Physical Realization Research Articles

Research on Resource Allocation Method of Integrated Avionics System considering Fault Propagation Risk

The integrated modular avionics (IMA) system has coupled cross-linked support characteristics between physical resource entities and logical functions, and the existing resource allocation methods, which mainly consider system performance and resource utilization, do not consider the associated impact of fault propagation among resource entities. Aiming at the fault propagation risk in the resource allocation process of the IMA system, a hierarchical model of the IMA system is established. The fault propagation behavior caused by coupling association during the physical realization of the function layer logical architecture is analyzed, and the impact of different resource allocation methods on the fault propagation behavior is determined. Secondly, resource capacity constraints are established according to the resource requirement for hosted function, and the fault propagation risk model of the IMA system is constructed by considering the fault propagation impact factor, the relative importance of nodes, and the function safety criticality. The resource allocation method is evaluated according to the fault propagation risk model, and a heuristic algorithm is applied to optimize the resource allocation method of the IMA system. The simulation results show that the average propagation probability of the optimized resource allocation scheme decreases by 17.4%, and the overall fault propagation risk of the resource network decreases by 50.3%, indicating that the proposed resource allocation method can effectively improve the safety of the IMA system.

Active disturbance rejection control for non-minimum phase systems under plant reconstruction

Active disturbance rejection control (ADRC) for non-minimum phase (NMP) systems is a challenging problem due to the conflict between stability and feedback tuning. The key point on this issue is to avoid heavy feedback tuning for robustness enhancement. We perform plant reconstruction to obtain an explicit expression of internal disturbance, such that it can be reduced by cascade compensation. Then, a new ADRC scheme is developed based on plant reconstruction and the internal stability criterion for ADRC system is derived. The stability conditions provide guidelines on the design of the cascade compensator and disturbance observer. It also indicates that the cascade compensation contributes to the robust stability of NMP systems. Simulation results of two typical NMP systems are provided to show the efficacy of the proposed ADRC scheme. Physical realizability is also demonstrated through experiments on a motion NMP system.

Variational Determination of Multiqubit Geometrical Entanglement in Noisy Intermediate-Scale Quantum Computers

Current noise levels in physical realizations of qubits and quantum operations limit the applicability of conventional methods to characterize entanglement. In this adverse scenario, we follow a quantum variational approach to estimate the geometric measure of entanglement of multiqubit pure states. The algorithm requires only single-qubit gates and measurements, so it is well suited for noisy intermediate-scale quantum devices. This is demonstrated by successfully implementing the method on IBM Quantum devices for Greenberger-Horne-Zeilinger states of three, four, and five qubits. Numerical simulations with random states show the robustness and accuracy of the method. The scalability of the protocol is numerically demonstrated via matrix-product-state techniques up to $25$ qubits.

Dynamic analysis and circuit realization of a novel variable-wing 5D memristive hyperchaotic system with line equilibrium

By introducing flux-controlled memristor and linear feedback term into the three-dimensional (3D) chaotic system, and using the state feedback control method to increase dimension, a novel variable-wing 5D memristive hyperchaotic system has been proposed in this paper. The proposed memristive hyperchaotic system has a line equilibrium point whose position is directly determined by the control parameter. The remarkable feature of the system is that the influence of positive feedback memristor and negative feedback memristor on the system and their similarities and differences are considered. Meanwhile, by analyzing the complex dynamic behavior of the system under different control parameters and initial values, it can be found that the proposed memristive hyperchaotic system shows many interesting phenomena including hidden extreme multistability, transient chaotic transition behavior and variable-wing characteristics. Finally, the hardware electronic circuit of the memristive hyperchaotic system is designed. The hardware experimental results are highly consistent with the numerical simulation ones, which demonstrate the physical realizability of the proposed system.

Stabilizing lattice gauge theories through simplified local pseudogenerators

The postulate of gauge invariance in nature does not lend itself directly to implementations of lattice gauge theories in modern setups of quantum synthetic matter. Unavoidable gauge-breaking errors in such devices require gauge invariance to be enforced for faithful quantum simulation of gauge-theory physics. This poses major experimental challenges, in large part due to the complexity of the gauge-symmetry generators. Here, we show that gauge invariance can be reliably stabilized by employing simplified local pseudogenerators designed such that within the physical sector they act identically to the actual local generator. Dynamically, they give rise to emergent exact gauge theories up to time scales polynomial and even exponential in the protection strength. This obviates the need for implementing often complex multibody full gauge symmetries, thereby further reducing experimental overhead in physical realizations. We showcase our method in the ${\mathbb{Z}}_{2}$ lattice gauge theory, and discuss experimental considerations for its realization in modern ultracold-atom setups.

Static and Reconfigurable Huygens’ Metasurfaces: Use in Antenna Beamforming and Beam Steering

In this article, we review recent advances in static and reconfigurable Huygens’ metasurfaces (HMSs) for antenna beamforming and beam steering. First, the fundamental theory of HMSs is summarized along with basic approaches for their physical realization. Subsequently, precise antenna beamforming without feeding networks by utilizing static HMSs is described. This is followed by the description of using HMSs as radomes for extending the scan range of phased arrays. Finally, several strategies are described for realizing reconfigurable HMS by means of electronic control devices.

Reversible Circuit Synthesis Method Using Sub-graphs of Shared Functional Decision Diagrams

Abstract Reversible circuit synthesis methods based on decision diagrams achieve low quantum costs but do not account for quantum bit (qubit) limits for the application of reversible logic in quantum computing. Here, a synthesis method using sub-graphs of shared functional decision diagrams (SFDDs) is proposed for reducing the number of lines when synthesizing reversible circuits. An SFDD is partitioned into sub-graphs by exploiting the longest dominant-active paths, and the sub-graphs are mapped to reversible gate cascades. To further reduce the number of lines, template root matching is presented for reusing circuit lines. Experimental results indicate that the proposed method achieves the known minimum number of lines in many cases and has good scalability. Although the proposed method increases the quantum cost over a prior method based on functional decision diagrams, it significantly reduces the number of lines in most cases. Compared with the one-pass method using quantum multiple-valued decision diagrams, the proposed method reduces the quantum cost without increasing the number of lines in many cases. When compared with the lookup table-based method using a direct mapping flow, the method reduces the number of lines in a few cases. Thus, the method aids in the physical realization of a quantum circuit.

New single VDCC Based Electronically Adjustable FDNR using Grounded Capacitances

A FDNR (Frequency Dependent Negative Resistance) simulator has been presented, which uses single Voltage Differencing Current Conveyor (VDCC) along with two grounded capacitances to realize the pure FDNR function. The proposed FDNR simulator places itself as one of the most compact circuit architecture present in the available literature. It is a resistor-less realization and finds no requirement of any active/passive component/parameter matching to realize the FDNR behaviour. The presented analysis shows that the proposed circuit remains always stable under the effect of parasitics irrespective of any values of circuit parameters, which is not witnessed in many previously reported FDNRs. The usability of realized synthetic FDNR has been checked through validation of developed higher-order CDR filters by using the proposed FDNR. To verify the designed circuits, the presented configurations have been simulated under the PSPICE simulation environment. The experimental results are shown for the commercial ICs (AD844 and CA3080) based physical realization of described FDNR.

3d $\mathcal{N}=4$ Gauge Theories on an Elliptic Curve

This paper studies 3d3d\mathcal{N}=4𝒩=4 supersymmetric gauge theories on an elliptic curve, with the aim to provide a physical realisation of recent constructions in equivariant elliptic cohomology of symplectic resolutions. We first study the Berry connection for supersymmetric ground states in the presence of mass parameters and flat connections for flavour symmetries, which results in a natural construction of the equivariant elliptic cohomology variety of the Higgs branch. We then investigate supersymmetric boundary conditions and show from an analysis of boundary ’t Hooft anomalies that their boundary amplitudes represent equivariant elliptic cohomology classes. We analyse two distinguished classes of boundary conditions known as exceptional Dirichlet and enriched Neumann, which are exchanged under mirror symmetry. We show that the boundary amplitudes of the latter reproduce elliptic stable envelopes introduced by Aganagic-Okounkov, and relate boundary amplitudes of the mirror symmetry interface to the mother function in equivariant elliptic cohomology. Finally, we consider correlation functions of Janus interfaces for varying mass parameters, recovering the chamber R-matrices of elliptic integrable systems.

Why difference-making mental causation does not save free will

ABSTRACT Many philosophers take mental causation to be required for free will. But it has also been argued that the most popular view of the nature of mental states, i.e. non-reductive physicalism, excludes the existence of mental causation, due to what is known as the ‘exclusion argument’. In this paper, I discuss the difference-making account of mental causation proposed by [List, C., and Menzies, P. 2017. “My Brain Made Me Do It: The Exclusion Argument Against Free Will, and What’s Wrong with It.” In H. Beebee, C. Hitchcock, & H. Price (eds.), Making a Difference: Essays on the Philosophy of Causation. Oxford Scholarship Online: Oxford University Press], who argue that their account not only solves the problem of causal exclusion but also saves free will. More precisely, they argue that it rebuts what they call ‘the Neurosceptical Argument’, the argument that if actions are caused by neural states and processes unavailable to us, there is no free will. I argue that their argument fails for two independent reasons. The first reason is that they fail to show that difference-makers are independent causes. The second reason is that physical realizers of mental states can be individuated in a way that makes both mental states and their realizers difference-makers.

Planar magnetic texture on the surface of a topological insulator

We study the planar magnetic textures coupled to a two-dimensional Dirac surface state, where both the magnetic texture and surface state form in the magnetic topological insulator surface layer. It is shown that the radial vortex with winding number $w=\ifmmode\pm\else\textpm\fi{}1$ leads to the confinement of Dirac states, where a mapping to the Schr\"odinger equation of a two-dimensional hydrogen atom is found. The fully spin-polarized zero-energy bound state forms a flat band that resembles the zeroth Landau level of Dirac electrons in a uniform out-of-plane magnetic field. Remarkably, the number of the zero-energy state is topologically robust. Interestingly, when such a system is proximity coupled to an $s$-wave superconductor, the existence of Majorana zero modes at the Abrikosov vortex depends only on the relative value of the magnetic exchange coupling and the pairing strength. We conclude with a brief discussion on the physical realization with such magnetic textures.

Design and circuit implementations of multimemristive hyperchaotic system

To enhance the order and Kolmogorov entropy of the memristive hyperchaotic system and improve the realizability of the circuit, a sixth-order memristive hyperchaotic system that consists of two flux-controlled memristors and one charge-controlled memristor is designed. Combined with Lyapunov exponential spectrum, phase trajectory diagram and bifurcation diagram, dynamic characteristics of the system are analyzed, and the effects of system control parameters and initial state on the system dynamic behavior are explored. Equivalent circuit models of flux-controlled and charge-controlled memristors with cubic nonlinear characteristics are constructed by the basic operation modules, and the hardware simulation design of the memristive hyperchaotic system is completed. The experimental results show that the proposed system can exhibit kinds of attractors, such as periodic-loop, single-scroll, double-scroll and superposition by adjusting system control parameters, and the system can show the behavior of period doubling bifurcation entering chaos and anti-period doubling exiting chaos under the different system initial states, which corresponds to the multistable coexistence phenomena of the system, such as quasi-period and hyperchaos. Meanwhile, the sixth-order hyperchaotic system is implemented by hardware circuit simulation. The phase diagrams of the circuit simulation are consistent with that of the numerical simulation, which verifies the physical realizability of the hyperchaotic system. Based on the strong initial value sensitivity and large K entropy, the memristive hyperchaotic system can be applied to the image encryption, and the confidentiality and security of images can be effectively enhanced.

Quantum teleportation using Ising anyons

Anyons have been extensively investigated as information carriers in topological quantum computation. However, how to characterize the information flow in quantum networks composed of anyons is less understood, which motivates us to study quantum communication protocols in anyonic systems. Here we propose a general topologically protected protocol for quantum teleportation based on the Ising anyon model and prove that with our protocol an unknown anyonic state of any number of Ising anyons can be teleported from Alice to Bob. Our protocol naturally generalizes quantum state teleportation from systems of locally distinguishable particles to systems of Ising anyons, which may promote our understandings of anyonic quantum entanglement as a quantum resource. In addition, our protocol is expected to be realized with the Majorana zero modes, one of the possible physical realizations for the Ising anyon in experiments.

Something Can Come of Nothing: Surface Approaches to Quantum Fluctuations and the Casimir Force

The Casimir force provides a striking example of the effects of quantum fluctuations in a mesoscopic system. Because it arises from the objects’ electromagnetic response, the necessary calculations in quantum field theory are most naturally expressed in terms of electromagnetic scattering from each object. In this review, we illustrate a variety of such techniques, with a focus on those that can be expressed in terms of surface effects, including both idealized boundary conditions and their physical realization in terms of material properties.

A Delay Compensation Framework for Connected Testbeds

This work considers connected testbeds, i.e., engineering testbeds that are remotely accessible over a network, and focuses on the challenge of achieving a high-fidelity closed-loop integration despite the network delays. To address this challenge, a model-free framework is presented. In previous work, a model-free delay compensation framework with a single design parameter was developed. However, having only one design parameter could limit tuning flexibility and thus delay compensation performance. Furthermore, this framework has not yet been validated on an actual connected testbed. To address these two shortcomings, in this article, this delay compensation framework is first expanded into a two-parameter form, and its open-loop stability and performance are studied for constant delays. The predictor stability criterion is established in terms of the two design parameters and the constant network delay. To evaluate the transient delay compensation performance of this framework and understand its advantages and limitations, simulation case studies are conducted on a connected engine testbed representing a medium-duty diesel pickup truck. These studies include two testbed architectures, constant and variable delays, two drive cycles, two levels of driver aggressiveness, and a comparison against wave transformation as a state-of-the-art benchmark. Finally, the framework is tested experimentally on a physical realization of the same connected testbed. The results validate the robustness of the delay compensation performance of the framework under dynamic operations, and show up to 30% higher integration fidelity due to the additional design degree of freedom introduced through the two-parameter form.

Study of a novel conservative chaotic system with special initial offset boosting behaviors

Conservative systems are increasingly being studied, while little research on fractional-order conservative systems has been reported. In this paper, a novel five-dimensional conservative chaotic system is proposed and solved in a fractional-order form using the Adomian decomposition method. This system is dissipative in the phase volume, but the sum of all Lyapunov exponents is zero. During the exploration, some special dynamical behaviors are analyzed in detail by using phase diagrams, bifurcation diagrams, Lyapunov exponential spectra, timing diagrams, and so on. After extensive simulation, several rare dynamical behaviors, including completely homogeneous, homogeneous, and heterogeneous initial offset boosting behaviors, are revealed. Among them, the initial offset boosting behaviors with identical phase trajectory structures have not been reported before, and the previously proposed homogeneous phase trajectories are locally different. By comparing with the integer-order system, two influence factors that affect the system to produce completely homogeneous and heterogeneous conservative flows are discovered. Eventually, the circuit is built on the digital signal processing (DSP) platform to demonstrate the physical realizability of the system. The experimental results are shown by the oscilloscope and agree with the theoretical analysis.

A theoretical analysis of superconducting pairing in correlated metallic systems

We have introduced a Coulomb correlated normal state to study the superconducting pairing within a Fermi liquid (FL)-like background in a 3-dimensional system. The role of the Coulomb correlation has been actively incorporated by means of the Gutzwiller projection scheme, in the presence of phonon mediated attractive electron–electron (AEE) interaction throughout the entire regime of its applicability. We variationally modulate the Coulomb correlation strength from the weak to the strong regime in our calculational procedure. The main highlight of our results is the appearance of a ‘2-gap-like’ structure in the superconducting phase, arising out of the two-body interacting matrix elements, calculated in the presence of the active Coulomb correlation. We have made use of the ‘two-square well model’ potential to evaluate the superconducting pairing gaps at zero temperature. Our Calculational scheme has been applied to a simple cubic lattice system for a physical realization. All the consequences are elaborated and discussed.

Toward Physically Realizable Quantum Neural Networks

There has been significant recent interest in quantum neural networks (QNNs), along with their applications in diverse domains. Current solutions for QNNs pose significant challenges concerning their scalability, ensuring that the postulates of quantum mechanics are satisfied and that the networks are physically realizable. The exponential state space of QNNs poses challenges for the scalability of training procedures. The no-cloning principle prohibits making multiple copies of training samples, and the measurement postulates lead to non-deterministic loss functions. Consequently, the physical realizability and efficiency of existing approaches that rely on repeated measurement of several copies of each sample for training QNNs are unclear. This paper presents a new model for QNNs that relies on band-limited Fourier expansions of transfer functions of quantum perceptrons (QPs) to design scalable training procedures. This training procedure is augmented with a randomized quantum stochastic gradient descent technique that eliminates the need for sample replication. We show that this training procedure converges to the true minima in expectation, even in the presence of non-determinism due to quantum measurement. Our solution has a number of important benefits: (i) using QPs with concentrated Fourier power spectrum, we show that the training procedure for QNNs can be made scalable; (ii) it eliminates the need for resampling, thus staying consistent with the no-cloning rule; and (iii) enhanced data efficiency for the overall training process since each data sample is processed once per epoch. We present a detailed theoretical foundation for our models and methods' scalability, accuracy, and data efficiency. We also validate the utility of our approach through a series of numerical experiments.

Sixth-Order Degenerate Band Edge in Coupled Microstrip Waveguides

We show the physical realization and experimental demonstration of an exceptional point of sixth-order degeneracy in a triple-ladder (or three-way) microwave waveguide realized using three coupled microstrips on a grounded dielectric substrate. This three-way waveguide supports six Bloch eigenmodes, and all coalesce into a degenerate single eigenmode at a given frequency. The three-way waveguide is gainless, and this exceptional point is associated with a vanishing-group velocity and its multiple derivatives. Indeed, the $\ensuremath{\omega}\ensuremath{-}k$ dispersion diagram that we call the sixth-order degenerate band edge (6DBE) has six coalescing branches. We provide experimental verification of a sixth-order exceptional point by evaluating the degenerate wave number--frequency-dispersion diagram from the measurement of scattering parameters of a six-port unit cell. We also show the resonant behavior of a cavity made of the three-way waveguide with finite length. The unique properties of 6DBE can be exploited to design innovative high-Q resonators, oscillators, filters, and pulse-shaping devices.

Anderson transition in stoichiometric Fe2VAl: high thermoelectric performance from impurity bands

Discovered more than 200 years ago in 1821, thermoelectricity is nowadays of global interest as it enables direct interconversion of thermal and electrical energy via the Seebeck/Peltier effect. In their seminal work, Mahan and Sofo mathematically derived the conditions for ’the best thermoelectric’—a delta-distribution-shaped electronic transport function, where charge carriers contribute to transport only in an infinitely narrow energy interval. So far, however, only approximations to this concept were expected to exist in nature. Here, we propose the Anderson transition in a narrow impurity band as a physical realisation of this seemingly unrealisable scenario. An innovative approach of continuous disorder tuning allows us to drive the Anderson transition within a single sample: variable amounts of antisite defects are introduced in a controlled fashion by thermal quenching from high temperatures. Consequently, we obtain a significant enhancement and dramatic change of the thermoelectric properties from p-type to n-type in stoichiometric Fe2VAl, which we assign to a narrow region of delocalised electrons in the energy spectrum near the Fermi energy. Based on our electronic transport and magnetisation experiments, supported by Monte-Carlo and density functional theory calculations, we present a novel strategy to enhance the performance of thermoelectric materials.