Quantum decoherence is considered a core obstacle in quantum computing; therefore, suppressing decoherence is a primary task. Based on the integral representation of the solution to the thermal master equation, we focus on the evolution of decoherence in a degenerate parametric amplifier system described by a known Hamiltonian in a thermal environment. We also investigate the evolution of the photon number distribution, Wigner distribution, and von Neumann entropy in a thermal environment. This work can provide a theoretical reference for experimental studies of degenerate parametric amplifier systems.
We investigate the skin effect and localization characteristics in a one-dimensional non-Hermitian Su−Schrieffer−Heeger (SSH) chain induced by unidirectional Anderson disorder. Based on the theory of the renormalized generalized Brillouin zone, we observe that this system exhibits an energy-dependent skin effect (EDSE), whose directions are strongly dependent on the competitive interplay between the disorder strength and the averaged hopping amplitudes along the two directions. The emergence of EDSE gives rise to multiple localization transitions in this system, manifesting as repeated transitions between different types of EDSE and Anderson localization. Furthermore, the EDSEs differ distinctly between topologically nontrivial and trivial regions. These findings offer novel insights into understanding the role of unidirectional disorder in one-dimensional non-Hermitian SSH structures.
Two-dimensional (2D) layered materials lacking inversion symmetry are promising candidates for nano-electromechanical and electronic technologies. Building upon the experimentally synthesized SnPSe crystal, we computationally propose a novel series of inherently asymmetric group-IV-V-VI semiconductors through elemental substitution. This series encompasses monolayers of SiPSe, SiAsS, SiAsSe, SiAsTe, GePS, GePSe, GeAsS, GeAsSe, GeSbS, SnPS, SnPSe, SnAsS, SnAsSe, SnAsTe and SnSbS. All these structures exhibit robust energetic and dynamic stability, along with excellent resistance to oxidation when exposed to air. These monolayers have moderate bandgaps ranging from 1.04 to 2.36 eV; notably, the monolayers of SiAsSe, SiAsTe, GePS, GeAsSe and SnAsTe are direct-bandgap semiconductors. More importantly, these group-IV-V-VI monolayers exhibit significant in-plane piezoelectricity, with coefficients (d11) as high as 22.94 pm/V. Additionally, SnPSe bilayer exhibit significant out-of-plane piezoelectricity (d33) with coefficients exceeding 5 pm/V. Moreover, the coexistence of room-temperature ferroelectricity in these monolayers is unambiguously confirmed by their intrinsic spontaneous polarization and remarkably low ferroelectric switching barriers. These findings establish a new paradigm for integrating piezoelectricity and ferroelectricity with diverse 2D materials, thereby opening exciting opportunities for designing multifunctional materials and developing novel electronic devices.
The rapid development of 6G terahertz communication systems renders it critical to design low-cost and high-performance integrated antennas. Concurrently, orbital angular momentum (OAM), as an emerging physical dimension, shows immense potential in 6G communication and high-resolution imaging. Here, an all-dielectric integrated meta-antenna operating in the 6G terahertz communication window is demonstrated, which can generate a tightly focused vortex beam. By manipulating the propagation phase of terahertz waves, integrated meta-antennas with different topological charges are designed to generate vortex beams carrying OAM, which greatly enhances the design freedom of the antennas. Under physical size constraints, the design concept is demonstrated and experimentally validated at 0.14 THz. The integrated meta-antenna was fabricated using photocuring 3D printing technology. The electric field distributions of the meta-antennas carrying different topological charges are analyzed, and the experimental results show good agreement with the simulations. This work provides a general approach for designing compact and cost-efficient all-dielectric integrated meta-antennas capable of generating vortex beams, which offers broad prospects for applications in high-capacity 6G communication and high-resolution imaging.
Due to its fast and robust characteristics, nonadiabatic geometric quantum computation with various optimized techniques has received much attention. However, these strategies either require precise pulse control or can only mitigate partial systematic errors, hindering their experimental development. Here, we propose a scheme for optimized composite nonadiabatic geometric quantum gates (OCNGQGs), which can further enhance the gate performance of the composite nonadiabatic geometric scheme. Specifically, by optimizing the path parameter, our scheme effectively resists systematic errors in both directions, i.e., Rabi frequency and detuning errors, while preserving the flexibility of pulse shapes. Numerical simulations demonstrate that our scheme offers superior gate robustness against these two types of errors compared to conventional schemes. Additionally, we propose to implement our scheme on superconducting transmon qubits, where the numerical results show the robustness of universal gates remaining evident within current technology. Therefore, our proposal provides a promising approach to achieve robust quantum gates for future scalable quantum computation.
Half-Heusler intermetallic compounds have emerged as a fertile platform for investigating correlated quantum phenomena, encompassing superconductivity, quantum criticality, heavy fermion physics, and topological states. Here, we conduct a systematic comparative study between the trivial semimetal GdPdBi and its topological counterpart GdPtBi − a prototype Weyl semimetal, motivated by their isostructural nature and analogous magnetic configurations. While both compounds exhibit similar characteristics in electrical resistivity, magnetic susceptibility, and heat capacity measurements, striking differences emerge in their magnetotransport properties. The angular dependence of magnetoresistance, anomalous Hall angle evolution, and planar Hall resistivity demonstrate pronounced material-specific variations. Through this comparative analysis, we elucidate the critical interplay between topological band structure and magnetic ordering in modulating emergent transport phenomena. Specifically, we can distinguish the effect of topologically non-trivial bands on MR, anomalous Hall effect, and planar Hall effect from that of usual magnetic scattering. These findings provide fundamental insights into tailoring quantum transport properties through crystallographic and electronic structure engineering.
Identifying quantum chaos in Floquet systems with mixed classical phase spaces requires robust experimentally accessible signatures. We investigate the time-averaged quantum Fisher information (QFI) and the fidelity out-of-time-ordered correlator (FOTOC) of continuous periodically driven systems. We uncover two distinct power-law scalings of the time-averaged QFI with respect to system size: the standard quantum limit and the Heisenberg limit. These scalings correspond to initial states localized in the regular and chaotic regions of the classical phase space, respectively. Remarkably, we show that the time-averaged FOTOC can accurately identify the transition from mixed phase space to fully chaotic sea (at a critical driving strength ) as verified by the maximum Lyapunov exponent. The results suggest that both time-averaged QFI and FOTOC can be used as excellent quantum signatures for probing mixed phase-space structures and our adopted protocol for measuring the FOTOC eliminates the need for time-reversal operations. This work establishes a practical framework for investigating quantum chaos in Floquet systems, bridging theoretical insights with experimental applications.
Within the framework of linear response theory, we theoretically investigated the interband longitudinal optical conductivities (LOCs) in two-dimensional (2D) tilted Dirac bands using a tight-binding (TB) model, incorporating the effects of band tilting and Dirac-point shifting. We identified four characteristic critical frequencies in the interband LOCs of the TB model: the conventional critical frequencies, the partner frequencies, the sharp-peak frequency, and the cutoff frequency. The latter three types are consistently absent in the corresponding linearized model. Notably, the sharp-peak frequency and cutoff frequency remain robust against variations in band tilting and Dirac-point shifting. By employing analytical expressions derived via the Lagrange multiplier method, we elucidate the origins of the conventional critical frequencies and their partner counterparts. In contrast, the sharp-peak frequency and cutoff frequency are associated with interband optical transitions at high-symmetry points of the energy bands, arising from the Pauli exclusion principle and the finite boundaries of the Brillouin zone. Our theoretical predictions are intended to guide future experimental studies on tilt-dependent optical phenomena in 2D tilted Dirac systems.