Quantum walks act in obviously different ways from their classical counterparts, but decoherence will lessen and close this gap between them. To understand this process, it is necessary to investigate the evolution of...Quantum walks act in obviously different ways from their classical counterparts, but decoherence will lessen and close this gap between them. To understand this process, it is necessary to investigate the evolution of quantum walks under different decoherence situations. In this article, we study a non-Markovian decoherent quantum walk on a line. In a short time regime, the behavior of the walk deviates from both ideal quantum walks and classical random walks. The position variance as a measure of the quantum walk collapses and revives for a short time, and tends to have a linear relation with time. That is, the walker’s behavior shows a diffusive spread over a long time limit, which is caused by non-Markovian dephasing affecting the quantum correlations between the quantum walker and his coin. We also study both quantum discord and measurement-induced disturbance as measures of the quantum correlations, and observe both collapse and revival in the short time regime, and the tendency to be zero in the long time limit. Therefore, quantum walks with non-Markovian decoherence tend to have diffusive spreading behavior over long time limits, while in the short time regime they oscillate between ballistic and diffusive spreading behavior, and the quantum correlation collapses and revives due to the memory effect.展开更多
We investigate the stabilization mechanism of open quantum batteries driven by a classical field in the weak or strong system-reservoir coupling regime.A protocol to improve the steady-state energy storage performance...We investigate the stabilization mechanism of open quantum batteries driven by a classical field in the weak or strong system-reservoir coupling regime.A protocol to improve the steady-state energy storage performance is proposed by engineering the spectral density of a band-gap environment which is described as the superposition of two inhomogeneous Lorentzian spectrums with different weights.We find out that the interplay between the batteryenvironment-bound state and the reservoir memory effect plays a crucial role in the stabilization performance against energy dissipation.The formation of the bound state and the nonMarkovian effect will be strengthened by adjusting the weights of the environment spectral density.In the charging process,the classical field contributes to enhancing the steady ergotropy.Moreover,the manipulation of the spectrum weights results in the speedup scheme of carrying out the energy storage due to the existence of bound states.In the self-discharging process,increasing the spectral weight allows the battery to maintain a higher steady ergotropy.These results provide a practical approach to achieving optimal quantum batteries with better stabilization performance.展开更多
The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compa...The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compared to those with lower-order spatial forms. We formulated the decoherence rate caused by the variance of the differential energy shift and photon jumping rate. Then, we constructed blue-detuned harmonic and quartic optical dipole traps, and experimentally investigated the coherence time of a trapped single cesium atom.Specifically, we demonstrated a significant improvement in the coherence time of a single atom by employing a quartic trap with the same characteristic trap potential and size as its harmonic counterpart—achieving an enhancement from 315 ms to 474 ms. The experimental results qualitatively verified our theory. Our approach provides a novel method to enhance the coherence time of optically trapped neutral atoms.展开更多
Qubit,as the basic unit of quantum operations,has at least two quantum states for superposition.Diamond itself has no superimposable quantum states,but after injecting N atoms,the resulted nitrogenvacancy centers form...Qubit,as the basic unit of quantum operations,has at least two quantum states for superposition.Diamond itself has no superimposable quantum states,but after injecting N atoms,the resulted nitrogenvacancy centers form excellent-performance qubits.For the same purpose,we can also obtain qubits by modifying the matrix without effective quantum states.HKUST-1({Cu_(3)(BTC)_(2)(H_(2)O)_(3)},BTC=1,3,5-benzene-tricarboxylate)with S=0 ground state is electron paramagnetic resonance(EPR)silent,so it is not a qubit candidate.However,the spontaneously hydrolyzed HKUST-1 produces dilute uncoupled Cu^(Ⅱ)ions with S=1/2.In this paper,we utilized the hydrolysis products of HKUST-1 to obtain qubits and assembled a core-shell structural HKUST-1@ZIF-8 by ZIF-8({Zn(mim)_(2)},mim=2-methylimidazole)coated over HKUST-1 for controlling the hydrolysis.The experimental results clearly show that the qubits come from hydrolyzed Cu^(Ⅱ)ions.Furthermore,the dilute uncoupled Cu^(Ⅱ)ions in this assembly can effectively reduce the decoherence of qubits.The EPR studies show that the T_(2) of this compound is 1067 ns at 10 K.展开更多
Energy transfer processes between two aggregates in a coupled chromophoric-pigment （protein） system are studied via the standard master equation approach. Each pigment of the two aggregates is modeled as a two-level...Energy transfer processes between two aggregates in a coupled chromophoric-pigment （protein） system are studied via the standard master equation approach. Each pigment of the two aggregates is modeled as a two-level system. The excitation energy is assumed to be transferred from the donor aggregate to the acceptor aggregate. The model can be used to theoretically simulate many aspects of light-harvesting complexes （LHCs）. By applying the real bio-parameters of photosynthesis, we numerically investigate the efficiency of energy transfer （EET） between the two aggregates in terms of some factors, e.g., the initial coherence of the donor aggregate, the coupling strengthes between the two aggregates and between different pigments, and the effects of noise from the environment. Our results provide evidence for that the actual numbers of pigments in the chromophoric tings of LHCs should be the optimum parameters for a high EET. We also give a detailed analysis of the effects of noise on the EET.展开更多
Based on the Perelmann mappings from the homogenous 5D onto the inhomogeneous Lorentz 4D manifold at liquid water phase temperature range, it is shown that coherent and decoherent molecules, water, carbon, hydrogen an...Based on the Perelmann mappings from the homogenous 5D onto the inhomogeneous Lorentz 4D manifold at liquid water phase temperature range, it is shown that coherent and decoherent molecules, water, carbon, hydrogen and oxygen naturally replace the Quarks in the standard model at Bethe fusion temperature as the SU(3) generators, leading to the formation of nitrogenous bases to house the monopole boson eigenstates that can exist within the RNA and DNA. Through which the growth of organic cells by inducing the Off Diagonal Long-Range Order of “p” type hole states in organic rings and bio-cells and thus “Life”.展开更多
We develop a fabrication process for the superconducting phase qubits in which Josephson junctions for both the qubit and superconducting quantum interference device（SQUID） detector are prepared by shadow evaporatio...We develop a fabrication process for the superconducting phase qubits in which Josephson junctions for both the qubit and superconducting quantum interference device（SQUID） detector are prepared by shadow evaporation with a suspended bridge. Al junctions with areas as small as 0.05 μm^2 are fabricated for the qubit, in which the number of the decoherencecausing two-level systems（TLS） residing in the tunnel barrier and proportional to the junction area are greatly reduced. The measured energy spectrum shows no avoided crossing arising from coherent TLS in the experimentally reachable flux bias range of the phase qubit, which demonstrates the energy relaxation time T1 and dephasing time Tφ on the order of 100 ns and 50 ns, respectively. We discuss several possible origins of decoherence from incoherent or weakly-coupled coherent TLS and further improvements of the qubit performance.展开更多
Recently,bidirectional quantum teleportation has attracted a great deal of research attention.However,existing bidirectional teleportation schemes are normally discussed on the basis of perfect quantum environments.In...Recently,bidirectional quantum teleportation has attracted a great deal of research attention.However,existing bidirectional teleportation schemes are normally discussed on the basis of perfect quantum environments.In this paper,we first put forward a bidirectional teleportation scheme to transport three-qubit Greenberger-Horne-Zeilinger（GHZ） states based on controled-not（CNOT） operation and single-qubit measurement.Then,we generalize it to the teleportation of multi-qubit GHZ states.Further,we discuss the influence of quantum noise on our scheme by the example of an amplitude damping channel,then we obtain the fidelity of the teleportation.Finally,we utilize the weak measurement and the corresponding reversing measurement to protect the quantum entanglement,which shows an effective enhancement of the teleportation fidelity.展开更多
Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entangl...Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.展开更多
We investigate a two=level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of t...We investigate a two=level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non=interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.展开更多
Taking the intrinsic decoherence effect into account, this paper investigates the entanglement of a two-qubit anisotropic Heisenberg XYZ model in the presence of nonuniform external magnetic fields by employing the co...Taking the intrinsic decoherence effect into account, this paper investigates the entanglement of a two-qubit anisotropic Heisenberg XYZ model in the presence of nonuniform external magnetic fields by employing the concurrence as entanglement measure. It is found that both the intrinsic decoherence and the anisotropy of the system give a significant suppression to the entanglement. Moreover it finds that the initial state of the system plays an important role in the time evolution of the entanglement, which means that the entanglement of the system is independent of the nonuniformity and uniformity of the magnetic field when the system is in the initial state ｜ψ （0）） = ｜00） and [ψ′ （0）） = m ｜01） ＋ n ｜10）, respectively.展开更多
Multi-qubit entanglement states are the key resources for various multipartite quantum communication tasks. For a class of generalized three-qubit quantum entanglement, W-like state, we demonstrate that the weak measu...Multi-qubit entanglement states are the key resources for various multipartite quantum communication tasks. For a class of generalized three-qubit quantum entanglement, W-like state, we demonstrate that the weak measurement and the reversal measurement are capable of suppressing the amplitude damping decoherence by reducing the initial damping factor into a smaller equivalent damping factor. Furthermore, we propose an iteration method in the weak measurement and the reversal measurement to enhance the success probability of the total measurements. Finally, we discuss how the number of the iterations influences the overall effect of decoherence suppression, and find that the ＂half iteration＂ method is a better option that has more practical value.展开更多
We propose a simple scheme to not only generate GHZ states and W states of the multiparticle but also form a new category of multiparticle entangled states by letting the A-type three-level atoms simultaneously intera...We propose a simple scheme to not only generate GHZ states and W states of the multiparticle but also form a new category of multiparticle entangled states by letting the A-type three-level atoms simultaneously interacting with a coherent cavity field followed by the selective measurements on the cavity mode. We investigate the influence of the cavity dissipation on the generated entangled state and discuss the experimental feasibility of our scheme. It is shown that the intensity of the coherent cavity field plays an instructive role in contribution to state preparation process while the cavity decay and the detuning between the atoms and cavity mode result in the deterioration of the generated entangled state.展开更多
In this paper, we study the control problem of adiabatic decoherence in a three-level atom. We will find the decoupling bang-bang group for various configurations, including the V configuration and the cascade type of...In this paper, we study the control problem of adiabatic decoherence in a three-level atom. We will find the decoupling bang-bang group for various configurations, including the V configuration and the cascade type of three-levelatom subjected to adiabatic decoherence. We also give the programs to design a sequence of periodic twinborn pulses to suppress the decoherence.展开更多
We use the mean field method to study the dynamics of thermal entanglement and also the measurementinduced disturbance for a mixed qutrit-qubit system coupled to an environment, comprised of an Ising spin-chain with l...We use the mean field method to study the dynamics of thermal entanglement and also the measurementinduced disturbance for a mixed qutrit-qubit system coupled to an environment, comprised of an Ising spin-chain with long range interactions, embedded in a transverse magnetic field. It is revealed that both quantities die down in long enough time and the fade out time is a decreasing function of temperature; however, the environmental magnetic field holds back the decoherence, and increases the fade out time; thus, providing a means to control and postpone the decoherence process. Moreover, it is observed that the discrepancy between the interaction strength of the qubit and the qutrit with the environment, substantially affects the decoherence behavior of the system.展开更多
We investigate the influences of non-Markovian dissipation and global dephasing process on the dynamical behaviors of global discord among four qubits.We find that for the non-Markovian dissipation model W state is th...We investigate the influences of non-Markovian dissipation and global dephasing process on the dynamical behaviors of global discord among four qubits.We find that for the non-Markovian dissipation model W state is the most robust to decoherence compared to Dicke and GHZ states;however,for the global dephasing model Dicke state is the most robust to decoherence among them.Also the dynamical behaviors of global quantum discord are quite different from that of the multipartite entanglement for the non-Markovian dissipation model,while they are very similar to each other for the global dephasing model.展开更多
Taking the intrinsic decoherence effect into account, the entanglement ofa two-qubit anisotropic Heisenberg XYZ chain in the presence of the Dzyaloshinski Moriya （DM） anisotropic antisymetric interaction is investig...Taking the intrinsic decoherence effect into account, the entanglement ofa two-qubit anisotropic Heisenberg XYZ chain in the presence of the Dzyaloshinski Moriya （DM） anisotropic antisymetric interaction is investigated in this paper. Concurrence, the measurement of entanglement, is calculated. Compared with the anisotropic in XY plane, the DM interaction is another kind of anisotropic antisymmetrie exchange interaction. It is shown that the intrinsic decoherence obviously suppresses the time evolution of the entanglement. The DM interaction only acts on the time evolution of the entanglement when the initial state is [ψ（0）〉 = cosα｜01〉 ＋ sinα｜10〉 and weakens the degree of entanglement. The anisotropic in XY plane merely impacts on the time evolution of the entanglement when the system ＆ initially in a state ｜ψ（0）〉 = cos α｜00〉 ＋ sin α｜11 〉. The sufficiently weak anisotropic in XY plane can effectively enhance the degree of entanglement.展开更多
A measure of non-classicality of even and odd coherent states is studied. We first calculate the Wigner functions of the even and odd coherent states, which consists of two terms： the positive-definite Gaussian term ...A measure of non-classicality of even and odd coherent states is studied. We first calculate the Wigner functions of the even and odd coherent states, which consists of two terms： the positive-definite Gaussian term and the wave term with negativity, and then calculate the integrated value εmax of the wave term of the Wigner functions of the even and odd coherent states in their area with negativity, and use εmax to measure non-classicality of the even and odd coherent states. For the even and odd coherent states with certain photon count, it is very convenient for us to use εmax to measure their non-classicality. The methods of our definition and calculation for εmax have theoretical reference value.展开更多
Quantum teleportation is investigated by using the entangled states of two-qubit Heisenberg XX chain in an external uniform magnetic field as resources in the model of Milburn＇s intrinsic decoherence. Though intrinsi...Quantum teleportation is investigated by using the entangled states of two-qubit Heisenberg XX chain in an external uniform magnetic field as resources in the model of Milburn＇s intrinsic decoherence. Though intrinsic decoherence on quantum entanglement and quantum teleportation exerts different effects in different initial systems, proper magnetic fields and probabilities of different eigenstates in the initial states can weaken the effects.展开更多
基金the National Natural Science Foundation of China(Grant Nos.10974192,11004029,and 11174052)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK2010422)+2 种基金the Ph.D.Program of the Ministry of Education of Chinathe Excellent Young Teachers Program of Southeast University,Chinathe National Basic Research Program of China(Grant No.2011CB921203)
文摘Quantum walks act in obviously different ways from their classical counterparts, but decoherence will lessen and close this gap between them. To understand this process, it is necessary to investigate the evolution of quantum walks under different decoherence situations. In this article, we study a non-Markovian decoherent quantum walk on a line. In a short time regime, the behavior of the walk deviates from both ideal quantum walks and classical random walks. The position variance as a measure of the quantum walk collapses and revives for a short time, and tends to have a linear relation with time. That is, the walker’s behavior shows a diffusive spread over a long time limit, which is caused by non-Markovian dephasing affecting the quantum correlations between the quantum walker and his coin. We also study both quantum discord and measurement-induced disturbance as measures of the quantum correlations, and observe both collapse and revival in the short time regime, and the tendency to be zero in the long time limit. Therefore, quantum walks with non-Markovian decoherence tend to have diffusive spreading behavior over long time limits, while in the short time regime they oscillate between ballistic and diffusive spreading behavior, and the quantum correlation collapses and revives due to the memory effect.
基金supported by Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX24_3424)funded by SCOAP^(3)。
文摘We investigate the stabilization mechanism of open quantum batteries driven by a classical field in the weak or strong system-reservoir coupling regime.A protocol to improve the steady-state energy storage performance is proposed by engineering the spectral density of a band-gap environment which is described as the superposition of two inhomogeneous Lorentzian spectrums with different weights.We find out that the interplay between the batteryenvironment-bound state and the reservoir memory effect plays a crucial role in the stabilization performance against energy dissipation.The formation of the bound state and the nonMarkovian effect will be strengthened by adjusting the weights of the environment spectral density.In the charging process,the classical field contributes to enhancing the steady ergotropy.Moreover,the manipulation of the spectrum weights results in the speedup scheme of carrying out the energy storage due to the existence of bound states.In the self-discharging process,increasing the spectral weight allows the battery to maintain a higher steady ergotropy.These results provide a practical approach to achieving optimal quantum batteries with better stabilization performance.
基金supported by the National Key Research and Development Program of China (Grant No.2021YFA1402002)the Innovation Program for Quantum Science and Technology (Grant No.2023ZD0300400)the National Natural Science Foundation of China (Grant Nos.U21A6006,U21A20433,92465201,12474360,and 92265108)。
文摘The coherence time of an optically trapped neutral atom is a crucial parameter for quantum technologies.We found that optical dipole traps with higher-order spatial forms inherently offer lower decoherence rates compared to those with lower-order spatial forms. We formulated the decoherence rate caused by the variance of the differential energy shift and photon jumping rate. Then, we constructed blue-detuned harmonic and quartic optical dipole traps, and experimentally investigated the coherence time of a trapped single cesium atom.Specifically, we demonstrated a significant improvement in the coherence time of a single atom by employing a quartic trap with the same characteristic trap potential and size as its harmonic counterpart—achieving an enhancement from 315 ms to 474 ms. The experimental results qualitatively verified our theory. Our approach provides a novel method to enhance the coherence time of optically trapped neutral atoms.
基金supported by the National Key Research and Development Program of China(No.2021YFA1600304)the Joint Fund for Regional Innovation and Development(No.U20A2073)+3 种基金the National Natural Science Foundation of China(Nos.21973038,62005297 and 22105089)the Interdisciplinary Program of Wuhan National High Magnetic Field Center(No.WHMFC_(2)02133)Natural Science Foundation of Jiangxi Province(No.20224BAB214005)Jiangxi Provincial Key Laboratory of Functional Molecular Materials Chemistry(No.20212BCD42018)。
文摘Qubit,as the basic unit of quantum operations,has at least two quantum states for superposition.Diamond itself has no superimposable quantum states,but after injecting N atoms,the resulted nitrogenvacancy centers form excellent-performance qubits.For the same purpose,we can also obtain qubits by modifying the matrix without effective quantum states.HKUST-1({Cu_(3)(BTC)_(2)(H_(2)O)_(3)},BTC=1,3,5-benzene-tricarboxylate)with S=0 ground state is electron paramagnetic resonance(EPR)silent,so it is not a qubit candidate.However,the spontaneously hydrolyzed HKUST-1 produces dilute uncoupled Cu^(Ⅱ)ions with S=1/2.In this paper,we utilized the hydrolysis products of HKUST-1 to obtain qubits and assembled a core-shell structural HKUST-1@ZIF-8 by ZIF-8({Zn(mim)_(2)},mim=2-methylimidazole)coated over HKUST-1 for controlling the hydrolysis.The experimental results clearly show that the qubits come from hydrolyzed Cu^(Ⅱ)ions.Furthermore,the dilute uncoupled Cu^(Ⅱ)ions in this assembly can effectively reduce the decoherence of qubits.The EPR studies show that the T_(2) of this compound is 1067 ns at 10 K.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174233)the National Basic Research Program of China(Grant No.2011CB311807)
文摘Energy transfer processes between two aggregates in a coupled chromophoric-pigment （protein） system are studied via the standard master equation approach. Each pigment of the two aggregates is modeled as a two-level system. The excitation energy is assumed to be transferred from the donor aggregate to the acceptor aggregate. The model can be used to theoretically simulate many aspects of light-harvesting complexes （LHCs）. By applying the real bio-parameters of photosynthesis, we numerically investigate the efficiency of energy transfer （EET） between the two aggregates in terms of some factors, e.g., the initial coherence of the donor aggregate, the coupling strengthes between the two aggregates and between different pigments, and the effects of noise from the environment. Our results provide evidence for that the actual numbers of pigments in the chromophoric tings of LHCs should be the optimum parameters for a high EET. We also give a detailed analysis of the effects of noise on the EET.
文摘Based on the Perelmann mappings from the homogenous 5D onto the inhomogeneous Lorentz 4D manifold at liquid water phase temperature range, it is shown that coherent and decoherent molecules, water, carbon, hydrogen and oxygen naturally replace the Quarks in the standard model at Bethe fusion temperature as the SU(3) generators, leading to the formation of nitrogenous bases to house the monopole boson eigenstates that can exist within the RNA and DNA. Through which the growth of organic cells by inducing the Off Diagonal Long-Range Order of “p” type hole states in organic rings and bio-cells and thus “Life”.
基金supported by the National Basic Research Program of China(Grant Nos.2014CB921202,2015CB921104,and 2016YFA0300601)the National Natural Science Foundation of China(Grant Nos.91321208 and 11674380)
文摘We develop a fabrication process for the superconducting phase qubits in which Josephson junctions for both the qubit and superconducting quantum interference device（SQUID） detector are prepared by shadow evaporation with a suspended bridge. Al junctions with areas as small as 0.05 μm^2 are fabricated for the qubit, in which the number of the decoherencecausing two-level systems（TLS） residing in the tunnel barrier and proportional to the junction area are greatly reduced. The measured energy spectrum shows no avoided crossing arising from coherent TLS in the experimentally reachable flux bias range of the phase qubit, which demonstrates the energy relaxation time T1 and dephasing time Tφ on the order of 100 ns and 50 ns, respectively. We discuss several possible origins of decoherence from incoherent or weakly-coupled coherent TLS and further improvements of the qubit performance.
基金Project supported by the National Natural Science Foundation of China(Grant No.61172071)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.16JK1711)+1 种基金the International Scientific Cooperation Program of Shaanxi Province,China(Grant No.2015KW-013)the Natural Science Foundation Research Project of Shaanxi Province,China(Grant No.2016JQ6033)
文摘Recently,bidirectional quantum teleportation has attracted a great deal of research attention.However,existing bidirectional teleportation schemes are normally discussed on the basis of perfect quantum environments.In this paper,we first put forward a bidirectional teleportation scheme to transport three-qubit Greenberger-Horne-Zeilinger（GHZ） states based on controled-not（CNOT） operation and single-qubit measurement.Then,we generalize it to the teleportation of multi-qubit GHZ states.Further,we discuss the influence of quantum noise on our scheme by the example of an amplitude damping channel,then we obtain the fidelity of the teleportation.Finally,we utilize the weak measurement and the corresponding reversing measurement to protect the quantum entanglement,which shows an effective enhancement of the teleportation fidelity.
文摘Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.
基金Project supported by National Natural Science Foundation of China (Grant No. 10774143)
文摘We investigate a two=level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non=interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB921604)the National Natural Science Foundation of China (Grant Nos 60708003,60578050 and 10434060)
文摘Taking the intrinsic decoherence effect into account, this paper investigates the entanglement of a two-qubit anisotropic Heisenberg XYZ model in the presence of nonuniform external magnetic fields by employing the concurrence as entanglement measure. It is found that both the intrinsic decoherence and the anisotropy of the system give a significant suppression to the entanglement. Moreover it finds that the initial state of the system plays an important role in the time evolution of the entanglement, which means that the entanglement of the system is independent of the nonuniformity and uniformity of the magnetic field when the system is in the initial state ｜ψ （0）） = ｜00） and [ψ′ （0）） = m ｜01） ＋ n ｜10）, respectively.
基金supported by the National Natural Science Foundation of China(Grant No.61172071)the International Scientific Cooperation Program of Shaanxi Province,China(Grant No.2015KW-013)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.16JK1711)
文摘Multi-qubit entanglement states are the key resources for various multipartite quantum communication tasks. For a class of generalized three-qubit quantum entanglement, W-like state, we demonstrate that the weak measurement and the reversal measurement are capable of suppressing the amplitude damping decoherence by reducing the initial damping factor into a smaller equivalent damping factor. Furthermore, we propose an iteration method in the weak measurement and the reversal measurement to enhance the success probability of the total measurements. Finally, we discuss how the number of the iterations influences the overall effect of decoherence suppression, and find that the ＂half iteration＂ method is a better option that has more practical value.
基金Supported by the Natural Science Foundation of Hunan Province under Grant No.06jj50014Key Project Foundation of the Education Commission of Hunan Province under Grant No.06A055the Young Core Teachers Foundation of Hunan Provincial Education Department
文摘We propose a simple scheme to not only generate GHZ states and W states of the multiparticle but also form a new category of multiparticle entangled states by letting the A-type three-level atoms simultaneously interacting with a coherent cavity field followed by the selective measurements on the cavity mode. We investigate the influence of the cavity dissipation on the generated entangled state and discuss the experimental feasibility of our scheme. It is shown that the intensity of the coherent cavity field plays an instructive role in contribution to state preparation process while the cavity decay and the detuning between the atoms and cavity mode result in the deterioration of the generated entangled state.
文摘In this paper, we study the control problem of adiabatic decoherence in a three-level atom. We will find the decoupling bang-bang group for various configurations, including the V configuration and the cascade type of three-levelatom subjected to adiabatic decoherence. We also give the programs to design a sequence of periodic twinborn pulses to suppress the decoherence.
文摘We use the mean field method to study the dynamics of thermal entanglement and also the measurementinduced disturbance for a mixed qutrit-qubit system coupled to an environment, comprised of an Ising spin-chain with long range interactions, embedded in a transverse magnetic field. It is revealed that both quantities die down in long enough time and the fade out time is a decreasing function of temperature; however, the environmental magnetic field holds back the decoherence, and increases the fade out time; thus, providing a means to control and postpone the decoherence process. Moreover, it is observed that the discrepancy between the interaction strength of the qubit and the qutrit with the environment, substantially affects the decoherence behavior of the system.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11274043 and 11375025
文摘We investigate the influences of non-Markovian dissipation and global dephasing process on the dynamical behaviors of global discord among four qubits.We find that for the non-Markovian dissipation model W state is the most robust to decoherence compared to Dicke and GHZ states;however,for the global dephasing model Dicke state is the most robust to decoherence among them.Also the dynamical behaviors of global quantum discord are quite different from that of the multipartite entanglement for the non-Markovian dissipation model,while they are very similar to each other for the global dephasing model.
基金supported by the Natural Science Foundation of Hunan Province under Grant No. 06JJ50118
文摘Taking the intrinsic decoherence effect into account, the entanglement ofa two-qubit anisotropic Heisenberg XYZ chain in the presence of the Dzyaloshinski Moriya （DM） anisotropic antisymetric interaction is investigated in this paper. Concurrence, the measurement of entanglement, is calculated. Compared with the anisotropic in XY plane, the DM interaction is another kind of anisotropic antisymmetrie exchange interaction. It is shown that the intrinsic decoherence obviously suppresses the time evolution of the entanglement. The DM interaction only acts on the time evolution of the entanglement when the initial state is [ψ（0）〉 = cosα｜01〉 ＋ sinα｜10〉 and weakens the degree of entanglement. The anisotropic in XY plane merely impacts on the time evolution of the entanglement when the system ＆ initially in a state ｜ψ（0）〉 = cos α｜00〉 ＋ sin α｜11 〉. The sufficiently weak anisotropic in XY plane can effectively enhance the degree of entanglement.
文摘A measure of non-classicality of even and odd coherent states is studied. We first calculate the Wigner functions of the even and odd coherent states, which consists of two terms： the positive-definite Gaussian term and the wave term with negativity, and then calculate the integrated value εmax of the wave term of the Wigner functions of the even and odd coherent states in their area with negativity, and use εmax to measure non-classicality of the even and odd coherent states. For the even and odd coherent states with certain photon count, it is very convenient for us to use εmax to measure their non-classicality. The methods of our definition and calculation for εmax have theoretical reference value.
基金Acknowledgments We would like to thank Z.H. He＇s wife for helpful discussion and his newly born baby Yiyi for her powerful inspiration. We are grateful to Southwest University for the financial support on this project under Grant No. SWNUQ2004019.
文摘Quantum teleportation is investigated by using the entangled states of two-qubit Heisenberg XX chain in an external uniform magnetic field as resources in the model of Milburn＇s intrinsic decoherence. Though intrinsic decoherence on quantum entanglement and quantum teleportation exerts different effects in different initial systems, proper magnetic fields and probabilities of different eigenstates in the initial states can weaken the effects.
