Yong-gang Tan

Louyang Normal University, Luoyang, Yunnan, China

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Publications (9)17.82 Total impact

  • Yao-Hua Hu, Yong-Gang Tan
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    ABSTRACT: By considering a double Jaynes–Cummings (JC) model with linear modulation of the atom-field coupling coefficients, we investigate the entanglement evolution between two atoms, and focuss on the effect of the linear sweep on the entanglement. The results show that the entanglement is very sensitive to the linear modulation of the atom-field coupling coefficients. Both for one-photon processes and for two-photon processes, the disappearance of the initial entanglement is delayed due to the linear modulation as compared to the double standard JC model, and the delayed time is long or short depending on the value of the parameters in the modulation function. Moreover, the entanglement of the two atoms in the double standard JC model disappears periodically. However, this periodicity is completely lost in the linear modulation case. In addition, the larger the photon numbers in the cavities, the shorter the delayed time of the disappearance of the initial entanglement.
    Physica Scripta 06/2014; 89(7):075103. DOI:10.1088/0031-8949/89/7/075103 · 1.30 Impact Factor
  • Yong-gang Tan, Yao-Hua Hu, Qiang Liu, Hua Lu
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    ABSTRACT: Consider a system prepared in one of the quantum states of the ensemble {ρ i } with a priori probability p i . We prove that the quantum state can be deterministically distinguished if and only if the information gain from the measurement reaches the Holevo bound. We find it can be applied to distinguish spatially separated Bell states. A single copy of spatially separated Bell state cannot be distinguished under local operation and classical communication (LOCC), but it can be identified with an ancillary qubit. When two ancillary qubits are used, a spatially separated Bell state can be identified without demolition.
    International Journal of Theoretical Physics 03/2014; 53(3). DOI:10.1007/s10773-013-1897-4 · 1.19 Impact Factor
  • Yong-gang Tan, Qiang Liu, Yao-Hua Hu, Hua Lu
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    ABSTRACT: Freedom to choose the input parameters in Bell tests had not attracted much attention until T. Scheidl et al. pointed out the possible freedom-of-choice loophole that can make the Bell violation be interpreted by local realism (Proc. Natl. Acad. Sci. 107, 19708 (2010)). They claimed that this loophole could be closed by truely random setting choices, thus the deterministic local realism is excluded. In this paper, however, we raise the improved argument that random setting choices alone are not enough in closing the freedom-of-choice loophole. A deterministic local realism model based on this loophole will be proposed. In this model, we will prove that Bell violation with random setting choices is efficient in rejecting this local realism in ideal condition, but it can still exist when inefficient detectors (efficiency η ≤ 50 %) are used.
    International Journal of Theoretical Physics 02/2014; 53(7). DOI:10.1007/s10773-014-2040-x · 1.19 Impact Factor
  • Yong-Gang Tan, Qiang Liu, Yao-Hua Hu, Hua Lu
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    ABSTRACT: In this paper, we will explore the essence of the phenomenon that state with less entanglement may generate greater Bell violation in the two-qubit Bell tests with CH-type inequalities, i.e., more nonlocality with less entanglement. We will show that this interesting but counterintuitive phenomenon is caused by the rotational asymmetry of the nonmaximally entangled state in the measurement plane. This asymmetry allows the both-side detection probabilities and the one-side detection probabilities obtain their maximal values with nonmaximally entangled state. But the maximal Bell violation may not always happen on nonmaximally entangled state, because these probabilities will compete with each other, and the Bell violation behaves differently for various CH-type inequalities.
    Communications in Theoretical Physics 12/2013; 61(1). DOI:10.1088/0253-6102/61/1/07 · 1.05 Impact Factor
  • Yong-gang Tan, Hua Lu, Qing-yu Cai
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    ABSTRACT: A Comment on the Letter by Michel Boyer, Dan Kenigsberg, and Tal Mor, [Phys. Rev. Lett. 99, 140501 (2007)10.1103/PhysRevLett.99.140501]. The authors of the Letter offer a Reply.
    Physical Review Letters 04/2009; 102(9):098901; author reply 098902. DOI:10.1103/PhysRevLett.102.098901 · 7.73 Impact Factor
  • Yong-Gang Tan, Qing-Yu Cai, Ting-Yun Shi
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    ABSTRACT: This paper proves that it is impossible to identify orthogonally time-separated Bell states. If two qubits of A Bell state interact with the measurement apparatus at different time, any attempt to identify this state will disturb it.
    Chinese Physics B 09/2008; 17(9):3194-3197. DOI:10.1088/1674-1056/17/9/007 · 1.39 Impact Factor
  • Source
    Yong-gang Tan, Qing-yu Cai
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    ABSTRACT: Classical communications are used in the post-processing procedure of quantum key distribution. Since the security of quantum key distribution is based on the principles of quantum mechanics, intuitively the secret key can only be derived from the quantum states. We find that classical communications are incorrectly used in the so-called quantum dialogue type protocols. In these protocols, public communications are used to transmit secret messages. Our calculations show that half of Alice's and Bob's secret message is leaked through classical channel. By applying Holevo bound, we can see that the quantum efficiency claimed in the quantum dialogue type of protocols is not achievable.
    International Journal of Quantum Information 03/2008; 6(2). DOI:10.1142/S021974990800344X · 0.99 Impact Factor
  • Qing-yu Cai, Yong-gang Tan
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    ABSTRACT: In this paper, a photon-number-resolving decoy-state quantum key distribution (QKD) scheme is presented based on recent experimental advancements. A new upper bound on the fraction of counts caused by multiphoton pulses is given, which seems inherent as long as weak coherent sources and high lossy channel are used. This implies that our scheme is optimal in long-distance QKD with weak coherent sources. We show that Eve’s coherent multiphoton pulse (CMP) attack is more efficient than a symmetric individual attack when the quantum bit error rate is small, so that the CMP attack should be considered to ensure the security of the final key. Our results show that a not-so-weak pulse can be used to transmit the key. Optimal intensity of the laser source is presented which provides a 23.9 km increase in the transmission distance.
    Physical Review A 03/2006; 73(3). DOI:10.1103/PhysRevA.73.032305 · 2.99 Impact Factor
  • Source
    Qing-yu Cai, Yong-gang Tan
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    ABSTRACT: In this paper, a photon-number-resolving decoy state quantum key distribution scheme is presented based on recent experimental advancements. A new upper bound on the fraction of counts caused by multiphoton pulses is given. This upper bound is independent of intensity of the decoy source, so that both the signal pulses and the decoy pulses can be used to generate the raw key after verified the security of the communication. This upper bound is also the lower bound on the fraction of counts caused by multiphoton pulses as long as faint coherent sources and high lossy channels are used. We show that Eve's coherent multiphoton pulse (CMP) attack is more efficient than symmetric individual (SI) attack when quantum bit error rate is small, so that CMP attack should be considered to ensure the security of the final key. finally, optimal intensity of laser source is presented which provides 23.9 km increase in the transmission distance. 03.67.Dd

Publication Stats

58 Citations
17.82 Total Impact Points

Institutions

  • 2009–2014
    • Louyang Normal University
      Luoyang, Yunnan, China
  • 2008
    • Chinese Academy of Sciences
      • Graduate School
      Peping, Beijing, China
  • 2006–2008
    • Wuhan Institute of Physics and Mathematics
      Wu-han-shih, Hubei, China