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Sufficient condition for a quantum state to be genuinely quantum non-Gaussian
摘要： We show that the expectation value of the operator position and momentum operators x? and p? with a positive parameter c can serve as a tool to identify quantum non-Gaussian states, that is states that cannot be represented as a mixture of Gaussian states. Our condition can be readily tested employing a highly efficient homodyne detection which unlike quantum-state tomography requires the measurements of only two orthogonal quadratures. We demonstrate that our method is even able to detect quantum non-Gaussian states with positive–definite Wigner functions. This situation cannot be addressed in terms of the negativity of the phase-space distribution. Moreover, we demonstrate that our condition can characterize quantum non-Gaussianity for the class of superposition states consisting of a vacuum and integer multiples of four photons under more than 50 % signal attenuation.
关键词： Wigner functions,quantum information,continuous variables,non-Gaussian states,quadrature measurements,Gaussian state
更新于2025-09-23 15:21:01
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Two-step Degradation of a-InGaZnO Thin Film Transistors under DC Bias Stress
摘要： A unified explanation is proposed to consistently explain the two-step degradation of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) under DC positive bias temperature instability (PBTI) stress without or with different drain stress voltages (Vds). For PBTI stress without stress Vds, this initial negative Vth shift is believed to be induced by donor-like defect states corresponding to H2O molecule and intrinsic defects, while for PBTI stress with stress Vds, the negative shift is believed to be induced by donor-like defect states corresponding to oxygen vacancies. The gate-bias-induced electron trapping mechanism is responsible for positive Vth shift. These transitions from negative to positive Vth shift are resulted from the competition between the donor-like states creation and electron trapping.
关键词： PBTI,donor-like states creation,two–step degradation,electron trapping,IGZO TFTs,H2O molecule
更新于2025-09-23 15:21:01
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Hybrid atom-molecule quantum walks in a one-dimensional optical lattice
摘要： We study hybrid atom-molecule quantum walks in one-dimensional optical lattices with two interacting bosonic atoms which may be converted into a molecule. The hybrid atom-molecule energy bands include a continuum band and two isolated bands, which respectively correspond to scattering states and dressed bound states (DBSs). Because of the atom-molecule coupling, the DBSs may appear even in the absence of atom-atom interaction. From an initial state of two atoms occupying the same site, in addition to independent quantum walks which correspond to scattering states, correlated quantum walks appear as a signature of DBSs. Even if the atom-atom interaction and the atom-molecule coupling are much stronger than the tunneling strengths, independent quantum walks may still appear under certain resonant conditions. The correlated quantum walks show two light cones with different propagation velocities, which can be analytically explained by the effective tunneling strengths of the two different DBSs. Furthermore, the effective nearest-neighbor tunneling of DBSs can be suppressed to zero, which can be explained by the destructive interference between the atomic pair and the molecule.
关键词： Quantum walks,dressed bound states,atom-molecule coupling,tunneling,optical lattices
更新于2025-09-23 15:21:01
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functions
摘要： We propose a quantum optical device to experimentally realize quantum processes, which perform the regularization of the—in general highly singular—Glauber–Sudarshan P functions of arbitrary quantum states before their application and/or measurement. This allows us to produce a broad class of nonclassical states with regular P functions, also called nonclassicality quasiprobabilities. For this purpose, the input states are combined on highly transmissive beam splitters with specific Gaussian or non-Gaussian classical states. We study both balanced and unbalanced homodyne detections for the direct sampling of the output states of the implemented processes, which requires no further regularization or state-reconstruction. By numerical simulations we demonstrate the feasibility of our approach and we outline the generalization to multimode light.
关键词： quantum processes,Glauber–Sudarshan P functions,homodyne detection,nonclassical states,quantum optics
更新于2025-09-23 15:21:01
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Crystalline structure, electronic and lattice-dynamics properties of NbTe2
摘要： Layered-structure materials are currently relevant given their quasi-2D nature. Knowledge of their physical properties is currently of major interest. Niobium ditelluride possesses a monoclinic layered-structure with a distortion in the tellurium planes. This structural complexity has hindered the determination of its fundamental physical properties. In this work, NbTe2 crystals were used to elucidate its structural, compositional, electronic and vibrational properties. These findings have been compared with calculations based on density functional theory. The chemical composition and elemental distribution at the nanoscale were obtained through atom probe tomography. Ultraviolet photoelectron spectroscopy allowed the first determination of the work function of NbTe2. Its high value, 5.32 eV, and chemical stability allow foreseeing applications such as contact in optoelectronics. Raman spectra were obtained using different excitation laser lines: 488, 633, and 785 nm. The vibrational frequencies were in agreement with those determined through density functional theory. It was possible to detect a theoretically-predicted, low-frequency, low-intensity Raman active mode not previously observed. The dispersion curves and electronic band structure were calculated, along with their corresponding density of states. The electrical properties, as well as a pseudo-gap in the density of states around the Fermi energy are characteristics proper of a semi metal.
关键词： Electronic band structure,Ultraviolet photoelectron spectroscopy,Density functional theory,Atom probe tomography,Niobium ditelluride,Layered-structure materials,Raman spectra,Density of states,Semimetal
更新于2025-09-23 15:21:01
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The analysis of the electrical characteristics and interface state densities of Re/n-type Si Schottky barrier diodes at room temperature
摘要： The main electrical characteristics of current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature of the Re/n-type Si Schottky barrier diodes prepared by pulsed laser deposition (PLD) method have been examined. The values of the basic electrical properties such as forward saturation current (Io), ideality factors (n), barrier heights (Фbo), recti?cation ratio (RR) and series resistances (RS) were obtained from I-V and C-V measurements using di?erent calculation methods. At low voltages (V ≤ 0.3 V), the electrical conduction was formed to take place by thermionic emission, whereas at high voltages (V > 0.3 V), a space charge limited conduction mechanism was shown. Furthermore, the interface state densities (NSS) as a function of energy distribution (ESS- EV) was obtained from the I-V data by taking into account the bias dependence of the e?ective barrier height (Φb) for the Re/n-type Si Schottky barrier diodes.
关键词： interface states,surface potential,recti?cation ratio,Electrical parameters,series resistance
更新于2025-09-23 15:21:01
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Apparent Spectral Shift of Thermally Generated Surface Phonon-Polariton Resonance Mediated by a Nonresonant Film
摘要： The physical origin of the spectral shift of a thermally generated surface phonon-polariton (SPhP) resonance of a silicon carbide (SiC) bulk mediated by a nonresonant film is explained. The local density of electromagnetic states (LDOS) in a nonresonant intrinsic silicon (Si) film due to thermal emission by SiC, derived using fluctuational electrodynamics, exhibits a local maximum near the SPhP-resonant frequency in addition to a lower frequency resonance generated by gap modes emerging in the vacuum gap separating the SiC and Si layers. Multiple reflections within the vacuum gap also induce a LDOS drop around the SPhP-resonant frequency. As a result, depending on the film thickness to vacuum gap ratio and the location where the LDOS is calculated in the film, the low-frequency resonance can dominate the LDOS, such that the SPhP resonance appears to be redshifted. A similar spectral behavior is observed on the monochromatic radiative heat flux absorbed by the Si film. It is shown that apparent spectral (red and blue) shifts of the SPhP resonance mediated by a nonresonant film are bounded by the transverse and longitudinal optical phonon frequencies of SiC. This work is of importance in applications involving dissimilar materials, such as thermophotovoltaics and thermal rectification, where gap modes may significantly disrupt flux resonance. Gap modes may also be at the origin of the resonance redshift systematically observed in near-field thermal spectroscopy.
关键词： local density of electromagnetic states,thermal emission,surface phonon-polariton,spectral shift,near-field thermal spectroscopy
更新于2025-09-23 15:21:01
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Photonic Topological Insulating Phase Induced Solely by Gain and Loss
摘要： We reveal a one-dimensional topological insulating phase induced solely by gain and loss control in non-Hermitian optical lattices. The system comprises units of four uniformly coupled cavities, where the successive two have loss; the others experience gain, and they are balanced under two magnitudes. The gain and loss parts are effectively dimerized, and a bulk band gap, topological transition, midgap topological edge, and interface states in finite systems can all be achieved by controlled pumping. We also clarify non-Hermitian topological invariants and edge states in gapless conditions.
关键词： Topological Transition,Photonic Topological Insulating Phase,Non-Hermitian Optical Lattices,Midgap Topological Edge States,Gain and Loss Control
更新于2025-09-23 15:21:01
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System Composed of Three Types of Electronic Angular Momenta: A <b>J</b> – <b>S</b> – <b>L</b> Triad in a Photoexcited π-Radical Bis(phthalocyaninato)terbium Single-Molecule Magnet
摘要： Interactions of three different types of electronic angular momenta, namely, spin, orbital, and total angular momenta from different origins in a photoexcited neutral bis(phthalocyaninato)terbium single-molecule magnet (Pc2Tb, where Pc2? denotes a phthalocyaninato anion) have been studied. We have conducted varied-temperature and varied-magnetic-field magnetic circular dichroism (MCD) measurements on the highest occupied molecular orbital?lowest unoccupied molecular orbital electronic transition in the ligand side of the neutral Pc2Tb to reveal the quantum nature of the system composed of a π-radical with a spin angular momentum S, the 4f system with a total angular momentum J, and the cyclic π conjugate system with a photoinduced orbital angular momentum L. We have constructed a new theoretical model that gives a quantitative agreement to the temperature and magnetic field dependence of MCD. The theoretical analysis revealed that the system takes eight quantum states that can be expressed as |JzSzLz? = |±±±?, where the three angular momenta are quantized along the fourfold symmetry axis. Thus, we have identified the existence of the magnetic interactions among the three angular momenta and quantitatively determined their magnitudes for the first time.
关键词： single-molecule magnet,electronic angular momenta,quantum states,magnetic circular dichroism,magnetic interactions
更新于2025-09-23 15:21:01
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The Oscillatory Photoelectron Signal of <i>N</i> -Methylmorpholine as a Test Case for the Algebraic-Diagrammatic Construction Method of Second Order
摘要： Motivated by recent progress in the application of time-resolved photoelectron spectroscopy (TRPES) to molecular Rydberg states, we report herein a detailed assessment of the performance of the second-order algebraic diagrammatic construction (ADC(2)) method in the simulation of their TRPES spectra. As the test case, we employ the tertiary aliphatic amine N -methylmorpholine (NMM), which is notable for the fact that the signal of its 3s state exhibits long-lived oscillations along the electron binding energy axis. The relaxation process of photoexcited NMM is simulated via the Born-Oppenheimer molecular dynamics method, and the resulting TRPES spectrum is generated basing on ionization energies and approximate Dyson orbital norms calculated with the continuum orbital technique. On the whole, the simulated TRPES spectrum achieves satisfactory agreement with experiment, which suggests that the ADC(2) method provides a realistic description of the potential energy surfaces of the relevant excited and ionized states. In particular, the simulations reproduce the ?ne oscillatory structure of the signal of the 3s state, and provide evidence to the e?ect that it results from a coherent vibrational wavepacket evolving along the deformation modes of the six-membered ring. However, it is found that ADC(2) underestimates of electron binding energies by up to a few tenths of an electronvolt. The case of NMM demonstrates the usefulness of ADC(2) as a tool to aid the interpretation of the TRPES spectra of large organic molecules.
关键词： Dyson orbital,TRPES,ADC(2),time-resolved photoelectron spectroscopy,NMM,N-methylmorpholine,Rydberg states,Born-Oppenheimer molecular dynamics,continuum orbital technique,algebraic diagrammatic construction
更新于2025-09-23 15:21:01