen den basalen Plasmawerten der beiden Steroide und ihrem Δ max (% max. Anstieg 96Std. nach Injektion von 5000 I.U. hCG): r = -06, p0,01. Das weist daraufhin, das die enzymatischen Schritte des Δ-4-Abbaues der Steroidogenese begrenzt sind fur die Synthese von Testosteron. Das max der beiden Steroide ist ebenso invers korreliert mit den circulierenden Werten von LH (r = -05, -06; p

Transcatheter Approach for Fontan Failure due to Ventricular Volume Overload Systemic ventricle volume overload is an uncommon cause of failure of Fontan circulation. It may be due to ventricular valve malfunction or residual forward flow to pulmonary circulation. In selected cases, interventional cardiac catheterization may be effective and life-saving. This paper reports on 2 cases of Fontan failure due to volume overload and preserved ventricular function successfully treated by percutaneous approach.

Bulk electrical dissipation caused by charge-density-wave (CDW) depinning and sliding is a classic subject. We present a novel local, nanoscale mechanism describing the occurrence of mechanical dissipation peaks in the dynamics of an atomic force microscope tip oscillating above the surface of a CDW material. Local surface 2π slips of the CDW phase are predicted to take place giving rise to mechanical hysteresis and large dissipation at discrete tip surface distances. The results of our static and dynamic numerical simulations are believed to be relevant to recent experiments on NbSe2; other candidate systems in which similar effects should be observable are also discussed.

Inducing topological transitions by a time-periodic perturbation offers a route to controlling the properties of materials. Here we show that the adiabatic preparation of a non-trivial state involves a selective population of edge-states, due to exponentially-small gaps preventing adiabaticity. We illustrate this by studying graphene-like ribbons with hopping's phases of slowly increasing amplitude, as for, e.g., a circularly polarized laser slowly turned-on. The induced currents have large periodic oscillations, but flow solely at the edges upon time-averaging, and can be controlled by focusing the laser on either edge. The bulk undergoes a non-equilibrium topological transition, as signaled by the local Chern marker introduced by Bianco & Resta in equilibrium. The failure of the adiabatic picture in presence of intraband resonances is discussed., Revised version, improved discussion of resonant case, new clearer figures, improved presentation; 5 pages, 4 figures, plus supplementary material

In this work we study the entanglement entropy of a uniform quantum Ising chain in transverse field undergoing a periodic driving of period $\tau$ . By means of Floquet theory we show that, for any subchain, the entanglement entropy tends asymptotically to a value $\tau$ - periodic in time. We provide a semi-analytical formula for the leading term of this asymptotic regime: It is constant in time and obeys a volume law. The entropy in the asymptotic regime is always smaller than the thermal one: because of integrability the system locally relaxes to a Generalized Gibbs Ensemble (GGE) density matrix. The leading term of the asymptotic entanglement entropy is completely determined by this GGE density matrix. Remarkably, the asymptotic entropy shows marked features in correspondence to some non-equilibrium quantum phase transitions undergone by a Floquet state analog of the ground state., Comment: 24 pages, 4 figures, version published in J. Stat. Mech. (2016) 073101

We show clear evidence of a quadratic speedup of a quantum annealing (QA) Schroedinger dynamics over a Glauber master-equation simulated annealing (SA) for a random Ising model in one dimension, via an equal-footing exact deterministic dynamics of the Jordan-Wigner fermionized problems. This is remarkable, in view of the arguments of Katzgraber et al., PRX 4, 021008 (2014), since SA does not encounter any phase transition, while QA does. We also find a second remarkable result: that a "quantum-inspired" imaginary-time Schroedinger QA provides a further exponential speedup, i.e., an asymptotic residual error decreasing as a power-law $\tau^{-\mu}$ of the annealing time $\tau$., Comment: Revised Abstract and Introduction. Removed 1 figure. Added references. Results unchanged. 5 pages, 2 figures

The critical fluctuations at second order structural transitions in a bulk crystal may affect the dissipation of mechanical probes even if completely external to the crystal surface. Here, we show that noncontact force microscope dissipation bears clear evidence of the antiferrodistortive phase transition of SrTiO_{3}, known for a long time to exhibit a unique, extremely narrow neutron scattering "central peak." The noncontact geometry suggests a central peak linear response coupling connected with strain. The detailed temperature dependence reveals for the first time the intrinsic central peak width of order 80 kHz, 2 orders of magnitude below the established neutron upper bound.

Ventricular septal defect (VSD) is a life-threatening complication of acute myocardial infarction (MI), resulting in high mortality rate even in the case of a timely approach by surgical repair. Transcatheter closure is nowadays a reliable alternative to surgery, although currently deemed challenging or unsuitable in large and complex VSD. This article reports on a successful transcatheter approach in a critically ill patient with subacute right coronary-related, complex postinfarction VSD. In this patient, two sequentially deployed Amplatzer Septal Occluder devices stabilized the clinical conditions and hemodynamic parameters.

Recent experiments on Au break junctions [Phys. Rev. Lett. 88 (2002) 216803] have characterized the nonlinear conductance of stretched short Au nanowires. They reveal in the voltage range 10–20 meV the signatures of dissipation effects, likely due to phonons in the nanowire, reducing the conductance below the quantized value of 2 e 2 / h . We present here a theory, based on a model tight-binding Hamiltonian and on non-equilibrium Green's function techniques, which accounts for the main features of the experiment. The theory helps in revealing details of the experiment which need to be addressed with a more realistic, less idealized, theoretical framework.