Quantum satellite communication performance adjustment method based on heliotropism of sunflower

Abstract

The present disclosure proposes a quantum satellite communication performance adjustment method based on the heliotropism of sunflowers, including establishing a quantum satellite communication system model in a snowfall environment; the quantum satellite communication system model includes an analog quantum satellite communication system; analyzing the influence of snowfall intensity and quantum satellite communication elevation angle on the quantum satellite communication link in the quantum satellite communication system, obtaining the attenuation result of the quantum satellite communication link in the snowfall environment, and the relationship between the photon transmission distance of the quantum satellite and the communication elevation angle; according to the attenuation result of the quantum satellite communication link and the relationship between the photon transmission distance of the quantum satellite and the communication elevation angle, using the heliotropism principle of sunflowers, the optimal average photon number performance adjustment function relationship of each pulse in the quantum satellite communication system in the snowfall environment is obtained under the decoy state protocol. The present disclosure can effectively cope with the influence of snowfall and small elevation angle on the performance of quantum satellite communication.

Description

Technical Field

[0001] This disclosure relates to the field of satellite communication control technology, and in particular to a method for adjusting the performance of quantum satellite communication based on the phototaxis of sunflowers. Background Technology

[0002] Compared to classical communication, quantum communication, based on quantum superposition and entanglement properties and quantum mechanics principles, theoretically possesses absolute security and strong anti-interference capabilities. However, when photons propagate in free space, they are inevitably affected by atmospheric factors such as turbulence, rain, snow, fog, clouds, and dust. Especially in snowy conditions, snowflake particles absorb and scatter the photon signal, leading to decoherence of the photon qubits. This can cause sudden interference in quantum satellite communication, severely degrading the transmission quality of the communication link, which has become a pressing technical problem to be solved.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for adjusting the performance of quantum satellite communication based on sunflower phototaxis (SPAS), which can effectively address the impact of snowfall and low elevation angles on quantum satellite communication performance. Specifically, it includes the following steps:

[0005] A model of a quantum satellite communication system under snowfall conditions is established; the model includes a simulated quantum satellite communication system.

[0006] The influence of snowfall intensity and the communication angle of the quantum satellite on the quantum satellite communication link in the quantum satellite communication system was analyzed. The attenuation results of the quantum satellite communication link under snowfall conditions and the relationship between the photon transmission distance of the quantum satellite and the communication angle were obtained.

[0007] Based on the attenuation results of the quantum satellite communication link, and the relationship between the photon transmission distance of the quantum satellite and the communication angle, using the sunflower phototaxis principle, under the decoy state protocol, the optimal average photon number per pulse performance adjustment function relationship of the quantum satellite communication system under snowfall conditions is obtained.

[0008] In an exemplary embodiment of this disclosure, in the step of analyzing the impact of snowfall intensity and the quantum satellite's communication angle on the quantum satellite communication link in the quantum satellite communication system, obtaining the attenuation result of the quantum satellite communication link under snowfall conditions, and the relationship between the quantum satellite's photon transmission distance and the communication angle,

[0009] The snowfall intensity is divided into four levels based on the amount of snowfall within 24 hours:

[0010] Level S1, light snow, with snowfall ranging from 0 to 2.5 mm / day. -1 ;

[0011] Level S2, moderate snow, with snowfall of (2.5–5) mm / day. -1 ;

[0012] Level S3, heavy snow, with snowfall of (5-10) mm / day. -1 ;

[0013] Level S4, blizzard, with snowfall ranging from (10 to +∞) mm / d. -1 ;

[0014] Where mm represents millimeters; d represents days.

[0015] In an exemplary embodiment of this disclosure, the formula for the attenuation result of the quantum satellite communication link includes:

[0016] A atm =10lg(I0 / I)=10·lge·L·σ snow (1)

[0017] Among them, A atm The attenuation result of the quantum satellite communication link is represented by I0; I0 represents the initial energy of the photon; I represents the energy of the photon after traveling a distance L in a snowy environment; L represents the photon transmission distance in a snowy environment; σ snow The extinction coefficient of snowflakes is expressed in dB·km. -1 .

[0018] In an exemplary embodiment of this disclosure, the formula for the extinction coefficient of the snowflake includes:

[0019]

[0020] Where N(D) represents the snowfall spectrum distribution function; Q ext (D,λ,m) represents the extinction efficiency factor; D represents the equivalent diameter of the snowflake; λ represents the wavelength of the optical signal used in quantum satellite communication; and m represents the shape factor of the snowflake.

[0021] In an exemplary embodiment of this disclosure, the relationship between the photon transmission distance of the quantum satellite and the communication angle includes:

[0022] h=L·sinθ(3)

[0023] Where L represents the photon transmission distance under snowfall conditions; θ represents the communication angle of the quantum satellite; and h represents the instantaneous orbital altitude of the quantum satellite.

[0024] In an exemplary embodiment of this disclosure, the formula for calculating the communication angle includes:

[0025]

[0026] Where R represents the Earth's radius; h represents the instantaneous orbital altitude of the quantum satellite; c = sinN a-call ·sinN a-sat +cos|N o-call -N o-sat |·cosN a-call cosN a-sat N o-call Indicates the longitude of the quantum satellite ground station; N a-call This indicates the latitude of the quantum satellite ground station.

[0027] In an exemplary embodiment of this disclosure, the step of obtaining the optimal average photon count performance adjustment function relationship per pulse in the quantum satellite communication system under a snowfall environment, based on the attenuation result of the quantum satellite communication link and the relationship between the photon transmission distance of the quantum satellite and the communication angle, and utilizing the sunflower phototropism principle under a decoy state protocol, includes:

[0028] Based on the extinction coefficient of the snowflake in the attenuation result of the quantum satellite communication link, and the relationship between the photon transmission distance of the quantum satellite and the communication angle, the pulse transmittance of the average number of photons per pulse in the quantum satellite communication system under snowfall conditions is obtained;

[0029] Using the pulse transmittance of the average number of photons per pulse and the secure key generation rate of the decoherent light source decoy state protocol, the functional relationship of the secure key generation rate of the quantum satellite communication system is calculated.

[0030] By utilizing the functional relationship of the secure key generation rate of the quantum satellite communication system, the performance adjustment function relationship of the optimal average photon number per pulse in the quantum satellite communication system is obtained.

[0031] In an exemplary embodiment of this disclosure, in the step of obtaining the pulse transmittance of the average number of photons per pulse in the quantum satellite communication system under snowfall conditions based on the extinction coefficient of the snowflake in the attenuation result of the quantum satellite communication link, and the relationship between the photon transmission distance of the quantum satellite and the communication angle, the formula for calculating the pulse transmittance of the average number of photons per pulse includes:

[0032]

[0033] Among them, Q μ Y0 represents the pulse transmittance with an average photon count per pulse of μ; Y0 represents the probability of a dark count by the detector at the receiver of the quantum satellite communication system; μ represents the average photon count per pulse; η rec σ represents the receiver detectivity of a quantum satellite communication system. snow The extinction coefficient of snowflakes is expressed in dB·km. -1 θ represents the communication angle of the quantum satellite; h represents the instantaneous orbital altitude of the quantum satellite.

[0034] In an exemplary embodiment of this disclosure, the step of calculating the functional relationship of the secure key generation rate of the quantum satellite communication system using the pulse transmittance of the average number of photons per pulse and the secure key generation rate of the decoy state protocol of the weakly coherent light source includes: the formula for the functional relationship of the secure key generation rate of the quantum satellite communication system includes:

[0035] R key ≥η snow μe -μ [1-H2(e d )]-η snow μf(e d H2(e) d (6)

[0036] Among them, R key η represents the secure key generation rate of a quantum satellite communication system. snow This represents the product of the transmission rate between the sender and receiver and the receiver's probe rate, i.e., L represents the photon transmission distance under snowfall conditions; H2(e d H2(e) is a binary entropy function. d )=-lb(e d )-(1-e d )lb(1-e d );f(e d ) indicates bidirectional error correction efficiency; e d This represents the probability that a photon will reach the wrong detector due to detector noise.

[0037] In an exemplary embodiment of this disclosure, in the step of obtaining the optimal average photon number performance adjustment function relationship per pulse in the quantum satellite communication system using the functional relationship of the secure key generation rate of the quantum satellite communication system model, the formula of the optimal average photon number performance adjustment function relationship per pulse includes:

[0038]

[0039] Where μ' represents the optimal average number of photons per pulse; N0 represents the snowfall concentration parameter; and Sn represents the snowfall intensity.

[0040] The technical solution provided in this disclosure may include the following beneficial effects:

[0041] This disclosure analyzes the impact of changes in snowfall intensity and elevation angle on the performance of quantum satellite communication. By utilizing the sunflower phototropism principle, an adaptive adjustment method for the optimal average photon number of quantum satellite is obtained under the decoy state protocol. This method can adjust the signal transmitting end in real time according to the elevation angle of the quantum satellite and the snowfall intensity, thereby enabling the entire quantum satellite communication system to reach the optimal state and effectively addressing the impact of snowfall and low elevation angle on the performance of quantum satellite communication.

[0042] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0043] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0044] Figure 1 A schematic diagram illustrating the steps of a quantum satellite communication performance adjustment method based on sunflower phototropism in an exemplary embodiment of this disclosure;

[0045] Figure 2 This diagram illustrates a quantum satellite communication faith angle model under snowfall conditions in an exemplary embodiment of this disclosure.

[0046] Figure 3 This diagram illustrates the relationship between the communication angle and link attenuation of a quantum satellite under snowfall conditions in an exemplary embodiment of this disclosure.

[0047] Figure 4This diagram illustrates the relationship between link attenuation, snowfall intensity, and communication angle of a quantum satellite under snowfall conditions in an exemplary embodiment of this disclosure.

[0048] Figure 5 A schematic diagram illustrating the phototaxis principle of sunflowers in an exemplary embodiment of this disclosure is shown;

[0049] Figure 6 This diagram illustrates the relationship between snowfall intensity, communication angle, and optimal average photon number in a quantum satellite communication performance adjustment method based on sunflower phototropism in an exemplary embodiment of this disclosure.

[0050] Figure 7 This diagram illustrates the relationship between channel bit error rate and communication angle under different snowfall intensities in a simulation experiment of an exemplary embodiment of this disclosure.

[0051] Figure 8 The diagram illustrates the relationship between the channel belief angle and the channel survival function under different snowfall intensities in a simulation experiment of an exemplary embodiment of this disclosure. Detailed Implementation

[0052] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0053] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0054] This exemplary implementation first aspect provides a method for adjusting the performance of quantum satellite communication based on the phototaxis of sunflowers, referring to... Figure 1 As shown, it includes the following steps:

[0055] Step S101: Establish a quantum satellite communication system model under snowfall conditions; this quantum satellite communication system model includes a simulated quantum satellite communication system;

[0056] Step S102: Analyze the impact of snowfall intensity and the quantum satellite's communication angle on the quantum satellite communication link in the quantum satellite communication system, obtain the attenuation results of the quantum satellite communication link under snowfall conditions, and the relationship between the quantum satellite's photon transmission distance and the communication angle;

[0057] Step S103: Based on the attenuation results of the quantum satellite communication link and the relationship between the photon transmission distance and the communication angle of the quantum satellite, using the sunflower phototropism principle, under the decoy state protocol, the optimal average photon number per pulse performance adjustment function relationship of the quantum satellite communication system under snowfall environment is obtained.

[0058] The steps of the method described above in this example implementation will now be explained in more detail, referring to... Figure 1 As shown:

[0059] In step S101, snowfall, as a common weather phenomenon, can have a sudden impact on the quantum satellite communication link. In order to study and respond to the sudden interference caused by snowfall to the quantum satellite communication system, it is first necessary to establish a model simulating the quantum satellite communication system under snowfall conditions; the quantum satellite communication system model includes a simulated quantum satellite communication system.

[0060] In step S102, the influence of snowfall intensity and the communication angle of the quantum satellite on the quantum satellite communication link in the quantum satellite communication system is analyzed to obtain the attenuation results of the quantum satellite communication link under snowfall conditions, as well as the relationship between the photon transmission distance of the quantum satellite and the communication angle.

[0061] Here, snowfall intensity is used as a parameter to describe the amount of snowfall, denoted as S. n Snowfall intensity is classified according to the amount of snowfall within 24 hours, and can be divided into four levels as shown in Table 1 below, with each level corresponding to a different amount of snowfall:

[0062] Table 1 Classification of Snowfall Intensity Levels

[0063]

[0064] Table 1 shows the snowfall amount corresponding to different levels of snowfall intensity:

[0065] Level S1, light snow, with snowfall ranging from 0 to 2.5 mm / day. -1 ;

[0066] Level S2, moderate snow, with snowfall of (2.5–5) mm / day. -1 ;

[0067] Level S3, heavy snow, with snowfall of (5-10) mm / day. -1 ;

[0068] Level S4, blizzard, with snowfall ranging from (10 to +∞) mm / d. -1 ;

[0069] Where mm represents millimeters; d represents days.

[0070] Since snowflakes are generally irregular in shape, they are often represented by the equivalent diameter D of a water droplet formed when a snowflake melts. The snowfall spectrum distribution function can be described using the Γ distribution, i.e., N(D) = N₀D. m e -ΛD ;

[0071] In the formula, N0 represents the snowfall concentration parameter; D represents the equivalent diameter of the snowflake; m represents the shape factor, which is generally taken as 0; Λ represents the slope of the snowfall spectrum distribution, which is related to the snowfall intensity and can be expressed as: Λ = 25.5S -0.48 .

[0072] According to Lambert's law, the energy attenuation of a photon propagating in snow can be expressed as: I = I0exp(-σ snow ·L), where I0 represents the initial energy of the photon; I represents the energy of the photon after traveling a distance L in a snowy environment; σ snow The extinction coefficient of snowflakes is expressed in dB·km. -1 .

[0073] Based on Mie scattering theory and the snowfall spectral distribution function, the formula for the extinction coefficient of snowflakes can be obtained:

[0074]

[0075] Among them, Q ext (D,λ,m) represents the extinction efficiency factor; D represents the equivalent diameter of the snowflake; λ represents the wavelength of the optical signal used in quantum satellite communication; and m represents the shape factor of the snowflake.

[0076] Generally, the wavelength range of optical signals used in quantum satellite communication is 850-1550 nm, while the minimum diameter of a snowflake is greater than 10 μm, far exceeding the wavelength of optical signals. Therefore, Q... ext (D,λ,m) approaches 2. The formula I=I0exp(-σ snow Taking the logarithm of L, we can obtain the attenuation formula for the quantum satellite communication link under snowfall conditions:

[0077] A atm =10lg(I0 / I)=10·lge·L·σ snow (1)

[0078] When the longitude of the quantum satellite's base station is N o-callDimension N a-call At that time, the formula for the communication angle of a quantum satellite is:

[0079]

[0080] Where R represents the Earth's radius; h represents the instantaneous orbital altitude of the quantum satellite; c = sinN a-call ·sinN a-sat +cos|N o-call -N o-sat |·cosN a-call cosN a-sat N o-call Indicates the longitude of the quantum satellite ground station; N a-call This indicates the latitude of the quantum satellite ground station.

[0081] At this point, the relationship between the photon transmission distance of the quantum satellite in a snowy environment and the communication angle can be expressed as:

[0082] h=L·sinθ(3)

[0083] Where L represents the photon transmission distance under snowfall conditions; θ represents the communication angle of the quantum satellite; and h represents the instantaneous orbital altitude of the quantum satellite.

[0084] Reference Figure 2 and Figure 3 As shown in Figure 2, snowfall intensity is represented by Sn, where n∈(1,2,3,4). Considering that the snowfall occurs in the troposphere with a thickness of 10-20 km, we can take h = 15 km and snowfall intensity S2 = 5. Ignoring the influence of other atmospheric factors, we analyze the impact of changes in the communication angle on link attenuation. As shown in Figure 2, as the communication angle θ gradually approaches 0° from 90°, the attenuation of the quantum satellite communication link gradually increases. When θ > 45°, the increase in quantum satellite communication link attenuation is slow and nearly stable; when θ < 45°, the attenuation increases rapidly. It can be seen that when θ is small, the impact of the communication angle on the quantum satellite communication link is more significant, greatly reducing the service time of the quantum satellite. Therefore, it can be seen that the impact of changes in the communication angle under snowfall conditions on the quantum satellite communication link cannot be ignored.

[0085] Reference Figure 4 As shown, Figure 4This paper presents the relationship between snowfall intensity, communication angle, and the attenuation coefficient of the quantum satellite communication link. It can be seen that when the snowfall intensity is 0, the quantum satellite communication link attenuation is 0, which is the ideal state. As the quantum satellite link attenuation decreases, it eventually stabilizes. However, the communication angle cannot be 0, because the quantum satellite communication link will be interrupted at this value, which is consistent with actual conditions. When the communication angle θ = 60°, and the snowfall intensity increases from S2 = 4.4 (moderate snow) to S3 = 9.55 (heavy snow), the quantum satellite link attenuation increases from 0.124 dB·km. -1 Increased to 0.347 dB·km -1 Therefore, it is evident that the intensity of snowfall and changes in the communication angle have a significant impact on the link transmission of quantum satellites.

[0086] In step S103, based on the attenuation results of the quantum satellite communication link and the relationship between the photon transmission distance and the communication angle of the quantum satellite, the optimal average photon count per pulse performance adjustment function in the quantum satellite communication system under a snowfall environment is obtained using the sunflower phototaxis principle and the decoy state protocol. This step includes the following sub-steps:

[0087] Sub-step S1031: Based on the extinction coefficient of snowflakes in the attenuation results of the quantum satellite communication link, and the relationship between the photon transmission distance and the communication angle of the quantum satellite, obtain the pulse transmittance of the average number of photons per pulse in the quantum satellite communication system under snowfall conditions;

[0088] Sub-step S1032: Using the pulse transmittance of the average number of photons per pulse and the secure key generation rate of the decoherent light source decoy state protocol, calculate the functional relationship of the secure key generation rate of the quantum satellite communication system.

[0089] Sub-step S1033: Using the functional relationship of the secure key generation rate of the quantum satellite communication system, the performance adjustment function relationship of the optimal average photon number per pulse in the quantum satellite communication system is obtained.

[0090] Reference Figure 5As shown, sunflowers are a common plant with a diurnal rhythm. Their stems contain auxins that promote plant growth. When exposed to sunlight, these auxins migrate to the shaded areas within the stem. Due to variations in auxin concentration, sunflowers exhibit phototropism, achieving their optimal state. When the sunflower's light intensity is synchronized with its surroundings, reaching optimal coordination, the auxin concentration in its stem is also at its optimal value. Therefore, from an abstract communication perspective, under a decoy state protocol, auxin concentration corresponds to the number of pulsed photons, and snowfall intensity corresponds to the surrounding environment. If the number of photons is too high, the security of the communication system cannot be guaranteed; if the number of photons is too low, the efficiency of the communication system will decrease, neither of which allows the entire communication system to reach its optimal state. Therefore, if the photon number is correlated with auxin concentration, it is necessary to find the optimal photon number based on snowfall intensity and communication angle, and to balance communication performance and system security by adjusting the number of pulsed photons at the transmitting end in real time.

[0091] In sub-step S1031, in practical quantum key distribution systems, since single-photon sources are difficult to prepare, weakly coherent light sources obtained by highly attenuating laser sources are typically used. Assuming the pulse phase is random, the weakly coherent state of the weakly coherent light source can be expressed as:

[0092]

[0093] The average photon number of the signal from the presupposed weakly coherent light source is μ; The density matrix can be expressed as:

[0094]

[0095] In the formula, α represents a weakly coherent state. The corresponding phase, the probability distribution of the number of photons per pulse follows a Poisson distribution, that is, The gain of the quantum satellite communication system, i.e., the pulse transmittance, is:

[0096]

[0097] In the formula, μ represents the average number of photons per pulse; Y n When n photons are sent to the transmitter, the detection probability at the receiver can be expressed as: Y n =η snow +Y0-η n Y0, where Y0 is the probability of dark counting by the receiver detector; η n The probability that the receiver receives a photon when the transmitter sends an n-photon pulse, i.e., the corresponding pulse transmittance, can be expressed as η. n =1-(1-η) snow ) n η snowThe total transmission rate of the channel in a snowy environment can be expressed as the product of the transmission rate from the transmitter to the receiver and the receiver's detection rate, i.e.:

[0098]

[0099] Finally, by using the formula h=L·sinθ and Y n =η snow +Y0-η n Y0, substitute into the formula In the above, the formula for calculating pulse transmittance, which is the average number of photons per pulse in a quantum satellite communication system model under snowfall conditions, is obtained:

[0100]

[0101] Among them, Q μ Y0 represents the pulse transmittance with an average photon count of μ per pulse; Y0 represents the probability of dark counting by the detector at the receiver of the quantum satellite communication system; μ represents the average photon count per pulse; η rec σ represents the receiver detection rate; snow The extinction coefficient of snowflakes is expressed in dB·km. -1 θ represents the communication angle of the quantum satellite.

[0102] As can be seen from formula (5), increasing the μ value can improve the pulse transmittance under snowfall conditions, thereby increasing the bit rate and communication efficiency of the quantum satellite communication system. However, due to the presence of multiple photon components in weakly coherent light sources, eavesdroppers can use photon-number splitting (PNS) attacks to eavesdrop on the quantum satellite communication system. Therefore, increasing the photon number will reduce the security of the quantum satellite communication system.

[0103] In sub-step S1032, theoretical analysis shows that a good estimate close to an infinite number of decoy states can be obtained using a finite number of decoy states (e.g., a three-state decoy protocol). Based on the three-state decoy protocol, this disclosure uses a fixed ratio of decoy state, signal state, and vacuum state of 1:2:1 at the transmitting end. According to the secure code rate formula (i.e., the GLLP formula), it addresses the link loss and communication performance degradation caused by the decrease in the communication faith angle and the increase in snowfall intensity in the depolarized channel. It seeks the optimal average number of photons per pulse to compensate for the performance degradation of the quantum satellite communication system using the three-state decoy protocol under sudden interference in snowfall environments.

[0104] In this step, the density operator of a qubit can be expressed by the spin polarization vector as follows: Where 'I' represents the identity operator, and the photons interact with snowflake particles during their propagation through the atmosphere, causing the quantum states to decoherent. The initial quantum superposition state is... Where χ1 and χ2 are complex numbers, and |χ1| 2 +|χ2| 2 =1. Let |e> represent the quantum state of the snowfall environment, then the joint evolution of the system consisting of the quantum state and the snowfall environment is:

[0105]

[0106] The snowfall environment state is represented as:

[0107] And let |e + >=|e I >,|e - >=|e Z >,|e' + >=|e X >,|e' - >=|e Y >, then the unitary evolution of the composite system consisting of qubits and snowfall environment can be expressed as:

[0108]

[0109] Where p is the probability of a bit flipping error occurring in the depolarized channel after a sudden snowfall disturbance. For the initial environmental state |e I The density operator of qubits can be obtained by taking the partial trace from the four orthogonal bases derived from the evolution:

[0110]

[0111] Among them, A p For the measurement operator, A + p For A p The Hermitian coordinating operator, P(0), is the initial value of the spin polarization vector. From the above equation, it can be seen that the spin polarization vector is reduced to its initial value. times.

[0112] Given a snowfall background, the average number of photons per pulse of the signal optical source is μ. Then its coherent density of states operator can be expressed as: ρ μ =e -u |0><0|+μe -μ |1><1|+aρ a In the formula, a = 1 - e -μ -μe -μ ρ is the density operator coefficient; a Let be the density operator for the multiphoton component in a weakly coherent light source. According to the GLLP formula, the secure key generation rate of the decoy-state quantum key distribution protocol (i.e., QKD protocol) based on a weakly coherent light source is:

[0113] Rkey ≥q{-Q μ f(E μ H2(E) μ )+Q1[1-H2(e1)]}

[0114] Where q is the system efficiency, which is generally taken as... H2(x) = -lb(x) - (1-x)lb(1-x) is the binary entropy function; f(x) represents the bidirectional error correction efficiency; x represents the bit error rate of the received photons.

[0115] The bit error rate of a quantum satellite communication system with a photon source having an average of μ photons per pulse in a snowy environment can be expressed as:

[0116]

[0117] Among them, e n Let e ​​be the probability of false detection at the receiver when the transmitter sends an n-photon pulse. d Let e ​​represent the probability that a photon reaches the wrong detector due to detector noise. d Represented as:

[0118] but

[0119] It can be changed to:

[0120]

[0121] Substitute into formula R key ≥q{-Q μ f(E μ H2(E) μ From )+Q1[1-H2(e1)]}, we can obtain the formula for the functional relationship of the secure key generation rate of the quantum satellite communication system model:

[0122] R key ≥η snow μe -μ [1-H2(e d )]-η snow μf(e d H2(e) d (6)

[0123] Among them, R key η represents the secure key generation rate of a quantum satellite communication system model. snow This represents the product of the transmission rate between the sender and receiver and the receiver's probe rate, i.e., L represents the transmission distance of photons in a snowy environment; H2(e d H2(e) is a binary entropy function.d )=-lb(e d )-(1-e d )lb(1-e d );f(e d ) indicates bidirectional error correction efficiency; e d This represents the probability that a photon will reach the wrong detector due to detector noise.

[0124] In sub-step S1033, using the formula for the secure key generation rate of the quantum satellite communication system model obtained above, R is calculated using MATLAB. key The decoy state strength at its maximum value is obtained, which is an implicit function. Approximating μ' yields the optimal average photon number per pulse performance adjustment function in the quantum satellite communication system:

[0125]

[0126] Where μ' represents the optimal average number of photons per pulse; N0 represents the snowfall concentration parameter; and Sn represents the snowfall intensity.

[0127] Formula (7) is the functional relationship between snowfall intensity Sn and communication angle θ. The number of photons at the transmitting end when the quantum satellite communication system is in the best state can be obtained based on the snowfall intensity and communication angle. The light source signal state can be adjusted in real time through the method proposed in this disclosure so that the quantum satellite communication system can reach the optimal state.

[0128] Reference Figure 6 As shown in the figure, when both the snowfall intensity and the communication angle are 0, the optimal average photon number μ' for signal state adjustment of the communication system using the SPAS disclosed in this disclosure under the decoy state protocol is 0.256. With the decrease of the communication angle and the increase of the snowfall intensity, μ' gradually increases due to the continuous increase in quantum satellite communication link attenuation. When θ < 40° and S > 5, the value of μ' in the quantum satellite communication system increases rapidly due to the sudden attenuation caused by snowfall, i.e., the effect of small elevation angles. When the snowfall intensity S4 = 12 mm·d... -1 (Blizzard) When the communication angle θ = 10°, the value of μ' is approximately 0.5. It can be seen that the SPAS method disclosed herein can adjust the optimal average number of photons per pulse of the signal state according to the quantum satellite communication environment, effectively coping with the interference of snowfall environment and communication angle, especially small elevation angles, on communication performance.

[0129] Simulation and Analysis

[0130] To verify the superiority of the SPAS method proposed in this example implementation, the following simulation experiments were conducted, and the simulation results are analyzed in detail:

[0131] First, we simulate the impact of SPAS on the channel bit error rate.

[0132] In snowy conditions, the bit error rate of the BB84-based decoy state QKD protocol is:

[0133]

[0134] Combining formulas The bit error rate can ultimately be expressed as:

[0135]

[0136] Using snowfall intensities of S2 = 3 (moderate snow) and S4 = 10 (heavy snow), the bit error rate of the quantum satellite communication system was simulated, with reference to... Figure 7 As shown in Figures a and 7b, the simulation results show that the greater the snowfall intensity, the higher the system's bit error rate (BER). Furthermore, the BER of the quantum satellite communication system gradually decreases with increasing communication angle. When θ > 45°, the BER decreases rapidly. After adjustment using the SPAS method disclosed in this paper, the BER of the quantum satellite communication system decreases from 0.07 to 0.046, and from 0.11 to 0.063. When the communication angle θ = 30° and the snowfall intensity Sn = 10 (heavy snow), the BER of the quantum satellite communication system decreases from 0.11 to 0.067. Therefore, it can be definitively concluded that adjusting using the SPAS method can significantly improve the reliability of the quantum satellite communication system.

[0137] Secondly, simulations were performed to demonstrate the impact of SPAS on the channel survival function.

[0138] In a snowfall environment, the survival function of a depolarized channel can be expressed as:

[0139]

[0140] Among them, F snow The channel fidelity of a quantum satellite communication system under snowfall conditions can be defined as: Here, represents the search for a trace.

[0141] Set the initial quantum state density matrix as Under the influence of snowfall decoherence, it evolves into:

[0142]

[0143] The final fidelity of the quantum satellite communication system is:

[0144]

[0145] Combining formula A atm =10lg(I0 / I)=10·lge·L·σ snow (1)

[0146] Therefore, the survival function of the channel under snowfall conditions can ultimately be expressed as:

[0147]

[0148] The equation was simulated with snowfall intensities of S2 = 3 (moderate snow) and S3 = 10 (heavy snow). The simulation results are referenced. Figure 8 As shown in Figures a and 8b, the greater the snowfall intensity Sn, the lower the channel survivability of the quantum satellite communication system. When the elevation angle θ < 45°, the channel survivability gradually increases; when θ < 45°, the channel survivability increases slowly and eventually stabilizes. After adjustment using the SPAS method, the survivability of the quantum satellite communication system is significantly improved under both moderate and heavy snow conditions, enabling the quantum satellite communication system to cope with more intense snowfall. Simultaneously, for communication at low elevation angles, the SPAS method improves the channel survivability under both moderate and heavy snow conditions. If a minimum channel survivability angle of 30° is required, the survivability of the quantum satellite system increases from 0.81 to 0.92 under a snowfall intensity S3 = 10 (heavy snow). If a channel survivability of 0.8 is required, the minimum channel survivability angle can be adjusted from 26° to 18° under an S3 = 10 (heavy snow) condition, significantly improving the satellite's service duration. Therefore, it is evident that the SPAS adaptive adjustment method can effectively improve the survivability of the quantum satellite communication system under snowfall interference.

[0149] In summary, this publication investigated the problem of sudden interference in quantum satellite communication links under snowfall conditions, analyzed the impact of changes in snowfall intensity (i.e., the communication angle) on the performance of the quantum satellite communication system, and proposed an adaptive adjustment method for the optimal average photon number per pulse using the decoy state protocol, based on the phototaxis principle of sunflowers. This method adjusts the signal transmitter in real time according to the communication angle and snowfall intensity, thereby optimizing the entire quantum satellite communication system. Theoretical analysis and simulation results show that sudden interference during snowfall, i.e., changes in the communication angle, especially during low-elevation-angle communication, causes significant attenuation in the quantum satellite communication link. After adjustment using the SAPS method, the bit error rate and survivability of the quantum satellite communication system are significantly improved. Therefore, the SPAS method provides a theoretical basis for solving snowfall interference and low-elevation-angle communication, and is of great significance for improving the service duration of low-Earth orbit quantum satellites and the reliability of quantum satellite communication link transmission under snowfall conditions.

[0150] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A method for adjusting the performance of quantum satellite communication based on the phototaxis of sunflowers, characterized in that, A model of a quantum satellite communication system under snowfall conditions is established; the model includes a simulated quantum satellite communication system. The influence of snowfall intensity and the communication angle of the quantum satellite on the quantum satellite communication link in the quantum satellite communication system was analyzed. The attenuation results of the quantum satellite communication link under snowfall conditions and the relationship between the photon transmission distance of the quantum satellite and the communication angle were obtained. Based on the attenuation results of the quantum satellite communication link, and the relationship between the photon transmission distance of the quantum satellite and the communication angle, using the sunflower phototropism principle, under the decoy state protocol, the optimal average photon number per pulse performance adjustment function relationship of the quantum satellite communication system under snowfall environment is obtained; The steps for obtaining the optimal average photon count performance adjustment function relationship per pulse in the quantum satellite communication system under a snowfall environment, based on the attenuation results of the quantum satellite communication link, the relationship between the photon transmission distance of the quantum satellite and the communication angle, and utilizing the sunflower phototaxis principle under the decoy state protocol, include: Based on the extinction coefficient of snowflakes in the attenuation results of the quantum satellite communication link, and the relationship between the photon transmission distance of the quantum satellite and the communication angle, the pulse transmittance of the average number of photons per pulse in the quantum satellite communication system under snowfall conditions is obtained. Using the pulse transmittance of the average number of photons per pulse and the secure key generation rate of the decoherent light source decoy state protocol, the functional relationship of the secure key generation rate of the quantum satellite communication system is calculated. By utilizing the functional relationship of the secure key generation rate of the quantum satellite communication system, the performance adjustment function relationship of the optimal average photon number per pulse in the quantum satellite communication system is obtained.

2. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 1, characterized in that, In the steps of analyzing the impact of snowfall intensity and the quantum satellite's communication angle on the quantum satellite communication link in the quantum satellite communication system, obtaining the attenuation results of the quantum satellite communication link under snowfall conditions, and the relationship between the quantum satellite's photon transmission distance and the communication angle, The snowfall intensity is divided into four levels based on the amount of snowfall within 24 hours: Level S1, light snow, with snowfall ranging from 0 to 2.5 mm. mm.d -1 ; Level S2, moderate snow, with snowfall of (2.5~5) mm.d -1 ; Level S3, heavy snow, with snowfall of (5~10) mm.d -1 ; Level S4, blizzard, snowfall amount (10~+) ) mm.d -1 ; in, mm Indicates millimeters; d It means every day.

3. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 2, characterized in that, The formula for the attenuation result of the quantum satellite communication link includes: （1） in, This indicates the attenuation result of the quantum satellite communication link; This represents the initial energy of the photon; This indicates the distance photons travel in a snowy environment. L The energy afterward; L This indicates the photon transmission distance under snowfall conditions; The extinction coefficient of a snowflake is expressed in units of 1000 ppm. .

4. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 3, characterized in that, The formula for the extinction coefficient of the snowflake includes: （2） in, Represents the snowfall spectrum distribution function; Indicates the extinction efficiency factor; Indicates the equivalent diameter of a snowflake; This indicates the wavelength of the optical signal used in quantum satellite communication; The shape factor representing a snowflake.

5. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 2, characterized in that, The relationship between the photon transmission distance of the quantum satellite and the communication angle includes: （3） in, L This indicates the photon transmission distance under snowfall conditions; The communication angle of the quantum satellite; h This indicates the instantaneous orbital altitude of the quantum satellite.

6. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 5, characterized in that, The formula for calculating the faith angle includes: （4） in, Indicates the Earth's radius; Indicates the instantaneous orbital altitude of the quantum satellite; , Indicates the longitude of the quantum satellite ground station; This indicates the latitude of the quantum satellite ground station.

7. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 1, characterized in that, In the step of obtaining the pulse transmittance of the average number of photons per pulse in the quantum satellite communication system under snowfall conditions, based on the extinction coefficient of the snowflake in the attenuation results of the quantum satellite communication link, and the relationship between the photon transmission distance of the quantum satellite and the communication angle, the formula for calculating the pulse transmittance of the average number of photons per pulse is as follows: include: （5） in, This indicates the average number of photons per pulse. Pulse transmittance; This represents the probability of a detector's dark count being transmitted from the receiver of a quantum satellite communication system; This represents the average number of photons per pulse. This indicates the receiver detection rate of a quantum satellite communication system; The extinction coefficient of a snowflake is expressed in units of 1000 ppm. ; The communication angle of the quantum satellite; h This indicates the instantaneous orbital altitude of the quantum satellite.

8. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 7, characterized in that, In the step of calculating the functional relationship of the secure key generation rate of the quantum satellite communication system using the pulse transmittance of the average number of photons per pulse and the secure key generation rate of the decoy state protocol of the weakly coherent light source, the formula for the functional relationship of the secure key generation rate of the quantum satellite communication system includes: （6） in, This indicates the secure key generation rate of the quantum satellite communication system; This represents the product of the transmission rate between the sender and receiver and the receiver's probe rate, i.e., ; L This indicates the photon transmission distance under snowfall conditions; It is a binary entropy function. ; Indicates the efficiency of two-way error correction; This represents the probability that a photon will reach the wrong detector due to detector noise.

9. The method for adjusting the performance of quantum satellite communication based on sunflower phototropism according to claim 8, characterized in that, In the step of obtaining the optimal average photon number performance adjustment function per pulse in the quantum satellite communication system using the functional relationship of the secure key generation rate, the formula for the optimal average photon number performance adjustment function per pulse includes: （7） in, This represents the optimal average number of photons per pulse; N 0 indicates the snowfall concentration parameter; Sn Indicates the intensity of snowfall.

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