Quantum simulation of PT-arbitrary-phase-symmetric systems

Parity-time-reversal (PT) symmetric quantum mechanics promotes the increasing research interest of non-Hermitian (NH) systems for the theoretical value, novel properties, and links to open and dissipative systems in various areas. Recently, anti-PT-symmetric systems and its featured properties start to be investigated. In this work, we develop the PT- and anti-PT symmetry to PT-arbitrary-phase symmetry (or PT-φ symmetry) for the first time, being analogous to bosons, fermions and anyons. It can also be seen as a complex extension of the PT-symmetry, unifying the PT and anti-PT symmetries and having properties intermediate between them. Many of the established concepts and mathematics in the PT-symmetric system are still compatible. We mainly investigate quantum simulation of this novel NH-system of two-dimensions in detail and discuss for higher-dimensional cases in general using the linear combinations of unitaries in the scheme of duality quantum computing, enabling implementations and experimental investigations of novel properties on both small quantum devices and near-term quantum computers.

Coupled Lateral and Torsional Vibration of Rub-Impact Rotor during Hovering Flight

When aircraft make a maneuvering during flight, additional loads acting on the engine rotor system are generated, which may induce rub-impact faults between the rotor and stator. To study the rub-impact response characteristics of the rotor system during hovering flight, the dynamic model of a rub-impact rotor system is established with lateral-torsional vibration coupling effect under arbitrary maneuvering flight conditions using the finite element method and Lagrange equation. An implicit numerical integral method combining the Newmark-β and Newton–Raphson methods is used to solve the vibration response. The results indicate that the dynamic characteristics of the rotor system will change during maneuvering flight, and the subharmonic vibrations are amplified in both lateral and torsional vibrations due to maneuvering overload. The form of the rub-impact is different during level and hovering flight conditions: the rub-impact may occur at an arbitrary phase of the whole cycle under the condition of level flight, while only local rub-impact occurs during hovering flight. Under the both flight conditions, the rub-impact has a large effect on the spectral characteristics, periodicity, and stability of the rotor system.

Invisible surfaces enabled by the coalescence of anti-reflection and wavefront controllability in ultrathin metasurfaces

Reflection inherently occurs on the interfaces between different media. In order to perfectly manipulate waves on the interfaces, integration of antireflection function in metasurfaces is highly desired. In this work, we demonstrate an approach to realize exceptional metasurfaces that combine the two vital functionalities of antireflection and arbitrary phase manipulation in the deep subwavelength scale. Such ultrathin devices confer reflection-less transmission through impedance-mismatched interfaces with arbitrary wavefront shapes. Theoretically and experimentally, we demonstrate a three-layer antireflection metasurface that achieves an intriguing phenomenon: the simultaneous elimination of the reflection and refraction effects on a dielectric surface. Incident waves transmit straightly through the dielectric surface as if the surface turns invisible. We further demonstrate a wide variety of applications such as invisible curved surfaces, “cloaking” of dielectric objects, reflection-less negative refraction and flat axicons on dielectric-air interfaces, etc. The coalescence of antireflection and wavefront controllability in the deep subwavelength scale brings new opportunities for advanced interface optics with high efficiency and great flexibility.

Simulation of multimodal optical coherence tomography for biomedical diagnostics: comprehensive full-wave description based on ballistic scattering of arbitrary-profile beams

We present a computationally efficient full-wave spectral model of OCT-scan formation with the following capabilities/features: (i) the illuminating beam may have arbitrary phase-amplitude profile with allowance of a sharp diaphragm; (ii) paraxial approximation that limits the degree of focusing/divergence is not used; (iii) the broadly used approximation of ballistic (single) scattering by discrete scatterers is assumed without additional limitations on the density of scatterers, their distribution in space and scattering strengths with possible frequency-dependence; (iv) besides rigorous accounting for the influence of focusing/divergence of the waves, factors describing the wave decay can readily be introduced by analogy with Monte-Carlo approaches; (v) arbitrary measurement noises can easily be added to simulate required signal-to-noise ratios. The model also allows one to account for arbitrary (e.g., random or flow/deformation-induced) displacements of scatterers between subsequently generated scans. Thus, in view of the above-listed features the model can be characterized as comprehensive in the framework of ballistic scattering by discrete scatterers. The model is computationally efficient due to the use of only rapid summations and fast Fourier transforms. Main model features are illustrated, including simulations of OCT scans for a nearly non-diverging Bessel beam and a focused Gaussian beam, with the possibility to introduce at the tissue boundary arbitrary aberrations represented via Zernike polynomials often utilized for describing aberrations in ophthalmology. The unprecedented flexibility and high computational efficacy of the model open a broad range of possibilities for studying OCT-scan properties and developing new methods of their processing for biomedical diagnostics.