In this paper, the theoretical investigation of remote preparation of an entangledstate is studied in nonideal conditions. Our studies include two parts. In the first part, we consider the remote state preparation （...In this paper, the theoretical investigation of remote preparation of an entangledstate is studied in nonideal conditions. Our studies include two parts. In the first part, we consider the remote state preparation （RSP） of an entangled state through two equally noisy quantum channel states, namely, a mixture of Bell states. Studies show there is a particular mixed-state channel for which all pure entangled states remain entangled after this inexact RSP. In the second part, we suppose that noises which quantum channels suffer from can be expressed as the Lindblad operators. The master equation of the system can be expressed in the Lindblad form. Through solving the master equation, we calculate the fidelity as a function of decoherence rates and parameters of the state to be prepared. For a given entangled state, we investigate the influence of different types of noises on the fidelity.展开更多
A scheme for teleporting an arbitrary n-bit one-photon and vacuum entangled Greenberger-Horne-Zeilinger （GHZ） state is proposed. In this scheme, the maximum entanglement GHZ state is used as a quantum channel. We fi...A scheme for teleporting an arbitrary n-bit one-photon and vacuum entangled Greenberger-Horne-Zeilinger （GHZ） state is proposed. In this scheme, the maximum entanglement GHZ state is used as a quantum channel. We find a method of distinguishing four Bell states just by detecting the atomic states three times, which is irrelevant to the qubit number of the state to be teleported.展开更多
Due to the ubiquitous open air links and complex electromagnetic environment in the satellite communications,how to ensure the security and reliability of the information through the satellite communications is an urg...Due to the ubiquitous open air links and complex electromagnetic environment in the satellite communications,how to ensure the security and reliability of the information through the satellite communications is an urgent problem.This paper combines the AES(Advanced Encryption Standard) with LDPC(Low Density Parity Check Code) to design a secure and reliable error correction method — SEEC(Satellite Encryption and Error Correction).This method selects the LDPC codes,which is suitable for satellite communications,and uses the AES round key to control the encoding process,at the same time,proposes a new algorithm of round key generation.Based on a fairly good property in error correction in satellite communications,the method improves the security of the system,achieves a shorter key size,and then makes the key management easier.Eventually,the method shows a great error correction capability and encryption effect by the MATLAB simulation.展开更多
The spin ladder with Dzyaloshinsky-Moriya interaction is investigated by using the quantum renormalization-group method.The entanglement and fidelity are periodic functions of the time and oscillate between zero and o...The spin ladder with Dzyaloshinsky-Moriya interaction is investigated by using the quantum renormalization-group method.The entanglement and fidelity are periodic functions of the time and oscillate between zero and one.The oscillation period decreases with either the interaction in the spin ladder or the Dzyaloshinsky-Moriya interaction increasing.When the system relates to the environment,both entanglement and fidelity oscillate with a damping rate related to intrinsic decoherence rate,the interaction in the spin ladder,and the Dzyaloshinsky-Moriya interaction.展开更多
In this paper, the two-mode excited squeezed vacuum state （TESVS） is studied by using the statistical method. By calculating the normalization of the TESVS, a new form of Jacobi polynomials and some new identities a...In this paper, the two-mode excited squeezed vacuum state （TESVS） is studied by using the statistical method. By calculating the normalization of the TESVS, a new form of Jacobi polynomials and some new identities are obtained. The photon number distribution of the TESVS is given and it is a simple form of Jacobi polynomials. Using the entangled state representation of Wigner operator, the Wigner function of the TESVS is obtainded and the variations of the Wigner function with the parameters m, n, and r are discussed. Here from the phase space point of view the TESVS can be well interpreted and described.展开更多
We investigate the influence of the Stark shift on the entanglement transfer from the two-mode squeezed vacuum state field to two spatially separated atoms in two-photon processes. Our results show that the Stark shif...We investigate the influence of the Stark shift on the entanglement transfer from the two-mode squeezed vacuum state field to two spatially separated atoms in two-photon processes. Our results show that the Stark shift plays an important role in such entanglement transfer. We find that when the Stark shift parameter r is small, the degree of entanglement between the two atoms increases with the increasing of the squeezing parameter ξ first, and after achieving its maximal value, the degree of entanglement will decrease to zero with the increasing of ξ; while for big r, E will increase with the increasing of ξ.展开更多
Using multipohton Tavis-Cummings model,the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity.The influences of coupli...Using multipohton Tavis-Cummings model,the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity.The influences of coupling constants between atoms,the atomic initial states and the photon number of transition on the entanglement evolution of two coupling two-level atoms are discussed.The results obtained using the numerical method show that the entanglement of two atoms is related with coupling constants between atoms,the atomic initial states and the photon number of transition.The two-atom entanglement state will forever stay in the maximum entanglement state when the initial state is β11〉.When the initial state of two atoms is β01〉,the entanglement of two atoms displays periodic oscillation behavior.And its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.On the other hand,when the initial state is β00〉 or β10〉,the entanglement of two atoms displays quasiperiodic oscillation behavior and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.展开更多
The q-deformed entangled states are introduced by using deformation quantization methods and new normal ordering of the vacuum projection operator for q-deformed boson oscillator. In similar way, by virtue of the tech...The q-deformed entangled states are introduced by using deformation quantization methods and new normal ordering of the vacuum projection operator for q-deformed boson oscillator. In similar way, by virtue of the technique of integration within an ordered product （IWOP） of operators, the new completeness and orthogonMity relations composed of the bra and ket, which are not mutually Hermitian conjugates are obtained. Furthermore, the property of squeezing operator represented by the q-deformed entangled states is exhibited. Lastly, the nonclassical properties of the q-deformed two-mode squeezed vacuum state are studied.展开更多
Entanglement purification is to distill high-quality entangled states from low-quality entangled states.It is a key step in quantum repeaters,determines the efficiency and communication rates of quantum communication ...Entanglement purification is to distill high-quality entangled states from low-quality entangled states.It is a key step in quantum repeaters,determines the efficiency and communication rates of quantum communication protocols,and is hence of central importance in long-distance communications and quantum networks.In this work,we report the first experimental demonstration of deterministic entanglement purification using polarization and spatial mode hyperentanglement.After purification,the fidelity of polarization entanglement arises from 0.268±0.002 to 0.989±0.001.Assisted with robust spatial mode entanglement,the total purification efficiency can be estimated as 10^(9) times that of the entanglement purification protocols using two copies of entangled states when one uses the spontaneous parametric down-conversion sources.Our work may have the potential to be implemented as a part of full repeater protocols.展开更多
After the development trend of high-speed long-haul optical communication systems and the theory of the concatenated code are analyzed,the comparative researches on the performances of the two concatenated codes of th...After the development trend of high-speed long-haul optical communication systems and the theory of the concatenated code are analyzed,the comparative researches on the performances of the two concatenated codes of the inner-outer type and the improved interleaving type are performed in detail.The theoretical analyses and simulation results show that the inner-outer type concatenated code has the greater redundancy,and the improved interleaving type concatenated code is a superior concatenated code with the advantages of the better error correction performance,moderate redundancy and easy implementation.As a result,the improved interleaving type concatenated code can be better used in high-speed long-haul optical communication systems.展开更多
In this article, we derive the explicit entanglement and fidelity expressions for a larger class of two-qubit states, namely, a seven-parameter family of so ca^led X-states. The ana/ytical expressions of the entanglem...In this article, we derive the explicit entanglement and fidelity expressions for a larger class of two-qubit states, namely, a seven-parameter family of so ca^led X-states. The ana/ytical expressions of the entanglement, the output entanglement and the average fidelity are obtained for this genera/model by using the concept of concurrence and average fidelity. We study the relations between quantum entanglement, the output entanglement, and the average fidelity for standard teleportation of one-qubit and partial teleportation of two-qubit state. We discover that the average fidelity and entanglement is not a simple dependence relation. The higher entangled system is helpful for teleportation.展开更多
By means of the reduced-density linear entropy, we investigate the properties of dynamical entanglement of vibrations in integrable dimer and realistic small molecules which are initially in the two-mode squeezed vacu...By means of the reduced-density linear entropy, we investigate the properties of dynamical entanglement of vibrations in integrable dimer and realistic small molecules which are initially in the two-mode squeezed vacuum state. It is found that the entropy of the integrable dimer is periodic for weak coupling strength cl and small squeezing parameter r, and there exists a beat phenomenon for strong el and large r. Moreover, the entropy of the small molecules is quasi-periodic for small r, ＆nd the begt phenomenon occurs in the entropy evolution of the two molecules C2D2 and S02 for large r. Our results might be used for molecular quantum computing based on vibrational states.展开更多
In this paper, we propose a scheme to generate an entangled state between two spatially separated movable mirrors by injecting the two-mode squeezed optical reservoir to the dissipative optomechanics, in which the mov...In this paper, we propose a scheme to generate an entangled state between two spatially separated movable mirrors by injecting the two-mode squeezed optical reservoir to the dissipative optomechanics, in which the movable mirrors can modulate the linewidth of the cavity modes. When the coupling between the mirrors and the corresponding cavity modes is weak, the two driven cavity fields can respectively behave as the squeezed-vacuum reservoir for the two movable mirrors by utilizing the effect of completely destructive interference of quantum noise. Thus the mechanical modes are prepared in a two-mode squeezed vacuum state. Moreover,when the coupling between the two mirrors and the cavities modes is strong, the entanglement between the two movable mirrors decreases because photonic excitation can preclude the completely destructive interference of quantum noise, but the movable mirrors are still entangled.展开更多
基金The project partially supported by National Natural Science Foundation of China under Grant Nos. 90103026 and 60478029 . We would like to acknowledge useful discussions with Prof. Wu Ying.
文摘In this paper, the theoretical investigation of remote preparation of an entangledstate is studied in nonideal conditions. Our studies include two parts. In the first part, we consider the remote state preparation （RSP） of an entangled state through two equally noisy quantum channel states, namely, a mixture of Bell states. Studies show there is a particular mixed-state channel for which all pure entangled states remain entangled after this inexact RSP. In the second part, we suppose that noises which quantum channels suffer from can be expressed as the Lindblad operators. The master equation of the system can be expressed in the Lindblad form. Through solving the master equation, we calculate the fidelity as a function of decoherence rates and parameters of the state to be prepared. For a given entangled state, we investigate the influence of different types of noises on the fidelity.
基金Project supported by the Natural Science Foundation of Henan Province, China （Grant No 0511010600） and the Education Department of Henan Province, China （Grant No 2006140005）.
文摘A scheme for teleporting an arbitrary n-bit one-photon and vacuum entangled Greenberger-Horne-Zeilinger （GHZ） state is proposed. In this scheme, the maximum entanglement GHZ state is used as a quantum channel. We find a method of distinguishing four Bell states just by detecting the atomic states three times, which is irrelevant to the qubit number of the state to be teleported.
基金supported by the National 863 Project of China under Grant No.2012AA01A509,No.2012AA120800
文摘Due to the ubiquitous open air links and complex electromagnetic environment in the satellite communications,how to ensure the security and reliability of the information through the satellite communications is an urgent problem.This paper combines the AES(Advanced Encryption Standard) with LDPC(Low Density Parity Check Code) to design a secure and reliable error correction method — SEEC(Satellite Encryption and Error Correction).This method selects the LDPC codes,which is suitable for satellite communications,and uses the AES round key to control the encoding process,at the same time,proposes a new algorithm of round key generation.Based on a fairly good property in error correction in satellite communications,the method improves the security of the system,achieves a shorter key size,and then makes the key management easier.Eventually,the method shows a great error correction capability and encryption effect by the MATLAB simulation.
基金Supported by the National Natural Science Foundation of China under Grant No.11074184the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The spin ladder with Dzyaloshinsky-Moriya interaction is investigated by using the quantum renormalization-group method.The entanglement and fidelity are periodic functions of the time and oscillate between zero and one.The oscillation period decreases with either the interaction in the spin ladder or the Dzyaloshinsky-Moriya interaction increasing.When the system relates to the environment,both entanglement and fidelity oscillate with a damping rate related to intrinsic decoherence rate,the interaction in the spin ladder,and the Dzyaloshinsky-Moriya interaction.
基金The project supported by National Natural Science Foundation of China under Grant No.10574060the Natural Science Foundation of Shandong Province of China under Grant No.Y2004A09
文摘In this paper, the two-mode excited squeezed vacuum state （TESVS） is studied by using the statistical method. By calculating the normalization of the TESVS, a new form of Jacobi polynomials and some new identities are obtained. The photon number distribution of the TESVS is given and it is a simple form of Jacobi polynomials. Using the entangled state representation of Wigner operator, the Wigner function of the TESVS is obtainded and the variations of the Wigner function with the parameters m, n, and r are discussed. Here from the phase space point of view the TESVS can be well interpreted and described.
基金The project supported by National Natural Science Foundation of China under Grant No.10374007
文摘We investigate the influence of the Stark shift on the entanglement transfer from the two-mode squeezed vacuum state field to two spatially separated atoms in two-photon processes. Our results show that the Stark shift plays an important role in such entanglement transfer. We find that when the Stark shift parameter r is small, the degree of entanglement between the two atoms increases with the increasing of the squeezing parameter ξ first, and after achieving its maximal value, the degree of entanglement will decrease to zero with the increasing of ξ; while for big r, E will increase with the increasing of ξ.
基金Supported by the Natural Science Foundation of Fujian Province under Grant (No.2008J0217)
文摘Using multipohton Tavis-Cummings model,the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity.The influences of coupling constants between atoms,the atomic initial states and the photon number of transition on the entanglement evolution of two coupling two-level atoms are discussed.The results obtained using the numerical method show that the entanglement of two atoms is related with coupling constants between atoms,the atomic initial states and the photon number of transition.The two-atom entanglement state will forever stay in the maximum entanglement state when the initial state is β11〉.When the initial state of two atoms is β01〉,the entanglement of two atoms displays periodic oscillation behavior.And its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.On the other hand,when the initial state is β00〉 or β10〉,the entanglement of two atoms displays quasiperiodic oscillation behavior and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.
文摘The q-deformed entangled states are introduced by using deformation quantization methods and new normal ordering of the vacuum projection operator for q-deformed boson oscillator. In similar way, by virtue of the technique of integration within an ordered product （IWOP） of operators, the new completeness and orthogonMity relations composed of the bra and ket, which are not mutually Hermitian conjugates are obtained. Furthermore, the property of squeezing operator represented by the q-deformed entangled states is exhibited. Lastly, the nonclassical properties of the q-deformed two-mode squeezed vacuum state are studied.
基金supported by the National Key Research and Development Program of China(2021YFE0113100 and 2017YFA0304100)the National Natural Science Foundation of China(11774335,11734015,11874345,11821404,11904357,11974189,12174367,and 12175106)+4 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS,QYZDYSSW-SLH003)Science Foundation of the CAS(ZDRW-XH-2019-1)the Fundamental Research Funds for the Central UniversitiesUSTC Tang ScholarshipScience and Technological Fund of Anhui Province for Outstanding Youth(2008085J02)。
文摘Entanglement purification is to distill high-quality entangled states from low-quality entangled states.It is a key step in quantum repeaters,determines the efficiency and communication rates of quantum communication protocols,and is hence of central importance in long-distance communications and quantum networks.In this work,we report the first experimental demonstration of deterministic entanglement purification using polarization and spatial mode hyperentanglement.After purification,the fidelity of polarization entanglement arises from 0.268±0.002 to 0.989±0.001.Assisted with robust spatial mode entanglement,the total purification efficiency can be estimated as 10^(9) times that of the entanglement purification protocols using two copies of entangled states when one uses the spontaneous parametric down-conversion sources.Our work may have the potential to be implemented as a part of full repeater protocols.
基金supported by the National Natural Science Foundation of China (Nos.61071117 and 61003256)the Natural Science Foundation of CQ CSTC (No.2010BB2409)the Science and Technology Foundation of Chongqing Municipal Education Commission (No.KJ110519)
文摘After the development trend of high-speed long-haul optical communication systems and the theory of the concatenated code are analyzed,the comparative researches on the performances of the two concatenated codes of the inner-outer type and the improved interleaving type are performed in detail.The theoretical analyses and simulation results show that the inner-outer type concatenated code has the greater redundancy,and the improved interleaving type concatenated code is a superior concatenated code with the advantages of the better error correction performance,moderate redundancy and easy implementation.As a result,the improved interleaving type concatenated code can be better used in high-speed long-haul optical communication systems.
基金Supported by the Youth Foundation of Institute of Science under Grant Nos. QN-SL-2010-01,QN-SL-2010-10Pre-Research Foundation of PLA University of Science and Technology under Grant Nos. 20110515 and 20110101
文摘In this article, we derive the explicit entanglement and fidelity expressions for a larger class of two-qubit states, namely, a seven-parameter family of so ca^led X-states. The ana/ytical expressions of the entanglement, the output entanglement and the average fidelity are obtained for this genera/model by using the concept of concurrence and average fidelity. We study the relations between quantum entanglement, the output entanglement, and the average fidelity for standard teleportation of one-qubit and partial teleportation of two-qubit state. We discover that the average fidelity and entanglement is not a simple dependence relation. The higher entangled system is helpful for teleportation.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11174081,11034002,11104075,60708003,and 11134003the National Basic Research Program of China under Grant Nos.2011CB921602 and 2012CB821302
文摘By means of the reduced-density linear entropy, we investigate the properties of dynamical entanglement of vibrations in integrable dimer and realistic small molecules which are initially in the two-mode squeezed vacuum state. It is found that the entropy of the integrable dimer is periodic for weak coupling strength cl and small squeezing parameter r, and there exists a beat phenomenon for strong el and large r. Moreover, the entropy of the small molecules is quasi-periodic for small r, ＆nd the begt phenomenon occurs in the entropy evolution of the two molecules C2D2 and S02 for large r. Our results might be used for molecular quantum computing based on vibrational states.
基金supported by the National Natural Science Foundation of China(Grant Nos.61275123,11474119 and 11304024)the National Basic Research Program of China(Grant No.2012CB921602)
文摘In this paper, we propose a scheme to generate an entangled state between two spatially separated movable mirrors by injecting the two-mode squeezed optical reservoir to the dissipative optomechanics, in which the movable mirrors can modulate the linewidth of the cavity modes. When the coupling between the mirrors and the corresponding cavity modes is weak, the two driven cavity fields can respectively behave as the squeezed-vacuum reservoir for the two movable mirrors by utilizing the effect of completely destructive interference of quantum noise. Thus the mechanical modes are prepared in a two-mode squeezed vacuum state. Moreover,when the coupling between the two mirrors and the cavities modes is strong, the entanglement between the two movable mirrors decreases because photonic excitation can preclude the completely destructive interference of quantum noise, but the movable mirrors are still entangled.
