US 12,225,118 B2
Method for securely transmitting sequences of quantum states between a plurality of online participants over a quantum communication channel
Marc Kaplan, Montrouge (FR); and George Harder, Paris (FR)
Assigned to VERIQLOUD, Montrouge (FR)
Appl. No. 17/640,763
Filed by VERIQLOUD, Montrouge (FR)
PCT Filed Sep. 3, 2020, PCT No. PCT/EP2020/074576
§ 371(c)(1), (2) Date Mar. 4, 2022,
PCT Pub. No. WO2021/043891, PCT Pub. Date Mar. 11, 2021.
Claims priority of application No. 1909839 (FR), filed on Sep. 6, 2019.
Prior Publication US 2022/0311604 A1, Sep. 29, 2022
Int. Cl. H04L 9/08 (2006.01)
CPC H04L 9/0858 (2013.01) [H04L 9/0855 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A method for securely transmitting a sequence of Q quantum states qq encoded in the form of a sequence of Q photons, q being an integer comprised between 1 and Q, between a first participant (Ci) and a second participant (Cj), selected amongst a plurality of N distinct participants (C1), . . . (Ci), . . . (Cj), . . . (CN) of the same quantum communication channel forming a communication chain between an emitter (C1) and a receiver (CN), where N is an integer greater than or equal to 3, wherein the first participant (Ci) is located upstream of the second participant (Cj) in the communication chain and wherein the first participant (Ci) is different from the emitter (C1) and/or the second participant (Ci) is different from the receiver (CN), said method comprising, in order:
the succession of the following steps, repeated from q=1 to Q:
a first action performed by the emitter (C1) comprising the preparation by the emitter (C1) of a photon in a start quantum state |u> of an orthonormal encoding base Ba with a dimension d and of base states |e0>, |e1>, . . . |ed-1>, with a randomly chosen between 0 and 1,
transmission of the prepared photon in the communication chain,
a second action performed by the first participant (Ci) on said photon, of decision of transformation or not of the quantum state of the transmitted photon, in an orthogonal base quantum state in the encoding base B0 and in the encoding base B1
a third action performed by the second participant (Cj) on said photon, of decision of transformation or not of the quantum state of the photon received from the immediately preceding participant (Cj-1) into a corresponding orthogonal quantum state in the encoding base B0 and in the encoding base B1
a fourth action performed by the receiver (CN) comprising the measurement, in the standard base B0 or in the base B1, of the final state |alphafinal> of the photon transmitted in the communication chain by the receiver (CN),
exchanges on a conventional communication channel between at least part of the participants, at least part of the decisions among those of the start base a, of the start state |u>, of the measurement base chosen by said receiver (CN) and the result of the measurement of |alphafinal> in this measurement base,
obtaining, between the first and second participants (Ci) and (Cj), a description of the transmitted quantum state qq corresponding to one of the base states |e0>, |e1>, . . . |ed−1>, thanks to said part of the decisions and said result of the measurement;
then, the reconstitution, by the first and second participants (Ci) and (Cj), by concatenation, of a sequence of the descriptions of the transmitted Q quantum states qq, for q ranging from 1 to Q.