We demonstrate a method to preserve entanglement and improve fidelity of three-qubit quantum states undergoing amplitude-damping decoherence using weak measurement and quantum measurement reversal. It is shown that we...We demonstrate a method to preserve entanglement and improve fidelity of three-qubit quantum states undergoing amplitude-damping decoherence using weak measurement and quantum measurement reversal. It is shown that we are able to enhance entanglement to the greatest extent, and to circumvent entanglement sudden death by increasing the weak measurement strength both for the GHZ state and the W state. The weak measurement technique can also enhance the fidelity to the quantum region and even close to 1 for the whole range of the decoherence parameter in both of the two cases. In addition, the W state can maintain more fidelity than the GHZ state in the protection protocol. However, the GHZ state has a higher success probability than the W state.展开更多
Fidelity plays an important role in quantum information processing,which provides a basic scale for comparing two quantum states.At present,one of the most commonly used fidelities is Uhlmann-Jozsa(U-J)fidelity.Howeve...Fidelity plays an important role in quantum information processing,which provides a basic scale for comparing two quantum states.At present,one of the most commonly used fidelities is Uhlmann-Jozsa(U-J)fidelity.However,U-J fidelity needs to calculate the square root of the matrix,which is not trivial in the case of large or infinite density matrices.Moreover,U-J fidelity is a measure of overlap,which has limitations in some cases and cannot reflect the similarity between quantum states well.Therefore,a novel quantum fidelity measure called quantum Tanimoto coefficient(QTC)fidelity is proposed in this paper.Unlike other existing fidelities,QTC fidelity not only considers the overlap between quantum states,but also takes into account the separation between quantum states for the first time,which leads to a better performance of measure.Specifically,we discuss the properties of the proposed QTC fidelity.QTC fidelity is compared with some existing fidelities through specific examples,which reflects the effectiveness and advantages of QTC fidelity.In addition,based on the QTC fidelity,three discrimination coefficients d_(1)^(QTC),d_(2)^(QTC),and d_^(3)^(QTC)are defined to measure the difference between quantum states.It is proved that the discrimination coefficient d_(3)^(QTC)is a true metric.Finally,we apply the proposed QTC fidelity-based discrimination coefficients to measure the entanglement of quantum states to show their practicability.展开更多
We propose a quantity called modulus fidelity to measure the closeness of two quantum pure states. We use it to investigate the closeness of eigenstates in one-dimensional hard-core bosons. When the system is integrab...We propose a quantity called modulus fidelity to measure the closeness of two quantum pure states. We use it to investigate the closeness of eigenstates in one-dimensional hard-core bosons. When the system is integrable, eigenstates close to their neighbor or not, which leads to a large fluctuation in the distribution of modulus fidelity. When the system becomes chaos, the fluctuation is reduced dramatically, which indicates all eigenstates become close to each other. It is also found that two kind of closeness, i.e., closeness of eigenstates and closeness of eigenvalues, are not correlated at integrability but correlated at chaos. We also propose that the closeness of eigenstates is the underlying mechanism of eigenstate thermalization hypothesis （ETH） which explains the thermalization in quantum many-body systems.展开更多
In the paper, taking the atomic EPR entanglement of quantum teleportation of atomic state in thermal environment damping-density operator approach, and the average fidelities are channel state ｜φ = （1/√2）（｜00）...In the paper, taking the atomic EPR entanglement of quantum teleportation of atomic state in thermal environment damping-density operator approach, and the average fidelities are channel state ｜φ = （1/√2）（｜00） ＋ ｜11〉） is more robust than ｜φ｜ they are subject to the dissipative environments. states as quantum channel, we investigate the fidelity and vacuum reservoir by means of quantum theory of calculated, the results show that the atomic quantum = （1/√2）（｜01〉 ＋ ｜10〉） in teleportation process when they are subject to the dissipative environments.展开更多
The thermodynamic influence of quantum probing on an object is studied.Here,quantum probing is understood to be a pre-measurement based on a non-demolition interaction,which records some information of the probed obje...The thermodynamic influence of quantum probing on an object is studied.Here,quantum probing is understood to be a pre-measurement based on a non-demolition interaction,which records some information of the probed object but does not change its energy state when both the probing apparatus and the probed object are isolated from the environment.It is argued that when the probing apparatus and the probed object are immersed in the same equilibrium environment,the probing can affect the effective temperature of the object or induce a quantum isothermal process for the object to transfer its energy.This thermodynamic feature can be regarded as a witness of quantum probing.展开更多
In this paper we study the entanglement in a two-qubit spin in the XYZ model, and teleport a two-qubit entangled state using this spin chain in the condition of the thermal equilibrium as a quantum channel. We investi...In this paper we study the entanglement in a two-qubit spin in the XYZ model, and teleport a two-qubit entangled state using this spin chain in the condition of the thermal equilibrium as a quantum channel. We investigate the effects of the interaction of z-component Jz, the inhomogeneous magnetic field b, the anisotropy γ and the temperature T on the entanglement and fidelity. In order to characterize the quality of the teleported state, we research the average fidelity Fα. High average fidelity of the teleportation is obtained when the temperature is very low. Under some condition, we also find that when innomogeneity increases to a certain value, the average fidelity can exhibit a larger revival than that for less values of b.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.11074072)the Natural Science Foundation of Hunan Province of China (Grant No.10JJ3088)+1 种基金the Major Program for the Research Foundation of the Education Bureau of Hunan Province of China (Grant No.10A026)the Program for the Research Foundation of the Education Bureau of Hunan Province of China (Grant No.10C0658)
文摘We demonstrate a method to preserve entanglement and improve fidelity of three-qubit quantum states undergoing amplitude-damping decoherence using weak measurement and quantum measurement reversal. It is shown that we are able to enhance entanglement to the greatest extent, and to circumvent entanglement sudden death by increasing the weak measurement strength both for the GHZ state and the W state. The weak measurement technique can also enhance the fidelity to the quantum region and even close to 1 for the whole range of the decoherence parameter in both of the two cases. In addition, the W state can maintain more fidelity than the GHZ state in the protection protocol. However, the GHZ state has a higher success probability than the W state.
基金supported by the National Natural Science Foundation of China(62003280,61976120)Chongqing Talents:Exceptional Young Talents Project(cstc2022ycjh-bgzxm0070)+2 种基金Natural Science Foundation of Chongqing(2022NSCQ-MSX2993)Natural Science Key Foundation of Jiangsu Education Department(21KJA510004)Chongqing Overseas Scholars Innovation Program(cx2022024)。
文摘Fidelity plays an important role in quantum information processing,which provides a basic scale for comparing two quantum states.At present,one of the most commonly used fidelities is Uhlmann-Jozsa(U-J)fidelity.However,U-J fidelity needs to calculate the square root of the matrix,which is not trivial in the case of large or infinite density matrices.Moreover,U-J fidelity is a measure of overlap,which has limitations in some cases and cannot reflect the similarity between quantum states well.Therefore,a novel quantum fidelity measure called quantum Tanimoto coefficient(QTC)fidelity is proposed in this paper.Unlike other existing fidelities,QTC fidelity not only considers the overlap between quantum states,but also takes into account the separation between quantum states for the first time,which leads to a better performance of measure.Specifically,we discuss the properties of the proposed QTC fidelity.QTC fidelity is compared with some existing fidelities through specific examples,which reflects the effectiveness and advantages of QTC fidelity.In addition,based on the QTC fidelity,three discrimination coefficients d_(1)^(QTC),d_(2)^(QTC),and d_^(3)^(QTC)are defined to measure the difference between quantum states.It is proved that the discrimination coefficient d_(3)^(QTC)is a true metric.Finally,we apply the proposed QTC fidelity-based discrimination coefficients to measure the entanglement of quantum states to show their practicability.
基金supported by the Natural Science Foundation of Zhejiang Province,China(Grant No.LY16A050004)the Fundamental Research Funds for the Central Universities,China(Grant No.2017FZA3005)the National Natural Science Foundation of China(Grant No.11475146)
文摘We propose a quantity called modulus fidelity to measure the closeness of two quantum pure states. We use it to investigate the closeness of eigenstates in one-dimensional hard-core bosons. When the system is integrable, eigenstates close to their neighbor or not, which leads to a large fluctuation in the distribution of modulus fidelity. When the system becomes chaos, the fluctuation is reduced dramatically, which indicates all eigenstates become close to each other. It is also found that two kind of closeness, i.e., closeness of eigenstates and closeness of eigenvalues, are not correlated at integrability but correlated at chaos. We also propose that the closeness of eigenstates is the underlying mechanism of eigenstate thermalization hypothesis （ETH） which explains the thermalization in quantum many-body systems.
基金Supported by the Natural Science Foundation of Hunan Province of China under Grant No.10JJ3088Funds of Hunan Education Bureau under Grant No.10C0616the Key Research Foundation of the Education Bureau of Hunan Province under Grant Nos.10A026 and 08A015
文摘In the paper, taking the atomic EPR entanglement of quantum teleportation of atomic state in thermal environment damping-density operator approach, and the average fidelities are channel state ｜φ = （1/√2）（｜00） ＋ ｜11〉） is more robust than ｜φ｜ they are subject to the dissipative environments. states as quantum channel, we investigate the fidelity and vacuum reservoir by means of quantum theory of calculated, the results show that the atomic quantum = （1/√2）（｜01〉 ＋ ｜10〉） in teleportation process when they are subject to the dissipative environments.
基金supported by the National Natural Science Foundation of China (10874091)National Basic Research Program of China (2006CB921205)
文摘The thermodynamic influence of quantum probing on an object is studied.Here,quantum probing is understood to be a pre-measurement based on a non-demolition interaction,which records some information of the probed object but does not change its energy state when both the probing apparatus and the probed object are isolated from the environment.It is argued that when the probing apparatus and the probed object are immersed in the same equilibrium environment,the probing can affect the effective temperature of the object or induce a quantum isothermal process for the object to transfer its energy.This thermodynamic feature can be regarded as a witness of quantum probing.
基金the Special Research Foundation for the Doctoral Program of Higher Education under Grant No.20050285002the Natural Science Foundation of Jiangsu Province under Grant No.04KJB140119
文摘In this paper we study the entanglement in a two-qubit spin in the XYZ model, and teleport a two-qubit entangled state using this spin chain in the condition of the thermal equilibrium as a quantum channel. We investigate the effects of the interaction of z-component Jz, the inhomogeneous magnetic field b, the anisotropy γ and the temperature T on the entanglement and fidelity. In order to characterize the quality of the teleported state, we research the average fidelity Fα. High average fidelity of the teleportation is obtained when the temperature is very low. Under some condition, we also find that when innomogeneity increases to a certain value, the average fidelity can exhibit a larger revival than that for less values of b.
