Continuous-variable quantum key distribution device and method
This application discloses a continuous-variable quantum key distribution (CV-QKD) device and method. The device includes a light source, a modulation unit, a first random number generator, and a processor, where the processor is configured to obtain a first data sequence based on a preset quantity of modulation format symbols, a distribution probability of each symbol, and a first random number sequence generated by the first random number generator, and obtain a second data sequence based on the first data sequence; and the modulation unit is configured to modulate, based on to the first data sequence, a signal emitted by the light source to output a second optical signal, where the second optical signal does not need to include quantum states with a quantity in an order of magnitude of 2 8 ×2 8 required in an existing Gaussian protocol.
1. A continuous-variable quantum key distribution (CV-QKD) sending device, wherein the device comprises a light source, a modulation unit, a first random number generator, and a processor,
wherein the light source generates a first optical signal;
the first random number generator generates a first random number sequence;
the processor receivesthe first random numbersequence, obtain a first data sequence based on a preset quantity of modulation format symbols, a distribution probability of each symbol, and the first random number sequence, and obtain a second data sequence based on the first data sequence, wherein the first data sequence and the second data sequence are used for obtaining a secure bit rate;
the modulation unit receives the first optical signal, and modulate the first optical signal based on a control signal to output a second optical signal, wherein the control signal is generated based on the first data sequence, the second optical signal comprises n quantum states, and n is a positive integer not less than 8;
wherein the receiver receives a third data sequence, and the third data sequence comprises a random portion of data of a measurement value obtained after the second optical signal passes through an optical channel;
the processor is further configured to obtain a covariance matrix
γ
ACB
=
(
γ
A
ϕ
AC
ϕ
AB
ϕ
AC
T
γ
C
ϕ
CB
ϕ
AB
T
ϕ
CB
T
γ
B
)
based on the second data sequence and the third data sequence, wherein 7A, TAC, and yc are preset values, and CCB is obtained based on the second data sequence and the third data sequence, yB is obtained based on the third data sequence, and a superscript T represents matrix First Named Inventor transposition; obtain, based on the covariance matrix, a value of cpm satisfying a first condition, wherein the first condition is: yAcB+iQN>0, QN is an N×N block matrix whose data on a diagonal is Ω,
Ω
=
(
0
1
-
1
0
)
,
and N is a positive integer not less than 3; and
all calculate secure bit rate values corresponding to all values of CPAB satisfying the first condition, to obtain a CV-QKD secure bit rate, wherein the CV-QKD secure bit rate is a minimum value among the secure bit rate values; and
wherein the sending device sends the secure bit and coherent state to a receiving device through an untrusted channel.
2. The device according to claim 1 , wherein the obtaining a second data sequence based on the first data sequence specifically comprises: obtainingthe second data sequence based on a selected probability distribution function in a preset probability distribution function set and an obtained second random number sequence, wherein the selected probability distribution function isdetermined based on data in the first data sequence and representsa distribution probability of data in the second data sequence.
3. The device according to claim 1 , wherein the obtaining a second data sequence based on the first data sequence specifically comprises: obtainingfourth data based on a preset probability distribution function and an obtained second random number sequence, and adding a selected value to the fourth data to obtain second data, wherein the preset probability distribution function represents a distribution probability of the fourth data, the selected value is determined based on data in the first data sequence, and the second data sequence comprises a plurality of pieces of the second data.
4. The device according to claim 2 , wherein the obtaining the second data sequence based on a selected probability distribution function and an obtained second random number sequence specifically comprises: obtaining a value set of second data and an occurrence probability of each value in the value set based on the selected probability distribution function and a preset value range of the second data; and selecting a value of the second data from the value set based on a correspondence between a value represented by M second random numbers and a value in the value set, wherein the correspondence is set based on an occurrence probability of each value represented by the M second random numbers and the occurrence probability of each value in the value set, at least one value represented bythe M second random numbers corresponds to a value in the value set, a sum of occurrence probabilities of the at least one value is the same as a sum of occurrence probabilities of correspondingvalues in the value set, and M is a positive integer.
5. A continuous-variable quantum key distribution (CV-QKD) sending method, wherein the method comprises:
generating a first optical signal and a first random number sequence;
obtaining a first data sequence based on a preset quantity of modulation format symbols, a distribution probability of each symbol, and the first random number sequence, and obtaining a second data sequence based on the first data sequence, wherein the first data sequence and the second data sequence are used for obtaininga secure bit rate;
modulating the first optical signal based on the first data sequence to output a second optical signal, wherein the second optical signal comprises n quantum states, and n is a positive integer not less than 8;
obtaining a covariance matrix
γ
ACB
=
(
γ
A
ϕ
AC
ϕ
AB
ϕ
AC
T
γ
C
ϕ
CB
ϕ
AB
T
ϕ
CB
T
γ
B
)
based on the second data sequence and a third data sequence, wherein 7A, TAC, and yc are preset values, and DCB is obtained based on the second data sequence and the third data sequence, yB is obtained based on the third data sequence, a superscript T represents matrix transposition, and the third data sequence comprises a random portion of data of a measurement value obtained after the second optical signal passes through an optical channel; obtaining, based on the covariance matrix, a value of 4 AS satisfying a first condition, wherein the first condition is: 7ACS+iQN>0, QN is an N×N block matrix whose data on a diagonal is all Ω,
Ω
=
(
0
1
-
1
0
)
,
and N is a positive integer not less than 3; and
calculating secure bit rate values corresponding to all values of 4AB satisfying the first condition, to obtain a CV-QKD secure bit rate, wherein the CV-QKD secure bit rate is a minimum value among the secure bit rate values; and
wherein the sending device sends the secure bit and coherent state to a receiving device through an untrusted channel.
6. The method according to claim 5 , wherein before the obtaining a second data sequence based on the first data sequence, the method further comprises: generating a second random number sequence; and the obtaininga second data sequence based on the first data sequence specifically comprises: obtainingthe second data sequence based on a selected probability distribution function in a preset probability distribution function set and the second random number First Named Inventor sequence, wherein the selected probability distribution function is determined based on data in the first data sequence and represents a distribution probability of data in the second data sequence.
7. The method according to claim 5 , wherein before the obtaining a second data sequence based on the first data sequence, the method further comprises: generating a second random number sequence; and the obtaininga second data sequence based on the first data sequence specifically comprises: obtaining fourth data based on a preset probability distribution function and the obtained second random number sequence, and adding a selected value to the fourth data to obtain second data, wherein the selected value is determined based on data in the first data sequence, the second data sequence comprisesa plurality of pieces of the second data, and the preset probability distribution function represents a distribution probability of data in the second data sequence.
8. The method according to claim 6 , wherein the obtaining the second data sequence based on a selected probability distribution function and the second random number sequence specifically comprises: obtaining a value set of second data and an occurrence probability of each value in the value set based on the selected probability distribution function and a preset value range of the second data; and selecting a value of the second data from the value set based on a correspondence between a value represented by M second random numbers and a value in the value set, wherein the correspondence is set based on an occurrence probability of each value represented by the M second random numbers and the occurrence probability of each value in the value set, at least one value represented by the M second random numbers corresponds to a value in the value set, a sum of occurrence probabilities of the at least one value is the same as a sum of occurrence probabilities of corresponding values in the value set, and M is a positive integer.