Orbital angular momentum coding optical logic operation system based on mixing phase matching

Abstract

The invention discloses an orbital angular momentum coding optical logic operation system based on mixing phase matching, which relates to the technical field of optical logic operation and comprises a control terminal, a light source module, an OAM coding module, a mixing phase matching module and a magnetic field regulation and control module. A light source module generates orbital angular momentum light beams of quantum bits under logic gates corresponding to a detection field, a coupling field and a signal field respectively, an OAM coding module converts the orbital angular momentum light beams under different quantum bits into corresponding Laguerre-Gaussian light beams based on a spatial light modulator, and the Laguerre-Gaussian light beams are coded according to transmission of corresponding OAM in an atomic medium. Quantum bit coding of Laguerre-Gaussian beams in different modes is completed by setting topological charges, the mixing phase matching module sets a rubidium atom gas chamber and completes mixing phase matching of the Laguerre-Gaussian beams, and the magnetic field regulation and control module deploys an adjustable electromagnetic field device so as to carry out electromagnetic field constraint regulation and control of the Laguerre-Gaussian beams. And orbital angular momentum coding optical logic operation is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of optical logic operations, and specifically to an orbital angular momentum encoded optical logic operation system based on mixed-frequency phase matching. Background Technique

[0002] Due to its helical phase characteristics, the orbital angular momentum beam (OAM beam) can provide an infinite-dimensional quantum state encoding space and is an important carrier for quantum information processing. Traditional OAM detection techniques rely on complex optical interference devices, while quantum logic operations are mostly based on superconducting circuits or ion traps, suffering from problems such as high system complexity and difficulty in integration. In recent years, the nonlinear optical effect based on atomic media has provided a new approach for OAM control, but the combination of mixed-frequency phase matching and magnetic field control in the existing technology is not yet mature, and the logic operation fidelity and real-time detection accuracy still need to be improved. Summary of the Invention

[0003] In order to solve the above problems, the purpose of the present invention is to provide an orbital angular momentum encoded optical logic operation system based on mixed-frequency phase matching.

[0004] The purpose of the present invention can be achieved through the following technical solutions: An orbital angular momentum encoded optical logic operation system based on mixed-frequency phase matching, including a control terminal, which is communicatively connected to a light source module, an OAM encoding module, a mixed-frequency phase matching module, and a magnetic field control module; The light source module is used to generate orbital angular momentum beams corresponding to the quantum bits under the respective logic gates of the probe field, the coupling field, and the signal field; The OAM encoding module, based on a spatial light modulator, converts the orbital angular momentum beams under different quantum bits into corresponding Laguerre-Gaussian beams, and completes the quantum bit encoding in different modes of the Laguerre-Gaussian beams by setting the topological charge number according to the transfer of the OAM corresponding to the Laguerre-Gaussian beams in the atomic medium; The mixed-frequency phase matching module is used to set a rubidium atomic gas cell, and then complete the mixed-frequency phase matching corresponding to the Laguerre-Gaussian beam; The magnetic field control module is used to deploy an adjustable electromagnetic field device, and perform electromagnetic field constraint control corresponding to the Laguerre-Gaussian beam through the adjustable electromagnetic field device to complete the orbital angular momentum encoded optical logic operation.

[0005] Further, the process of the light source module generating orbital angular momentum beams corresponding to the quantum bits under the respective logic gates of the probe field, the coupling field, and the signal field includes: The light source module performs light source configuration and parameter initialization; Two external cavity semiconductor lasers are used as the light sources for the probe field, the coupling field, and the signal field respectively to generate the object. Set the adjustment range of the light source wavelength, the output power, and the fluctuation range of the light source wavelength. According to the subordinate relationship between the fluctuation amplitude and the fluctuation range of the light source wavelength, determine whether it is necessary to intervene and adjust the light source wavelength; The light source module performs beam splitting and modulation, dividing the light source beam output by the external cavity semiconductor laser into orbital angular momentum beams under different field sources. The different field sources include the probe field, the coupling field, and the signal field.

[0006] Furthermore, the process by which the OAM encoding module converts the orbital angular momentum beams under different qubits into corresponding Laguerre-Gaussian beams based on the spatial light modulator includes: Perform SLM parameter configuration and beam alignment operations on the spatial light modulator; Construct a phase hologram. When the SLM loads the phase hologram, the light source beam incident on the central region of the SLM is modulated into a Laguerre-Gaussian beam carrying different values. The Laguerre-Gaussian beam is also called the LG beam; When = +1, an LG beam with an annular intensity distribution and a counterclockwise spiral phase is generated; When = -1, an LG beam with a clockwise spiral phase is generated; Perform different types of mode detections on the Laguerre-Gaussian beam. The mode detections include intensity distribution detection and phase structure detection.

[0007] Furthermore, the process of the SLM parameter configuration and the beam alignment operation includes: The SLM parameter configuration is: set the SLM pixel resolution, refresh rate, and phase modulation depth of the spatial light modulator, and calibrate the phase-voltage response curve of the SLM according to the light source wavelength to ensure that the phase modulation linearity ≥ 99%; The beam alignment operation is: vertically incident the light source beam incident from the light source module onto the set central region of the SLM, and calibrate the incident optical path of the light source beam through the set quadrant photodetector QPD to keep the beam center of the incident light source beam aligned with the SLM pixel matrix corresponding to the central region of the SLM.

[0008] Furthermore, the process of completing the qubit encoding in different modes of the Laguerre-Gaussian beam by setting the topological charge number according to the transfer of the OAM corresponding to the Laguerre-Gaussian beam in the atomic medium includes: The atomic medium for the transfer of the OAM corresponding to the Laguerre-Gaussian beam is rubidium atoms; When the Laguerre-Gaussian beam propagates in rubidium atoms, different topological charge numbers are selected and set to encode the spatial mode of the LG beam, the expression of the amplitude distribution of the LG beam is constructed, and the first-order density matrix elements and the third-order density matrix elements of the input field and the output field of the LG beam under each field source are obtained; The spatial modes of the LG beam include and , and which are respectively defined as the ground states |0⟩ and |1⟩ in quantum logic computing, and the corresponding OAMs of the LG beam are and , and during the logic operation process, the spatial mode information of the LG and is encoded as the basic qubits; The mapping relationship defined between the topological charge number and the qubit is obtained.

[0009] Furthermore, the mapping relationship defined between the topological charge number and the qubit includes: When the qubit state is |0⟩, the topological charge number is set to 1; When the qubit state is |1⟩, the topological charge number is set to -1; When there are multi-qubit operations, the mapping relationship between the qubits and the topological charge numbers is extended. The qubit states for multi-qubit operations include |00⟩, |01⟩, |10⟩, and |11⟩, and the values of the correspondingly set topological charge numbers are = +2, = -2, = +3, and = -3.

[0010] Furthermore, the frequency mixing phase matching module sets the rubidium atomic cell, and the process of completing the frequency mixing phase matching corresponding to the Laguerre-Gaussian beam includes: Construct a rubidium atomic cell. A cylindrical rubidium atomic cell is used, the cell height and cell diameter of the cylindrical rubidium atomic cell are set, the temperature inside the cylindrical rubidium atomic cell is controlled, and the rubidium vapor density is maintained within a set range; Wrap a Helmholtz coil outside the cylindrical rubidium atomic cell to provide a uniform axial magnetic field for regulating the Zeeman splitting of atomic energy levels. Integrate a thermocouple and a PID temperature control system to control the temperature fluctuation inside the cylindrical rubidium atomic cell ≤ ±0.5 °C. Then, the rubidium atomic cell is constructed, and the optical path incident design configuration of the rubidium atomic cell is continued, and the experimental conditions for the Laguerre-Gaussian beam to complete the frequency mixing phase matching are set.

[0011] Furthermore, the specific process of setting the experimental conditions for the Laguerre-Gaussian beam to achieve mixing phase matching includes: Using three external cavity semiconductor lasers with a wavelength set to 780 nm to generate a probe light, a coupling light, and a signal light respectively. Through a spatial light modulator, the three beams are converted into specific topological charges. Furthermore, the mixing phase matching module sets a rubidium atomic cell, and the process of achieving the mixing phase matching corresponding to the Laguerre-Gaussian beam includes: Construct a rubidium atomic cell. Use a cylindrical rubidium atomic cell, set the cell height and cell diameter of the cylindrical rubidium atomic cell, control the temperature inside the cylindrical rubidium atomic cell, and maintain the rubidium atomic vapor density within a set range; Wrap a Helmholtz coil outside the cylindrical rubidium atomic cell to provide a uniform axial magnetic field for regulating the Zeeman splitting of atomic energy levels. Integrate a thermocouple and a PID temperature control system to control the temperature fluctuation inside the cylindrical rubidium atomic cell ≤ ±0.5 °C. Then, the rubidium atomic cell is constructed, and the optical path incident design configuration of the rubidium atomic cell is continued to set the experimental conditions for the Laguerre-Gaussian beam to achieve mixing phase matching.

[0012] Furthermore, the specific process of setting the experimental conditions for the Laguerre-Gaussian beam to achieve mixing phase matching includes: Using three external cavity semiconductor lasers with a wavelength set to 780 nm to generate a probe light, a coupling light, and a signal light respectively. Through a spatial light modulator, the three beams are converted into LG modes with specific topological charges . After the probe light, the coupling light, and the signal light are incident on the rubidium atomic cell at a preset angle, set the phase matching conditions for the three beams to perform mixing phase matching. The phase matching conditions that the incident beams corresponding to the probe light, the coupling light, and the signal light need to satisfy are as follows: After the probe light, the coupling light, and the signal light are incident on the rubidium atomic cell at a preset angle, set the phase matching conditions for the three beams to perform mixing phase matching. The phase matching conditions that the incident beams corresponding to the probe light, the coupling light, and the signal light need to satisfy are as follows: ; Among them, , and are the phase values of the incident beams corresponding to the probe light, the coupling light, and the signal light respectively, is the numerical difference between the phase values of the three incident beams; When , adjust the incident angles and polarization directions of the incident beams of the probe light, the coupling light, and the signal light until the phase matching conditions of the three beams are satisfied; When When it is, no operation is performed.

[0013] Furthermore, the magnetic field regulation module deploys an adjustable electromagnetic field device, and performs electromagnetic field constraint regulation corresponding to the Laguerre-Gaussian beam through the adjustable electromagnetic field device. The process of completing the orbital angular momentum encoding optical logic operation includes: Using Helmholtz coils as components of the adjustable electromagnetic field device; Configuring a programmable DC power supply, integrating a magnetic field sensor for real-time monitoring of the magnetic field strength of the electromagnetic field generated by the Helmholtz coils, setting the induction accuracy of the magnetic field sensor, fixing the Helmholtz coils on a non-magnetic bracket, and installing them coaxially with the rubidium atomic gas cell; Setting the target magnetic field strength for electromagnetic field constraint regulation, adjusting the coil current through the power supply controller corresponding to the programmable DC power supply, and controlling the magnetic field direction of the electromagnetic field through the current direction of the coil current; The electromagnetic field constraint regulation also includes calibration of the uniformity of the electromagnetic field; After the electromagnetic field constraint regulation is completed, an electromagnetic field constraint regulation test experiment is performed to complete the orbital angular momentum encoding optical logic operation.

[0014] Compared with the prior art, the beneficial effects of the present invention are: by combining the frequency mixing phase matching module with the nonlinear optical effect, the phase matching condition is optimized, the signal strength and the nonlinear susceptibility are enhanced, and the fidelity and calculation efficiency of the orbital angular momentum encoding optical logic operation are improved; the magnetic field regulation module is used to regulate the Zeeman splitting and refractive index distribution of rubidium atoms, and the programmable DC power supply is combined to achieve high-precision control of the magnetic field strength and direction, improving the system integration and real-time regulation ability; through the mapping relationship between the topological charge number and the qubit, multi-qubit expansion is realized, breaking through the traditional two-dimensional qubit limit, supporting multi-dimensional quantum state encoding, and providing a theoretical basis for complex logic gate operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the orbital angular momentum encoding optical logic operation system based on frequency mixing phase matching according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] As Figure 1 shown, the orbital angular momentum encoding optical logic operation system based on frequency mixing phase matching includes a control terminal, and the control terminal is communicatively connected to a light source module, an OAM encoding module, a frequency mixing phase matching module, and a magnetic field regulation module; The light source module is used to generate orbital angular momentum beams corresponding to the qubits under the logic gates of the probe field, the coupling field, and the signal field respectively; The OAM encoding module is based on a spatial light modulator, which converts the orbital angular momentum beams under different qubits into corresponding Laguerre-Gaussian beams, and completes the qubit encoding of different modes of the Laguerre-Gaussian beams by setting the topological charge number according to the transmission of the OAM corresponding to the Laguerre-Gaussian beams in the atomic medium; The frequency mixing phase matching module is used to set the rubidium atomic gas cell, and then complete the frequency mixing phase matching corresponding to the Laguerre-Gaussian beam; The magnetic field regulation module is used to deploy an adjustable electromagnetic field device, and perform electromagnetic field constraint regulation corresponding to the Laguerre-Gaussian beam through the adjustable electromagnetic field device to complete the orbital angular momentum encoding optical logic operation.

[0017] It should be further noted that in the specific implementation process, the process of the light source module generating the orbital angular momentum beams corresponding to the qubits under the respective logic gates of the detection field, the coupling field, and the signal field includes: The light source module performs light source configuration and parameter initialization; The content of the light source configuration and parameter initialization is: Two external cavity semiconductor lasers are used as the light source generation objects for the detection field, the coupling field, and the signal field respectively. The light source wavelength corresponding to the external cavity semiconductor laser is set to 780 nm, and the adjustment range of the output power is set to 10 - 100 mW; Set the fluctuation range corresponding to the light source wavelength, and denote the fluctuation range as Ω; Then Ω = [-0.1 nm, +0.1 nm], which means that when the fluctuation amplitude of the light source wavelength generated by the external cavity semiconductor laser is within ±0.1 nm, it meets the light source configuration expectation. Otherwise, intervention adjustment of the light source wavelength is performed to ensure the coherence of the optical field.

[0018] The light source module performs beam splitting modulation; The content of the beam splitting modulation is: The external cavity semiconductor laser outputs a light source beam. After the beam splitter receives the output light source beam, the light source beam is divided into orbital angular momentum beams corresponding to different field sources; The different field sources specifically include the detection field, the coupling field, and the signal field; The qubit representations of the orbital angular momentum beams of different field sources corresponding to the logic gates are as follows: Detection field: Used as the control bit or auxiliary field of the logic gate; Coupling field: Used to induce the electromagnetically induced transparency effect of the rubidium atomic medium and serve as the response bit of the logic gate; Signal field: Used as the target bit or output bit of the logic operation.

[0019] It should be noted that based on the basic theory of the principle of interaction between light and matter, the light source module realizes the clear division of qubits in the detection field, coupling field, and signal field under logical operations, and generates preliminary orbital angular momentum beams under different field sources.

[0020] It should be further noted that in the specific implementation process, the process by which the OAM encoding module converts the orbital angular momentum beams under different qubits into corresponding Laguerre-Gaussian beams based on a spatial light modulator includes: Performing SLM parameter configuration and beam alignment operations on the spatial light modulator; The content of the SLM parameter configuration is: setting the SLM pixel resolution, refresh rate, and phase modulation depth corresponding to the spatial light modulator, and respectively recording the corresponding parameter values of the SLM pixel resolution, refresh rate, and phase modulation depth as 1920×1080, 60Hz, and 0-2π; calibrating the phase-voltage response curve of the SLM according to the light source wavelength to ensure that the phase modulation linearity ≥ 99%.

[0021] The content of the beam alignment operation is: vertically incident the light source beam incident from the light source module into the set central area of the SLM, and use the set quadrant photodetector QPD to calibrate the incident optical path of the light source beam to keep the beam center of the incident light source beam aligned with the SLM pixel matrix corresponding to the central area of the SLM; collimate the light source beam incident on the central area of the SLM through a lens group with a focal length f = 200mm to avoid distortion problems caused by the divergence of the light source beam.

[0022] Construct a phase hologram. When the SLM loads the phase hologram, the light source beam incident on the central area of the SLM is modulated into a Laguerre-Gaussian beam carrying different values. The Laguerre-Gaussian beam is also called an LG beam; When = +1, an LG beam with an annular intensity distribution and a counterclockwise spiral phase is generated; When = -1, an LG beam with a clockwise spiral phase is generated; Perform different types of mode detections on the Laguerre-Gaussian beam; The mode detection includes intensity distribution detection and phase structure detection.

[0023] The execution process of the intensity distribution detection is: collecting the beam cross-section through a CCD camera and verifying the corresponding relationship between the radius of the annular light spot presented by the beam cross-section and the value, where is the topological charge number corresponding to the light source beam, and recording the radius of the annular light spot as ; There is a corresponding relationship: ; The execution process of the phase structure detection is as follows: By the Gaussian beam interference method, observe the number and direction of the fork interference fringes, and then determine the sign and magnitude of the

[0024] It should be further noted that in the specific implementation process, according to the transfer of the OAM corresponding to the Laguerre-Gaussian beam in the atomic medium, the process of completing the qubit encoding in different modes of the Laguerre-Gaussian beam by setting the topological charge number includes: The atomic medium for the transfer of the OAM corresponding to the Laguerre-Gaussian beam is rubidium atoms; When the Laguerre-Gaussian beam propagates in rubidium atoms, select and set different topological charge numbers to encode the spatial modes corresponding to the LG beam, and then complete the qubit encoding corresponding to the Laguerre-Gaussian beam in different modes; specifically as follows: First, the expression of the amplitude distribution corresponding to the LG beam is as follows: (1): ; Among them, is the complex amplitude of the LG beam, The subscript P in is the number of nodes of the LG beam in the radial direction, is the beam radius of the LG beam in the z direction, is the polar coordinate of a certain point on the cross section of the beam corresponding to the LG beam, is the imaginary unit, used to describe the complex phase structure, is the rotation angle of a certain point on the cross section of the beam in the polar coordinate system of the LG beam relative to the optical axis, that is is the azimuth angle, where 0 ≤ < 2 , is the natural exponential function, is the associated Laguerre polynomial, and the associated Laguerre polynomial describes the radial distribution of the LG beam. In order to reduce the transmission loss and facilitate encoding, set the number of nodes P in the radial mode to 0, and only consider the topological charge number corresponding to the vortex light for the incident light source beam, and set the topological charge number to = 1.

[0025] Obtain the first-order density matrix elements and third-order density matrix elements corresponding to the input field and output field of the Laguerre-Gaussian beam for each field source respectively; The first-order density matrix elements and third-order density matrix elements are carried out through the three-level structure experiment and the perturbation chain theory ; Among them, represents the initial density matrix, , and are the first-order density matrix element, the second-order density matrix element, and the third-order density matrix element, respectively. , and are the electric field strengths of the input optical fields corresponding to the signal field, the probe field, and the coupling field, respectively. In the formula, The corresponding subscripts 00, 10, and 20 represent energy level transitions. The first-order density matrix elements and the third-order density matrix elements corresponding to the input field and the output field are respectively expressed as follows: (2): ; (3): ; In equations (2) and (3), represents the first-order density matrix element, represents the third-order density matrix element. The density matrix elements of different orders are used to describe the transition probability amplitudes between the energy levels |1> and |0> of the quantum system. The superscript (1) represents the first-order nonlinear polarization response, and the superscript (3) represents the third-order nonlinear polarization response. is the imaginary unit, which is used to construct the phase term in the complex form. represents the Rabi frequency, which is used to describe the coupling strength between the optical field and the atomic energy level. Among them, , and are the Rabi frequencies of the probe field, the coupling field, and the signal field, respectively. In equations (2) and (3), and are the energy level decay rates, which are used to describe the rate of spontaneous emission of atoms from high energy levels to low energy levels. represents the decay rate from the energy level |1> to |0>, represents the decay rate from the energy level |2> to |0>. and are the detuning amounts, which are used to represent the difference between the optical field frequency and the atomic transition frequency. When the optical field frequency is , the transition frequency from the energy level |1> to |0> is denoted as , and the transition frequency from the energy level |2> to |0> is denoted as ; Then there is , ; In equations (2) and (3), is the periodic factor of the Laguerre-Gaussian beam along the propagation direction. Due to the existence of the periodic factor, the third-order susceptibility becomes a periodic susceptibility, reflecting the periodic characteristics. Among them, is the phase-matching term, which is related to the spatial modulation and interference of the optical field. is the wave vector. , is the optical wavelength. is the phase angle; is the azimuth angle, which describes the angular position of a point on the cross-section of the LG beam corresponding to the beam. The azimuth angle ranges from [0, 2 );

[0026] For the output signal , the relationship between the third-order density matrix element and the corresponding susceptibility is as follows: (4): ; Among them, is the third-order nonlinear susceptibility tensor, which is used to characterize the nonlinear response intensity of the atomic medium to the signal field represented by , the probe field represented by and the coupling field represented by to the respective input optical fields. The larger the value of , the more significant the corresponding nonlinear effect. , and are the electric field strengths of the signal field, the probe field, and the coupling field corresponding to the respective input optical fields. Through the third-order nonlinear interaction , they jointly drive the generation of the output signal ; In this nonlinear process, introducing OAM into the corresponding input optical fields, the OAM transfer expression of the corresponding beam can be obtained through formulas (1) and (4) as follows: (5): ; Among them, represents the topological charge number corresponding to the output signal of the LG beam, , and are the topological charge numbers of the signal field, the probe field, and the coupling field respectively; According to formula (1), different topological charge numbers are selected to encode the spatial mode of the LG beam, and then a quantum logic gate is realized in the rubidium atom three-level system. The specific process is to use the spatial mode of the Laguerre-Gaussian beam and Are respectively defined as the ground states |0⟩ and |1⟩ in quantum logic computing, and the OAMs of the corresponding LG beams are respectively and , and the spatial mode information of LG and are used as basic qubits for encoding during the logic operation process.

[0027] Obtain the defined mapping relationship between the topological charge number and the qubit; When the qubit state is |0⟩, set the topological charge number = 1; When the qubit state is |1⟩, set the topological charge number = -1; When there are multi-qubit operations, expand the mapping relationship between the qubits and the topological charge numbers. The example is as follows: The qubit states for multi-qubit operations include |00⟩, |01⟩, |10⟩, and |11⟩, and the values of the topological charge numbers corresponding to the extended settings in sequence are = +2, = -2, = +3 and = -3; The multi-qubit operation breaks through the traditional two-dimensional limit.

[0028] Construct a rubidium atom three-level inverted V system, input different types of field sources into it, and then generate a non-linear polarization output signal through four-wave mixing. For different types of field sources in the rubidium atom three-level inverted V system, the OAM of the non-linear polarization output signal follows the following conservation law: ; For example: the topological charge number of the probe field, the topological charge number of the coupling field, and the topological charge number of the signal field are such that the topological charge number corresponding to the non-linear polarization output signal is expressed as ; Furthermore, by adjusting the value of the topological charge number , the qubit state can be programmatically controlled.

[0029] It should be further noted that in the specific implementation process, the process of setting the rubidium atom gas cell by the frequency mixing phase matching module to complete the frequency mixing phase matching corresponding to the Laguerre-Gaussian beam includes: Construct a rubidium atom gas cell. Use a cylindrical rubidium atom gas cell, set the height of the cylindrical rubidium atom gas cell to 10 cm and the diameter to 2 cm, and fill natural rubidium in the cylindrical rubidium atom gas cell. Natural rubidium is and a mixed vapor composed of isotope compositions; Using an indium furnace or a resistance wire heating device, the temperature inside the cylindrical rubidium atomic gas cell is controlled at 50 - 80 °C to maintain the rubidium atomic vapor density within a set range (about 10 12 -10 13 atoms / cm³) to enhance the nonlinear effect; Anti-reflection films are coated on both ends of the gas cell of the cylindrical rubidium atomic gas cell to keep the reflectivity at both ends of the gas cell ≤ 0.5%. A Helmholtz coil is wrapped outside the cylindrical rubidium atomic gas cell to provide a uniform axial magnetic field (adjustable from 0 - 100 mT) for regulating the Zeeman splitting of atomic energy levels. A thermocouple and a PID temperature control system are integrated to ensure that the temperature fluctuation inside the cylindrical rubidium atomic gas cell is ≤ ±0.5 °C, avoiding phase mismatch caused by atomic density fluctuation.

[0030] After completing all the above configuration operations, the mixing phase matching module sets up the rubidium atomic gas cell and continues with the optical path incident design configuration of the rubidium atomic gas cell, and then sets up the Laguerre-Gaussian beam to complete the experimental conditions for mixing phase matching; Specifically: Three external cavity semiconductor lasers with a wavelength set to 780 nm are used to generate a probe light, a coupling light, and a signal light respectively. The three beams of light are converted into LG modes with specific topological charges by a spatial light modulator (such as taking values of +1, 0, and -1).

[0031] After the probe light, the coupling light, and the signal light are incident on the rubidium atomic gas cell at a preset angle, the phase matching conditions for the three beams of light to perform mixing phase matching are set. The phase matching conditions that the beams of light corresponding to the probe light, the coupling light, and the signal light need to satisfy when incident are as follows: ; where , and are the phase values of the beams of light corresponding to the probe light, the coupling light, and the signal light when incident respectively, and is the numerical difference between the phase values of the three incident beams of light; When , the incident angles and polarization directions of the beams of light corresponding to the probe light, the coupling light, and the signal light are adjusted until the phase matching conditions for the three beams of light are satisfied; When , no operation is performed.

[0032] It should be further noted that in the specific implementation process, the magnetic field regulation module deploys an adjustable electromagnetic field device, and through the adjustable electromagnetic field device, the electromagnetic field constraint regulation corresponding to the Laguerre-Gaussian beam is carried out. The process of completing the orbital angular momentum encoded optical logic operation includes: The Helmholtz coil is used as the core component of the adjustable electromagnetic field device. The ratio of the coil diameter to the coil spacing of the Helmholtz coil is set to 1:1, and it is adapted to the size of the rubidium atomic cell. The coil material is selected as high-conductivity copper wire, with the number of turns being 200 - 300 turns, supporting a continuous current of 0 - 5A, corresponding to a magnetic field strength of 0 - 100mT; Configure a programmable DC power supply, and integrate a magnetic field sensor to monitor the magnetic field strength of the electromagnetic field generated by the Helmholtz coil in real time. Set the induction accuracy of the magnetic field sensor to ±0.1mT. Fix the Helmholtz coil on a non-magnetic bracket and install it coaxially with the rubidium atomic cell to ensure that the magnetic field direction is along the light beam propagation axis.

[0033] Set the target magnetic field strength for electromagnetic field constraint regulation. Adjust the coil current through the power supply controller corresponding to the programmable DC power supply. The magnetic field direction of the electromagnetic field is controlled by the current direction of the coil current. A positive current corresponds to a clockwise magnetic field direction, and a negative current corresponds to a counterclockwise magnetic field direction; For example, set the target magnetic field strength B for OAM rotation regulation to 30mT. The magnetic field formula of the corresponding Helmholtz coil is expressed as follows: ; Among them, is the number of coil turns, is the coil current, is the coil radius, is the magnetic field regulation coefficient.

[0034] The electromagnetic field constraint regulation also includes the uniformity calibration of the electromagnetic field. Specifically: Use a three-dimensional magnetic field probe to scan the magnetic field distribution in the rubidium atomic cell area, adjust the coil spacing or add additional shimming coils to ensure that the magnetic field uniformity error ≤ 1%. After the uniformity calibration is completed, generate a magnetic field strength - current mapping table and embed it in the control software to achieve fast parameter calling for later electromagnetic field constraint regulation.

[0035] The principle of the interaction between the electromagnetic field constraint regulation and the Laguerre - Gaussian beam: The electromagnetic field induces the Zeeman splitting of the rubidium atomic energy levels, changing the refractive index distribution of the medium. For example, in an inverted V - type three - level system, an increase in the magnetic field strength will cause the offset of the electromagnetically induced transparency (EIT) window, affecting the efficiency of the mixing phase matching. By adjusting the magnetic field strength, the nonlinear susceptibility is dynamically regulated to optimize the signal strength of optical logic operations.

[0036] The interaction between the electromagnetic field and the Laguerre - Gaussian beam causes the rotation of the phase distribution of the beam cross - section. The rotation angle and the magnetic field strength are linearly related. The linear relationship is expressed as follows: ; Among them, is the magneto - optical coefficient corresponding to rubidium atoms, is the action length of the Laguerre - Gaussian beam in the rubidium atomic cell, The maximum value of should satisfy being less than or equal to the cell height of the rubidium atomic cell; For example: when = 30 mT, = 2.5×10 −4 ×30×10 = 0.075 rad ≈ 4.3°; After the electromagnetic field constraint regulation is completed, perform an electromagnetic field constraint regulation test experiment to implement the orbital angular momentum - encoded optical logic operation. The corresponding experimental steps are as follows: Step 1: Initial magnetic field setting; 1a): Start the programmable DC power supply and set the initial current (such as the magnetic field strength corresponding to a current of 1 A is 20 mT); 1b): Verify the magnetic field strength through a magnetic field sensor and adjust the coil current of the Helmholtz coil to the set target value (for example: if the target magnetic field strength is 30 mT, then set the coil current of the Helmholtz coil to 1.5 A); Step 2: Detection of the rotation of the Laguerre - Gaussian beam; 2a): Input the LG beam of . After it is incident on the rubidium atomic cell, the output spot of the interference image is collected by the CCD; 2b): Gradually and uniformly increase the magnetic field strength, record the change in the rotation angle of the spot, and verify the linear relationship (for example: from 10 mT to 50 mT, increase the magnetic field strength step by step by 5 mT each time); Step 3: Dynamic regulation of the logic gate; 3a): In the C - NOT gate operation, when the control bit is |1> ( ), the target magnetic field strength is automatically switched to 30 mT, inducing the OAM of the target bit to flip; 3b): By detecting the rotation angle of the output spot through the CCD (such as 4.3°), it is confirmed that the logic operation is successful.

[0037] It should be noted that the principle of orbital angular momentum detection under the action of the magnetic field combines the nonlinear Kerr effect of hot rubidium atomic vapor in magnetic field control and the orbital angular momentum transmission characteristics. The rotation angle of the interference image collected by the CCD corresponds to the magnetic field change intensity. The change in the magnetic field strength causes the interference image to rotate. When the magnetic field strength is the same, the rotation angles of the transverse cross - sections of Laguerre - Gaussian beams carrying different OAMs are different, and the spatial intensity distributions of different beam modes are different, thereby identifying the OAM values they carry.

[0038] The above embodiments are only used to illustrate the technical method of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical method of the present invention.

Claims

1. An orbital angular momentum encoding optical logic operation system based on mixing phase matching, including a control terminal, characterized in that, The control terminal is communicatively connected to a light source module, an OAM encoding module, a frequency mixing phase matching module, and a magnetic field regulation module; The light source module is used to generate orbital angular momentum beams corresponding to the qubits under the respective logic gates of the detection field, the coupling field, and the signal field; Based on a spatial light modulator, the OAM encoding module converts the orbital angular momentum beams under different qubits into corresponding Laguerre-Gaussian beams, and according to the transmission of the OAM corresponding to the Laguerre-Gaussian beams in the atomic medium, the qubit encoding under different modes of the Laguerre-Gaussian beams is completed by setting the topological charge number; The frequency mixing phase matching module is used to set a rubidium atomic gas cell, and further complete the frequency mixing phase matching corresponding to the Laguerre-Gaussian beam; The magnetic field regulation module is used to deploy an adjustable electromagnetic field device, and perform electromagnetic field constraint regulation corresponding to the Laguerre-Gaussian beam through the adjustable electromagnetic field device to complete the orbital angular momentum encoding optical logic operation.

2. The orbital angular momentum encoding optical logic operation system based on mixing phase matching according to claim 1, wherein The process by which the light source module generates orbital angular momentum beams corresponding to the qubits under the respective logic gates of the detection field, the coupling field, and the signal field includes: The light source module performs light source configuration and parameter initialization; Two external cavity semiconductor lasers are used as the light source generation objects for the detection field, the coupling field, and the signal field respectively. The adjustment ranges of the light source wavelength and the output power are set, as well as the fluctuation range of the light source wavelength. According to the subordination relationship between the fluctuation amplitude and the fluctuation range of the light source wavelength, it is judged whether it is necessary to intervene and adjust the light source wavelength; The light source module performs beam splitting modulation, and divides the light source beam output by the external cavity semiconductor laser into orbital angular momentum beams under different field sources. The different field sources include the detection field, the coupling field, and the signal field.

3. The orbital angular momentum encoding optical logic operation system based on mixing frequency phase matching according to claim 2, wherein The process by which the OAM encoding module converts the orbital angular momentum beams under different qubits into corresponding Laguerre-Gaussian beams based on a spatial light modulator includes: Perform SLM parameter configuration and beam alignment operations on the spatial light modulator; Construct a phase hologram. After the phase hologram is loaded onto the SLM, the light source beam incident on the central region of the SLM is modulated into Laguerre-Gaussian beams carrying different values. The Laguerre-Gaussian beam is also called the LG beam. When = +1, an LG beam with a circular intensity distribution and a counterclockwise spiral phase is generated; When = -1, an LG beam with a clockwise spiral phase is generated; Perform different types of mode detections on the Laguerre-Gaussian beam. The mode detections include intensity distribution detection and phase structure detection.

4. The orbital angular momentum encoding optical logic operation system based on mixing phase matching according to claim 3, characterized in that The process of the SLM parameter configuration and the beam alignment operation includes: The SLM parameter configuration is: set the SLM pixel resolution, refresh rate, and phase modulation depth of the spatial light modulator, and calibrate the phase-voltage response curve of the SLM according to the light source wavelength to ensure that the phase modulation linearity ≥ 99%; The beam alignment operation is: vertically incident the light source beam incident from the light source module onto the central area of the set SLM, and calibrate the incident light path of the light source beam through the set quadrant photodetector QPD to keep the beam center of the incident light source beam aligned with the SLM pixel matrix corresponding to the central area of the SLM.

5. The orbital angular momentum encoding optical logic operation system based on mixing frequency phase matching according to claim 4, wherein The process of completing the qubit encoding under different modes of the Laguerre-Gaussian beam by setting the topological charge number according to the transmission of the OAM corresponding to the Laguerre-Gaussian beam in the atomic medium includes: The atomic medium through which the OAM corresponding to the Laguerre-Gaussian beam is transmitted is rubidium atoms; When the Laguerre-Gaussian beam propagates in rubidium atoms, different topological charge numbers are selected and set to encode the spatial mode of the LG beam, the expression of the amplitude distribution of the LG beam is constructed, and the first-order density matrix elements and the third-order density matrix elements of the input field and the output field of the LG beam under each field source are obtained; The spatial modes of the LG beam include and , and which are respectively defined as the ground states |0⟩ and |1⟩ in quantum logic computing, and the corresponding OAMs of the LG beam are and respectively. During the logical operation process, the spatial mode information of the LG and is encoded as the basic qubits; Obtain the mapping relationship defined between the topological charge number and the qubit.

6. The orbital angular momentum encoding optical logic operation system based on mixing phase matching according to claim 5, wherein The mapping relationship defined between the topological charge number and the qubit includes: When the qubit state is |0ñ, set the topological charge number = 1; When the qubit state is |1ñ, set the topological charge number = -1; When there are multi-qubit operations, the mapping relationship between qubits and topological charge numbers is extended. The qubit states for multi-qubit operations include |00ñ, |01ñ, |10ñ, and |11ñ, and the corresponding values of the set topological charge numbers are = +2, = -2, = +3 and = -3.

7. The orbital angular momentum encoding optical logic operation system based on mixing phase matching according to claim 6, wherein The process of setting the rubidium atomic gas cell by the frequency mixing phase matching module and then completing the frequency mixing phase matching corresponding to the Laguerre-Gaussian beam includes: Construct a rubidium atomic gas cell, use a cylindrical rubidium atomic gas cell, set the cell height and cell diameter of the cylindrical rubidium atomic gas cell, control the temperature inside the cylindrical rubidium atomic gas cell, and maintain the rubidium atomic vapor density within a set range; Wrap a Helmholtz coil outside the cylindrical rubidium atomic gas cell to provide a uniform axial magnetic field for regulating the Zeeman splitting of atomic energy levels, integrate a thermocouple and a PID temperature control system, control the temperature fluctuation inside the cylindrical rubidium atomic gas cell ≤ ±0.5 °C, and then complete the construction of the rubidium atomic gas cell, and continue with the optical path incident design configuration of the rubidium atomic gas cell, and set the experimental conditions for the Laguerre-Gaussian beam to complete frequency mixing phase matching.

8. The orbital angular momentum encoding optical logic operation system based on mixing phase matching according to claim 7, wherein The specific process of setting the experimental conditions for the Laguerre-Gaussian beam to complete frequency mixing phase matching includes: Use three external cavity semiconductor lasers with a wavelength set at 780 nm to generate a probe light, a coupling light, and a signal light respectively, and convert the three beams of light into LG modes with specific topological charge numbers through a spatial light modulator; After the probe light, the coupling light, and the signal light are incident on the rubidium atomic gas cell at a preset angle, set the phase matching conditions for the three beams to perform frequency mixing phase matching. The phase matching conditions that the probe light, the coupling light, and the signal light need to satisfy for their respective incident beams are as follows: ； Among them, , and are the phase values of the light beams respectively corresponding to the incident probe light, coupled light and signal light, is the numerical difference between the phase values of the light beams incident by the three; When adjust the incident angles and polarization directions of the beams of the probe light, the coupling light, and the signal light respectively until the phase matching condition of the three beams of light is satisfied; When nothing is done.

9. The orbital angular momentum encoding optical logic operation system based on mixing phase matching according to claim 8, wherein The magnetic field regulation module deploys an adjustable electromagnetic field device and performs electromagnetic field constraint regulation corresponding to the Laguerre-Gaussian beam through the adjustable electromagnetic field device. The process of completing the orbital angular momentum encoded optical logic operation includes: Use a Helmholtz coil as a component of the adjustable electromagnetic field device; Configure a programmable DC power supply, integrate a magnetic field sensor to monitor the magnetic field strength of the electromagnetic field generated by the Helmholtz coil in real time, set the induction accuracy of the magnetic field sensor, fix the Helmholtz coil on a non-magnetic bracket, and install it coaxially with the rubidium atomic gas cell; Set the target magnetic field strength for electromagnetic field constraint regulation, adjust the coil current through the power supply controller corresponding to the programmable DC power supply, and control the magnetic field direction of the electromagnetic field through the current direction of the coil current; The electromagnetic field constraint regulation also includes the uniformity calibration of the electromagnetic field; After the electromagnetic field constraint regulation is completed, perform a test experiment on the electromagnetic field constraint regulation once to complete the orbital angular momentum encoded optical logic operation.

Images