US 12,074,970 B2
Quantum key distribution method, device, and system
Jeonghwan Shin, Seoul (KR); Kyung-Woon Lee, Seoul (KR); and Min Soo Lee, Gyeonggi-do (KR)
Assigned to KT CORPORATION, Gyeonggi-do (KR)
Appl. No. 17/615,375
Filed by KT CORPORATION, Gyeonggi-do (KR)
PCT Filed Jun. 17, 2020, PCT No. PCT/KR2020/007846
§ 371(c)(1), (2) Date Nov. 30, 2021,
PCT Pub. No. WO2020/256408, PCT Pub. Date Dec. 24, 2020.
Claims priority of application No. 10-2019-0071799 (KR), filed on Jun. 17, 2019; and application No. 10-2019-0120521 (KR), filed on Sep. 30, 2019.
Prior Publication US 2022/0231845 A1, Jul. 21, 2022
Int. Cl. H04L 9/08 (2006.01); G02B 5/30 (2006.01); G02B 27/28 (2006.01); H04B 10/532 (2013.01); H04B 10/70 (2013.01)
CPC H04L 9/0858 (2013.01) [G02B 5/3025 (2013.01); G02B 27/283 (2013.01); H04B 10/532 (2013.01); H04B 10/70 (2013.01); H04L 9/0827 (2013.01); G02B 27/286 (2013.01); H04L 9/0852 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A quantum key distribution system for distributing a quantum cryptographic key to a transmitter and a receiver, the quantum key distribution system comprising:
the transmitter configured to split an optical signal into a first optical signal passing through a first path (P1) and a second optical signal passing through a second path (P2), which is longer than the first path (P1), and to sequentially transmit the first optical signal and the second optical signal; and
the receiver configured to receive the first optical signal and the second optical signal incident through a quantum channel and transmit the first optical signal and the second optical signal back to the transmitter passing through the quantum channel after passing through a polarization-dependent element, being reflected by a Faraday mirror, and passing through the polarization-dependent element again,
wherein a difference (dL=LP2−LP1) between a length (LP1) of the first path (P1) and a length (LP2) of the second path (P2) in the transmitter is equal to or greater than twice a distance (=D) between the polarization-dependent element and the Faraday mirror (dL>2D).