US 12,136,020 B2
High-fidelity entangled link generation method based on quantum time-space
Rigui Zhou, Shanghai (CN); Ruiqing Xu, Shanghai (CN); and Yaochong Li, Shanghai (CN)
Assigned to Shanghai Maritime University, Shanghai (CN)
Filed by Shanghai Maritime University, Shanghai (CN)
Filed on Jun. 6, 2023, as Appl. No. 18/329,952.
Claims priority of application No. 202210871284.6 (CN), filed on Jul. 22, 2022.
Prior Publication US 2024/0338588 A1, Oct. 10, 2024
Int. Cl. G06N 10/40 (2022.01); B82Y 20/00 (2011.01); G01B 9/02 (2022.01); H01Q 1/46 (2006.01); H04B 10/70 (2013.01); H04W 72/0453 (2023.01)
CPC G06N 10/40 (2022.01) [B82Y 20/00 (2013.01); G01B 9/02048 (2013.01); H01Q 1/46 (2013.01); H04B 10/70 (2013.01); H04W 72/0453 (2013.01)] 5 Claims
OG exemplary drawing
 
1. An elementary entangled link generation method based on quantum time-space, comprising:
S101, directing, by a communication provider, a laser beam to a nonlinear crystal, thereby enabling probabilistically bursting out of a photon beam, polarizing the photon beam to be in an entangled state, and completing the preparation of a polarized entangled photon pair by the communication provider;
S102, at an entanglement distribution stage, transmitting a first photon of an EPR entanglement source by the communication provider to the first communication node through a quantum trajectory, while transmitting a second photon to the second communication node through a quantum trajectory; by using a quantum switch to simulate each quantum trajectory, the distributed entangled photon state ρABQ between the first communication node and the second communication node is represented in the following form:

OG Complex Work Unit Math
wherein the given |Ψ1<AB is the initial polarized entangled photon pair prepared by the communication provider, which is now distributed to the first communication node A and the second communication node B,

OG Complex Work Unit Math
 |00custom character and |11custom character are ground states of two particles, and the ground states of the two particles are uniformly superposed to form a maximum entangled state of the two particles; A1=(1−p)(1−q), B1=(1−p)q, C1=p(1−q), D1=pq; Ψi=|Ψicustom charactercustom characterΨi|, and |Ψ2custom character=(|00custom character+|11custom character)/√2, |Ψ3custom character=(|01custom character+|10custom character)/√2, |Ψ4custom character=(|01custom character−|10custom character)/√2, p, q are respectively error probabilities of a qubit flip channel and a quantum phase flip channel; and
S103, after an elementary entangled link is generated between the two communication nodes, owing to the entangled state distributed between two communication nodes determined by control qubit, requiring the first communication node or the second communication node to select the same measurement basis for m control qubits CAi or C_Bi, i={1,2, . . . , m} when assuming m copies of entangled photon pairs from entanglement source are distributed through quantum trajectories to communication nodes with the time interval T, such that 2m memory qubits (M_Ai, M_Bi) of two adjacent nodes may store m exactly the same distributed entangled states.