Decoy state


Decoy state quantum key distribution (QKD) protocol is the most widely implemented QKD scheme.

Origin

In QKD protocols, such as BB84, a single photon source is assumed to be used by the sender, Alice. In reality, a perfect single photon source does not exist. Instead, practical sources, such as weak coherent state laser source, are widely used for QKD. The key problem with these practical QKD sources is the multi-photon components which they contain. A serious security loophole exists when Alice uses multi-photon states as quantum information carriers (see, Quantum key distribution#Photon number splitting attack). In order to minimize the effects of multi-photon states, Alice has to use an extremely weak laser source, which results a relatively low speed of QKD. Decoy state QKD is proposed to solve this multi-photon issue by using a few different photon intensities instead of one. With decoy states, the practical sources, such as coherent-state source or heralded parametric down-conversion (PDC) source, performs almost as well as a single photon source.

Security

The security of decoy state QKD has been proven by Lo, Ma and Chen.[1] In the security proof, a photon number channel model is proposed and an infinite number of decoy states are assumed to be prepared by Alice.

Practical schemes

Later, a practical decoy state QKD scheme with only two decoy states, vacuum+weak, is proposed.[2]

Experimental implementation

The (vacuum+weak) decoy state protocol was firstly experimentally demonstrated in Toronto.[3] This protocol is also demonstrated by a few groups throughout the world.[4][5][6][7]

Decoy-state QKD using non-coherent-state sources

Decoy state QKD protocols with non-coherent-state sources have also been analyzed. Passive decoy state protocol, where the decoy states are prepared passively, is proposed as a parametric down-conversion source.[8][9]

See also

References

  1. ↑ Hoi-Kwong Lo, Xiongfeng Ma, and Kai Chen, "Decoy State Quantum Key Distribution", Physical Review Letters, 94, 230504 (2005)
  2. ↑ Xiongfeng Ma, Bing Qi, Yi Zhao, and Hoi-Kwong Lo, "Practical decoy state for quantum key distribution", Phys. Rev. A 72, 012326 (2005)
  3. ↑ Yi Zhao, Bing Qi, Xiongfeng Ma, Hoi-Kwong Lo, and Li Qian, "Experimental Quantum Key Distribution with Decoy States", Phys. Rev. Lett. 96, 070502 (2006)
  4. ↑ Danna Rosenberg et al., "Long-Distance Decoy-State Quantum Key Distribution in Optical Fiber", Phys. Rev. Lett. 98, 010503 (2007)
  5. ↑ Tobias Schmitt-Manderbach et al., "Experimental Demonstration of Free-Space Decoy-State Quantum Key Distribution over 144 km", Phys. Rev. Lett. 98, 010504 (2007)
  6. ↑ Cheng-Zhi Peng et al., "Experimental Long-Distance Decoy-State Quantum Key Distribution Based on Polarization Encoding", Phys. Rev. Lett. 98, 010505 (2007)
  7. ↑ Z. L. Yuan, A. W. Sharpe, and A. J. Shields, "Unconditionally secure one-way quantum key distribution using decoy pulses", Appl. Phys. Lett. 90, 011118 (2007)
  8. ↑ Yoritoshi Adachi, Takashi Yamamoto, Masato Koashi, and Nobuyuki Imoto, "Simple and Efficient Quantum Key Distribution with Parametric Down-Conversion", Phys. Rev. Lett. 99, 180503 (2007)
  9. ↑ Xiongfeng Ma and Hoi-Kwong Lo, "Quantum key distribution with triggering parametric down-conversion sources", New J. Phys. 10 073018 (2008)

External links

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