An unsymmetrical quantum key distribution protocol is proposed, in which Greenherger-Horne-Zeilinger （GHZ） triplet states are used to obtain the secret key. Except the lost qubits due to the unperfectness of the phy...An unsymmetrical quantum key distribution protocol is proposed, in which Greenherger-Horne-Zeilinger （GHZ） triplet states are used to obtain the secret key. Except the lost qubits due to the unperfectness of the physical devices, the unsymmetrical characteristic makes all transmitted qubits useful. This leads to：an excellent efficiency, which reaches 100% in an ideal case. The ＇security is studied from the aspect of information theory. By using the correlation of the GHZ tripartite entanglement state, eavesdropping can be easily checked out, which indicates that the presented protocol is more secure.展开更多
I present a new scheme for probabilistic remote preparation of a general two-qubit state from a sender to either of two receivers.The quantum channel is composed of a partial entangled tripartite Greenberger-Horne-Zei...I present a new scheme for probabilistic remote preparation of a general two-qubit state from a sender to either of two receivers.The quantum channel is composed of a partial entangled tripartite Greenberger-Horne-Zeilinger (GHZ) state and a W-type state.I try to realize the remote two-qubit preparation by using the usual projective measurement and the method of positive operator-valued measure,respectively.The corresponding success probabilities of the scheme with different methods as well as the total classical communication cost required in this scheme are also calculated.展开更多
We introduce the three-mode entangled state and set up an experiment to generate it. Then we discuss the three-mode squeezing operator squeezed ｜p, X2, X3〉→μ^-3/2｜p/μ, X2/μ, X3/μ） and the optical implement to...We introduce the three-mode entangled state and set up an experiment to generate it. Then we discuss the three-mode squeezing operator squeezed ｜p, X2, X3〉→μ^-3/2｜p/μ, X2/μ, X3/μ） and the optical implement to realize such a squeezed state. We also reveal that c-number .asymmetric shrink transform in the three-mode entangled state, i.e. ｜p, X2,X3）→μ^-1/2｜p/μ, X2,X3）, maps onto a kind of one-sided three-mode squeezing operator {iλ （∑i^3=1 Pi） （∑i^3=1 Qi） -λ/2}. Using the technique of integration within an ordered product （IWOP） of operators, we derive their normally ordered forms and construct the corresponding squeezed states.展开更多
A four-party scheme is put forward for a sender to partition arbitrary single-qubit information among three receivers by utilizing a class of asymmetric four-qubit W state as quantum channels. In the scheme the sender...A four-party scheme is put forward for a sender to partition arbitrary single-qubit information among three receivers by utilizing a class of asymmetric four-qubit W state as quantum channels. In the scheme the sender＇s quantum information can be recovered by the three receivers if and only if they collaborate together. Specifically, they collaborate to perform first two different 2-qubit collective unitary operations and then a single-qubit unitary operation. The scheme is symmetric and （3, 3）-threshold with regard to the reconstruction, for any receiver can be assigned to conclusively recover the quantum information with the other two＇s assistances.展开更多
This study proposes a new coding function for the symmetric W state. Based on the new coding function, a theoretical protocol of deterministic quanama communication （DQC） is proposed. The sender can use the proposed...This study proposes a new coding function for the symmetric W state. Based on the new coding function, a theoretical protocol of deterministic quanama communication （DQC） is proposed. The sender can use the proposed coding function to encode his/her message, and the receiver can perform the imperfect Bell measurement to obtain the sender＇s message. In comparison to the existing DQC protocols that also use the W class state, the proposed protocol is more efficient and also more practical within today＇s technology. Moreover, the security of this protocol is analyzed to show that any eavesdropper will be detected with a very high probability under both the ideal and the noisy quantum channel.展开更多
Symmetry is conventionally described in a polarized manner that the system is either completely symmetric or completely asymmetric.Using group theoretical approach to overcome this dichotomous problem,we introduce the...Symmetry is conventionally described in a polarized manner that the system is either completely symmetric or completely asymmetric.Using group theoretical approach to overcome this dichotomous problem,we introduce the degree of symmetry(DoS) as a non-negative continuous number ranging from zero to unity.Do S is defined through an average of the fidelity deviations of Hamiltonian or quantum state over its transformation group G,and thus is computable by making use of the completeness relations of the irreducible representations of G.The monotonicity of Do S can effectively probe the extended group for accidental degeneracy while its multi-valued natures characterize some(spontaneous) symmetry breaking.展开更多
We investigate a spin-to-charge conversion mechanism which maps the spin singlet and triplet states to two charge states differing by one electron mediated by an intermediate metastable charge state. This mechanism al...We investigate a spin-to-charge conversion mechanism which maps the spin singlet and triplet states to two charge states differing by one electron mediated by an intermediate metastable charge state. This mechanism allows us to observe fringes in the spin-unblocked region beyond the triplet transition line in the measurement of the exchange oscillations between singlet and triplet states in a four-electron dou- ble quantum dot. Moreover, these fringes are amplified and π-phase shifted, compared with those in the spin blockade region. Unlike the signal enhancement mechanism reported before which produces similar effects, this mechanism only requires one dot coupling to the lead, which is a commonly encountered case especially in imperfect devices. Besides, the crucial tunnel rate asymmetry is provided by the dependence on spin state, not by the asymmetric couplings to the leads. We also design a scheme to control the amplification process, which enables us to extract the relevant time parameters. This mechanism will have potential applications in future investigations of spin qubits.展开更多
基金Research supported by the National Natural Science Foundation of China(10947143)the Natural Science Foundation for Colleges and Universities of Jiangsu Province(09KJB140010)the Doctorial Start-up Fund of Xuzhou Normal University(08XLR02)
基金The project supported by National Natural Science Foundation of China under Grant Nos. 60472018 and 10547125
文摘An unsymmetrical quantum key distribution protocol is proposed, in which Greenherger-Horne-Zeilinger （GHZ） triplet states are used to obtain the secret key. Except the lost qubits due to the unperfectness of the physical devices, the unsymmetrical characteristic makes all transmitted qubits useful. This leads to：an excellent efficiency, which reaches 100% in an ideal case. The ＇security is studied from the aspect of information theory. By using the correlation of the GHZ tripartite entanglement state, eavesdropping can be easily checked out, which indicates that the presented protocol is more secure.
基金Supported by the 211 Project of Anhui University under Grant No.2009QN028B
文摘I present a new scheme for probabilistic remote preparation of a general two-qubit state from a sender to either of two receivers.The quantum channel is composed of a partial entangled tripartite Greenberger-Horne-Zeilinger (GHZ) state and a W-type state.I try to realize the remote two-qubit preparation by using the usual projective measurement and the method of positive operator-valued measure,respectively.The corresponding success probabilities of the scheme with different methods as well as the total classical communication cost required in this scheme are also calculated.
基金Open Foundation of Laboratory of High- Intensity Optics
文摘We introduce the three-mode entangled state and set up an experiment to generate it. Then we discuss the three-mode squeezing operator squeezed ｜p, X2, X3〉→μ^-3/2｜p/μ, X2/μ, X3/μ） and the optical implement to realize such a squeezed state. We also reveal that c-number .asymmetric shrink transform in the three-mode entangled state, i.e. ｜p, X2,X3）→μ^-1/2｜p/μ, X2,X3）, maps onto a kind of one-sided three-mode squeezing operator {iλ （∑i^3=1 Pi） （∑i^3=1 Qi） -λ/2}. Using the technique of integration within an ordered product （IWOP） of operators, we derive their normally ordered forms and construct the corresponding squeezed states.
基金Supported by the Program for New Century Excellent Talents at the University of China under Grant No.NCET-06-0554the National Natural Science Foundation of China under Grant Nos.10975001,60677001,10747146,and 10874122+3 种基金the Science-Technology Fund of Anhui Province for Outstanding Youth under Grant No.06042087the Key Fund of the Ministry of Education of China under Grant No.206063the General Fund of the Educational Committee of Anhui Province under Grant No.2006KJ260Bthe Natural Science Foundation of Guangdong Province under Grant Nos.06300345 and 7007806
文摘A four-party scheme is put forward for a sender to partition arbitrary single-qubit information among three receivers by utilizing a class of asymmetric four-qubit W state as quantum channels. In the scheme the sender＇s quantum information can be recovered by the three receivers if and only if they collaborate together. Specifically, they collaborate to perform first two different 2-qubit collective unitary operations and then a single-qubit unitary operation. The scheme is symmetric and （3, 3）-threshold with regard to the reconstruction, for any receiver can be assigned to conclusively recover the quantum information with the other two＇s assistances.
基金supported by the National Science Council of the Republic of China(Grant No.NSC 98-2221-E-006-097-MY3)
文摘This study proposes a new coding function for the symmetric W state. Based on the new coding function, a theoretical protocol of deterministic quanama communication （DQC） is proposed. The sender can use the proposed coding function to encode his/her message, and the receiver can perform the imperfect Bell measurement to obtain the sender＇s message. In comparison to the existing DQC protocols that also use the W class state, the proposed protocol is more efficient and also more practical within today＇s technology. Moreover, the security of this protocol is analyzed to show that any eavesdropper will be detected with a very high probability under both the ideal and the noisy quantum channel.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11421063,11534002,11475254the National 973Program under Grant Nos.2014CB921403,2012CB922104,and 2014CB921202
文摘Symmetry is conventionally described in a polarized manner that the system is either completely symmetric or completely asymmetric.Using group theoretical approach to overcome this dichotomous problem,we introduce the degree of symmetry(DoS) as a non-negative continuous number ranging from zero to unity.Do S is defined through an average of the fidelity deviations of Hamiltonian or quantum state over its transformation group G,and thus is computable by making use of the completeness relations of the irreducible representations of G.The monotonicity of Do S can effectively probe the extended group for accidental degeneracy while its multi-valued natures characterize some(spontaneous) symmetry breaking.
基金supported by the National Key Research and Development Program (2016YFA0301700)the National Natural Science Foundation of China (11674300, 11304301, 11575172,61674132, and 91421303)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (XDB01030000)the Fundamental Research Fund for the Central UniversitiesThis work was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication
文摘We investigate a spin-to-charge conversion mechanism which maps the spin singlet and triplet states to two charge states differing by one electron mediated by an intermediate metastable charge state. This mechanism allows us to observe fringes in the spin-unblocked region beyond the triplet transition line in the measurement of the exchange oscillations between singlet and triplet states in a four-electron dou- ble quantum dot. Moreover, these fringes are amplified and π-phase shifted, compared with those in the spin blockade region. Unlike the signal enhancement mechanism reported before which produces similar effects, this mechanism only requires one dot coupling to the lead, which is a commonly encountered case especially in imperfect devices. Besides, the crucial tunnel rate asymmetry is provided by the dependence on spin state, not by the asymmetric couplings to the leads. We also design a scheme to control the amplification process, which enables us to extract the relevant time parameters. This mechanism will have potential applications in future investigations of spin qubits.
