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
At present,most quantum secret sharing(QSS)protocols are more or less designed with the incorporation of classical secret sharing schemes.With the increasing maturity of quantum technology,QSS protocols based on pure ...At present,most quantum secret sharing(QSS)protocols are more or less designed with the incorporation of classical secret sharing schemes.With the increasing maturity of quantum technology,QSS protocols based on pure quantum mechanics are becoming more important.Classical secret sharing schemes cannot achieve absolute security,and their involvement can compromise the security of QSS protocols.This paper proposes a QSS scheme based on Greenberger-Horn-Zeilinger(GHZ)basis measurement and quantum entanglement exchange.In this protocol,the secret sender stores the secret information using Pauli operations.Participants obtain their shares by measuring the product state sequentially.Finally,participants complete the secret reconstruction through quantum entanglement exchange and other related quantum operations.In addition,the particles held by participants in the protocol do not contain any secret information.Each participant's particles are in a state of maximum entanglement,and no participant can deduce the particle information of other participants through their own particles.At the same time,the protocol is based on pure quantum mechanics and does not involve classical schemes,which avoids the problem of reduced security of the protocol.Security analysis indicates that the protocol is not vulnerable to retransmission interception and collusion attacks.Moreover,it is capable of detecting and terminating the protocol promptly when facing with attacks from dishonest participants.展开更多
The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investi...The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole-dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms-field, atom-atom, and atom-field can be prepared via two two-level atoms interacting with a single-mode vacuum field.展开更多
We present a method to teleport multi-qubit quantum information in an easy way from a sender to a receiver via the control of many agents in a network. Only when all the agents collaborate with the quantum information...We present a method to teleport multi-qubit quantum information in an easy way from a sender to a receiver via the control of many agents in a network. Only when all the agents collaborate with the quantum information receiver can the unknown states in the sender＇s qubits be fully reconstructed in the receiver＇s qubits. In our method, agents＇s control parameters are obtained via quantum entanglement swapping. As the realization of the many-agent controlled teleportation is concerned, compared to the recent method [G.P. Yang, et al., Phys. Rev. A 70 （2004） 022329], our present method considerably reduces the preparation difficulty of initial states and the identification difficulty of entangled states, moreover, it does not need local Hadamard operations and it is more feasible in technology.展开更多
We propose a scheme to realize the nonlocal quantum entanglement of three three-level particles by using a threeparticle entangled state of three levels as a quantum channel with the aid of some local unitary transfor...We propose a scheme to realize the nonlocal quantum entanglement of three three-level particles by using a threeparticle entangled state of three levels as a quantum channel with the aid of some local unitary transformations. This scheme can be directly generalized to the nonlocal quantum entanglement of N three-level particles.展开更多
In this paper, we propose a classical secret broadcasting and splitting joint protocol in a quantum scenario. With those genuinely entangled states, the boss can always broadcast some of his secrets and split some oth...In this paper, we propose a classical secret broadcasting and splitting joint protocol in a quantum scenario. With those genuinely entangled states, the boss can always broadcast some of his secrets and split some others to multi- receivers at the same time. The efficiency of the joint protocol is also compared with that of two separate ones which realise classical secret broadcasting and classical secret splitting respectively, and based on the comparison we can see the promising advantage of our joint protocol is that it can realise the two tasks more efficiently and more conveniently.展开更多
In our previous papers,the classical fractional Fourier transform theory was incorporated into the quantum theoretical system using the theoretical method of quantum optics,and the calculation produced quantum mechani...In our previous papers,the classical fractional Fourier transform theory was incorporated into the quantum theoretical system using the theoretical method of quantum optics,and the calculation produced quantum mechanical operators corresponding to the generation of fractional Fourier transform.The core function of the coordinate-momentum exchange operators in the addition law of fractional Fourier transform was analyzed too.In this paper,the bivariate operator Hermite polynomial theory and the technique of integration within an ordered product of operators(IWOP)are used to establish the entanglement fractional Fourier transform theory to the extent of quantum.A new function generating formula and an operator for generating quantum entangled fractional Fourier transform are obtained using the fractional Fourier transform relationship in a pair of conjugated entangled state representations.展开更多
Quantum entanglement and quantum nonlocality of N-photon entangled states ｜ψNm） m Cm [cos γ｜N - m） 1 ｜m）2 ＋ e^iθm sinγ｜m）1｜N- m）2] and their superpositions are studied. We point out that the relative ph...Quantum entanglement and quantum nonlocality of N-photon entangled states ｜ψNm） m Cm [cos γ｜N - m） 1 ｜m）2 ＋ e^iθm sinγ｜m）1｜N- m）2] and their superpositions are studied. We point out that the relative phase θm affects the quantum nonlocality but not the quantum entanglement for the state ｜ψNm）. We show that quantum nonlocality can be controlled and manipulated by adjusting the state parameters of ｜ψNm）, superposition coefficients, and the azimuthal angles of the Bell operator. We also show that the violation of the Bell inequality can reach its maximal value under certain conditions. It is found that quantum superpositions based on ｜ψNm） can increase the amount of entanglement, and give more ways to reach the maximal violation of the Bell inequality.展开更多
We theoretically study the reversible process of quantum entanglement state by means of weak measurement and corresponding reversible operation.We present a protocol of the reversion operation in two bodies based on t...We theoretically study the reversible process of quantum entanglement state by means of weak measurement and corresponding reversible operation.We present a protocol of the reversion operation in two bodies based on the theory of reversion of single photon and then expend it in quantum communication channels.The theoretical results demonstrate that the protocol does not break the information transmission after a weak measurement and a reversible measurement with the subsequent process in the transmission path.It can reverse the perturbed entanglement intensity evolution to its original state.Under the condition of different weak measurement intensity the protocol can reverse the perturbed quantum entanglement system perfectly.In the process we can get the classical information described by information gain from the quantum system through weak measurement operation.On the other hand,in order to realize complete reversibility,the classical information of the quantum entanglement system must obey a limited range we present in this paper in the reverse process.展开更多
Quantum entanglement dynamics of two Tavis-Cummings atoms interacting with the quantum light sourcesin a cavity is investigated.The results show the phenomenon that the concurrence disappears abruptly in a finite time...Quantum entanglement dynamics of two Tavis-Cummings atoms interacting with the quantum light sourcesin a cavity is investigated.The results show the phenomenon that the concurrence disappears abruptly in a finite time,which depends on the initial atomic states and the properties of squeezed states.We find that there are two decoherencefreestates in squeezed vacuum fields:one is the singlet state,and the other entangled state is the state that combinesboth excited states and ground states with a relative phase being equal to the phase of the squeezed state.展开更多
The dynamical correlation between quantum entanglement and intramolecular energy in realistic molecular vibrations is explored using the Lie algebraic approach. The explicit expression of entanglement measurement can ...The dynamical correlation between quantum entanglement and intramolecular energy in realistic molecular vibrations is explored using the Lie algebraic approach. The explicit expression of entanglement measurement can be achieved using algebraic operations. The common and different characteristics of dynamical entanglement in different molecular vibrations are also provided. The dynamical study of quantum entanglement and intramolecular energy in small molecular vibrations can be helpful for controlling the entanglement and further understanding the intramolecular dynamics.展开更多
We theoretically investigate coherent scattering of single photons and quantum entanglement of two giant atoms with azimuthal angle differences in a waveguide system.Using the real-space Hamiltonian,analytical express...We theoretically investigate coherent scattering of single photons and quantum entanglement of two giant atoms with azimuthal angle differences in a waveguide system.Using the real-space Hamiltonian,analytical expressions are derived for the transport spectra scattered by these two giant atoms with four azimuthal angles.Fano-like resonance can be exhibited in the scattering spectra by adjusting the azimuthal angle difference.High concurrence of the entangled state for two atoms can be implemented in a wide angle-difference range,and the entanglement of the atomic states can be switched on/off by modulating the additional azimuthal angle differences from the giant atoms.This suggests a novel handle to effectively control the single-photon scattering and quantum entanglement.展开更多
This article discusses the role of covariance correlation tensor in the establishment of the criterion of quantum entanglement. It gives a simple example to show the powerfulness in the treatment of quantum dense codi...This article discusses the role of covariance correlation tensor in the establishment of the criterion of quantum entanglement. It gives a simple example to show the powerfulness in the treatment of quantum dense coding,and illustrates the fact that this method also provides theoretical basis for establishing corresponding knotted pictures.展开更多
Quantum dots comprise a type of quantum impurity system. The entanglement and co- herence of quantum states are significantly influenced by the strong electron-electron interactions among impurities and their dissipat...Quantum dots comprise a type of quantum impurity system. The entanglement and co- herence of quantum states are significantly influenced by the strong electron-electron interactions among impurities and their dissipative coupling with the surrounding environment. Competition between many-body effects and transfer couplings plays an important role in determining the entanglement among localized impurity spins. In this work, we employ the hierarchical-equations-of-rnotion approach to explore the entanglement of a strongly correlated double quantum dots system. The relation between the total system entropy and those of subsystems is also investigated.展开更多
We reveal that the two-variable Hermite function hm,n, which is the generalized Bargmann representation of the two-mode Fock state, involves quantum entanglement of harmonic oscillator＇s wave functions. The Schmidt d...We reveal that the two-variable Hermite function hm,n, which is the generalized Bargmann representation of the two-mode Fock state, involves quantum entanglement of harmonic oscillator＇s wave functions. The Schmidt decomposition of hm,n is derived. It also turns out that hm,n can be generated by windowed Fourier transform of the single-variable Hermite functions. As an application, the wave function of the two-variable Hermite polynomial state S（γ）Hm,n （μa1^＋, μa2^＋│00〉, which is the minimum uncertainty state for sum squeezing, in （ η│representation is calculated.展开更多
We analyze entanglement properties of entangled coherent state （ECS）, ｜α,0） 1,2 ＋｜0,α） 1,2, with and without photon losses. By separating the coherent state into ]a） = co｜0） ＋ √-Co2｜α）, we derive exac...We analyze entanglement properties of entangled coherent state （ECS）, ｜α,0） 1,2 ＋｜0,α） 1,2, with and without photon losses. By separating the coherent state into ]a） = co｜0） ＋ √-Co2｜α）, we derive exact results of the logarithmic negativity EN, which quantifies the degree of entanglement between the two bosonic modes. Without particle losses, E~ = 1 for the NOON state; while for the ECS, E jr increases from 0 to 1 as ｜α｜-→∞. In the presence of photon losses, we find that the ECS with large enough photon number is more robust than that of the NOON state. An optimal ECS is obtained by maximizing E~ with respect to l a 12.展开更多
The matrix product state （MPS） is utilized to investigate the ground state properties and quantum phase transitions （OPTs） of the dimerized antiferromagnetic Heisenberg （DAH） model. The ground state MPS wavefunc...The matrix product state （MPS） is utilized to investigate the ground state properties and quantum phase transitions （OPTs） of the dimerized antiferromagnetic Heisenberg （DAH） model. The ground state MPS wavefunctions determined by the infinite time-evolving block decimation （iTEBD） algorithm are shown to be very efficient descriptions of DAH model. In the thermodynamic limit, the quantum entanglement, the bond energy~ and the nearest-neighbor correlations are calculated. It is revealed that the singular behavior of the bipartite entanglement can detect the QPTs directly. The critical point J2c= 1.0 is determined evidently, and the quantum phase transition is argued to belong to the second-order category. At the critical point, logarithmic divergent character of the block entanglement is observed, and the system can be described by a free bosonic field theory.展开更多
Entangled states are crucial to quantum computation and quantum communication,and are usually treated as the target states to be accessed by quantum control methods.While most of the researches focus on the generation...Entangled states are crucial to quantum computation and quantum communication,and are usually treated as the target states to be accessed by quantum control methods.While most of the researches focus on the generation of the desired entangled state at the terminal state|ψf〉,this paper considers the time-varying entanglement of the transient state|ψ(t)〉throughout the qubit transfer process.It is found that the degree of entanglement of|ψ(t)〉determines how fast and accurately the terminal state|ψf〉can be achieved.Four quantitative indices of entanglement are employed here to evaluate the degree of entanglement of|ψ(t))and to estimate the qubit control performance resulting from different control gains in the Lyapunov control law.Our results show that increasing the degree of entanglement during the qubit transfer process is helpful to improve the convergence to the target state;however,increasing control gain tends to destroy the entanglement and attenuate the multi-qubit transfer efficiency.The lack of sufficient quantum correlation between some initial state|ψ0〉and terminal state is the main reason for unavailable qubit transfer between them.For these states,the insertion of an intermediate entangled state|ψs〉can effectively increase the degree of entanglement and help to realize the qubit transfer|ψ0〉→|ψf〉via the transition processs|ψ0〉→|ψs〉→|ψf〉.展开更多
We investigate the dynamics of entanglement in the excitation transfer through a model consisting of three interacting molecules coupled to environments. It is shown that the entanglement can be further enhanced if th...We investigate the dynamics of entanglement in the excitation transfer through a model consisting of three interacting molecules coupled to environments. It is shown that the entanglement can be further enhanced if the distance between the molecules is oscillating. Our results demonstrate that the motional effect plays a constructive role on quantum entanglement in the dynamics of excitation transfer. This mechanism might provide a useful guideline for designing artificial systems to battle against decoherence.展开更多
In this paper we develop and study, as the second part of one more general development, the energy transmutation equation for the material singularity, previously obtained through the symmetrisation of a wave packet, ...In this paper we develop and study, as the second part of one more general development, the energy transmutation equation for the material singularity, previously obtained through the symmetrisation of a wave packet, that is, we develop the correlation between the terms of this equation, which accounts for the formation of matter from a previous vibrational state, and the different possible energy species. These energetic species are ascribed, in a simplified form, to the equation E¯ω=E¯k+E¯f, which allows us, through its associated phase factor, to gain an insight into the wave character of the kinetic energy and thus to attain the basis of the matter-wave, and all sorts of related phenomenologies, including that concerning quantum entanglement. The formation of the matter was previously identified as an energetic process, analogous to the kinetic one, in which finally the inertial mass is consolidated as a mass in a different phase, now, in addition, the mass of the material singularity is identified as a volumetric density of waves of toroidal geometry created in the process of singularisation or energy transfer between species, which makes it possible to establish the real relation or correspondence between the corpuscular and photonic energy equation (E=mc2=hν), i.e. to explain through m the intimate sense of the first equivalence, which explains what νis in the second one.展开更多
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Project supported by the National Natural Science Foundation of China(Grant No.62002105)the Key Research and Development Program of Hubei,China(Grant No.2021BEA163)。
文摘At present,most quantum secret sharing(QSS)protocols are more or less designed with the incorporation of classical secret sharing schemes.With the increasing maturity of quantum technology,QSS protocols based on pure quantum mechanics are becoming more important.Classical secret sharing schemes cannot achieve absolute security,and their involvement can compromise the security of QSS protocols.This paper proposes a QSS scheme based on Greenberger-Horn-Zeilinger(GHZ)basis measurement and quantum entanglement exchange.In this protocol,the secret sender stores the secret information using Pauli operations.Participants obtain their shares by measuring the product state sequentially.Finally,participants complete the secret reconstruction through quantum entanglement exchange and other related quantum operations.In addition,the particles held by participants in the protocol do not contain any secret information.Each participant's particles are in a state of maximum entanglement,and no participant can deduce the particle information of other participants through their own particles.At the same time,the protocol is based on pure quantum mechanics and does not involve classical schemes,which avoids the problem of reduced security of the protocol.Security analysis indicates that the protocol is not vulnerable to retransmission interception and collusion attacks.Moreover,it is capable of detecting and terminating the protocol promptly when facing with attacks from dishonest participants.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole-dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms-field, atom-atom, and atom-field can be prepared via two two-level atoms interacting with a single-mode vacuum field.
文摘We present a method to teleport multi-qubit quantum information in an easy way from a sender to a receiver via the control of many agents in a network. Only when all the agents collaborate with the quantum information receiver can the unknown states in the sender＇s qubits be fully reconstructed in the receiver＇s qubits. In our method, agents＇s control parameters are obtained via quantum entanglement swapping. As the realization of the many-agent controlled teleportation is concerned, compared to the recent method [G.P. Yang, et al., Phys. Rev. A 70 （2004） 022329], our present method considerably reduces the preparation difficulty of initial states and the identification difficulty of entangled states, moreover, it does not need local Hadamard operations and it is more feasible in technology.
基金Project supported by the National Natural Science Foundation of China （Grant No 60261002） and the Science Foundation of Yanbian University （Grant No 2005-20）.
文摘We propose a scheme to realize the nonlocal quantum entanglement of three three-level particles by using a threeparticle entangled state of three levels as a quantum channel with the aid of some local unitary transformations. This scheme can be directly generalized to the nonlocal quantum entanglement of N three-level particles.
文摘In this paper, we propose a classical secret broadcasting and splitting joint protocol in a quantum scenario. With those genuinely entangled states, the boss can always broadcast some of his secrets and split some others to multi- receivers at the same time. The efficiency of the joint protocol is also compared with that of two separate ones which realise classical secret broadcasting and classical secret splitting respectively, and based on the comparison we can see the promising advantage of our joint protocol is that it can realise the two tasks more efficiently and more conveniently.
基金Project supported by the National Natural Science Foundation of China(Grant No.11775208)the Foundation for Young Talents at the College of Anhui Province,China(Grant Nos.gxyq2021210 and gxyq2019077)the Natural Science Foundation of the Anhui Higher Education Institutions of China(Grant Nos.KJ2020A0638 and 2022AH051586)。
文摘In our previous papers,the classical fractional Fourier transform theory was incorporated into the quantum theoretical system using the theoretical method of quantum optics,and the calculation produced quantum mechanical operators corresponding to the generation of fractional Fourier transform.The core function of the coordinate-momentum exchange operators in the addition law of fractional Fourier transform was analyzed too.In this paper,the bivariate operator Hermite polynomial theory and the technique of integration within an ordered product of operators(IWOP)are used to establish the entanglement fractional Fourier transform theory to the extent of quantum.A new function generating formula and an operator for generating quantum entangled fractional Fourier transform are obtained using the fractional Fourier transform relationship in a pair of conjugated entangled state representations.
文摘Quantum entanglement and quantum nonlocality of N-photon entangled states ｜ψNm） m Cm [cos γ｜N - m） 1 ｜m）2 ＋ e^iθm sinγ｜m）1｜N- m）2] and their superpositions are studied. We point out that the relative phase θm affects the quantum nonlocality but not the quantum entanglement for the state ｜ψNm）. We show that quantum nonlocality can be controlled and manipulated by adjusting the state parameters of ｜ψNm）, superposition coefficients, and the azimuthal angles of the Bell operator. We also show that the violation of the Bell inequality can reach its maximal value under certain conditions. It is found that quantum superpositions based on ｜ψNm） can increase the amount of entanglement, and give more ways to reach the maximal violation of the Bell inequality.
基金Project supported by the National Natural Science Foundation of China(Grant No.11504135)University Science and Technology Plan Project of Shandong Province,China(Grant Nos.J16LJ53).
文摘We theoretically study the reversible process of quantum entanglement state by means of weak measurement and corresponding reversible operation.We present a protocol of the reversion operation in two bodies based on the theory of reversion of single photon and then expend it in quantum communication channels.The theoretical results demonstrate that the protocol does not break the information transmission after a weak measurement and a reversible measurement with the subsequent process in the transmission path.It can reverse the perturbed entanglement intensity evolution to its original state.Under the condition of different weak measurement intensity the protocol can reverse the perturbed quantum entanglement system perfectly.In the process we can get the classical information described by information gain from the quantum system through weak measurement operation.On the other hand,in order to realize complete reversibility,the classical information of the quantum entanglement system must obey a limited range we present in this paper in the reverse process.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10974125, 60978017, and 60821004in part by the Educational Committee of Fujian Province (JA09041)Fujian Normal University (2008100220)
文摘Quantum entanglement dynamics of two Tavis-Cummings atoms interacting with the quantum light sourcesin a cavity is investigated.The results show the phenomenon that the concurrence disappears abruptly in a finite time,which depends on the initial atomic states and the properties of squeezed states.We find that there are two decoherencefreestates in squeezed vacuum fields:one is the singlet state,and the other entangled state is the state that combinesboth excited states and ground states with a relative phase being equal to the phase of the squeezed state.
基金supported by the National Natural Science Foundation of China(Grant Nos.11147019 and 91021009)
文摘The dynamical correlation between quantum entanglement and intramolecular energy in realistic molecular vibrations is explored using the Lie algebraic approach. The explicit expression of entanglement measurement can be achieved using algebraic operations. The common and different characteristics of dynamical entanglement in different molecular vibrations are also provided. The dynamical study of quantum entanglement and intramolecular energy in small molecular vibrations can be helpful for controlling the entanglement and further understanding the intramolecular dynamics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12365003,12364024,and 11864014)the Jiangxi Provincial Natural Science Foundation(Grant Nos.20212BAB201014 and 20224BAB201023)。
文摘We theoretically investigate coherent scattering of single photons and quantum entanglement of two giant atoms with azimuthal angle differences in a waveguide system.Using the real-space Hamiltonian,analytical expressions are derived for the transport spectra scattered by these two giant atoms with four azimuthal angles.Fano-like resonance can be exhibited in the scattering spectra by adjusting the azimuthal angle difference.High concurrence of the entangled state for two atoms can be implemented in a wide angle-difference range,and the entanglement of the atomic states can be switched on/off by modulating the additional azimuthal angle differences from the giant atoms.This suggests a novel handle to effectively control the single-photon scattering and quantum entanglement.
文摘This article discusses the role of covariance correlation tensor in the establishment of the criterion of quantum entanglement. It gives a simple example to show the powerfulness in the treatment of quantum dense coding,and illustrates the fact that this method also provides theoretical basis for establishing corresponding knotted pictures.
基金supported by the Ministry of Science and Technology of China(No.2016YFA0400900 and No.2016YFA0200600)the National Natural Science Foundation of China(No.21573202 and No.21633006)the Fundamental Research Funds for the Central Universities(No.2340000074)
文摘Quantum dots comprise a type of quantum impurity system. The entanglement and co- herence of quantum states are significantly influenced by the strong electron-electron interactions among impurities and their dissipative coupling with the surrounding environment. Competition between many-body effects and transfer couplings plays an important role in determining the entanglement among localized impurity spins. In this work, we employ the hierarchical-equations-of-rnotion approach to explore the entanglement of a strongly correlated double quantum dots system. The relation between the total system entropy and those of subsystems is also investigated.
文摘We reveal that the two-variable Hermite function hm,n, which is the generalized Bargmann representation of the two-mode Fock state, involves quantum entanglement of harmonic oscillator＇s wave functions. The Schmidt decomposition of hm,n is derived. It also turns out that hm,n can be generated by windowed Fourier transform of the single-variable Hermite functions. As an application, the wave function of the two-variable Hermite polynomial state S（γ）Hm,n （μa1^＋, μa2^＋│00〉, which is the minimum uncertainty state for sum squeezing, in （ η│representation is calculated.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174028)the Fundamental Research Funds for the Central Universities of China(Grant No.2011JBZ013)the Program for New Century Excellent Talents in University of China(Grant No.NCET-11-0564)
文摘We analyze entanglement properties of entangled coherent state （ECS）, ｜α,0） 1,2 ＋｜0,α） 1,2, with and without photon losses. By separating the coherent state into ]a） = co｜0） ＋ √-Co2｜α）, we derive exact results of the logarithmic negativity EN, which quantifies the degree of entanglement between the two bosonic modes. Without particle losses, E~ = 1 for the NOON state; while for the ECS, E jr increases from 0 to 1 as ｜α｜-→∞. In the presence of photon losses, we find that the ECS with large enough photon number is more robust than that of the NOON state. An optimal ECS is obtained by maximizing E~ with respect to l a 12.
基金Supported by the Chinese National Science Foundation under Grant Nos.11047160 and 10874003It is also partially supported by the National Basic Research Program of China under Grant No.2009CB939901
文摘The matrix product state （MPS） is utilized to investigate the ground state properties and quantum phase transitions （OPTs） of the dimerized antiferromagnetic Heisenberg （DAH） model. The ground state MPS wavefunctions determined by the infinite time-evolving block decimation （iTEBD） algorithm are shown to be very efficient descriptions of DAH model. In the thermodynamic limit, the quantum entanglement, the bond energy~ and the nearest-neighbor correlations are calculated. It is revealed that the singular behavior of the bipartite entanglement can detect the QPTs directly. The critical point J2c= 1.0 is determined evidently, and the quantum phase transition is argued to belong to the second-order category. At the critical point, logarithmic divergent character of the block entanglement is observed, and the system can be described by a free bosonic field theory.
文摘Entangled states are crucial to quantum computation and quantum communication,and are usually treated as the target states to be accessed by quantum control methods.While most of the researches focus on the generation of the desired entangled state at the terminal state|ψf〉,this paper considers the time-varying entanglement of the transient state|ψ(t)〉throughout the qubit transfer process.It is found that the degree of entanglement of|ψ(t)〉determines how fast and accurately the terminal state|ψf〉can be achieved.Four quantitative indices of entanglement are employed here to evaluate the degree of entanglement of|ψ(t))and to estimate the qubit control performance resulting from different control gains in the Lyapunov control law.Our results show that increasing the degree of entanglement during the qubit transfer process is helpful to improve the convergence to the target state;however,increasing control gain tends to destroy the entanglement and attenuate the multi-qubit transfer efficiency.The lack of sufficient quantum correlation between some initial state|ψ0〉and terminal state is the main reason for unavailable qubit transfer between them.For these states,the insertion of an intermediate entangled state|ψs〉can effectively increase the degree of entanglement and help to realize the qubit transfer|ψ0〉→|ψf〉via the transition processs|ψ0〉→|ψs〉→|ψf〉.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374085,61073048 and 11274010the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20113401110002+3 种基金the 211 Project of Anhui Universitythe Anhui Provincial Natural Science Foundation under Grant No 1408085MA20the Personnel Department of Anhui Provincethe 136 Foundation of Hefei Normal University under Grant No 2014136KJB04
文摘We investigate the dynamics of entanglement in the excitation transfer through a model consisting of three interacting molecules coupled to environments. It is shown that the entanglement can be further enhanced if the distance between the molecules is oscillating. Our results demonstrate that the motional effect plays a constructive role on quantum entanglement in the dynamics of excitation transfer. This mechanism might provide a useful guideline for designing artificial systems to battle against decoherence.
文摘In this paper we develop and study, as the second part of one more general development, the energy transmutation equation for the material singularity, previously obtained through the symmetrisation of a wave packet, that is, we develop the correlation between the terms of this equation, which accounts for the formation of matter from a previous vibrational state, and the different possible energy species. These energetic species are ascribed, in a simplified form, to the equation E¯ω=E¯k+E¯f, which allows us, through its associated phase factor, to gain an insight into the wave character of the kinetic energy and thus to attain the basis of the matter-wave, and all sorts of related phenomenologies, including that concerning quantum entanglement. The formation of the matter was previously identified as an energetic process, analogous to the kinetic one, in which finally the inertial mass is consolidated as a mass in a different phase, now, in addition, the mass of the material singularity is identified as a volumetric density of waves of toroidal geometry created in the process of singularisation or energy transfer between species, which makes it possible to establish the real relation or correspondence between the corpuscular and photonic energy equation (E=mc2=hν), i.e. to explain through m the intimate sense of the first equivalence, which explains what νis in the second one.
