Systems, methods, and media for implementing frequency division multiplexing of classical and quantum signals

Abstract

This invention provides a system, method, and medium for frequency division multiplexing of classical and quantum signals, including a transmitter signal generation and modulation module and a receiver signal detection module. The transmitter signal generation and modulation module includes an arbitrary waveform transmitter, a laser transmitter, an IQ modulator, a variable optical attenuator, an optical beam splitter, and an optical isolator. The receiver signal detection module includes two homodyne detectors, a variable optical attenuator, an optical isolator, and an optical beam splitter. This invention generates a composite optical signal by the transmitter signal generation and modulation module, which is a mixture of a classical signal modulated by quadrature phase shift keying (QPSK) and a quantum signal modulated by Gaussian coherent state. The receiver signal detection module detects the composite signal, and then performs coherent demodulation, filtering, phase drift recovery, balance compensation, and parameter evaluation. This achieves frequency division multiplexing of classical and quantum signals in the frequency domain, realizing frequency division multiplexing of classical and quantum signals on the same channel.

Description

Technical Field

[0001] This invention relates to the fields of classical communication and quantum secure communication technologies, specifically to a system, method, and medium for realizing frequency division multiplexing of classical and quantum signals. More particularly, it relates to a system and method for realizing frequency division multiplexing of orthogonal phase-shift keying modulated classical signals and Gaussian coherent state modulated quantum signals. Background Technology

[0002] Quantum secure communication is a communication technology that ensures secure information transmission. Its security is not based on computational security mechanisms, but rather on the fundamental properties of quantum physics. Therefore, even if the computing power of an eavesdropper surpasses that of the legitimate party, the security of information transmission can still be guaranteed. The core security key in quantum secure communication originates from quantum key distribution technology. Based on the quantum uncertainty principle and the no-cloning theorem, any illegal eavesdropping or tampering with the distributed key will be detected by the legitimate party, ensuring the security of key transmission. Depending on the implementation method, quantum key distribution is mainly divided into discrete variable quantum key distribution and continuous variable quantum key distribution. The former encodes discrete distribution information onto single photons and uses single-photon detection technology for detection; the latter encodes continuous distribution information onto non-commuting canonical components of an optical field and uses coherent detection technology for detection. After more than twenty years of development, the theoretical unconditional security of continuous variable quantum key distribution has been proven, and its practical performance indicators have also made breakthrough progress in recent years, showing promising application prospects.

[0003] Continuous-variable quantum key distribution (CVD), due to its protocol characteristics encoded on the canonical components of an optical field, exhibits the following features in practical implementation: First, coherent detection is commonly used for probing the canonical components. Its detectors are structurally similar to those in classical coherent optical communication, requiring no cooling devices and facilitating integration. Second, coherent detection technology possesses inherent filtering properties, suppressing background light interference and ensuring good co-fiber compatibility with classical optical communication. Currently, CVD lags behind discrete-variable quantum key distribution (DFD) in system maturity and secure transmission distance, but its secure key rate performs well within metropolitan area networks (MANs), and its practical application and chip-based device implementation have been preliminarily verified. Given the ever-increasing value of information and the growing demand for information security, further promoting the practical application of CVD is of great significance.

[0004] Quantum key distribution (QKD) technology is maturing and moving towards practical engineering applications. However, a series of fundamental scientific and core technological problems remain to be solved in its practical application, such as the efficient integration of quantum secure signals with classical fiber optic communication. Fiber optic communication systems, due to their superior performance in terms of high speed, large capacity, and long transmission distance, have become an essential infrastructure in today's information society. Integrating QKD with classical fiber optic communication systems will greatly promote the large-scale deployment and application of QKD. Currently, both discrete-variable and continuous-variable QKD technologies mostly employ wavelength division multiplexing (WDM) to achieve co-fiber integration with classical data transmission. This approach requires reserving a separate channel for quantum key distribution, and the quantum key distribution system and the classical communication system are relatively independent.

[0005] Patent document CN116405209A discloses a polarization compensation method and system for CV-QKD continuous variable quantum key distribution. The method includes: introducing reference light 1 and reference light 2, and estimating the polarization state of the quantum signal light by the polarization change of the reference light appearing alternately in two polarization directions; specifically, in the vertical polarization direction, the quantum light and reference light 1 are time-division multiplexed according to a preset ratio, and then polarization multiplexed with reference light 2 in the horizontal polarization direction. Simultaneously, missing pilot light data is supplemented by interpolation, so that two adjacent sets of reference light data are available to estimate the polarization change of the quantum signal light. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of this invention. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a system, method, and medium for realizing frequency division multiplexing of classical and quantum signals.

[0007] The system for frequency division multiplexing of classical and quantum signals according to the present invention includes: a signal generation and modulation module at the transmitting end and a signal detection module at the receiving end;

[0008] The transmitting end signal generation and modulation module includes an arbitrary waveform transmitter, a laser transmitter, an IQ modulator, a variable optical attenuator, an optical beam splitter, and an optical isolator.

[0009] The receiver signal detection module includes two zero-difference detectors, a variable optical attenuator, an optical isolator, and an optical beam splitter;

[0010] In the transmitting end signal generation and modulation module, the first and second channels of the arbitrary waveform generator are connected to the corresponding interfaces of the IQ modulator; after the laser emitter is connected to the first optical beam splitter, the smaller channel is connected to the optical isolator and then connected to the corresponding interface of the IQ modulator; the output of the IQ modulator is connected to the variable optical attenuator and then sent to the receiving end signal detection module; the larger channel of the optical beam splitter is directly sent to the receiving end signal detection module.

[0011] In the receiver signal detection module, one output of the IQ modulator is connected to the first 50:50 optical beam splitter and then sent to two homodyne detectors respectively; the larger output of the first optical beam splitter is first connected to an optical isolator, then to a variable optical attenuator, and finally sent to two homodyne detectors respectively through the second 50:50 optical beam splitter.

[0012] According to the method for frequency division multiplexing of classical and quantum signals provided by the present invention, the following steps are performed:

[0013] Step 1: Build a system for frequency division multiplexing of classical signals modulated by orthogonal phase shift keying and quantum signals modulated by Gaussian coherent states, including a signal generation and modulation module at the transmitting end and a signal detection module at the receiving end;

[0014] Step 2: Generate a random 01 sequence for transmission using quadrature phase shift keying modulation, generate a Gaussian distribution sequence for transmission using Gaussian coherent state modulation, add a sinusoidal carrier to the two sequences to form a continuous waveform, and then add the two waveforms together and send them to the arbitrary waveform generator in the signal generation and modulation module of the transmitting end. This is a composite electrical signal formed by the mixing of classical signals and quantum signals.

[0015] Step 3: Using the composite electrical signal output from the electrical signal generation module in the transmitting end signal generation and modulation module as the driving signal, and the optical signal output from the laser transmitter as the carrier, the composite electrical signal is modulated by an IQ modulator to modulate the information carried by the composite electrical signal onto the optical signal. The modulated composite optical signal carrying the information returns to the 50:50 beam splitter and interferes. The interference result enters the receiving end signal detection module and achieves coherent detection through two balanced zero-difference detectors.

[0016] Step 4: Use the program to process the signal detected by the receiver signal detection module, including coherent demodulation to separate the two signals, filtering, signal phase drift recovery, signal balance compensation, quadrant differentiation of classical signals by quadrature phase shift keying modulation, and parameter evaluation of quantum signals and classical signals.

[0017] Preferably, for classical quadrature phase shift keying (QPSK) modulation signals, the sinusoidal carrier formula is:

[0018]

[0019]

[0020] Where a1 and b1 are random 01 sequences, f c1 t is the carrier frequency of quadrature phase shift keying modulation;

[0021] For a Gaussian coherent state modulated quantum signal, the sinusoidal carrier formula is:

[0022]

[0023]

[0024] Where a2 and b2 are random sequences following a Gaussian distribution, f c2 Let t be the carrier frequency of the Gaussian coherent modulation, and t be time.

[0025] Let y a =y1+y3, let y b =y2+y4,y a With y b This refers to the composite electrical signal that will be sent to the signal generation and modulation module at the transmitting end.

[0026] Preferably, the carrier frequency of the classical quadrature phase shift keying (QPSK) modulation signal is higher than that of the Gaussian coherent modulation signal, so as to separate the two in the spectrum; the amplitude of the classical QPSK modulation signal is higher than that of the Gaussian coherent modulation signal, so as to achieve the power conditions during the transmission of the two.

[0027] Preferably, the coherent demodulation includes:

[0028] X and P are two canonical components of the light field. Initially, X and P are equal to y, respectively. a With y b During transmission, X and P have a phase shift θ, which can be derived as follows:

[0029] X = y a cosθ-y b sinθ

[0030] P = y b cosθ+y a sinθ

[0031] y a With y b Substituting the expression into the formula, we get:

[0032]

[0033]

[0034] Coherent demodulation of classical quadrature phase shift keying (QPSK) signals: Multiply X and P by... Summarized as follows:

[0035]

[0036]

[0037] in, f c1 The carrier frequency of quadrature phase shift keying modulation. f c2 Given the carrier frequency of the Gaussian coherent modulation, further separation is achieved through low-pass filtering, yielding:

[0038]

[0039]

[0040] This further restores the original random 01 sequences a1 and b1;

[0041] Coherent demodulation of Gaussian coherent state modulated quantum signals: Multiply X and P by respectively Summarized as follows:

[0042]

[0043]

[0044] in, f c1 The carrier frequency of quadrature phase shift keying modulation. f c2 Given the carrier frequency of the Gaussian coherent modulation, further separation is achieved through low-pass filtering, yielding:

[0045]

[0046]

[0047] This allows for the further reconstruction of the original Gaussian distribution sequences a2 and b2;

[0048] X Q With X G P Q With P G They are all of the same form and are collectively referred to as X. Q With X G Let X0 be the common name for P. Q With P G Let P0 be the base, and let a1 and a2 be collectively referred to as a, and let b1 and b2 be collectively referred to as b.

[0049] Preferably, the signal phase drift recovery includes: for the quadrature phase shift keying modulation signal and the Gaussian coherent state modulation signal, multiplying (X0+iP0) by... θ0 is the introduced independent variable. The value of variable θ0 is changed, and calculations are performed accordingly. The real and imaginary parts of the original sequence a and b are cross-correlation function values. The value θ0 when the cross-correlation function value is maximum is the drift phase θ. Knowing the value of θ, we can then solve the simultaneous equations... and Solving for a and b, for classical signals modulated by quadrature phase shift keying, the solutions are named X1 and P1, and for quantum signals modulated by Gaussian coherent states, the solutions are named X2 and P2.

[0050] Preferably, the signal balance compensation includes: employing a Schmitt orthogonalization operation, i.e., signal balance compensation, to restore the orthogonality of X1 and P1 and X2 and P2.

[0051] Preferably, the quadrature differentiation of the classical quadrature phase shift keying (QPSK) signal includes: drawing a constellation diagram of the classical QPSK signal based on the regular components X1 and P1 of the received classical QPSK signal, differentiating the quadrature based on the position of the points on the constellation diagram, and then encoding the received signal.

[0052] Preferably, the evaluation of quantum signal and classical signal parameters includes: calculating the electrical noise, shot noise, over-noise, and signal-to-noise ratio parameters of the Gaussian coherent state modulated quantum signal to evaluate whether quantum communication has unconditional security and whether the communication quality meets the standard; and calculating the bit error rate and signal-to-noise ratio parameters of the orthogonal phase shift keying modulated classical signal to evaluate whether the classical communication quality meets the standard.

[0053] According to the present invention, a computer-readable storage medium storing a computer program is provided, wherein when the computer program is executed by a processor, it implements the steps of the method for implementing frequency division multiplexing of classical and quantum signals.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) This invention provides a system and method for frequency division multiplexing of orthogonal phase shift keying classical signals and Gaussian coherent quantum signals. The canonical component of the coherent state carries both classical and quantum information, thus enabling the simultaneous transmission of classical data and quantum key data through a single carrier.

[0056] (2) The key distribution security in the method provided by the present invention has been proven to be equivalent to continuous variable quantum key distribution, and it also has unconditional security. The bit error rate of classical signals is also 0. This method improves the spectral utilization efficiency compared with the traditional wavelength division multiplexing method.

[0057] (3) In actual implementation, this invention only requires one set of communication transceiver equipment, which can realize the integration of classical communication and continuous variable quantum key distribution at the system level, significantly reducing the difficulty and overhead of deploying continuous variable quantum key distribution. Attached Figure Description

[0058] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0059] Figure 1 This is a system architecture diagram for realizing frequency division multiplexing of classical and quantum signals in this invention. Detailed Implementation

[0060] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0061] Example

[0062] like Figure 1 As shown, this invention provides a system for frequency division multiplexing of classical signals modulated by orthogonal phase shift keying and quantum signals modulated by Gaussian coherent states, including a transmitter signal generation and modulation module and a receiver signal detection module; the transmitter signal generation and modulation module consists of an arbitrary waveform transmitter, a laser transmitter, an IQ modulator, a variable optical attenuator, an optical beam splitter, and an optical isolator; the receiver signal detection module consists of two homodyne detectors, a variable optical attenuator, an optical isolator, and an optical beam splitter.

[0063] In the transmitting end signal generation and modulation module, the first and second channels of the arbitrary waveform generator are connected to the corresponding interfaces of the IQ modulator; after the laser emitter is connected to the first optical beam splitter, the smaller channel is connected to the optical isolator and then connected to the corresponding interface of the IQ modulator; the output of the IQ modulator is connected to the variable optical attenuator and then sent to the receiving end signal detection module; the larger channel of the optical beam splitter is directly sent to the receiving end signal detection module.

[0064] In the receiver signal detection module, one output of the IQ modulator is connected to the first 50:50 optical beam splitter and then sent to two homodyne detectors respectively; the larger output of the first optical beam splitter is first connected to an optical isolator, then to a variable optical attenuator, and finally sent to two homodyne detectors respectively through the second 50:50 optical beam splitter.

[0065] This invention also provides a method for frequency division multiplexing of classical signals modulated by quadrature phase shift keying and quantum signals modulated by Gaussian coherent states, comprising the following steps:

[0066] Step 1: Construct a device for frequency division multiplexing of classical signals modulated by orthogonal phase shift keying and quantum signals modulated by Gaussian coherent states, including a signal generation and modulation module at the transmitting end and a signal detection module at the receiving end.

[0067] Step 2: Generate a random 0-1 sequence for transmission using quadrature phase shift keying modulation; generate a Gaussian distributed sequence for transmission using Gaussian coherent state modulation. Add a sinusoidal carrier wave to the two sequences to form a continuous waveform. Then, add the two waveforms together and send the result to the arbitrary waveform generator in the signal generation and modulation module at the transmitting end. This results in a composite electrical signal formed by the mixture of classical and quantum signals.

[0068] Step 3: Using the composite electrical signal output from the electrical signal generation module in the transmitting end signal generation and modulation module as the driving signal, and the optical signal output from the laser transmitter as the carrier, the composite electrical signal is modulated by an IQ modulator, thus modulating the information carried by the composite electrical signal onto the optical signal. The modulated composite optical signal carrying the information simultaneously returns to the 50:50 beam splitter and interferes. The interference result enters the receiving end signal detection module, and coherent detection is achieved through two balanced homodyne detectors.

[0069] Step 4: Use the program to process the signal detected by the receiver signal detection module. The steps include coherent demodulation to separate the two signals, filtering, signal phase drift recovery, signal balance compensation, quadrature phase shift keying modulation classical signal pattern recognition, and quantum signal and classical signal parameter evaluation.

[0070] For classical quadrature phase shift keying (QPSK) modulation signals, the sinusoidal carrier formula is:

[0071] y1=a1cosφ1-b1sinφ1

[0072] y2=a1sinφ1+b1cosφ1

[0073] Where a1 and b1 are random 0-1 sequences, and φ1 = 2πf c1 t, f c1 t is the carrier frequency of quadrature phase shift keying modulation;

[0074] For a Gaussian coherent state modulated quantum signal, the sinusoidal carrier formula is:

[0075] y3=a2cosφ2-b2sinφ2

[0076] y4=a2sinφ2+b2cosφ2

[0077] Where a2 and b2 are random sequences following a Gaussian distribution, and φ2 = 2πf c2 t, f c2 Let t be the carrier frequency of the Gaussian coherent modulation, and t be time.

[0078] Let y a =y1+y3, let y b =y2+y4,y a With y b This refers to the composite electrical signal that will be sent to the signal generation and modulation module at the transmitting end.

[0079] The carrier frequency of the classical quadrature phase shift keying (QPSK) signal is higher than that of the Gaussian coherent modulation (Gaussian coherent modulation) signal in order to separate the two in the spectrum. The amplitude of the classical QPSK signal is also higher than that of the Gaussian coherent modulation signal to achieve the power conditions during their transmission.

[0080] Coherent demodulation is performed on the signal detected by the receiver signal detection module:

[0081] X and P are two canonical components of the light field. Initially, X and P are equal to y, respectively. a With y b During transmission, X and P will have a phase shift θ, which can be derived as follows:

[0082] X = y a cosθ-y b sinθ

[0083] P = y b cosθ+y a sinθ

[0084] y a With y b Substituting the expression into the formula, we get:

[0085] X=a1cos(φ1+θ)-b1sin(φ1+θ)+a2cos(φ2+θ)-b2sin(φ2+θ)

[0086] P=a1sin(φ1+θ)+b1cos(φ1+θ)+a2sin(φ2+θ)+b2cos(φ2+θ)

[0087] Coherent demodulation of classical quadrature phase shift keying (QPSK) signals: Multiplying X and P by cosφ1 respectively, and rearranging, we get:

[0088]

[0089]

[0090] Where, φ1=2πfc1 t, f c1 For the carrier frequency of quadrature phase shift keying modulation, φ2 = 2πf c2 t, f c2 The carrier frequency is Gaussian coherent modulation, and the frequencies are all very high. Low-pass filtering at this point can further separate the... To further restore the original random 01 sequences a1 and b1.

[0091] Coherent demodulation of a Gaussian coherent state modulated quantum signal: Multiplying X and P by cosφ2 respectively, and rearranging, we get:

[0092]

[0093]

[0094] Where, φ1=2πf c1 t, f c1 For the carrier frequency of quadrature phase shift keying modulation, φ2 = 2πf c2 t, f c2 The carrier frequency is Gaussian coherent modulation, and the frequencies are all very high. Low-pass filtering at this point can further separate the... To further restore the original Gaussian distribution sequences a2 and b2.

[0095] Because X Q With X G P Q With P G They are all of the same form and are collectively referred to as X. Q With X G Let X0 be the common name for P. Q With P G Let P0 be the reference point. Let a1 and a2 be collectively referred to as a, and b1 and b2 as b, for the convenience of the following explanation.

[0096] Phase drift recovery is performed on the coherently demodulated signal: For quadrature phase shift keying modulation signal and Gaussian coherent state modulation signal, (X0+iP0) is multiplied by e iθ 0, θ0 are the introduced independent variables. Change the value of variable θ0 and calculate (X0+iP0)·e iθ The real and imaginary parts of 0 are cross-correlation functions with the original sequences a and b. The value θ0, where the cross-correlation function is at its maximum, is the drift phase θ. Knowing the value of θ, we can then solve the simultaneous equations... and We can solve for a and b. For classical signals modulated by quadrature phase shift keying, we name the solutions X1 and P1. For quantum signals modulated by Gaussian coherent states, we name the solutions X2 and P2.

[0097] Phase-shifted signal balance compensation: Due to hardware limitations, the normally orthogonal canonical components X and P in the detected optical field are not orthogonal, i.e., X1 and P1 and X2 and P2 are not orthogonal. To restore the orthogonality of X1 and P1 and X2 and P2, a Schmitt orthogonalization operation is applied, which is the signal balance compensation.

[0098] Quadrant differentiation for classical quadrature phase shift keying (QPSK) signals: Based on the canonical components X1 and P1 of the received classical QPSK signals, a constellation diagram of the classical QPSK signals is drawn. The quadrants of the points on the constellation diagram are distinguished according to their positions, and then the received signals are encoded.

[0099] Parameter evaluation was performed on Gaussian coherent state modulated quantum signals and orthogonal phase shift keying modulated classical signals: the electrical noise, shot noise, over-noise, and signal-to-noise ratio parameters of Gaussian coherent state modulated quantum signals were calculated to assess whether quantum communication has unconditional security and whether the communication quality meets the standard; the bit error rate and signal-to-noise ratio parameters of orthogonal phase shift keying modulated classical signals were calculated to assess whether the classical communication quality meets the standard.

[0100] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0101] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0102] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A system for realizing frequency division multiplexing of classical and quantum signals, characterized in that, include: Transmitter signal generation and modulation module and receiver signal detection module; The transmitting end signal generation and modulation module includes an arbitrary waveform transmitter, a laser transmitter, an IQ modulator, a variable optical attenuator, an optical beam splitter, and an optical isolator. The receiver signal detection module includes two balanced zero-difference detectors, a variable optical attenuator, an optical isolator, and an optical beam splitter. In the transmitting end signal generation and modulation module, the first and second channels of the arbitrary waveform transmitter are connected to the corresponding interfaces of the IQ modulator; after the laser transmitter is connected to the first optical beam splitter, the smaller channel is connected to the optical isolator and then connected to the corresponding interface of the IQ modulator; the output of the IQ modulator is connected to the variable optical attenuator and then sent to the receiving end signal detection module; the larger channel of the optical beam splitter is directly sent to the receiving end signal detection module. In the receiver signal detection module, one output of the IQ modulator is connected to the first 50:50 optical beam splitter and then sent to two balanced homodyne detectors; the larger output of the first optical beam splitter is first connected to an optical isolator, then to a variable optical attenuator, and finally sent to two balanced homodyne detectors through the second 50:50 optical beam splitter.

2. A method for realizing frequency division multiplexing of classical and quantum signals, characterized in that, Using the system for frequency division multiplexing of classical and quantum signals as described in claim 1, the following steps are performed: Step 1: Build a system for frequency division multiplexing of classical signals modulated by orthogonal phase shift keying and quantum signals modulated by Gaussian coherent states, including a signal generation and modulation module at the transmitting end and a signal detection module at the receiving end; Step 2: Generate a random 01 sequence for transmission using quadrature phase shift keying modulation, generate a random sequence following a Gaussian distribution for transmission using Gaussian coherent state modulation, add a sinusoidal carrier to the above two sequences to form a continuous waveform, and then add the above two waveforms and send them to the arbitrary waveform transmitter in the signal generation and modulation module of the transmitting end. This is a composite electrical signal formed by the mixing of classical signals and quantum signals. Step 3: Using the composite electrical signal output from the electrical signal generation module in the transmitting end signal generation and modulation module as the driving signal, and the optical signal output from the laser transmitter as the carrier, the composite electrical signal is modulated by an IQ modulator to modulate the information carried by the composite electrical signal onto the optical signal. The modulated composite optical signal carrying the information returns to the 50:50 beam splitter and interferes. The interference result enters the receiving end signal detection module and achieves coherent detection through two balanced zero-difference detectors. Step 4: Use the program to process the signal detected by the receiver signal detection module, including coherent demodulation to separate the two signals, filtering, signal phase drift recovery, signal balance compensation, quadrant differentiation of classical signals by quadrature phase shift keying modulation, and parameter evaluation of quantum signals and classical signals.

3. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 2, characterized in that, For classical quadrature phase shift keying (QPSK) modulation signals, the sinusoidal carrier formula is: in, and It is a random 01 sequence. , The carrier frequency of quadrature phase shift keying modulation. It is time; For a Gaussian coherent state modulated quantum signal, the sinusoidal carrier formula is: in, and For a random sequence that follows a Gaussian distribution, , Let t be the carrier frequency of the Gaussian coherent modulation, and t be time. make = + ,make = + , and This refers to the composite electrical signal that will be sent to the signal generation and modulation module at the transmitting end.

4. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 3, characterized in that, The carrier frequency of the classical quadrature phase shift keying (QPSK) modulation signal is higher than that of the Gaussian coherent modulation signal in order to separate the two in the spectrum; the amplitude of the classical QPSK modulation signal is higher than that of the Gaussian coherent modulation signal in order to achieve the power conditions during the transmission of the two.

5. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 4, characterized in that, The coherent demodulation includes: X and P are two canonical components of the light field. Initially, X and P are respectively equal to and During transmission, X and P have a phase drift. Through derivation, we obtain: Will and Substituting the expression into the formula, we get: Coherent demodulation of classical quadrature phase shift keying (QPSK) signals: Multiply X and P by... After sorting, we get: in, , The carrier frequency of quadrature phase shift keying modulation. , Given the carrier frequency of the Gaussian coherent modulation, further separation is achieved through low-pass filtering, yielding: This further restores the original random 0-1 sequence. and ; Coherent demodulation of Gaussian coherent state modulated quantum signals: Multiply X and P by respectively After sorting, we get: in, , The carrier frequency of quadrature phase shift keying modulation. , Given the carrier frequency of the Gaussian coherent modulation, further separation is achieved through low-pass filtering, yielding: This further restores the original Gaussian distribution sequence. and ; and , and They are all the same in form and are collectively referred to as and for collectively referred to as and for collectively referred to as and collectively referred to as and b.

6. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 5, characterized in that, The signal phase drift recovery includes: for quadrature phase shift keying modulation signals and Gaussian coherent state modulation signals, Multiply by respectively , It is the introduced independent variable that changes the variable. The value of is calculated respectively. ) The cross-correlation function values ​​of the real and imaginary parts of the original sequences a and b, when the cross-correlation function value is maximized. The value is the drift phase. Known After obtaining the value, we can then solve the simultaneous equations. Solving for a and b, for a classical quadrature phase shift keying modulation signal, the solution is named... and For Gaussian coherent state modulated quantum signals, the solution is named and .

7. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 6, characterized in that, The signal balance compensation includes: employing a Schmitt orthogonalization operation, i.e., signal balance compensation, to restore... and and and Orthogonality.

8. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 7, characterized in that, The quadrature differentiation of the classical quadrature phase shift keying (QPSK) signal includes: based on the regularization component of the received classical QPSK signal. and A constellation diagram of a classic quadrature phase shift keying (QPSK) signal is drawn, and the quadrants in which the points on the constellation diagram are located are distinguished based on their positions, thereby encoding the received signal.

9. The method for realizing frequency division multiplexing of classical and quantum signals according to claim 8, characterized in that, The evaluation of quantum and classical signal parameters includes: calculating the electrical noise, shot noise, over-noise, and signal-to-noise ratio parameters of the Gaussian coherent state modulated quantum signal to evaluate whether quantum communication has unconditional security and whether the communication quality meets the standard; and calculating the bit error rate and signal-to-noise ratio parameters of the quadrature phase shift keying modulated classical signal to evaluate whether the classical communication quality meets the standard.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for frequency division multiplexing of classical and quantum signals as described in any one of claims 2 to 9.

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