The effects of different time-independent and time-dependent couplings on two-atom entanglement are studied. The results show that the effects depend on the initial state. For the initial state |eeO〉, it is found th...The effects of different time-independent and time-dependent couplings on two-atom entanglement are studied. The results show that the effects depend on the initial state. For the initial state |eeO〉, it is found that different time-independent couplings make the case without entanglement exhibit entanglement, and time-dependent couplings turn the irregular entanglement regions into regular one. Under the case of decay, for the initial state |eg0〉, the different time-dependent couplings have disbenefit.展开更多
We investigate the sudden birth and sudden death of entanglement of two qubits interacting with uncorrelated structured reservoirs. The system is initially prepared in two-qubit extended Werner-like state. We work out...We investigate the sudden birth and sudden death of entanglement of two qubits interacting with uncorrelated structured reservoirs. The system is initially prepared in two-qubit extended Werner-like state. We work out the dependence of the entanglement dynamics on both non-Markovian environments and the purity of initial state, and show that non-Markovian environments and the purity can control the time of the two-qubit entanglement sudden death and the reservoirs' entanglement sudden birth. Furthermore, under the conditions of different purity and initial entangIement, the revival of qubits' entanglement can manifest before, simultaneously or even after the disentanglement of their corresponding reservoirs.展开更多
We investigate the entanglement transfer in a four-qubit system and calculate the concurrence between any two qubits in different initial states. We show that both the pure entangled state and mixed entangled state ca...We investigate the entanglement transfer in a four-qubit system and calculate the concurrence between any two qubits in different initial states. We show that both the pure entangled state and mixed entangled state can be transferred. For some special coupling constants and some evolution time, entanglement can be completely transferred from one pair particles to another.展开更多
Taking advantage of our improved gates as well as the Giorgi-Pasquale-Paganelli (GPP) nondestructive gate [Phys. Rev. A 70 (2004) 022319], the sign of any term of the initial state in the GPP model can be flipped....Taking advantage of our improved gates as well as the Giorgi-Pasquale-Paganelli (GPP) nondestructive gate [Phys. Rev. A 70 (2004) 022319], the sign of any term of the initial state in the GPP model can be flipped. The success possibility of the sign flip of odd number of terms is probabilistic (11/4), while the success possibility of the sign flip of even number of terms is deterministic (1).展开更多
Quantum Zeno effect with mixed initial state is studied here. Frequent projective measurements performed on a bipartite joint pure state system will result in the quantum Zeno effect on the subsystem of interest. This...Quantum Zeno effect with mixed initial state is studied here. Frequent projective measurements performed on a bipartite joint pure state system will result in the quantum Zeno effect on the subsystem of interest. This shows the existence of Quantum Zeno effect in the system with mixed initial states.展开更多
We present an efficient scheme for sharing an arbitrary m-qubit state with n agents.In our scheme,the sender Alice first shares m Bell states with the agent Bob,who is designated to recover the original m-qubit state....We present an efficient scheme for sharing an arbitrary m-qubit state with n agents.In our scheme,the sender Alice first shares m Bell states with the agent Bob,who is designated to recover the original m-qubit state.Furthermore,Alice introduces n-1 auxiliary particles in the initial state |0>,applies Hadamard (H) gate and Controlled-Not(CNOT) gate operations on the particles,which make them entangled with one of m particle pairs in Bell states,and then sends them to the controllers (i.e.,other n-1 agents),where each controller only holds one particle in hand.After Alice performing m Bell-basis measurements and each controller a single-particle measurement,the recover Bobcan obtain the original unknown quantum state by applying the corresponding local unitary operations on his particles.Its intrinsic efficiency for qubits approaches 100%,and the total efficiency really approaches the maximal value.展开更多
The manuscript deals with the possibility of application of collective behavior of quantum particles to realize the quantum calculation procedure. The above collective behavior is likely resulted from interelectron co...The manuscript deals with the possibility of application of collective behavior of quantum particles to realize the quantum calculation procedure. The above collective behavior is likely resulted from interelectron correlations, characteristic for strongly correlated systems containing atoms with unoccupied 3d-, 4f- and 5f- shells. Among such systems can be the heterospin systems, complexes of paramagnetic ions of transition metals with organic radicals, because for such objects, spin-spin interaction between unpaired electron spins of different paramagnetic centers is typical. To apply the aforementioned possibility for the organization of real quantum calculations, it is necessary to synthesize such paramagnetic molecules (paramagnetic clusters), where the entangled states will be realized naturally by self-organization of atoms incorporated in these molecules, i.e., without additional external effect of q-bits on the system. The specified self-organization may be due to intramolecular processes and, in particular, intramolecular rearrangement called valence tautomerism, which leads to heterogeneous magnetic states, i.e., to phase layering in paramagnetic cluster owing to interelectron correlations. The states realized during the phase layering can be used for coding the digits. Since such states correspond to specific structures of para-magnetic molecule, they can exist as much as long under certain conditions. In turn, it means that the account of the interelectron correlations, which take place in strongly correlated compounds, allows (at least, in principle) one to create elementary quantum bit of the information capable of modeling the elementary logical operations. Creation of a network of such quantum bits combined in a certain sequence should be considered as a practical step on a way to experimental realization of the idea of quantum computer creation. The group consisting of three quantum points can make the basis of quantum computer. In such a gate, quantum points can be connected via the interaction modeled by spin-spin interaction, characteristic for ABX system in NMR spectroscopy. The tunnel effect, which can be easily realized and controlled, can act as an indicator of bonding in such a block. The calculation procedure can be organized assuming that the initial state of the group corresponds to 1. Infringement of such a state indicates to zero (or, on the contrary). Thus, the calculation in the binary system becomes organized. The creation of a network on the basis of combination of such processors in certain sequence should be considered as a practical step on a way to experimental realization of the idea of the quantum computer creation.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 bipartite entanglement dynamics of the system composed by three qubits A,B,and C.There is no interaction between A and B,and that of C and B is Dzyaloshinskii-Moriya (DM) spin-orbit interaction.We f...We investigate the bipartite entanglement dynamics of the system composed by three qubits A,B,and C.There is no interaction between A and B,and that of C and B is Dzyaloshinskii-Moriya (DM) spin-orbit interaction.We find that the purity of qubits A and B and the initial state of the qubit C are the two effective parameters tocontrol the entanglement dynamics of the bipartite subsystems.This study sheds some lights on the control of quantumentanglement,which would be helpful for quantum information processing.展开更多
We present a scheme for symmetric controlled remote preparation of an arbitrary 2-qudit state form a sender to either of the two receivers via positive operator-valued measurement and pure entangled two-particle state...We present a scheme for symmetric controlled remote preparation of an arbitrary 2-qudit state form a sender to either of the two receivers via positive operator-valued measurement and pure entangled two-particle states. The first sender transforms the quantum channel shared by all the agents via POVM according to her knowledge of prepared state. All the senders perform singIe- or two-particle projective measurements on their entangled particles and the receiver can probabilisticaly reconstruct the original state on her entangled particles via unitary transformation and auxiliary qubit. The scheme is optimal as the probability which the receiver prepares the original state equals to the entanglement of the quantum channel. Moreover, it is more convenience in application than others as it requires only two-particle entanglements for preparing an arbitrary two-qudit state.展开更多
We discuss the fidelity of states in the infinite-dimensional systems and give an elementary proof of the infinite-dimensional version of Uhlmann's theorem.This theorem is used to generalize several properties of ...We discuss the fidelity of states in the infinite-dimensional systems and give an elementary proof of the infinite-dimensional version of Uhlmann's theorem.This theorem is used to generalize several properties of the fidelity of the finite-dimensional case to the infinite-dimensional case.These are somewhat different from those for the finite-dimensional case.展开更多
We investigate the geometric picture of the level surfaces of quantum entanglement and geometric measure of quantum discord(GMQD) of a class of X-states, respectively. This pictorial approach provides us a direct unde...We investigate the geometric picture of the level surfaces of quantum entanglement and geometric measure of quantum discord(GMQD) of a class of X-states, respectively. This pictorial approach provides us a direct understanding of the structure of entanglement and GMQD. The dynamic evolution of GMQD under two typical kinds of quantum decoherence channels is also investigated. It is shown that there exists a class of initial states for which the GMQD is not destroyed by decoherence in a finite time interval. Furthermore, we establish a factorization law between the initial and final GMQD, which allows us to infer the evolution of entanglement under the influences of the environment.展开更多
It is known that the inevitable interaction of the entangled qubits with their environments may result in the degradation of quantum correlation.We study the decoherence of two remote qubits under general local single...It is known that the inevitable interaction of the entangled qubits with their environments may result in the degradation of quantum correlation.We study the decoherence of two remote qubits under general local single-and two-sided amplitude-damping channel(ADC).By using concurrence,quantum discord and Clauser-Horne-ShimonyHolt(CHSH)inequality,we find that the relation between the residual quantum correlations and the initial ones are different.Recently,Wang et al.[Int.J.Theor.Phys.54(2015)5]showed that there exist a set of partially entangled states that are more robust than maximally entangled states in terms of the residual quantum correlation measured by concurrence,fully entangled fraction and quantum discord,respectively.Here we find that both in single-and two-sided ADC,only the evolution of CHSH inequality with the initial parameter is proportional to that of the initial nonlocality.That means the initial state with maximally nonlocality will retain its role in the evolution.It implies that the evolution of nonlocality may reveal the characteristics of quantum state better.Furthermore,we discuss the evolutions of the three different quantum measurements with the initial parameter under generalized amplitude damping channel(GADC)and find that they are all proportional to that of the initial state.展开更多
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10347103 and 10305002 and the Natural Science Foundation of Liaoning Province under Grant No. 20031073
文摘The effects of different time-independent and time-dependent couplings on two-atom entanglement are studied. The results show that the effects depend on the initial state. For the initial state |eeO〉, it is found that different time-independent couplings make the case without entanglement exhibit entanglement, and time-dependent couplings turn the irregular entanglement regions into regular one. Under the case of decay, for the initial state |eg0〉, the different time-dependent couplings have disbenefit.
基金Supported by the National Natural Science Foundation of China under Grant No.10904033Natural Science Foundation of Hubei Province under Grant No.2009CDA145+1 种基金Educational Commission of Hubei Province under Grant No.D20092204the Postgraduate Programme of Hubei Normal University under Grant No.2007D20
文摘We investigate the sudden birth and sudden death of entanglement of two qubits interacting with uncorrelated structured reservoirs. The system is initially prepared in two-qubit extended Werner-like state. We work out the dependence of the entanglement dynamics on both non-Markovian environments and the purity of initial state, and show that non-Markovian environments and the purity can control the time of the two-qubit entanglement sudden death and the reservoirs' entanglement sudden birth. Furthermore, under the conditions of different purity and initial entangIement, the revival of qubits' entanglement can manifest before, simultaneously or even after the disentanglement of their corresponding reservoirs.
文摘We investigate the entanglement transfer in a four-qubit system and calculate the concurrence between any two qubits in different initial states. We show that both the pure entangled state and mixed entangled state can be transferred. For some special coupling constants and some evolution time, entanglement can be completely transferred from one pair particles to another.
基金The project supported by National Natural Science Foundation of China under Grant No. 10304022
文摘Taking advantage of our improved gates as well as the Giorgi-Pasquale-Paganelli (GPP) nondestructive gate [Phys. Rev. A 70 (2004) 022319], the sign of any term of the initial state in the GPP model can be flipped. The success possibility of the sign flip of odd number of terms is probabilistic (11/4), while the success possibility of the sign flip of even number of terms is deterministic (1).
基金Supported by National Natural Science Foundation of China under Grant Nos. 10704001, 61073048, and 11005029the Key Project of Chinese Ministry of Education under Grant No. 210092+2 种基金the Key Program of the Education Department of Anhui Province under Grant Nos. KJ2008A28ZC, 2010SQRL153ZD, and KJ2010A287the "211" Project of Anhui University, the Personnel Department of Anhui ProvinceAnhui Key Laboratory of Information Materials and Devices Anhui University
文摘Quantum Zeno effect with mixed initial state is studied here. Frequent projective measurements performed on a bipartite joint pure state system will result in the quantum Zeno effect on the subsystem of interest. This shows the existence of Quantum Zeno effect in the system with mixed initial states.
基金Supported by the Major Research Plan of the National Natural Science Foundation of China under Grant No.90818005the National Natural Science Foundation of China under Grant Nos.60903217,60773032 60773114the Ph.D.Program Foundation of Ministry of Education of China under Grant No.20060358014
文摘We present an efficient scheme for sharing an arbitrary m-qubit state with n agents.In our scheme,the sender Alice first shares m Bell states with the agent Bob,who is designated to recover the original m-qubit state.Furthermore,Alice introduces n-1 auxiliary particles in the initial state |0>,applies Hadamard (H) gate and Controlled-Not(CNOT) gate operations on the particles,which make them entangled with one of m particle pairs in Bell states,and then sends them to the controllers (i.e.,other n-1 agents),where each controller only holds one particle in hand.After Alice performing m Bell-basis measurements and each controller a single-particle measurement,the recover Bobcan obtain the original unknown quantum state by applying the corresponding local unitary operations on his particles.Its intrinsic efficiency for qubits approaches 100%,and the total efficiency really approaches the maximal value.
文摘The manuscript deals with the possibility of application of collective behavior of quantum particles to realize the quantum calculation procedure. The above collective behavior is likely resulted from interelectron correlations, characteristic for strongly correlated systems containing atoms with unoccupied 3d-, 4f- and 5f- shells. Among such systems can be the heterospin systems, complexes of paramagnetic ions of transition metals with organic radicals, because for such objects, spin-spin interaction between unpaired electron spins of different paramagnetic centers is typical. To apply the aforementioned possibility for the organization of real quantum calculations, it is necessary to synthesize such paramagnetic molecules (paramagnetic clusters), where the entangled states will be realized naturally by self-organization of atoms incorporated in these molecules, i.e., without additional external effect of q-bits on the system. The specified self-organization may be due to intramolecular processes and, in particular, intramolecular rearrangement called valence tautomerism, which leads to heterogeneous magnetic states, i.e., to phase layering in paramagnetic cluster owing to interelectron correlations. The states realized during the phase layering can be used for coding the digits. Since such states correspond to specific structures of para-magnetic molecule, they can exist as much as long under certain conditions. In turn, it means that the account of the interelectron correlations, which take place in strongly correlated compounds, allows (at least, in principle) one to create elementary quantum bit of the information capable of modeling the elementary logical operations. Creation of a network of such quantum bits combined in a certain sequence should be considered as a practical step on a way to experimental realization of the idea of quantum computer creation. The group consisting of three quantum points can make the basis of quantum computer. In such a gate, quantum points can be connected via the interaction modeled by spin-spin interaction, characteristic for ABX system in NMR spectroscopy. The tunnel effect, which can be easily realized and controlled, can act as an indicator of bonding in such a block. The calculation procedure can be organized assuming that the initial state of the group corresponds to 1. Infringement of such a state indicates to zero (or, on the contrary). Thus, the calculation in the binary system becomes organized. The creation of a network on the basis of combination of such processors in certain sequence should be considered as a practical step on a way to experimental realization of the idea of the quantum computer creation.
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Supported by the National Natural Science Foundation of China under Grant Nos.10535010 and 10775123Research Fund of Education Ministry under Grant No.20070284016+1 种基金the Natural Science and Technology Foundation of Guizhou Province under Grant Nos.[2009]2267the Doctor funding of Guizhou Normal University
文摘We investigate the bipartite entanglement dynamics of the system composed by three qubits A,B,and C.There is no interaction between A and B,and that of C and B is Dzyaloshinskii-Moriya (DM) spin-orbit interaction.We find that the purity of qubits A and B and the initial state of the qubit C are the two effective parameters tocontrol the entanglement dynamics of the bipartite subsystems.This study sheds some lights on the control of quantumentanglement,which would be helpful for quantum information processing.
基金Supported by Program for Natural Science Foundation of Guangxi under Grant No. 2011GxNSFB018062, Excellent Talents in Guangxi Higher Education Institutions under Grant No. [2012]41, Key program of Cuangxi University for Nationalities under Grant No. [2011]317 and the Bagui Scholarship Project
文摘We present a scheme for symmetric controlled remote preparation of an arbitrary 2-qudit state form a sender to either of the two receivers via positive operator-valued measurement and pure entangled two-particle states. The first sender transforms the quantum channel shared by all the agents via POVM according to her knowledge of prepared state. All the senders perform singIe- or two-particle projective measurements on their entangled particles and the receiver can probabilisticaly reconstruct the original state on her entangled particles via unitary transformation and auxiliary qubit. The scheme is optimal as the probability which the receiver prepares the original state equals to the entanglement of the quantum channel. Moreover, it is more convenience in application than others as it requires only two-particle entanglements for preparing an arbitrary two-qudit state.
基金supported by the National Natural Science Foundation of China(Grant Nos.11171249 and 11101250)the Youth Foundation of Shanxi Province(Grant No.2012021004)the Young Talents Plan for Shanxi University and a grant from the International Cooperation Program in Sciences and Technology of Shanxi(Grant No.2011081039)
文摘We discuss the fidelity of states in the infinite-dimensional systems and give an elementary proof of the infinite-dimensional version of Uhlmann's theorem.This theorem is used to generalize several properties of the fidelity of the finite-dimensional case to the infinite-dimensional case.These are somewhat different from those for the finite-dimensional case.
基金supported by the National Natural Science Foundation of China (Grant Nos.10905024, 11005029, 11104057 and 11204061)the Key Project of Chinese Ministry of Education (Grant No. 211080)+2 种基金the Key Program of the Education Department of Anhui Province (Grant Nos. KJ2011A243, KJ2012A244 and KJ2012A245)the Anhui Provincial Natural Science Foundation (Grant Nos. 11040606M16 and 10040606Q51)the Doctoral Startup Foundation of Hefei Normal University (Grant No. 2011rcjj03)
文摘We investigate the geometric picture of the level surfaces of quantum entanglement and geometric measure of quantum discord(GMQD) of a class of X-states, respectively. This pictorial approach provides us a direct understanding of the structure of entanglement and GMQD. The dynamic evolution of GMQD under two typical kinds of quantum decoherence channels is also investigated. It is shown that there exists a class of initial states for which the GMQD is not destroyed by decoherence in a finite time interval. Furthermore, we establish a factorization law between the initial and final GMQD, which allows us to infer the evolution of entanglement under the influences of the environment.
基金Supported by National Natural Science Foundation of China under Grant Nos.11204002,11274010,61073048,11005029the Specialized Research Fund for the Doctoral Program of Higher Education(20123401120003,20113401110002)+2 种基金the Key Project of Chinese Ministry of Education(Nos.211080,210092)the Key Program of the Education Department of Anhui Province under Grant No.KJ2012A020the"211"Project of Anhui University,the Talent Foundation of Anhui University,the personnel department of Anhui province
文摘It is known that the inevitable interaction of the entangled qubits with their environments may result in the degradation of quantum correlation.We study the decoherence of two remote qubits under general local single-and two-sided amplitude-damping channel(ADC).By using concurrence,quantum discord and Clauser-Horne-ShimonyHolt(CHSH)inequality,we find that the relation between the residual quantum correlations and the initial ones are different.Recently,Wang et al.[Int.J.Theor.Phys.54(2015)5]showed that there exist a set of partially entangled states that are more robust than maximally entangled states in terms of the residual quantum correlation measured by concurrence,fully entangled fraction and quantum discord,respectively.Here we find that both in single-and two-sided ADC,only the evolution of CHSH inequality with the initial parameter is proportional to that of the initial nonlocality.That means the initial state with maximally nonlocality will retain its role in the evolution.It implies that the evolution of nonlocality may reveal the characteristics of quantum state better.Furthermore,we discuss the evolutions of the three different quantum measurements with the initial parameter under generalized amplitude damping channel(GADC)and find that they are all proportional to that of the initial state.