We investigate the generation and the evolution of continuous-variable(CV) entanglement from a laserdriven four-state atom inside a doubly resonant cavity under Raman excitation.Two transitions in the four-state atom ...We investigate the generation and the evolution of continuous-variable(CV) entanglement from a laserdriven four-state atom inside a doubly resonant cavity under Raman excitation.Two transitions in the four-state atom independently interact with the two cavity modes,while two other transitions are driven by coupling laser fields.By including the atomic relaxation as well as cavity losses,we show that the CV entanglement with large mean number of photons can be generated in our scheme.We also show that the intensity of the coupling laser fields can influence effectively the entanglement period of the cavity field.Different from the conventional resonant excitation scheme where zero one-photon detuning are required,it is found that the intensity and period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be adjusted by properly modulating the frequency detuning.展开更多
This paper investigates the generation and evolution of continuous-variable entanglement in an asymmetric coupled-quantum well （CQW） system. Our numerical results show that this CQW system can be regarded as a sourc...This paper investigates the generation and evolution of continuous-variable entanglement in an asymmetric coupled-quantum well （CQW） system. Our numerical results show that this CQW system can be regarded as a source of macroscopic entangled light over a wide range of initial states of the cavity field. This investigation can be used for achieving the macroscopic entangled light in the CQW solid-state medium, which is much more praeticaJ than that in an atomic medium because of its flexible design and the controllable interference strength.展开更多
We investigate the fundamental limits to the achievable tripartite continuous-variable （CV） entanglement criterion of a generalized Vl criterion. Our numerical simulation results show that the non-degenerate eigenva...We investigate the fundamental limits to the achievable tripartite continuous-variable （CV） entanglement criterion of a generalized Vl criterion. Our numerical simulation results show that the non-degenerate eigenvalues do effect the performances of the estimated minimum variances. From below the threshold to above the threshold, with the increase of the pump parameter, the tripartite CV entanglement gradually disappears. The different off-diagonal elements seriously distort the weights for entanglement. We can obtain a good tripartite CV entanglement by appropriately controlling the values of off-diagonal elements eij.展开更多
Based on the quantum fluctuations, we adopt the method of generalized V1 criterion to investigate multipartite entan- glement characteristics in an optical parametric amplification system with the consideration of dis...Based on the quantum fluctuations, we adopt the method of generalized V1 criterion to investigate multipartite entan- glement characteristics in an optical parametric amplification system with the consideration of dispersion. The nonlinear interaction becomes strong because of the existence of dispersion coefficient σ. Considering the influence of dispersion factor σ, with increasing the pump parameter μ, the value of minimum variance V1 decreases and the squeezing curve nearly equals 1/（1 ＋ μ）. The larger particle number N results in a smaller variance and higher entanglement.展开更多
The influence of the extra classical noises in seed beams on the entanglement between the signal and the idler modes of the output fields generated by a non-degenerate optical parametric amplifier operating at deampli...The influence of the extra classical noises in seed beams on the entanglement between the signal and the idler modes of the output fields generated by a non-degenerate optical parametric amplifier operating at deamplification is investigated theoretically and experimentally. With the increase of the extra classical noises in the seed beams, the correlation degree of the output entangled optical fields, which is scaled by the quantum noise limit, decreases rapidly. The experimental results axe in good agreement with the theoretical calculations.展开更多
We investigate the entanglement entropy in quantum states featuring repeated sequential excitations of unit patterns in momentum space.In the scaling limit,each unit pattern contributes independently and universally t...We investigate the entanglement entropy in quantum states featuring repeated sequential excitations of unit patterns in momentum space.In the scaling limit,each unit pattern contributes independently and universally to the entanglement entropy,leading to a characteristic volume-law scaling.Crucially,this universal contribution remains identical for both free and interacting models,enabling decomposition of the total entanglement into patternspecific components.Numerical verification in fermionic and bosonic chains confirms this volume-law fragmentation phenomenon.For fermionic systems,we derive analytical expressions where many-body entanglement becomes expressible through few-body entanglement components.Notably,this analytical framework extends to spin-1/2 XXZ chains through appropriate identifications.展开更多
Methods of quantum information processing often appear in terms of specially selected states.For example,mutually unbiased bases(MUBs)and symmetric informationally complete measurements are widely applied.Finite frame...Methods of quantum information processing often appear in terms of specially selected states.For example,mutually unbiased bases(MUBs)and symmetric informationally complete measurements are widely applied.Finite frames have found use in many areas including quantum information.Due to its specific inner structure,a single equiangular tight frame(ETF)allows one to formulate criteria to detect non-classical correlations.This study aims to approach entanglement detection with the use of mutually unbiased ETFs.Such frames are an interesting generalization of widely recognized MUBs.It still uses rank-one operators,but the number of outcomes can exceed the dimensionality.Several approaches are considered including separability criteria and entanglement witnesses.Separability criteria for multipartite systems are finally obtained.展开更多
The rapid proliferation of multimodal misinformation on social media demands detection frameworks that are not only accurate but also robust to noise,adversarial manipulation,and semantic inconsistency between modalit...The rapid proliferation of multimodal misinformation on social media demands detection frameworks that are not only accurate but also robust to noise,adversarial manipulation,and semantic inconsistency between modalities.Existing multimodal fake news detection approaches often rely on deterministic fusion strategies,which limits their ability to model uncertainty and complex cross-modal dependencies.To address these challenges,we propose Q-ALIGNer,a quantum-inspired multimodal framework that integrates classical feature extraction with quantumstate encoding,learnable cross-modal entanglement,and robustness-aware training objectives.The proposed framework adopts quantumformalism as a representational abstraction,enabling probabilisticmodeling ofmultimodal alignment while remaining fully executable on classical hardware.Q-ALIGNer is evaluated on four widely used benchmark datasets—FakeNewsNet,Fakeddit,Weibo,and MediaEval VMU—covering diverse platforms,languages,and content characteristics.Experimental results demonstrate consistent performance improvements over strong text-only,vision-only,multimodal,and quantum-inspired baselines,including BERT,RoBERTa,XLNet,ResNet,EfficientNet,ViT,Multimodal-BERT,ViLBERT,and QEMF.Q-ALIGNer achieves accuracies of 91.2%,92.9%,91.7%,and 92.1%on FakeNewsNet,Fakeddit,Weibo,and MediaEval VMU,respectively,with F1-score gains of 3–4 percentage points over QEMF.Robustness evaluation shows a reduced adversarial accuracy gap of 2.6%,compared to 7%–9%for baseline models,while calibration analysis indicates improved reliability with an expected calibration error of 0.031.In addition,computational analysis shows that Q-ALIGNer reduces training time to 19.6 h compared to 48.2 h for QEMF at a comparable parameter scale.These results indicate that quantum-inspired alignment and entanglement can enhance robustness,uncertainty awareness,and efficiency in multimodal fake news detection,positioning Q-ALIGNer as a principled and practical content-centric framework for misinformation analysis.展开更多
Shor's algorithm outperforms its classical counterpart in efficient prime factorization.We explore the coherence and entanglement dynamics of the evolved states within Shor's algorithm,showing that the coheren...Shor's algorithm outperforms its classical counterpart in efficient prime factorization.We explore the coherence and entanglement dynamics of the evolved states within Shor's algorithm,showing that the coherence in each step relies on the dimension of register or the order,and discuss the relations between geometric coherence and geometric entanglement.We investigate how unitary operators induce variations in coherence and entanglement,and analyze the variations of coherence and entanglement within the entire algorithm,demonstrating that the overall effect of Shor's algorithm tends to deplete coherence and produce entanglement.Our research not only deepens the understanding of this algorithm but also provides methodological references for studying resource dynamics in other quantum algorithms.展开更多
We obtain an explicit formula to calculate the entanglement entropy of bipartite entangled state of general two-mode boson exponential quadratic operator with continuous variables in Fock space. The simplicity and gen...We obtain an explicit formula to calculate the entanglement entropy of bipartite entangled state of general two-mode boson exponential quadratic operator with continuous variables in Fock space. The simplicity and generality of our formula are shown by some examples.展开更多
Continuous-variable quantum key distribution(CVQKD) protocols with entanglement in the middle(EM) enable long maximal transmission distances for quantum communications. For the security analysis of the protocols, it i...Continuous-variable quantum key distribution(CVQKD) protocols with entanglement in the middle(EM) enable long maximal transmission distances for quantum communications. For the security analysis of the protocols, it is usually assumed that Eve performs collective Gaussian attacks and there is a lack of finite-size analysis of the protocols. However,in this paper we consider the finite-size regime of the EM-based CVQKD protocols by exposing the protocol to collective attacks and coherent attacks. We differentiate between the collective attacks and the coherent attacks while comparing asymptotic key rate and the key rate in the finite-size scenarios. Moreover, both symmetric and asymmetric configurations are collated in a contrastive analysis. As expected, the derived results in the finite-size scenarios are less useful than those acquired in the asymptotic regime. Nevertheless, we find that CVQKD with entanglement in the middle is capable of providing fully secure secret keys taking the finite-size effects into account with transmission distances of more than 30 km.展开更多
We seek to analyze a three-level cascade laser with a pair of nonlinearly coupled waveguides inside the cavity. Applying the pertinent master equation, we investigate the squeezing and entanglement properties intracav...We seek to analyze a three-level cascade laser with a pair of nonlinearly coupled waveguides inside the cavity. Applying the pertinent master equation, we investigate the squeezing and entanglement properties intracavity produced by our system. It is shown that with the help of nonlinearly coupled waveguides highly squeezed as well as macroscopic entangled light with high intensity can be achieved.展开更多
A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy A...A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy Alice or Bob. This method is able to enhance the efficiency of the CVQKD scheme attacked by local oscillator （LO） intensity attack in terms of the generated secret key rate in quantum communication. The other indication of the improvement is that the maximum transmission distance and the maximum loss tolerance can be increased significantly, especially for CVQKD schemes based on homodyne detection.展开更多
We demonstrate that the n-partite continuous-variable entanglement can be unconditionally prepared among n parties that share no common past, from n two-mode squeezed states. Both CHZ-like and cluster-like states can ...We demonstrate that the n-partite continuous-variable entanglement can be unconditionally prepared among n parties that share no common past, from n two-mode squeezed states. Both CHZ-like and cluster-like states can be generated for any nonzero squeezing in the entangled sources. An application of the resulting multipartite entangled state to a teleportation network is illustrated.展开更多
Quantum secure direct communication(QSDC) is a communication method based on quantum mechanics and it is used to transmit secret messages. Unlike quantum key distribution, secret messages can be transmitted directly o...Quantum secure direct communication(QSDC) is a communication method based on quantum mechanics and it is used to transmit secret messages. Unlike quantum key distribution, secret messages can be transmitted directly on a quantum channel with QSDC. Higher channel capacity and noise suppression capabilities are key to achieving longdistance quantum communication. Here, we report a continuous-variable QSDC scheme based on mask-coding and orbital angular momentum, in which the mask-coding is employed to protect the security of the transmitting messages and to suppress the influence of excess noise. The combination of orbital angular momentum and information block transmission effectively improves the secrecy capacity. In the 800 information blocks ×1310 bits length 10-km experiment, the results show a statistical average bit error rate of 0.38%, a system excess noise value of 0.0184 SNU, and a final secrecy capacity of 6.319×10~6 bps. Therefore, this scheme reduces error bits while increasing secrecy capacity, providing a solution for long-distance large-scale quantum communication, which is capable of transmitting text, images and other information of reasonable size.展开更多
The rapid advancement of radar and 5 G communication technologies has created an urgent need for materials that possess both low dielectric constants and superior mechanical strength to ensure efficient signal transmi...The rapid advancement of radar and 5 G communication technologies has created an urgent need for materials that possess both low dielectric constants and superior mechanical strength to ensure efficient signal transmission and minimal loss.Herein,a synergistic effect of multiple regulation strategies from the atomic scales to the molecular scales was proposed to develop Covalent Organic Frameworks(COFs)modified cyanate ester resins(COF-mCE).The strategy has proven highly effective in enhancing both dielectric and mechanical properties.With only 3 wt%COFs,the dielectric constant of COF-mCE is reduced from 3.32 to 2.84 at 1 MHz.Meanwhile,the mechanical performance of COF-mCE composites exhibits substantial improvements,with flexural strength increasing by 42.6% and tensile strength by 52.1% compared to pure mCE.The investigation explores that hydrogen bonding and π-π stacking interactions restrain the polarization feature and the mechanical property improvements of the COF-mCE derived from the entanglement effect of COF-polymer chains.Furthermore,the 3D-printed COF-mCE honeycomb structure demonstrates excellent electromagnetic wave transmittance and low reflectance,achieving a transmittance of 94.1% at 10 GHz with a 60°incidence angle.This multi-scale design strategy offers new insights into the development of low-k dielectric material for next-generation electronic science applications.展开更多
We introduce a new kind of four-mode continuous variable entangled state in Fock space. The completeness relation and the partly nonorthonormal property of such a state are proven. The scheme to generate this state is...We introduce a new kind of four-mode continuous variable entangled state in Fock space. The completeness relation and the partly nonorthonormal property of such a state are proven. The scheme to generate this state is presented by combining a symmetrical beamsplitter, a parametric down-conversion and a polarizer. After making a single-mode quadrature amplitude measurement, the remaining three modes are kept in entanglement. And its applications are also discussed.展开更多
Quantum entanglement is a bizarre, counterintuitive phenomenon which shows that entangled subatomic particles remain related even when they are far apart, which was described by Einstein as “spooky action at a dista...Quantum entanglement is a bizarre, counterintuitive phenomenon which shows that entangled subatomic particles remain related even when they are far apart, which was described by Einstein as “spooky action at a distance”. Although this phenomenon could be interpreted by a few theories, for example, the famous Copenhagen interpretation which describes that these states exist simultaneously by a wave function, however, there is still no unquestioned theory and it continues to puzzle people around the world. Here we propose a hypothesis that gravity cuts out stop functioning between subatomic particles based on the observations of a thought experiment. It is well known that the Universe is filled with various subatomic particles (e.g. cosmic neutrino background, CνB) and gravity is a universal force making any particle in the Universe attract any other. Based on these observations, it is expected that the CνB particles walking abreast will be combined together by their gravity after some time/distance, which will thus result in a greatly uneven distribution of CνB. However, the observational evidence showed that CνB is highly isotropic and homogenous, suggesting that gravity would no longer work at the subatomic scale. Thus, the relation of the paired subatomic particles would become some pure correlation of mass (or equivalent energy) status. In this case, time would be not required anymore due to the ineffectiveness of gravity. The proposed new interpretation matches the experimental observations well and finally possible thought experiments are presented to test this theory.展开更多
Entanglement plays a key role in quantum physics, but how much information it can extract from many-body systems is still an open question, particularly regarding quantum criticalities and emergent symmetries. In this...Entanglement plays a key role in quantum physics, but how much information it can extract from many-body systems is still an open question, particularly regarding quantum criticalities and emergent symmetries. In this work, we systematically study the entanglement entropy(EE) and derivative entanglement entropy(DEE) near quantum phase transitions in various quantum many-body systems. A one-parameter scaling relation between the DEE and system size at the critical point has been derived for the first time, which successfully obtains the critical exponent via data collapse. Furthermore, we find that the EE peaks at the(emergent) symmetryenhanced first-order transition, reflecting higher symmetry breaking. This work provides a new paradigm for quantum many-body research from the perspective of EE and DEE.展开更多
The rapid advancements of ultrafast intense laser technology have opened new avenues for investigating entanglement in laser-induced systems. However, the application of these advances in quantum technology requires a...The rapid advancements of ultrafast intense laser technology have opened new avenues for investigating entanglement in laser-induced systems. However, the application of these advances in quantum technology requires a reliable and universally applicable method for enhancing and regulating entanglement. Here we demonstrate how a few-cycle intense laser field can significantly enhance the degree of entanglement compared to its multi-cycle counterpart, using the example of electron–electron entanglement of orbital angular momentum(OAM) states in recollision-excitation non-sequential double ionization of Ar atoms. By confining the ionization dynamics to a specific narrow time window, the few-cycle pulse purifies the electron trajectories, thereby ensuring high coherence between entangled OAM channels and enhancing entanglement. Furthermore, the degree of entanglement can be efficiently modulated by varying the carrier envelope phase of the few-cycle laser pulse, which is achieved by altering the population across OAM channels. Optimizing coherence through electron trajectory purification with a designed specific temporal waveform of laser field provides a general pathway for enhancing entanglement in laser-induced systems.展开更多
基金Supported by National Natural Science Foundation of China under Grant Nos.10704017,11074036 and 10874050National Fundamental Research Program of China Grant No.2007CB936300
文摘We investigate the generation and the evolution of continuous-variable(CV) entanglement from a laserdriven four-state atom inside a doubly resonant cavity under Raman excitation.Two transitions in the four-state atom independently interact with the two cavity modes,while two other transitions are driven by coupling laser fields.By including the atomic relaxation as well as cavity losses,we show that the CV entanglement with large mean number of photons can be generated in our scheme.We also show that the intensity of the coupling laser fields can influence effectively the entanglement period of the cavity field.Different from the conventional resonant excitation scheme where zero one-photon detuning are required,it is found that the intensity and period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be adjusted by properly modulating the frequency detuning.
基金The project supported in part by Natural Science Foundation of China under Grant Nos. 10575040, 10634060, 10874050, and 10704017 ； National Foundation Research Program of China under Grant No. 2005CB724508； the Foundation from the Ministry of the National Education of China under Grant No. 200804870051 ； the Science Innovation Foundation of Huazhong University of Science and Technology under Grant No. HF-06-011-12-012
文摘This paper investigates the generation and evolution of continuous-variable entanglement in an asymmetric coupled-quantum well （CQW） system. Our numerical results show that this CQW system can be regarded as a source of macroscopic entangled light over a wide range of initial states of the cavity field. This investigation can be used for achieving the macroscopic entangled light in the CQW solid-state medium, which is much more praeticaJ than that in an atomic medium because of its flexible design and the controllable interference strength.
基金Projected supported by the National Natural Science Foundation of China(Grant No.11504074)the Science Fund from the State Key Laboratory of Quantum Optics and Quantum Optics Devices,Shanxi University,Shanxi,China(Grant No.KF201601)
文摘We investigate the fundamental limits to the achievable tripartite continuous-variable （CV） entanglement criterion of a generalized Vl criterion. Our numerical simulation results show that the non-degenerate eigenvalues do effect the performances of the estimated minimum variances. From below the threshold to above the threshold, with the increase of the pump parameter, the tripartite CV entanglement gradually disappears. The different off-diagonal elements seriously distort the weights for entanglement. We can obtain a good tripartite CV entanglement by appropriately controlling the values of off-diagonal elements eij.
基金Project supported by the State Key Laboratory of Quantum Optics and Quantum Optics Devices,Shanxi University,Taiyuan 030006,China(Grant No.KF201401)the National Natural Science Foundation of China(Grant No.11404084)
文摘Based on the quantum fluctuations, we adopt the method of generalized V1 criterion to investigate multipartite entan- glement characteristics in an optical parametric amplification system with the consideration of dispersion. The nonlinear interaction becomes strong because of the existence of dispersion coefficient σ. Considering the influence of dispersion factor σ, with increasing the pump parameter μ, the value of minimum variance V1 decreases and the squeezing curve nearly equals 1/（1 ＋ μ）. The larger particle number N results in a smaller variance and higher entanglement.
基金supported by the National Natural Science Foundation of China (Grants Nos. 60736040 and 11074157)Project for Excellent Research Team of the National Natural Science Foundation of China (Grant No. 60821004)the National Basic Research Program of China (Grant No. 2010CB923103)
文摘The influence of the extra classical noises in seed beams on the entanglement between the signal and the idler modes of the output fields generated by a non-degenerate optical parametric amplifier operating at deamplification is investigated theoretically and experimentally. With the increase of the extra classical noises in the seed beams, the correlation degree of the output entangled optical fields, which is scaled by the quantum noise limit, decreases rapidly. The experimental results axe in good agreement with the theoretical calculations.
基金support from the National Natural Science Foundation of China(NSFC)grant number 12205217Tianjin University Self-Innovation Fund Extreme Basic Research Project grant number 2025XJ21-0007。
文摘We investigate the entanglement entropy in quantum states featuring repeated sequential excitations of unit patterns in momentum space.In the scaling limit,each unit pattern contributes independently and universally to the entanglement entropy,leading to a characteristic volume-law scaling.Crucially,this universal contribution remains identical for both free and interacting models,enabling decomposition of the total entanglement into patternspecific components.Numerical verification in fermionic and bosonic chains confirms this volume-law fragmentation phenomenon.For fermionic systems,we derive analytical expressions where many-body entanglement becomes expressible through few-body entanglement components.Notably,this analytical framework extends to spin-1/2 XXZ chains through appropriate identifications.
文摘Methods of quantum information processing often appear in terms of specially selected states.For example,mutually unbiased bases(MUBs)and symmetric informationally complete measurements are widely applied.Finite frames have found use in many areas including quantum information.Due to its specific inner structure,a single equiangular tight frame(ETF)allows one to formulate criteria to detect non-classical correlations.This study aims to approach entanglement detection with the use of mutually unbiased ETFs.Such frames are an interesting generalization of widely recognized MUBs.It still uses rank-one operators,but the number of outcomes can exceed the dimensionality.Several approaches are considered including separability criteria and entanglement witnesses.Separability criteria for multipartite systems are finally obtained.
基金Princess Nourah bint Abdulrahman University Researchers Supporting Project number(PNURSP2026R77)Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia,the Deanship of Scientific Research at Northern Border University,Arar,Saudi Arabia,through the project number NBU-FFR-2026-2248-02.
文摘The rapid proliferation of multimodal misinformation on social media demands detection frameworks that are not only accurate but also robust to noise,adversarial manipulation,and semantic inconsistency between modalities.Existing multimodal fake news detection approaches often rely on deterministic fusion strategies,which limits their ability to model uncertainty and complex cross-modal dependencies.To address these challenges,we propose Q-ALIGNer,a quantum-inspired multimodal framework that integrates classical feature extraction with quantumstate encoding,learnable cross-modal entanglement,and robustness-aware training objectives.The proposed framework adopts quantumformalism as a representational abstraction,enabling probabilisticmodeling ofmultimodal alignment while remaining fully executable on classical hardware.Q-ALIGNer is evaluated on four widely used benchmark datasets—FakeNewsNet,Fakeddit,Weibo,and MediaEval VMU—covering diverse platforms,languages,and content characteristics.Experimental results demonstrate consistent performance improvements over strong text-only,vision-only,multimodal,and quantum-inspired baselines,including BERT,RoBERTa,XLNet,ResNet,EfficientNet,ViT,Multimodal-BERT,ViLBERT,and QEMF.Q-ALIGNer achieves accuracies of 91.2%,92.9%,91.7%,and 92.1%on FakeNewsNet,Fakeddit,Weibo,and MediaEval VMU,respectively,with F1-score gains of 3–4 percentage points over QEMF.Robustness evaluation shows a reduced adversarial accuracy gap of 2.6%,compared to 7%–9%for baseline models,while calibration analysis indicates improved reliability with an expected calibration error of 0.031.In addition,computational analysis shows that Q-ALIGNer reduces training time to 19.6 h compared to 48.2 h for QEMF at a comparable parameter scale.These results indicate that quantum-inspired alignment and entanglement can enhance robustness,uncertainty awareness,and efficiency in multimodal fake news detection,positioning Q-ALIGNer as a principled and practical content-centric framework for misinformation analysis.
基金supported by National Natural Science Foundation of China(Grant Nos.12161056,12075159,12171044)Natural Science Foundation of Jiangxi Province(Grant No.20232ACB211003)+1 种基金Beijing Natural Science Foundation(Grant No.Z190005)the specific research fund of the Innovation Platform for Academicians of Hainan Province。
文摘Shor's algorithm outperforms its classical counterpart in efficient prime factorization.We explore the coherence and entanglement dynamics of the evolved states within Shor's algorithm,showing that the coherence in each step relies on the dimension of register or the order,and discuss the relations between geometric coherence and geometric entanglement.We investigate how unitary operators induce variations in coherence and entanglement,and analyze the variations of coherence and entanglement within the entire algorithm,demonstrating that the overall effect of Shor's algorithm tends to deplete coherence and produce entanglement.Our research not only deepens the understanding of this algorithm but also provides methodological references for studying resource dynamics in other quantum algorithms.
基金supported by the National Fundamental Research Program under Grant No.2006CB921104National Natural Science Foundation of China under Grant No.60708003
文摘We obtain an explicit formula to calculate the entanglement entropy of bipartite entangled state of general two-mode boson exponential quadratic operator with continuous variables in Fock space. The simplicity and generality of our formula are shown by some examples.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61572529,61871407,and 61801522)the China Postdoctoral Science Foundation(Grant Nos.2013M542119 and 2014T70772)
文摘Continuous-variable quantum key distribution(CVQKD) protocols with entanglement in the middle(EM) enable long maximal transmission distances for quantum communications. For the security analysis of the protocols, it is usually assumed that Eve performs collective Gaussian attacks and there is a lack of finite-size analysis of the protocols. However,in this paper we consider the finite-size regime of the EM-based CVQKD protocols by exposing the protocol to collective attacks and coherent attacks. We differentiate between the collective attacks and the coherent attacks while comparing asymptotic key rate and the key rate in the finite-size scenarios. Moreover, both symmetric and asymmetric configurations are collated in a contrastive analysis. As expected, the derived results in the finite-size scenarios are less useful than those acquired in the asymptotic regime. Nevertheless, we find that CVQKD with entanglement in the middle is capable of providing fully secure secret keys taking the finite-size effects into account with transmission distances of more than 30 km.
基金Supported by the Natural Science Youth Teacher Foundation of Xuzhou Institute of Technology (Grant No. XKY2007317)
文摘We seek to analyze a three-level cascade laser with a pair of nonlinearly coupled waveguides inside the cavity. Applying the pertinent master equation, we investigate the squeezing and entanglement properties intracavity produced by our system. It is shown that with the help of nonlinearly coupled waveguides highly squeezed as well as macroscopic entangled light with high intensity can be achieved.
基金supported by the National Natural Science Foundation of China(Grant Nos.61379153,61401519,and 61572529)the Natural Science Foundation of Hunan Province,China(Grant No.2017JJ3415)+1 种基金the Science and Technology Project of Guangxi Zhuang Autonomous Region,China(Grant Nos.AC16380094and 1598008-29)the Natural Science Fund of Guangxi Zhuang Autonomous Region,China(Grant No.2015GXNSFAA139298)
文摘A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy Alice or Bob. This method is able to enhance the efficiency of the CVQKD scheme attacked by local oscillator （LO） intensity attack in terms of the generated secret key rate in quantum communication. The other indication of the improvement is that the maximum transmission distance and the maximum loss tolerance can be increased significantly, especially for CVQKD schemes based on homodyne detection.
基金Project supported by the National Natural Science Foundation of China (Grants Nos. 10674009,10874004 and 10821062)the National Key Basic Research Program of China (Grant No. 2006CB921601)
文摘We demonstrate that the n-partite continuous-variable entanglement can be unconditionally prepared among n parties that share no common past, from n two-mode squeezed states. Both CHZ-like and cluster-like states can be generated for any nonzero squeezing in the entangled sources. An application of the resulting multipartite entangled state to a teleportation network is illustrated.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62071381 and 62301430)Shaanxi Fundamental Science Research Project for Mathematics and Physics (Grant No. 23JSY014)+1 种基金Scientific Research Plan Project of Shaanxi Education Department (Natural Science Special Project (Grant No. 23JK0680)Young Talent Fund of Xi’an Association for Science and Technology (Grant No. 959202313011)。
文摘Quantum secure direct communication(QSDC) is a communication method based on quantum mechanics and it is used to transmit secret messages. Unlike quantum key distribution, secret messages can be transmitted directly on a quantum channel with QSDC. Higher channel capacity and noise suppression capabilities are key to achieving longdistance quantum communication. Here, we report a continuous-variable QSDC scheme based on mask-coding and orbital angular momentum, in which the mask-coding is employed to protect the security of the transmitting messages and to suppress the influence of excess noise. The combination of orbital angular momentum and information block transmission effectively improves the secrecy capacity. In the 800 information blocks ×1310 bits length 10-km experiment, the results show a statistical average bit error rate of 0.38%, a system excess noise value of 0.0184 SNU, and a final secrecy capacity of 6.319×10~6 bps. Therefore, this scheme reduces error bits while increasing secrecy capacity, providing a solution for long-distance large-scale quantum communication, which is capable of transmitting text, images and other information of reasonable size.
基金financially supported by the Sichuan Science and Technology Program(No.2024ZDZX0036)the National Ten Thousand Talent Plans for Young Top-notch Talents,and the National Natural Science Foundation of China(No.52021001).
文摘The rapid advancement of radar and 5 G communication technologies has created an urgent need for materials that possess both low dielectric constants and superior mechanical strength to ensure efficient signal transmission and minimal loss.Herein,a synergistic effect of multiple regulation strategies from the atomic scales to the molecular scales was proposed to develop Covalent Organic Frameworks(COFs)modified cyanate ester resins(COF-mCE).The strategy has proven highly effective in enhancing both dielectric and mechanical properties.With only 3 wt%COFs,the dielectric constant of COF-mCE is reduced from 3.32 to 2.84 at 1 MHz.Meanwhile,the mechanical performance of COF-mCE composites exhibits substantial improvements,with flexural strength increasing by 42.6% and tensile strength by 52.1% compared to pure mCE.The investigation explores that hydrogen bonding and π-π stacking interactions restrain the polarization feature and the mechanical property improvements of the COF-mCE derived from the entanglement effect of COF-polymer chains.Furthermore,the 3D-printed COF-mCE honeycomb structure demonstrates excellent electromagnetic wave transmittance and low reflectance,achieving a transmittance of 94.1% at 10 GHz with a 60°incidence angle.This multi-scale design strategy offers new insights into the development of low-k dielectric material for next-generation electronic science applications.
基金supported by the Natural Science Foundation of Jiangxi Province,China (Grant No 2007GZW0171)the Foundation of Education Department of Jiangxi Province,China (Grant No [2007] 136)
文摘We introduce a new kind of four-mode continuous variable entangled state in Fock space. The completeness relation and the partly nonorthonormal property of such a state are proven. The scheme to generate this state is presented by combining a symmetrical beamsplitter, a parametric down-conversion and a polarizer. After making a single-mode quadrature amplitude measurement, the remaining three modes are kept in entanglement. And its applications are also discussed.
文摘Quantum entanglement is a bizarre, counterintuitive phenomenon which shows that entangled subatomic particles remain related even when they are far apart, which was described by Einstein as “spooky action at a distance”. Although this phenomenon could be interpreted by a few theories, for example, the famous Copenhagen interpretation which describes that these states exist simultaneously by a wave function, however, there is still no unquestioned theory and it continues to puzzle people around the world. Here we propose a hypothesis that gravity cuts out stop functioning between subatomic particles based on the observations of a thought experiment. It is well known that the Universe is filled with various subatomic particles (e.g. cosmic neutrino background, CνB) and gravity is a universal force making any particle in the Universe attract any other. Based on these observations, it is expected that the CνB particles walking abreast will be combined together by their gravity after some time/distance, which will thus result in a greatly uneven distribution of CνB. However, the observational evidence showed that CνB is highly isotropic and homogenous, suggesting that gravity would no longer work at the subatomic scale. Thus, the relation of the paired subatomic particles would become some pure correlation of mass (or equivalent energy) status. In this case, time would be not required anymore due to the ineffectiveness of gravity. The proposed new interpretation matches the experimental observations well and finally possible thought experiments are presented to test this theory.
基金supported by the the National Natural Science Foundation of China(Grant Nos.12175015 for W.G.and 12174387 for L.Z.)the Chinese Academy of Sciences (Grant Nos.YSBR-057 and JZHKYPT-2021-08 for L.Z.)+1 种基金the Innovative Program for Quantum Science and Technology (Grant No.2021ZD0302600 for L.Z.)the start-up funding of Westlake University and the China Postdoctoral Science Foundation (Grant No.2024M752898 for Z.W.and Z.Y.)。
文摘Entanglement plays a key role in quantum physics, but how much information it can extract from many-body systems is still an open question, particularly regarding quantum criticalities and emergent symmetries. In this work, we systematically study the entanglement entropy(EE) and derivative entanglement entropy(DEE) near quantum phase transitions in various quantum many-body systems. A one-parameter scaling relation between the DEE and system size at the critical point has been derived for the first time, which successfully obtains the critical exponent via data collapse. Furthermore, we find that the EE peaks at the(emergent) symmetryenhanced first-order transition, reflecting higher symmetry breaking. This work provides a new paradigm for quantum many-body research from the perspective of EE and DEE.
基金supported by the National Natural Science Foundation of China (Grant Nos.12274273and 12450402)the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0302101)。
文摘The rapid advancements of ultrafast intense laser technology have opened new avenues for investigating entanglement in laser-induced systems. However, the application of these advances in quantum technology requires a reliable and universally applicable method for enhancing and regulating entanglement. Here we demonstrate how a few-cycle intense laser field can significantly enhance the degree of entanglement compared to its multi-cycle counterpart, using the example of electron–electron entanglement of orbital angular momentum(OAM) states in recollision-excitation non-sequential double ionization of Ar atoms. By confining the ionization dynamics to a specific narrow time window, the few-cycle pulse purifies the electron trajectories, thereby ensuring high coherence between entangled OAM channels and enhancing entanglement. Furthermore, the degree of entanglement can be efficiently modulated by varying the carrier envelope phase of the few-cycle laser pulse, which is achieved by altering the population across OAM channels. Optimizing coherence through electron trajectory purification with a designed specific temporal waveform of laser field provides a general pathway for enhancing entanglement in laser-induced systems.
