The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoreticaly studied by using the time-dependent quantum wave packet method. Both the internuclear distan...The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoreticaly studied by using the time-dependent quantum wave packet method. Both the internuclear distance-and velocity-dependent density functions are calculated and discussed. It is demonstrated that the interference pattern is determined by the phase difference and the delay time between two pump pulses. With two identical pulses with a delay time of 305 fs and a FWHM of 20 fs, more interference fringes can be observed, while with two pump pulses with a delay time of 80 fs and a FWHM of 20 fs, only a few interference fringes can be observed.展开更多
Trimaran hydrodynamics have been an important research topic in recent years.Trimarans have even been chosen for naval surface combatants.In this case,investigation of a trimaran with different outrigger positions is ...Trimaran hydrodynamics have been an important research topic in recent years.Trimarans have even been chosen for naval surface combatants.In this case,investigation of a trimaran with different outrigger positions is important and necessary for better hydrodynamic performance.This paper focuses on the numerical investigation of trimaran hydrodynamics.The trimaran model used in this study is a 1/80 scale high-speed displacement frigate-type concept developed by the Center for Innovation in Ship Design(CISD)at Naval Surface Warfare Center,Carderock Division(NSWCCD).The numerical simulations were conducted for different outrigger positions at low and moderate Froude numbers by using commercial CFD software solving URANS equations.A verification and validation study was carried out for the numerical method in one configuration and one ship velocity.The existing experimental results for the trimaran resistance in the literature were used for validation.Five different outrigger positions were analyzed and the form factor of each configuration was calculated by the Prohaska method.The total resistance was decomposed to its components using the form factor.The interference factor was calculated for each configuration in terms of total resistance,residual resistance and wave resistance.Also,wave profiles using the longitudinal wave cuts in different locations were obtained both numerically and experimentally.It was concluded that the outrigger position had different effects on the interference,total resistance and wave profile at different Froude numbers.It was also shown that the CFD results were in good agreement with the experimental data in all configurations.In conclusion,this study presents the results of interference effects for different trimaran configurations in terms of wave resistance in addition to the total resistance and residual resistance.The numerical method was validated not only with the total resistance test data but also the longitudinal wave profiles along the hull.展开更多
Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis o...Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis of several major interference waves inmines,the differences in time-distance curve,frequency,apparent velocity between theeffective wave and interference wave in the seismic reflection method for advanced explorationare obtained.According to the differences,the effective wave is extracted andthe interference wave is filtered and the system's precision and accuracy is improved.展开更多
This paper reports the implementation and theoretical model for analyzing an optical CDMA/DWDM hybrid system to reduce two major problems,the Inter-Symbol Interference(ISI)and the Four-Wave Mixing(FWM)effects and impr...This paper reports the implementation and theoretical model for analyzing an optical CDMA/DWDM hybrid system to reduce two major problems,the Inter-Symbol Interference(ISI)and the Four-Wave Mixing(FWM)effects and improve the performance of optical subscriber access networks by using Zero Cross-Correlation(ZCC)optical codes,which helps to reduce the effect of the Multiple Access Interference(MAI).A squeezing method is used in the proposed hybrid system to completely suppress the ISI.In this method,the sequence interval of the signature code is squeezed into a duration of less than one-bit.The hybrid system is capable of accommodating 120 optical CDMA users carried by only 10 DWDM wavelengths spaced by 0.2 nm with 60 Gb/s/wavelength transmitted over 105.075 km of optical fiber.The result shows that the optimum interval of the code sequence is a quarter(i.e.,25%)of the bit duration.Moreover,the results reveal that the CDMA technology based on the spread spectrum is capable of increasing the nonlinear tolerance of the proposed hybrid system as the energy of bits is distributed over the chip sequence code.Also,the number of ones/weight and the positions between them have a significant effect on the performance of the proposed hybrid system.展开更多
Laser self-mixing interference（SMI） wave plate measurement method is a burgeoning technique for its simplicity and efficiency. But for the non-coated sample, the reflected light from the surface can seriously affect...Laser self-mixing interference（SMI） wave plate measurement method is a burgeoning technique for its simplicity and efficiency. But for the non-coated sample, the reflected light from the surface can seriously affect the measurement results.To analyze the reason theoretically, a self-consistent model for laser operation with a sub-external and an external cavity is established, and the sub-external cavity formed by the sample and a cavity mirror is proved to be the main error source.A synchronous tuning method is proposed to eliminate the sub-external cavity effect. Experiments are carried out on the synchronously tuning double external cavities self-mixing interference system, and the error of the system is in the range of -0.435°~0.387° compared with the ellipsometer. The research plays an important role in improving the performance and enlarging the application range of the laser self-mixing interference system.展开更多
This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by -37 μm were crea...This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by -37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth -0.5 μK and volume -74 μm^3 are suitable to trap and manipulate an atomic Bose-Einstein condensation （BEC）. Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.展开更多
Wave-particle duality is one of the key features of quantum physics,characterized by the interference pattern.Meanwhile,Floquet spectroscopy is typically studied in the high-frequency region because the Floquet sideba...Wave-particle duality is one of the key features of quantum physics,characterized by the interference pattern.Meanwhile,Floquet spectroscopy is typically studied in the high-frequency region because the Floquet sidebands are very sharp,behaving like“particles”in frequency space,and no interference phenomena are observed.Here,we consider the larger quantum fluctuation region where the Floquet sidebands are broader,making interference between them possible.With the help of an optical lattice clock experimental platform and numerical simulations,such interference of Floquet modes in frequency space is clearly observed.Additionally,it exhibits many exotic phenomena,such as large Floquet sidebands between integer ones,sensitivity to the initial phase,and corresponding emergent symmetries.To analytically elucidate this,we propose the Floquet channel interference hypothesis,which surprisingly matches quantitatively well with both experimental and numerical results.Our research paves the way for developing a new type of interferometer that could be applicable to other Floquet systems.展开更多
In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(...In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(FDTD)method.The proposed structure has the hexagonal close packed of 16×20 circular rods that are suspended in the air substrate with a lattice constant of 606 nm.The plane wave expansion(PWE)method is used to obtain the band diagram for AODFF at an operating wavelength of 1550 nm.The proposed optical flip-flop achieves a low delay time of 0.2 ps and a high contrast ratio(CR)of 10.33 dB.The main advantage of this design is that the input power as low as 1 mW/μm^(2) is sufficient for its operation,since no nonlinear rods are included.In addition,the footprint of the proposed AODFF is 100μm^(2),which is smaller compared to the structures reported in the literature,and it has a fast switching frequency of 5 Tbit/s.展开更多
Millimeter wave(mmWave)massive multiple-input multiple-output(MIMO)plays an important role in the fifth-generation(5G)mobile communications and beyond wireless communication systems owing to its potential of high capa...Millimeter wave(mmWave)massive multiple-input multiple-output(MIMO)plays an important role in the fifth-generation(5G)mobile communications and beyond wireless communication systems owing to its potential of high capacity.However,channel estimation has become very challenging due to the use of massive MIMO antenna array.Fortunately,the mmWave channel has strong sparsity in the spatial angle domain,and the compressed sensing technology can be used to convert the original channel matrix into the sparse matrix of discrete angle grid.Thus the high-dimensional channel matrix estimation is transformed into a sparse recovery problem with greatly reduced computational complexity.However,the path angle in the actual scene appears randomly and is unlikely to be completely located on the quantization angle grid,thus leading to the problem of power leakage.Moreover,multiple paths with the random distribution of angles will bring about serious interpath interference and further deteriorate the performance of channel estimation.To address these off-grid issues,we propose a parallel interference cancellation assisted multi-grid matching pursuit(PIC-MGMP)algorithm in this paper.The proposed algorithm consists of three stages,including coarse estimation,refined estimation,and inter-path cyclic iterative inter-ference cancellation.More specifically,the angular resolution can be improved by locally refining the grid to reduce power leakage,while the inter-path interference is eliminated by parallel interference cancellation(PIC),and the two together improve the estimation accuracy.Simulation results show that compared with the traditional orthogonal matching pursuit(OMP)algorithm,the normalized mean square error(NMSE)of the proposed algorithm decreases by over 14dB in the case of 2 paths.展开更多
Due to the increase in the number of users, beam switching is used for suppressing interference, which leads to higher computational complexity in multi-cell millimeter wave communications. In order to resolve this pr...Due to the increase in the number of users, beam switching is used for suppressing interference, which leads to higher computational complexity in multi-cell millimeter wave communications. In order to resolve this problem, a beam interference model is introduced, and a lower complexity beam interference suppression algorithm based on user grouping is proposed. The proposed algorithm operates beam switching and mnlti-cell cooperative transmission for a part of the users when there exists beam interference due to high user density. In particular, considering the distinct interference suffered by each user, the proposed dual-threshold user grouping method can effectively solve the frequent switching problem at the base station caused by multi-cell cooperative transmission in multi-cell environments. Simulation results show that the proposed algorithm can reduce the computational complexity of beam switching and approach ideal system capacity, compared with conventional interference suppression algorithms that do not involve grouping of users.展开更多
We present examples of a controlled numerical experiment that contribute towards understanding of the physical phenomena that lead to the reduction of coherency of strong earthquake ground motion.We show examples for ...We present examples of a controlled numerical experiment that contribute towards understanding of the physical phenomena that lead to the reduction of coherency of strong earthquake ground motion.We show examples for separation distance of 100 m between the two points on the ground surface,which is in the range of engineering interest.Our examples illustrate the consequences of:(a)standing waves that result from interference of the incident and reflected waves from a near vertical contrast in material properties,(b)standing waves within a concave inhomogeneity(a semi-circular valley in our examples),and(c)smaller motions in the diffraction zone,behind the inhomogeneity.We show that it is possible to reduce coherency,to the extent observed for recorded strong earthquake ground motion,even by a single inclusion in a half space,for incident ground motion that is coherent.We also illustrate the combined effects of geometric spreading and finite fault width,superimposed on the otherwise dominating effects caused by interference.Our examples show reduction of coherence for specific angles of incident waves,while,for other angles of incidence,the coherence remains essentially equal to one.展开更多
In a four-level system of ultracold STRb atoms, through analytical and numerical calculations we propose an efficient scheme to achieve the enhanced four-wave mixing process and demonstrate its dynamical control by va...In a four-level system of ultracold STRb atoms, through analytical and numerical calculations we propose an efficient scheme to achieve the enhanced four-wave mixing process and demonstrate its dynamical control by various parameters such as the travel distance z, probe detuning δ and the probe pulse width T. In particular, we find that the maximal intensity of the nonlinearly generated signal pulse can be about 80% of the initial input probe under the optimal condition. This greatly enhanced conversion efficiency occurs due to the constructive quantum interference between two different components of the generated signal pulse.展开更多
We demonstrate efficient four-wave mixing with an intensity conversion efficiency of nearly 100% in theory without considering the Doppler-broadening effect in a four-level double-A system of hot 87Rb gas. The corresp...We demonstrate efficient four-wave mixing with an intensity conversion efficiency of nearly 100% in theory without considering the Doppler-broadening effect in a four-level double-A system of hot 87Rb gas. The corresponding experimental value of about 73% was reported in our earlier work under the same conditions. This dramatic efficiency is critically dependent on the constructive interference between two four-wave mixing processes relevant to the internally generated four-wave mixing signal.展开更多
Interferences in the quantum fluctuations of the output fields are demonstrated in four-wave mixing processes inside a cavity, which is driven by two quantized fields at the signal and the idler frequencies. These int...Interferences in the quantum fluctuations of the output fields are demonstrated in four-wave mixing processes inside a cavity, which is driven by two quantized fields at the signal and the idler frequencies. These interferences depend on the phase fluctuations of the input fields and induce mode splitting in the transmission spectra.展开更多
Interference of light and material particles is described with a unified model which does not need to assume the wave-particle duality. A moving particle is associated with a region of spatial correlated points named ...Interference of light and material particles is described with a unified model which does not need to assume the wave-particle duality. A moving particle is associated with a region of spatial correlated points named coherence cone. Its geometry depends on photon or particle momentum and on the parameters of the experimental setup. The final interference pattern is explained as a spatial distribution of particles caused by the coherence cone geometry. In the present context, the wave front superposition principle, wave-particle duality and wave-collapse lose their meaning. Fits of observed single electron and single molecule interference patterns together with the simulation of expected near-field molecule interference (Talbot carpet) demonstrate the model validity.展开更多
A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the C...A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the CR-TR-UWB system detects the band of PU,and then sends prolate spheroidal wave functions（PSWF） pulses with the same limited band as PU＇s to reduce interference with PU.The receiver uses a notch filter before autocorrelation to eliminate NBI from PU.The simulation results show that the bit error rate（BER） performance of the CR-TR-UWB system is close to that of TR-UWB systems without NBI when the system is interfered by single or double NBIs with a signal to interference ratio（SIR） of 0 dB,and if the signal to noise ratio（SNR） is 10 dB and the SIR varies from-20 to 10 dB,BER performance varies no more than an order of magnitude.The system has excellent resistance to NBI,strong robustness BER performance at different SNRs,and smaller interference with the same frequency band PU.展开更多
The influence of frequency modulation （FM） interfer- ence on correlation detection performance of the pseudo random code continuous wave （PRC-CW） radar is analyzed. It is found that the correlation output deterior...The influence of frequency modulation （FM） interfer- ence on correlation detection performance of the pseudo random code continuous wave （PRC-CW） radar is analyzed. It is found that the correlation output deteriorates greatly when the FM inter- ference power exceeds the anti-jamming limit of the radar. Accord- ing to the fact that the PRC-CW radar echo is a wideband pseudo random signal occupying the whole TF plane, while the FM in- terference only concentrates in a small portion, a new method is proposed based on adaptive short-time Fourier transform （STFT） and time-varying filtering for FM interference suppression. This method filters the received signal by using a binary mask to excise only the portion of the TF plane corrupted by the interference. Two types of interference, linear FM （LFM） and sinusoidal FM （SFM）, under different signal-to-jamming ratio （S JR） are studied. It is shown that the proposed method can effectively suppress the FM interference and improve the performance of target detection.展开更多
Differing from the general analysis,the process of continuous wave(CW) interference being despreaded in a direct sequence spread spectrum(DSSS) system is reanalyzed. It is proved that the result sequence of continuous...Differing from the general analysis,the process of continuous wave(CW) interference being despreaded in a direct sequence spread spectrum(DSSS) system is reanalyzed. It is proved that the result sequence of continuous wave interference being despreaded varies according to sinusoid in time.Its frequency and amplitude are derived.The processing gain is discussed under 3 cases in comparison with traditional analysis.Results show that the processing gain varies according to the frequency offset of CW to DSSS signal carrier.展开更多
An analysis is made of interference of two plane waves which in turn give rise to subsequent diffraction phenomena. This is done using two different approaches. One of them is straight forward but is difficult to inte...An analysis is made of interference of two plane waves which in turn give rise to subsequent diffraction phenomena. This is done using two different approaches. One of them is straight forward but is difficult to interpret. The second is less conventional but more intuitive thus giving more insight into the process. The geometry is kept very simple to focus on the process itself. Both approaches give rise to the same results thus offering a choice in tackling such prob-lems.展开更多
The AB(Aharonov-Bohm)effect is a pivotal quantum mechanical phenomenon that illustrates the fundamental role of the electromagnetic vector potential A in determining the phase of a charged particle’s wave function,ev...The AB(Aharonov-Bohm)effect is a pivotal quantum mechanical phenomenon that illustrates the fundamental role of the electromagnetic vector potential A in determining the phase of a charged particle’s wave function,even in regions where the magnetic field B is zero.This effect demonstrates that quantum particles are influenced not only by the fields directly present but also by the potentials associated with those fields.In the AB effect,an electron beam is split into two paths,with one path encircling a solenoid and the other bypassing it.Despite the absence of a magnetic field in the regions traversed by the beams,the vector potential A associated with the magnetic flux Φ through the solenoid induces a phase shift in the electron’s wave function.This phase shift,quantified by △φ=qΦ/hc,manifests as a change in the interference pattern observed in the detection screen.The phenomenon underscores the principle of gauge invariance in QED(quantum electrodynamics),where physical observables remain invariant under local gauge transformations of the vector and scalar potentials.This reinforces the notion that the vector potential A has a profound impact on quantum systems,beyond its classical role.This article outlines the AB effect,including its theoretical framework,experimental observations,and implications.The focus on the role of the vector potential in quantum mechanics provides a comprehensive understanding of this important phenomenon.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10674022 and 20633070)
文摘The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoreticaly studied by using the time-dependent quantum wave packet method. Both the internuclear distance-and velocity-dependent density functions are calculated and discussed. It is demonstrated that the interference pattern is determined by the phase difference and the delay time between two pump pulses. With two identical pulses with a delay time of 305 fs and a FWHM of 20 fs, more interference fringes can be observed, while with two pump pulses with a delay time of 80 fs and a FWHM of 20 fs, only a few interference fringes can be observed.
基金The second author was supported by the Scientific and Technological Research Council of Turkey(TUBITAK)2219 International Postdoctoral Research Fellowship Program。
文摘Trimaran hydrodynamics have been an important research topic in recent years.Trimarans have even been chosen for naval surface combatants.In this case,investigation of a trimaran with different outrigger positions is important and necessary for better hydrodynamic performance.This paper focuses on the numerical investigation of trimaran hydrodynamics.The trimaran model used in this study is a 1/80 scale high-speed displacement frigate-type concept developed by the Center for Innovation in Ship Design(CISD)at Naval Surface Warfare Center,Carderock Division(NSWCCD).The numerical simulations were conducted for different outrigger positions at low and moderate Froude numbers by using commercial CFD software solving URANS equations.A verification and validation study was carried out for the numerical method in one configuration and one ship velocity.The existing experimental results for the trimaran resistance in the literature were used for validation.Five different outrigger positions were analyzed and the form factor of each configuration was calculated by the Prohaska method.The total resistance was decomposed to its components using the form factor.The interference factor was calculated for each configuration in terms of total resistance,residual resistance and wave resistance.Also,wave profiles using the longitudinal wave cuts in different locations were obtained both numerically and experimentally.It was concluded that the outrigger position had different effects on the interference,total resistance and wave profile at different Froude numbers.It was also shown that the CFD results were in good agreement with the experimental data in all configurations.In conclusion,this study presents the results of interference effects for different trimaran configurations in terms of wave resistance in addition to the total resistance and residual resistance.The numerical method was validated not only with the total resistance test data but also the longitudinal wave profiles along the hull.
基金Supported by the National Natural Science Foundation of China(50375026)the National Basic Research Program of China(2005cb221500)+1 种基金the National Key Technology R&D Program(2006BAK03B01)the National Natural Science Foundation Key Program(50534080)
文摘Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis of several major interference waves inmines,the differences in time-distance curve,frequency,apparent velocity between theeffective wave and interference wave in the seismic reflection method for advanced explorationare obtained.According to the differences,the effective wave is extracted andthe interference wave is filtered and the system's precision and accuracy is improved.
基金This work was supported by Multimedia University(Malaysia),project SAP ID:MMUI/160092.
文摘This paper reports the implementation and theoretical model for analyzing an optical CDMA/DWDM hybrid system to reduce two major problems,the Inter-Symbol Interference(ISI)and the Four-Wave Mixing(FWM)effects and improve the performance of optical subscriber access networks by using Zero Cross-Correlation(ZCC)optical codes,which helps to reduce the effect of the Multiple Access Interference(MAI).A squeezing method is used in the proposed hybrid system to completely suppress the ISI.In this method,the sequence interval of the signature code is squeezed into a duration of less than one-bit.The hybrid system is capable of accommodating 120 optical CDMA users carried by only 10 DWDM wavelengths spaced by 0.2 nm with 60 Gb/s/wavelength transmitted over 105.075 km of optical fiber.The result shows that the optimum interval of the code sequence is a quarter(i.e.,25%)of the bit duration.Moreover,the results reveal that the CDMA technology based on the spread spectrum is capable of increasing the nonlinear tolerance of the proposed hybrid system as the energy of bits is distributed over the chip sequence code.Also,the number of ones/weight and the positions between them have a significant effect on the performance of the proposed hybrid system.
文摘Laser self-mixing interference（SMI） wave plate measurement method is a burgeoning technique for its simplicity and efficiency. But for the non-coated sample, the reflected light from the surface can seriously affect the measurement results.To analyze the reason theoretically, a self-consistent model for laser operation with a sub-external and an external cavity is established, and the sub-external cavity formed by the sample and a cavity mirror is proved to be the main error source.A synchronous tuning method is proposed to eliminate the sub-external cavity effect. Experiments are carried out on the synchronously tuning double external cavities self-mixing interference system, and the error of the system is in the range of -0.435°~0.387° compared with the ellipsometer. The research plays an important role in improving the performance and enlarging the application range of the laser self-mixing interference system.
基金supported by the National Natural Science Foundation of China (Grant Nos.10434060,10674047 and 10804031)the National Key Basic Research and Development Program of China (Grant No.2006CB921604)+2 种基金the Program for Changjiang Scholarand Innovative Research Team and Shanghai Leading Academic Discipline Project (Grant No.B408)the Youth Foundation of Jiangxi Educational Committee (Grant No.GJJ09530)the Scientific Research Foundation of ECIT (Grant No.DSH0417)
文摘This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by -37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth -0.5 μK and volume -74 μm^3 are suitable to trap and manipulate an atomic Bose-Einstein condensation （BEC）. Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.
基金supported by the National Natural Science Foundation of China(Grant No.12274045)support from the National Natural Science Foundation of China(Grant Nos.12274046,11874094,12147102,and 12347101)+2 种基金the Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-JQX0018)the Fundamental Research Funds for the Central Universities(Grant No.2021CDJZYJH-003)the Xiaomi Foundation/Xiaomi Young Talents Program。
文摘Wave-particle duality is one of the key features of quantum physics,characterized by the interference pattern.Meanwhile,Floquet spectroscopy is typically studied in the high-frequency region because the Floquet sidebands are very sharp,behaving like“particles”in frequency space,and no interference phenomena are observed.Here,we consider the larger quantum fluctuation region where the Floquet sidebands are broader,making interference between them possible.With the help of an optical lattice clock experimental platform and numerical simulations,such interference of Floquet modes in frequency space is clearly observed.Additionally,it exhibits many exotic phenomena,such as large Floquet sidebands between integer ones,sensitivity to the initial phase,and corresponding emergent symmetries.To analytically elucidate this,we propose the Floquet channel interference hypothesis,which surprisingly matches quantitatively well with both experimental and numerical results.Our research paves the way for developing a new type of interferometer that could be applicable to other Floquet systems.
文摘In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(FDTD)method.The proposed structure has the hexagonal close packed of 16×20 circular rods that are suspended in the air substrate with a lattice constant of 606 nm.The plane wave expansion(PWE)method is used to obtain the band diagram for AODFF at an operating wavelength of 1550 nm.The proposed optical flip-flop achieves a low delay time of 0.2 ps and a high contrast ratio(CR)of 10.33 dB.The main advantage of this design is that the input power as low as 1 mW/μm^(2) is sufficient for its operation,since no nonlinear rods are included.In addition,the footprint of the proposed AODFF is 100μm^(2),which is smaller compared to the structures reported in the literature,and it has a fast switching frequency of 5 Tbit/s.
基金supported in part by the Beijing Natural Science Foundation under Grant No.L202003the National Natural Science Foundation of China under Grant U22B2001 and 62271065the Project of China Railway Corporation under Grant N2022G048.
文摘Millimeter wave(mmWave)massive multiple-input multiple-output(MIMO)plays an important role in the fifth-generation(5G)mobile communications and beyond wireless communication systems owing to its potential of high capacity.However,channel estimation has become very challenging due to the use of massive MIMO antenna array.Fortunately,the mmWave channel has strong sparsity in the spatial angle domain,and the compressed sensing technology can be used to convert the original channel matrix into the sparse matrix of discrete angle grid.Thus the high-dimensional channel matrix estimation is transformed into a sparse recovery problem with greatly reduced computational complexity.However,the path angle in the actual scene appears randomly and is unlikely to be completely located on the quantization angle grid,thus leading to the problem of power leakage.Moreover,multiple paths with the random distribution of angles will bring about serious interpath interference and further deteriorate the performance of channel estimation.To address these off-grid issues,we propose a parallel interference cancellation assisted multi-grid matching pursuit(PIC-MGMP)algorithm in this paper.The proposed algorithm consists of three stages,including coarse estimation,refined estimation,and inter-path cyclic iterative inter-ference cancellation.More specifically,the angular resolution can be improved by locally refining the grid to reduce power leakage,while the inter-path interference is eliminated by parallel interference cancellation(PIC),and the two together improve the estimation accuracy.Simulation results show that compared with the traditional orthogonal matching pursuit(OMP)algorithm,the normalized mean square error(NMSE)of the proposed algorithm decreases by over 14dB in the case of 2 paths.
基金This work was supported in part by the Program for Changjiang Scholars and Innovative Research Team in University under grant No. IRT16R72the National Natural Science Foundation of China under Grant No. 61440062.
文摘Due to the increase in the number of users, beam switching is used for suppressing interference, which leads to higher computational complexity in multi-cell millimeter wave communications. In order to resolve this problem, a beam interference model is introduced, and a lower complexity beam interference suppression algorithm based on user grouping is proposed. The proposed algorithm operates beam switching and mnlti-cell cooperative transmission for a part of the users when there exists beam interference due to high user density. In particular, considering the distinct interference suffered by each user, the proposed dual-threshold user grouping method can effectively solve the frequent switching problem at the base station caused by multi-cell cooperative transmission in multi-cell environments. Simulation results show that the proposed algorithm can reduce the computational complexity of beam switching and approach ideal system capacity, compared with conventional interference suppression algorithms that do not involve grouping of users.
文摘We present examples of a controlled numerical experiment that contribute towards understanding of the physical phenomena that lead to the reduction of coherency of strong earthquake ground motion.We show examples for separation distance of 100 m between the two points on the ground surface,which is in the range of engineering interest.Our examples illustrate the consequences of:(a)standing waves that result from interference of the incident and reflected waves from a near vertical contrast in material properties,(b)standing waves within a concave inhomogeneity(a semi-circular valley in our examples),and(c)smaller motions in the diffraction zone,behind the inhomogeneity.We show that it is possible to reduce coherency,to the extent observed for recorded strong earthquake ground motion,even by a single inclusion in a half space,for incident ground motion that is coherent.We also illustrate the combined effects of geometric spreading and finite fault width,superimposed on the otherwise dominating effects caused by interference.Our examples show reduction of coherence for specific angles of incident waves,while,for other angles of incidence,the coherence remains essentially equal to one.
基金supported by National Natural Science Foundation of China (Grant Nos. 10774059 and 10904047)the National Basic Research Program of China (Grant No. 2006CB921103)+1 种基金the doctoral program foundation of institution of High Education of China (Grant No. 20060183046)the basic research foundation of Jilin University of China (Grant No. 200903326)
文摘In a four-level system of ultracold STRb atoms, through analytical and numerical calculations we propose an efficient scheme to achieve the enhanced four-wave mixing process and demonstrate its dynamical control by various parameters such as the travel distance z, probe detuning δ and the probe pulse width T. In particular, we find that the maximal intensity of the nonlinearly generated signal pulse can be about 80% of the initial input probe under the optimal condition. This greatly enhanced conversion efficiency occurs due to the constructive quantum interference between two different components of the generated signal pulse.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10904047 and 11104111)the National Basic Research Program of China (Grant No. 2011CB921603)the Basic Research Foundation of Jilin University,China
文摘We demonstrate efficient four-wave mixing with an intensity conversion efficiency of nearly 100% in theory without considering the Doppler-broadening effect in a four-level double-A system of hot 87Rb gas. The corresponding experimental value of about 73% was reported in our earlier work under the same conditions. This dramatic efficiency is critically dependent on the constructive interference between two four-wave mixing processes relevant to the internally generated four-wave mixing signal.
基金Project supported by the New Staff Research Support Plan of Xi’an Jiaotong University,China (Grant No. 08141015)
文摘Interferences in the quantum fluctuations of the output fields are demonstrated in four-wave mixing processes inside a cavity, which is driven by two quantized fields at the signal and the idler frequencies. These interferences depend on the phase fluctuations of the input fields and induce mode splitting in the transmission spectra.
文摘Interference of light and material particles is described with a unified model which does not need to assume the wave-particle duality. A moving particle is associated with a region of spatial correlated points named coherence cone. Its geometry depends on photon or particle momentum and on the parameters of the experimental setup. The final interference pattern is explained as a spatial distribution of particles caused by the coherence cone geometry. In the present context, the wave front superposition principle, wave-particle duality and wave-collapse lose their meaning. Fits of observed single electron and single molecule interference patterns together with the simulation of expected near-field molecule interference (Talbot carpet) demonstrate the model validity.
基金The National Research and Development Program of China(863 Program)(No.2007AA12Z238)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No. 12KJD510008)
文摘A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the CR-TR-UWB system detects the band of PU,and then sends prolate spheroidal wave functions（PSWF） pulses with the same limited band as PU＇s to reduce interference with PU.The receiver uses a notch filter before autocorrelation to eliminate NBI from PU.The simulation results show that the bit error rate（BER） performance of the CR-TR-UWB system is close to that of TR-UWB systems without NBI when the system is interfered by single or double NBIs with a signal to interference ratio（SIR） of 0 dB,and if the signal to noise ratio（SNR） is 10 dB and the SIR varies from-20 to 10 dB,BER performance varies no more than an order of magnitude.The system has excellent resistance to NBI,strong robustness BER performance at different SNRs,and smaller interference with the same frequency band PU.
文摘The influence of frequency modulation （FM） interfer- ence on correlation detection performance of the pseudo random code continuous wave （PRC-CW） radar is analyzed. It is found that the correlation output deteriorates greatly when the FM inter- ference power exceeds the anti-jamming limit of the radar. Accord- ing to the fact that the PRC-CW radar echo is a wideband pseudo random signal occupying the whole TF plane, while the FM in- terference only concentrates in a small portion, a new method is proposed based on adaptive short-time Fourier transform （STFT） and time-varying filtering for FM interference suppression. This method filters the received signal by using a binary mask to excise only the portion of the TF plane corrupted by the interference. Two types of interference, linear FM （LFM） and sinusoidal FM （SFM）, under different signal-to-jamming ratio （S JR） are studied. It is shown that the proposed method can effectively suppress the FM interference and improve the performance of target detection.
文摘Differing from the general analysis,the process of continuous wave(CW) interference being despreaded in a direct sequence spread spectrum(DSSS) system is reanalyzed. It is proved that the result sequence of continuous wave interference being despreaded varies according to sinusoid in time.Its frequency and amplitude are derived.The processing gain is discussed under 3 cases in comparison with traditional analysis.Results show that the processing gain varies according to the frequency offset of CW to DSSS signal carrier.
文摘An analysis is made of interference of two plane waves which in turn give rise to subsequent diffraction phenomena. This is done using two different approaches. One of them is straight forward but is difficult to interpret. The second is less conventional but more intuitive thus giving more insight into the process. The geometry is kept very simple to focus on the process itself. Both approaches give rise to the same results thus offering a choice in tackling such prob-lems.
文摘The AB(Aharonov-Bohm)effect is a pivotal quantum mechanical phenomenon that illustrates the fundamental role of the electromagnetic vector potential A in determining the phase of a charged particle’s wave function,even in regions where the magnetic field B is zero.This effect demonstrates that quantum particles are influenced not only by the fields directly present but also by the potentials associated with those fields.In the AB effect,an electron beam is split into two paths,with one path encircling a solenoid and the other bypassing it.Despite the absence of a magnetic field in the regions traversed by the beams,the vector potential A associated with the magnetic flux Φ through the solenoid induces a phase shift in the electron’s wave function.This phase shift,quantified by △φ=qΦ/hc,manifests as a change in the interference pattern observed in the detection screen.The phenomenon underscores the principle of gauge invariance in QED(quantum electrodynamics),where physical observables remain invariant under local gauge transformations of the vector and scalar potentials.This reinforces the notion that the vector potential A has a profound impact on quantum systems,beyond its classical role.This article outlines the AB effect,including its theoretical framework,experimental observations,and implications.The focus on the role of the vector potential in quantum mechanics provides a comprehensive understanding of this important phenomenon.
