title: Security of quantum key distribution with multiphoton components.
abstract: Most qubit-based quantum key distribution (QKD) protocols extract the secure key merely from single-photon component of the attenuated lasers. However, with the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) QKD protocol, the unconditionally secure key can be extracted from the two-photon component by modifying the classical post-processing procedure in the BB84 protocol. Employing the merits of SARG04 QKD protocol and six-state preparation, one can extract secure key from the components of single photon up to four photons. In this paper, we provide the exact relations between the secure key rate and the bit error rate in a six-state SARG04 protocol with single-photon, two-photon, three-photon, and four-photon sources. By restricting the mutual information between the phase error and bit error, we obtain a higher secure bit error rate threshold of the multiphoton components than previous works. Besides, we compare the performances of the six-state SARG04 with other prepare-and-measure QKD protocols using decoy states.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.|The CAS Center for Excellence in QIQP, Synergetic Innovation Center for QIQP, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Hua-Lei
authors.initials: HL
authors.lastname: Yin
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.|The CAS Center for Excellence in QIQP, Synergetic Innovation Center for QIQP, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Fu
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.|The CAS Center for Excellence in QIQP, Synergetic Innovation Center for QIQP, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Yingqiu
authors.initials: Y
authors.lastname: Mao
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.|The CAS Center for Excellence in QIQP, Synergetic Innovation Center for QIQP, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Zeng-Bing
authors.initials: ZB
authors.lastname: Chen