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 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
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
Hybrid entangled states(HESs),which involve different particles with various degrees of freedom,have garnered significant attention and been applied in a wide range of quantum technologies.However,similar to other cat...Hybrid entangled states(HESs),which involve different particles with various degrees of freedom,have garnered significant attention and been applied in a wide range of quantum technologies.However,similar to other categories of entanglement,maximally HESs inevitably degrade to mixed states due to the environmental noise and operational imperfections.To address the degradation problem,measurement-based entanglement purification offers a feasible and robust solution alternative to conventional gate-based purification methods.In this paper,we propose a measurement-based hybrid entanglement purification protocol(MB-HEPP)for a certain kind of HES which consists of polarization photons and coherent states.We extend our methodology to several conditions,such as the multi-copy and multi-party scenarios,and the photon-loss condition.Compared with previous HEPPs,this protocol has several advantages.First,it does not depend on post-selection and the purified HESs can be retained for further application.Second,it does not require the Bell state measurement,but only uses the parity check with conventional linear optical elements,which makes it have the higher success probability and more feasible.Our MB-HEPP has potential applications in future heterogeneous quantum networks.展开更多
Enhancing gelatin methacryloyl(GelMA)hydrogel mechanics without compromising biocompatibility remains challenging,as conventional chemical crosslinking often disrupts degradation behavior.A cooling-induced entan-gleme...Enhancing gelatin methacryloyl(GelMA)hydrogel mechanics without compromising biocompatibility remains challenging,as conventional chemical crosslinking often disrupts degradation behavior.A cooling-induced entan-glement strategy effectively improves mechanical performance while preserving biological properties;however,its underlying mechanisms remain unclear.This study demonstrates that extended cooling durations significantly enhance the mechanical properties of GelMA hydrogels.Microstructural analyses reveal cooling-induced forma-tion of compact polymer networks with reduced mesh sizes.Molecular dynamics(MD)simulations confirm that the cooling process promotes topological entanglements that govern mechanical reinforcement.Guided by these insights,we propose a theoretical model to predict the stress responses of GelMA hydrogels under various cooling durations,establishing quantitative correlations between entanglement mechanisms and mechanical outcomes.This study provides a fundamental understanding of the interplay between cooling conditions,microstructure,and mechanical performance,offering a robust framework for designing GelMA hydrogels with optimized me-chanical properties for advanced biomedical applications.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
A classification of multipartite entanglement is introduced for pure and mixed states.The classification is based on the distribution of entanglement between the qubits of a given system,with a mathematical framework ...A classification of multipartite entanglement is introduced for pure and mixed states.The classification is based on the distribution of entanglement between the qubits of a given system,with a mathematical framework used to characterize fully entangled states.Then we use current machine learning and deep learning techniques to automatically classify a random state of two,three,and four qubits without the need to compute the amount of the different types of entanglement in each run;rather this is done only in the learning process.The technique shows high,near-perfect,accuracy in the case of pure states.As expected,this accuracy drops,more or less,when dealing with mixed states and when increasing the number of parties involved.展开更多
Thermal entanglement,as influenced by interaction parameters,is investigated within the general Heisenberg XY Z model.We calculate the relationship between entanglement and the system interaction parameters,including ...Thermal entanglement,as influenced by interaction parameters,is investigated within the general Heisenberg XY Z model.We calculate the relationship between entanglement and the system interaction parameters,including spin-spin interaction parameters(SSIPs)and spin-orbit interaction parameters(SOIPs).By considering various parameter orientations,we identify four optimal combinations of the SSIPs and find that the optimal vector of the spin-orbit interaction aligns with the coordinate axis corresponding to the maximal SSIP component.Furthermore,we obtain three effective optimal combinations of the SOIPs corresponding to the optimal SSIPs,which can maximize the system entanglement when the parameters are tuned accordingly.To demonstrate the feasibility of our results under realistic experimental conditions,we propose an optical lattice scheme with tunable parameters.展开更多
We introduce a novel scheme for achieving quantum entanglement and Einstein–Podolsky–Rosen(EPR) steering between an atomic ensemble and a mechanical oscillator within a hybrid atom–optomechanical system. The system...We introduce a novel scheme for achieving quantum entanglement and Einstein–Podolsky–Rosen(EPR) steering between an atomic ensemble and a mechanical oscillator within a hybrid atom–optomechanical system. The system comprises an optical cavity, a two-level atomic ensemble and a mechanical resonator that possesses Duffing nonlinearity. The interaction between these components is mediated by the cavity mode, which is driven by an external laser. Our findings indicate that optimizing the coupling strengths between photons and phonons, as well as between atoms and the cavity,leads to maximal entanglement and EPR steering. The amplitude of the driving laser plays a pivotal role in enhancing the coupling between photons and phonons, and the system maintains robust entanglement and EPR steering even under high dissipation, thereby mitigating the constraints on initial conditions and parameter precision. Remarkably, the Duffing nonlinearity enhances the system's resistance to thermal noise, ensuring its stability and entanglement protection. Our analysis of EPR steering conditions reveals that the party with lower dissipation exhibits superior stability and a propensity to steer the party with higher dissipation. These discoveries offer novel perspectives for advancing quantum information processing and communication technologies.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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12175106 and 92365110)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX23-1028)。
文摘Hybrid entangled states(HESs),which involve different particles with various degrees of freedom,have garnered significant attention and been applied in a wide range of quantum technologies.However,similar to other categories of entanglement,maximally HESs inevitably degrade to mixed states due to the environmental noise and operational imperfections.To address the degradation problem,measurement-based entanglement purification offers a feasible and robust solution alternative to conventional gate-based purification methods.In this paper,we propose a measurement-based hybrid entanglement purification protocol(MB-HEPP)for a certain kind of HES which consists of polarization photons and coherent states.We extend our methodology to several conditions,such as the multi-copy and multi-party scenarios,and the photon-loss condition.Compared with previous HEPPs,this protocol has several advantages.First,it does not depend on post-selection and the purified HESs can be retained for further application.Second,it does not require the Bell state measurement,but only uses the parity check with conventional linear optical elements,which makes it have the higher success probability and more feasible.Our MB-HEPP has potential applications in future heterogeneous quantum networks.
基金supported by the Smart Medicine and Engineering Interdisciplinary Innovation Project of Ningbo University(Grant No.ZHYG003)the National Natural Science Foundation of China(Grant Nos.12372165 and 12202387)+1 种基金the Ningbo Top Medical and Health Research Program(Grant No.2022020203)the Zhejiang Engineering Research Center of Innovative technologies and diagnostic and thera-peutic equipment for urinary system diseases.
文摘Enhancing gelatin methacryloyl(GelMA)hydrogel mechanics without compromising biocompatibility remains challenging,as conventional chemical crosslinking often disrupts degradation behavior.A cooling-induced entan-glement strategy effectively improves mechanical performance while preserving biological properties;however,its underlying mechanisms remain unclear.This study demonstrates that extended cooling durations significantly enhance the mechanical properties of GelMA hydrogels.Microstructural analyses reveal cooling-induced forma-tion of compact polymer networks with reduced mesh sizes.Molecular dynamics(MD)simulations confirm that the cooling process promotes topological entanglements that govern mechanical reinforcement.Guided by these insights,we propose a theoretical model to predict the stress responses of GelMA hydrogels under various cooling durations,establishing quantitative correlations between entanglement mechanisms and mechanical outcomes.This study provides a fundamental understanding of the interplay between cooling conditions,microstructure,and mechanical performance,offering a robust framework for designing GelMA hydrogels with optimized me-chanical properties for advanced biomedical applications.
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supported through computational resources of HPC-MARWAN(www.marwan.ma/hpc)provided by CNRST,Rabat,Morocco。
文摘A classification of multipartite entanglement is introduced for pure and mixed states.The classification is based on the distribution of entanglement between the qubits of a given system,with a mathematical framework used to characterize fully entangled states.Then we use current machine learning and deep learning techniques to automatically classify a random state of two,three,and four qubits without the need to compute the amount of the different types of entanglement in each run;rather this is done only in the learning process.The technique shows high,near-perfect,accuracy in the case of pure states.As expected,this accuracy drops,more or less,when dealing with mixed states and when increasing the number of parties involved.
基金supported by the National Natural Science Foundation of China(Grant Nos.11204061,12204142,11904071)the Anhui Provincial Key Research and Development Project(Grant No.2022b13020002)the Outstanding Young Talents in College of Anhui Province(Grant No.gxyq2022059)。
文摘Thermal entanglement,as influenced by interaction parameters,is investigated within the general Heisenberg XY Z model.We calculate the relationship between entanglement and the system interaction parameters,including spin-spin interaction parameters(SSIPs)and spin-orbit interaction parameters(SOIPs).By considering various parameter orientations,we identify four optimal combinations of the SSIPs and find that the optimal vector of the spin-orbit interaction aligns with the coordinate axis corresponding to the maximal SSIP component.Furthermore,we obtain three effective optimal combinations of the SOIPs corresponding to the optimal SSIPs,which can maximize the system entanglement when the parameters are tuned accordingly.To demonstrate the feasibility of our results under realistic experimental conditions,we propose an optical lattice scheme with tunable parameters.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12204440)Fundamental Research Program of Shanxi Province (Grant Nos. 20210302123063 and 202103021223184)。
文摘We introduce a novel scheme for achieving quantum entanglement and Einstein–Podolsky–Rosen(EPR) steering between an atomic ensemble and a mechanical oscillator within a hybrid atom–optomechanical system. The system comprises an optical cavity, a two-level atomic ensemble and a mechanical resonator that possesses Duffing nonlinearity. The interaction between these components is mediated by the cavity mode, which is driven by an external laser. Our findings indicate that optimizing the coupling strengths between photons and phonons, as well as between atoms and the cavity,leads to maximal entanglement and EPR steering. The amplitude of the driving laser plays a pivotal role in enhancing the coupling between photons and phonons, and the system maintains robust entanglement and EPR steering even under high dissipation, thereby mitigating the constraints on initial conditions and parameter precision. Remarkably, the Duffing nonlinearity enhances the system's resistance to thermal noise, ensuring its stability and entanglement protection. Our analysis of EPR steering conditions reveals that the party with lower dissipation exhibits superior stability and a propensity to steer the party with higher dissipation. These discoveries offer novel perspectives for advancing quantum information processing and communication technologies.
