Robust Control of Single-Qubit Gates at the Quantum Speed Limit

Fastness and robustness are both critical in the implementation of high-fidelity gates for quantum computation, but in practice, a trade-off has to be made between them. In this paper, we investigate the underlying robust time-optimal control problem so as to make the best balance. Based on the Taylor expansion of the system's unitary propagator, we formulate the design problem as the optimal control of an augmented finite-dimensional system at its quantum speed limit (QSL), where the robustness is graded by the degree of series truncation. The gradient-descent algorithm is then introduced to sequentially seek QSLs corresponding to different orders of robustness. Numerical simulations for single-qubit systems show that the obtained time-optimal control pulses can effectively suppress gate errors (to the prescribed robustness order) caused by qubit frequency and field amplitude uncertainties. These results provide a practical guide for selecting pulse lengths in the pulse-level compilation of quantum circuits

New hanger design approach of tied-arch bridge to enhance its robustness

As the crucial components among the tied-arch bridge, the local failure of hangers may trigger a progressive collapse through the entire tied-arch bridge. However, the current design guidance as regards hangers still lacks consideration of structure robustness under an extreme hazard. To improve the structural robustness of tied-arch bridge under extreme conditions, a new hanger design method is proposed, which is termed as asymmetric parallel double-hanger system. Based on Miner’s linear cumulative damage law, an analysis on the fatigue life of the double-hanger system was conducted to verify the feasibility of the proposal, and then a dynamic time-history analysis was employed to simulate the transitory fracture impact due to one or more hangers fracturing. According to the simulation results, the structural robustness is greatly enhanced with asymmetric parallel-double hanger system design, when compared with single hanger system design. When one or more hangers reveal local damage, it will not trigger a progress failure to the whole structure in particular. Several practical suggestions of bridge system’s load-carrying capacity are also put forward for the future arch bridge design at the end of this paper. © 2018 Korean Society of Civil Engineer

Dendrimers as Carriers for siRNA Delivery and Gene Silencing: A Review

RNA interference (RNAi) was first literaturally reported in 1998 and has become rapidly a promising tool for therapeutic applications in gene therapy. In a typical RNAi process, small interfering RNAs (siRNA) are used to specifically downregulate the expression of the targeted gene, known as the term “gene silencing.” One key point for successful gene silencing is to employ a safe and efficient siRNA delivery system. In this context, dendrimers are emerging as potential nonviral vectors to deliver siRNA for RNAi purpose. Dendrimers have attracted intense interest since their emanating research in the 1980s and are extensively studied as efficient DNA delivery vectors in gene transfer applications, due to their unique features based on the well-defined and multivalent structures. Knowing that DNA and RNA possess a similar structure in terms of nucleic acid framework and the electronegative nature, one can also use the excellent DNA delivery properties of dendrimers to develop effective siRNA delivery systems. In this review, the development of dendrimer-based siRNA delivery vectors is summarized, focusing on the vector features (siRNA delivery efficiency, cytotoxicity, etc.) of different types of dendrimers and the related investigations on structure-activity relationship to promote safe and efficient siRNA delivery system

Effect of dry-wet cycles on dynamic properties and microstructures of sandstone: Experiments and modelling

Underground pumped storage power plant (UPSP) is an innovative concept for space recycling of abandoned mines. Its realization requires better understanding of the dynamic performance and durability of reservoir rock. This paper conducted ultrasonic detection, split Hopkinson pressure bar (SHPB) impact, mercury intrusion porosimetry (MIP), and backscatter electron observation (BSE) tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage. A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage. The results show that dry-wet cycles decrease the dynamic compressive strength (DCS) with a maximum reduction of 39.40%, the elastic limit strength is reduced from 41.75 to 25.62 MPa. The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle. The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles, which verifies the computational statistics analysis of particle deterioration. The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant. The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields

Mechanical-force-induced non-local collective ferroelastic switching in epitaxial lead-titanate thin films.

Ferroelastic switching in ferroelectric/multiferroic oxides plays a crucial role in determining their dielectric, piezoelectric, and magnetoelectric properties. In thin films of these materials, however, substrate clamping is generally thought to limit the electric-field- or mechanical-force-driven responses to the local scale. Here, we report mechanical-force-induced large-area, non-local, collective ferroelastic domain switching in PbTiO3 epitaxial thin films by tuning the misfit-strain to be near a phase boundary wherein c/a and a1/a2 nanodomains coexist. Phenomenological models suggest that the collective, c-a-c-a ferroelastic switching arises from the small potential barrier between the degenerate domain structures, and the large anisotropy of a and c domains, which collectively generates much larger response and large-area domain propagation. Large-area, non-local response under small stimuli, unlike traditional local response to external field, provides an opportunity of unique response to local stimuli, which has potential for use in high-sensitivity pressure sensors and switches