destructive interference
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Author(s):  
Daniel Braun ◽  
Ronny Müller

Abstract Quantum algorithms profit from the interference of quantum states in an exponentially large Hilbert space and the fact that unitary transformations on that Hilbert space can be broken down to universal gates that act only on one or two qubits at the same time. The former aspect renders the direct classical simulation of quantum algorithms difficult. Here we introduce higher-order partial derivatives of a probability distribution of particle positions as a new object that shares these basic properties of quantum mechanical states needed for a quantum algorithm. Discretization of the positions allows one to represent the quantum mechanical state of $\nb$ qubits by $2(\nb+1)$ classical stochastic bits. Based on this, we demonstrate many-particle interference and representation of pure entangled quantum states via derivatives of probability distributions and find the universal set of stochastic maps that correspond to the quantum gates in a universal gate set. We prove that the propagation via the stochastic map built from those universal stochastic maps reproduces up to a prefactor exactly the evolution of the quantum mechanical state with the corresponding quantum algorithm, leading to an automated translation of a quantum algorithm to a stochastic classical algorithm. We implement several well-known quantum algorithms, analyse the scaling of the needed number of realizations with the number of qubits, and highlight the role of destructive interference for the cost of the emulation.


2022 ◽  
Author(s):  
Sarin VP ◽  
Rohith K. Raj ◽  
Vasudevan K

Abstract In this paper, dipole-induced transparency in the microwave regime is proposed and verified using experimental and simulation studies. A single layer mirrored Split-Ring Resonator (SRR) metasurface array working under the H⊥excitation scenario is used to achieveout-of-phase electric dipole moments on the metasurface for a normal incident plane wave. The emergence of the transparency window is accompanied by the destructive interference between out-of-phase oscillating electric dipole moments on the metasurfaceand is verified in computations by studying the radar Cross Section in full-wave electromagnetic simulations.We used the multipole scattering theory to validate the results computationally. The coupling effects are studied numerically, and the emergence of the transparency window is studied experimentally using transmission measurements inside an anechoic chamber using a vector network analyzer.


Author(s):  
Yuhui Li ◽  
Yiping Xu ◽  
Jiabao Jiang ◽  
Liyong Ren ◽  
Shubo Cheng ◽  
...  

Abstract A monolayer graphene metamaterial composed of a graphene block and four graphene strips, which has the metal-like properties in terahertz frequency range, is proposed to generate an outstanding quadruple plasmon-induced transparency (PIT). Additional analyses show that the forming physical mechanism of the PIT with four transparency windows can be explained by strong destructive interference between the bright mode and the dark mode, and the distributions of electric field intensity and electric field vectors under the irradiation of the incident light. Coupled mode theory (CMT) and finite-difference time-domain (FDTD) method are employed to study the spectral response characteristics of the proposed structure, and the theoretical and simulated results are in good agreement. It is found that a tunable multi-frequency switch and excellent optical storage can be achieved in the wide PIT window. The maximum modulation depth is up to 99.7%, which corresponds to the maximum extinction ratio of 25.04 dB and the minimum insertion loss of 0.19 dB. In addition, the time delay is as high as 0.919 ps, the corresponding group refractive index is up to 2755. Thus, the proposed structure provides a new method for the design of terahertz multi-frequency switches and slow light devices.


Author(s):  
Pengju Yao ◽  
Biao Zeng ◽  
Enduo Gao ◽  
Hao Zhang ◽  
Chao Liu ◽  
...  

Abstract We propose a novel terahertz metamaterial structure based on patterned monolayer graphene. This structure produces an evident dual plasmon-induced transparency (PIT) phenomenon due to destructive interference between bright and dark modes. Since the Fermi level of graphene can be adjusted by an external bias voltage, the PIT phenomenon can be tuned by adjusting the voltage. Then the coupled-mode theory (CMT) is introduced to explore the internal mechanism of the PIT. After that, we investigate the variation of absorption rate at different graphene carrier mobilities, and it shows that the absorption rate of this structure can reach 50%, which is a guideline for the realization of graphene terahertz absorption devices. In addition, through the study of the slow-light performance for this structure, it is found that its group index is as high as 928, which provides a specific theoretical basis for the study of graphene slow-light devices.


Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 93
Author(s):  
Daniele Toffoli ◽  
Marco Medves ◽  
Giovanna Fronzoni ◽  
Emanuele Coccia ◽  
Mauro Stener ◽  
...  

We report a computational study at the time-dependent density functional theory (TDDFT) level of the chiro-optical spectra of chiral gold nanowires coupled in dimers. Our goal is to explore whether it is possible to overcome destructive interference in single nanowires that damp chiral response in these systems and to achieve intense plasmonic circular dichroism (CD) through a coupling between the nanostructures. We predict a huge enhancement of circular dichroism at the plasmon resonance when two chiral nanowires are intimately coupled in an achiral relative arrangement. Such an effect is even more pronounced when two chiral nanowires are coupled in a chiral relative arrangement. Individual component maps of rotator strength, partial contributions according to the magnetic dipole component, and induced densities allow us to fully rationalize these findings, thus opening the way to the field of plasmonic CD and its rational design.


2021 ◽  
Vol 8 ◽  
Author(s):  
Shuang Chen ◽  
Yuancheng Fan ◽  
Fan Yang ◽  
Kangyao Sun ◽  
Quanhong Fu ◽  
...  

The recent advent of acoustic metasurface displays tremendous potential with their unique and flexible capabilities of wavefront manipulations. In this paper, we propose an acoustic metagrating made of binary coiling-up space structures to coherently control the acoustic wavefront steering. The acoustic wave steering is based on the in-plane coherent modulation of waves in different diffraction channels. The acoustic metagrating structure with a subwavelength thickness is realized with 3D printed two coiling-up space metaunits. By adjusting structural parameters of the metaunits, the −1st-order diffraction mode can be retained, and the rest of the diffraction orders are eliminated as much as possible through destructive interference, forming a high-efficiency anomalous reflection in the scattering field. The anomalous reflection performance of the designed metagrating is achieved over a wide range of incident angles with high efficiency.


2021 ◽  
Author(s):  
Lei Wang ◽  
Zhen Yi ◽  
Li-hui Sun ◽  
Wen-Ju Gu

Abstract We study the nonreciprocal properties of transmitted photons in the chiral waveguide QED system, including single- and two-photon transmissions and second-order correlations. For the single-photon transmission, the nonreciprocity is induced by the effects of chiral coupling and atomic dissipation in the weak coupling region. It vanishes in the strong coupling regime when the effect of atomic dissipation becomes ignorable. In the case of two-photon transmission, there exist two ways of going through the emitter: independently as plane waves and formation of bound state. Besides the nonreciprocal behavior of plane waves, the bound state that differs in two directions also alters transmission probabilities. In addition, the second-order correlation of transmitted photons depends on the interference between plane wave and bound state. The destructive interference leads to the strong antibunching in the weak coupling region, while the effective formation of bound state leads to the strong bunching in the intermediate coupling region. However, the negligible interactions for left-propagating photons hardly change the statistics of the input coherent state.


2021 ◽  
Author(s):  
Kelsey Malloy ◽  
Ben P. Kirtman

Abstract Seasonal forecasts of summer continental United States (CONUS) rainfall have relatively low skill, partly due to a lack of consensus about its sources of predictability. The East Asian monsoon (EAM) can excite a cross-Pacific Rossby wave train, also known as the Asia-North America (ANA) teleconnection. In this study, we analyze the ANA teleconnection in observations and model simulations from the Community Atmospheric Model, version 5 (CAM5), comparing experiments with prescribed climatological SSTs and prescribed observed SSTs. Observations indicate a statistically significant relationship between a strong EAM and increased probability of positive precipitation anomalies over the U.S. west coast and the Plains-Midwest. The ANA teleconnection and CONUS rainfall patterns are improved in the CAM5 experiment with prescribed observed SSTs, suggesting that SST variability is necessary to simulate this teleconnection over CONUS. We find distinct ANA patterns between ENSO phases, with the La Niña-related patterns in CAM5_obsSST disagreeing with observations. Using linear steady-state quasi-geostrophic theory, we conclude that incorrect EAM forcing location greatly contributed to CAM5 biases, and jet stream disparities explained the ENSO-related biases. Finally, we compared EAM forcing experiments with different mean states using a simple dry nonlinear atmospheric general circulation model. Overall, the ANA pattern over CONUS and its modulation by ENSO forcing are well described by dry dynamics on seasonal-to-interannual timescales, including the constructive (destructive) interference between El Niño (La Niña) modulation and the ANA patterns over CONUS.


2021 ◽  
Author(s):  
Daniel Nelson Scott ◽  
Michael J Frank

Two key problems that span biological and industrial neural network research are how networks can be trained to generalize well and to minimize destructive interference between tasks. Both hinge on credit assignment, the targeting of specific network weights for change. In artificial networks, credit assignment is typically governed by gradient descent. Biological learning is thus often analyzed as a means to approximate gradients. We take the complementary perspective that biological learning rules likely confer advantages when they aren't gradient approximations. Further, we hypothesized that noise correlations, often considered detrimental, could usefully shape this learning. Indeed, we show that noise and three-factor plasticity interact to compute directional derivatives of reward, which can improve generalization, robustness to interference, and multi-task learning. This interaction also provides a method for routing learning quasi-independently of activity and connectivity, and demonstrates how biologically inspired inductive biases can be fruitfully embedded in learning algorithms.


Author(s):  
Jing-chun Yan ◽  
Shi-qian Zhang ◽  
Yong Zhang ◽  
Yu-lin Wang ◽  
Cheng-ping Huang

Abstract Planar split-ring resonators (SRRs) with broken symmetry, excited by the electric field of incident wave, have been widely used to realize the high-Q resonance. In this paper, we report by theory and experiment an alternative scheme to induce the SRR-based high-Q resonance. The proposed scheme utilizes a two-dimensional array of vertical SRRs with vertical air gaps, which enables the excitation of narrow resonance with magnetic field and strong enhancement of local electromagnetic fields. The working mechanism correlates with the strong directional dependence of the dipole radiation (i.e., the elimination of electric-dipole radiation of the SRRs in the propagation direction), rather than the destructive interference due to the structural symmetry breaking. The dependence of Q factor on the structural parameters has also been studied theoretically, suggesting that a Q factor more than 2000 can be achieved. The results may be useful for designing narrow-band filters and sensors in the microwave or THz regime.


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