Efficient entangled photon pair preparation method based on rhombic stacked two-dimensional material

Abstract

The invention discloses an efficient entangled photon pair preparation method based on a rhombic stacked two-dimensional material, and relates to the field of integrated quantum photonics and advanced nano photonic devices. According to the method, a two-dimensional material waveguide layer with periodic grooves in the light propagation direction is prepared on a substrate, pump light is coupled to a waveguide specific mode, spontaneous parametric down-conversion is completed by means of the second-order nonlinear effect of a two-dimensional material, photon pairs are generated and coupled to different modes of waveguide, and the wavelength of the pump light is changed. Quasi-phase matching is realized by utilizing the periodic grooves so as to compensate phase mismatching, and finally, polarization-coded entangled photons are output. The method is high in efficiency and compact in structure, is compatible with an existing nano photon integration process, provides support for development of an on-chip quantum light source, and is of great significance in promoting practicability of quantum communication and quantum calculation.

Description

Technical Field

[0001] This invention belongs to the field of integrated quantum photonics and advanced nanophotonic devices, specifically relating to a method for preparing highly efficient entangled photon pairs based on rhomboid stacked two-dimensional materials. Background Technology

[0002] Entangled photon pairs are a core resource for quantum information technologies such as quantum communication, quantum computing, and quantum precision measurement. Currently, the mainstream technology for generating entangled photon pairs is the spontaneous parametric down-conversion process based on bulk nonlinear crystals. Although this technology is mature and has good entanglement quality, bulk crystals have inherent limitations: their physical size is on the order of micrometers to millimeters, which is incompatible with the development path of miniaturized and integrated quantum photonic chips; and their optical mode fields are difficult to couple efficiently with nanophotonic waveguides, resulting in a large system size and poor stability, which cannot meet the requirements of scalable and large-scale quantum integration.

[0003] To overcome the aforementioned bottlenecks, two-dimensional layered materials with non-centrosymmetric crystal structures (such as transition metal sulfides) are considered an ideal platform for realizing on-chip nonlinear optics and quantum light sources. Their advantages are mainly reflected in three aspects: First, they inherently possess significant second-order nonlinear coefficients (χ²). (2) First, it eliminates the need for external methods like domain engineering to introduce nonlinearity. Second, its atomically flat layered structure endows it with unique van der Waals force integration characteristics, enabling low-damage, lattice-match-free heterogeneous integration with various substrates and photonic devices. Finally, its high refractive index helps achieve strong mode field confinement at the subwavelength scale, greatly enhancing the intensity and efficiency of light-matter interaction. However, integrated entangled light sources based on two-dimensional materials still face key technical obstacles: during waveguide transmission, the phase mismatch between the pump light and the down-conversion signal light causes the nonlinear conversion efficiency to oscillate periodically with propagation distance, making effective intensity accumulation impossible. Existing solutions, such as quasi-phase matching through precise control of the interlayer lattice orientation of two-dimensional materials, require extremely high precision in controlling the interlayer rotation and stacking, resulting in high process complexity and difficulty in adapting to the planar structure requirements of on-chip integrated waveguides.

[0004] Therefore, there is an urgent need in this field for a novel phase matching scheme and device structure that can effectively compensate for phase mismatch in two-dimensional material waveguides, improve the generation efficiency of entangled photon pairs, and is highly compatible with existing nanophotonic integration processes. Summary of the Invention

[0005] To overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a method for preparing entangled photon pairs based on rhomboid stacked two-dimensional materials. This method solves the problems of low nonlinear conversion efficiency of integrated entangled photon sources in two-dimensional materials, complex process of existing phase matching schemes and inability to achieve integrated waveguides, and complex and difficult-to-integrate entangled state generation and control structures in the prior art.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] A method for preparing efficient entangled photon pairs based on rhombic stacked two-dimensional materials includes the following steps:

[0008] S1. Prepare a substrate and fabricate a two-dimensional material periodic trench waveguide layer on the substrate. The two-dimensional material thin film waveguide extends along the light propagation direction Z-axis, and its cross-section is rectangular. It is etched with periodically arranged rectangular trenches along the Z-axis direction to form a waveguide structure with alternating wide and narrow regions. The width of the wide region is W0, the width of the narrow region is W1, and the trench period is Λ.

[0009] S2. Provide a 780 nm laser as a pump source, adjust the pump light to linear polarization in the x-direction, and then couple the adjusted pump light into the TEO mode of a two-dimensional material periodic trench waveguide layer;

[0010] S3. The pump light is propagated in a two-dimensional material periodic trench waveguide layer. The quasi-phase matching effect generated by the periodic trench structure is used to compensate for the phase mismatch between the pump light and the downconversion light. The spontaneous parametric downconversion process is realized through the second-order nonlinear optical effect of the two-dimensional material, generating signal photons and idler photon pairs.

[0011] S4. Utilizing the mode characteristics of a two-dimensional periodic trench waveguide layer, signal photons and idler photons are coupled to TE0 and TE1 modes respectively, so that the intensity of signal photons and idler photons can be continuously accumulated as the waveguide transmission distance increases, while maintaining their polarization entanglement characteristics. S5. Signal photons and idler photons in a polarization entanglement state are output from two different mode channels of the two-dimensional periodic trench waveguide layer respectively.

[0012] Furthermore, in step S1, the substrate material is silicon dioxide, and the surface roughness of the substrate is less than 1 nanometer. Here, silicon dioxide has high transparency and low optical loss in the 780 nm pump light and 1560 nm downconversion light bands, which can avoid light energy loss caused by substrate absorption or scattering, and ensure photon transmission efficiency. At the same time, the process requirement of a surface roughness of less than 1 nanometer ensures that the subsequent two-dimensional material layer can be uniformly grown or transferred to the substrate surface, avoiding problems such as uneven thickness of the two-dimensional material layer and decreased waveguide structure fabrication accuracy caused by substrate roughness, thus laying the foundation for the stable fabrication of the waveguide core functional layer.

[0013] Furthermore, if the substrate thickness is too low (less than 1 micrometer), light propagating in the medium is more likely to radiate to the substrate or even pass through it, causing mode leakage. A substrate thickness greater than 1 micrometer ensures that the mode decays to almost nothing by the time it reaches the bottom of the substrate, thus preventing leakage. Further, in step S1, the two-dimensional material is a transition metal sulfide with a non-centrosymmetric crystal structure. The transition metal sulfide is rhombic stacked molybdenum disulfide with a point group of D. 3h Here, the non-centrosymmetric crystal structure of rhombic stacked molybdenum disulfide (point group D) is observed. 3h ) is characterized by its significant second-order nonlinear optical coefficient (χ). (2) The core premise of ) and χ (2) It is a necessary condition for the spontaneous parametric downconversion process (the key physical process for generating entangled photon pairs) to occur. This design clarifies the types of two-dimensional materials that can meet the requirements of nonlinear effects, avoids the process failure problem of not being able to generate entangled photon pairs due to the selection of centrosymmetric two-dimensional materials, and provides material support for the core function of the device.

[0014] Further, in step S1, the height of the two-dimensional material periodic trench waveguide layer is H, and the value of H ranges from 300 nm to 500 nm. If the waveguide height is too low, its effective refractive index will be significantly reduced, weakening its ability to confine the optical field, leading to energy leakage and a decrease in coupling efficiency. Conversely, if the height is too large, the compactness advantage of thin-film technology will be lost; and when the height exceeds 400 nm, its ability to control the effective refractive index will gradually decrease. Further, in step S1, the value of W0 ranges from 600 nm to 1000 nm; Λ is determined by the formula Λ = 2π / |Δk|, where Δk is the difference in propagation constants between the pump light TE0 mode, the signal light TE0 mode, and the idler light TE1 mode. The W0 range of 600 nm to 1000 nm, as verified by modal simulation, can effectively constrain the TE0 mode of the 780 nm pump light and the TE0 and TE1 modes of the 1560 nm downconversion light simultaneously, avoiding mode leakage or mismatch caused by improper waveguide width. The calculation formula Λ = 2π / |Δk| can accurately calculate the phase mismatch Δk through pre-process modal simulation (such as Lumerical MODE simulation), thereby determining the trench period Λ, ensuring that the periodic trench can accurately compensate for the phase mismatch, and providing key process parameters for efficient quasi-phase matching.

[0015] Furthermore, in step S1, the trench ratio is r, where r = W1 / W0, and the value of r ranges from 0% to 20%. If r > 20% (the trench is too deep), it will cause an excessively large abrupt change in waveguide width, resulting in severe light scattering loss and reducing photon transmission efficiency; if r is too small or there is no trench, the quasi-phase matching effect cannot be generated.

[0016] Furthermore, in step S2, the pump light is coupled either through an end face or a grating. This provides a flexible coupling solution for the pump light, ensuring that the pump light can be efficiently coupled to the waveguide TEO mode in different integration scenarios, providing sufficient pump energy for subsequent nonlinear processes.

[0017] Furthermore, in step S3, the wavelengths of both the signal photon and the idler photon pair are 1560 nanometers. This wavelength design allows the entangled photon pair to be directly adapted to existing long-distance optical fiber communication devices, avoiding additional optical loss or system modifications caused by wavelength incompatibility.

[0018] The method for fabricating entangled photon pairs based on two-dimensional materials in this invention is as follows: First, a two-dimensional waveguide layer is fabricated on a substrate, extending along the Z-axis of the light propagation direction, with a rectangular cross-section and periodically etched rectangular trenches, to construct an alternating wide and narrow region structure, laying the foundation for subsequent quasi-phase matching. This waveguide fabrication process is compatible with existing micro-nano etching techniques. Next, a 780 nm pump light is polarized and coupled to the TEO mode of the waveguide to ensure efficient pump light input and compliance with optical field confinement requirements. Subsequently, the quasi-phase matching effect generated by the periodic trenches is used to compensate for the pump. The phase mismatch between the light and the downconversion light is addressed by leveraging the second-order nonlinear optical effect of two-dimensional materials to trigger spontaneous parametric downconversion and generate entangled photon pairs, thus solving the efficiency problem caused by the short nonlinear interaction length of two-dimensional materials. Then, by utilizing the waveguide mode characteristics, the generated entangled photon pairs are respectively entered into TE0 and TE1 modes to achieve "built-in" generation of entangled states, thereby simplifying the integrated structure. Finally, entangled photon pairs are output from different mode channels. The overall design not only ensures the efficiency of entangled photon pair generation but also adapts to existing nanophotonic integration processes, providing a feasible path for the development of on-chip quantum light sources.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) The present invention adopts a periodic trench structure and forms a wide and narrow alternating structure on a two-dimensional material waveguide through a mature micro-nano etching process. Without the need for complex domain flipping or interlayer rotation stacking and other difficult processes, it can accurately compensate for the phase mismatch between pump light and downconversion light, effectively overcome the bottleneck of short nonlinear interaction length caused by the thickness limitation of two-dimensional materials, and greatly improve the spontaneous parametric downconversion efficiency, laying the foundation for the efficient generation of entangled photon pairs.

[0021] (2) Based on the orthogonal relationship between the electric field x component of the TE0 mode and the electric field z component of the TE1 mode, this invention integrates the entangled state generation and photon separation functions into a single waveguide structure. The mode design and function integration are completed through the waveguide integrated fabrication process. No additional discrete control components are required, and the standard polarization entangled Bell state is directly output. This not only reduces the device insertion loss, but also avoids the phase instability introduced by discrete components, ensuring the high quality and output stability of entangled photon pairs.

[0022] (3) The present invention can use waveguide fabrication processes such as electron beam lithography and reactive ion etching, as well as pump optical coupling methods such as end face coupling or grating coupling. All of these are compatible with standard complementary metal oxide semiconductor processes and existing nanophotonic integration platforms. There is no need to develop new process equipment. It can directly rely on mature manufacturing systems to achieve large-scale, low-cost production and reduce the threshold for industrial application.

[0023] (4) This invention constructs a planar structure by stacking the substrate and the two-dimensional material waveguide layer through a layered stacking process, and all functions are realized in the waveguide at the micro-nano scale. The overall size of the device is only on the order of hundreds of nanometers, which is much smaller than the traditional bulk crystal light source. It can meet the requirements of high-density photonic chip integration and provide core device support for building large-scale on-chip quantum photonic systems.

[0024] (5) This invention clarifies the complete design process from waveguide mode analysis and phase mismatch calculation to optimization of key parameters such as trench period and width ratio. Combined with professional optical simulation tools, the process parameters can be accurately determined, avoiding the blindness of traditional trial-and-error R&D, enabling technicians to reliably prepare high-performance entangled light sources and ensuring the consistency and repeatability of device performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the waveguide cross-section structure of the present invention;

[0026] Figure 2 This is a left view of the waveguide structure;

[0027] Figure 3 This is a top view of the waveguide structure;

[0028] Figure 4 This is a schematic diagram of the layered structure of the waveguide before processing;

[0029] Figure 5 It is a three-dimensional schematic diagram of a waveguide with periodic grooves;

[0030] Figure 6 This is a schematic diagram of the crystal structure of rhombic stacked molybdenum disulfide;

[0031] Figure 7 This is a simulation result diagram of Embodiment 2 of the present invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] Example 1

[0036] This embodiment aims to illustrate how to use a rhombic stacked molybdenum disulfide waveguide structure to efficiently prepare entangled photon pairs, including specific parameter design and process steps.

[0037] refer to Figure 1 A method for preparing entangled photon pairs based on two-dimensional materials includes the following steps:

[0038] S1. Prepare commercially available silicon dioxide wafer substrates (surface roughness less than 1 nm and oxide layer thickness greater than 1 μm). Select rhombic stacked molybdenum disulfide with a non-centrosymmetric crystal structure as the two-dimensional material. Determine the height of the periodic trench waveguide layer of the two-dimensional material to be 400 nm. Use Lumerical... The MODE optical simulation software simulated the relationship between the effective refractive index and waveguide width of the TE0 and TE1 modes in the waveguide at a pump wavelength of 780 nm and a downconversion wavelength of 1560 nm. The waveguide width range that can simultaneously support strong confinement of the pump light TE0 mode and stable transmission of downconversion photons (signal photons and idler photons) in both TE0 and TE1 modes was selected. The width of the non-groove region was determined to be 800 nm. The phase mismatch between the pump light and the downconversion light was calculated according to the quasi-phase matching condition, and the trench period was determined to be 680 nm. The influence of the trench ratio in the range of 0% to 20% on the mode overlap factor and conversion efficiency was simulated. The trench ratio was determined to be 15%, and the trench depth was calculated to be 120 nm. A rhombic stacked molybdenum disulfide waveguide with a rectangular cross-section extending along the Z-axis of the light propagation direction was fabricated on a silicon dioxide substrate. The waveguide was etched with periodically arranged rectangular trenches along the Z-axis direction to form a waveguide structure with alternating wide and narrow regions.

[0039] S2. Provide a 780 nm laser as a pump source, adjust the pump light to be linearly polarized in the x-direction, and then couple the adjusted pump light into the TEO mode of the rhombic stacked molybdenum disulfide periodic trench waveguide layer;

[0040] S3. Generation of entangled photon pairs: The pump light is propagated in a periodic trench waveguide layer of rhombic stacked molybdenum disulfide. The quasi-phase matching effect generated by the periodic trench structure is used to compensate for the phase mismatch between the pump light and the downconversion light. The spontaneous parametric downconversion process is realized through the second-order nonlinear optical effect of rhombic stacked molybdenum disulfide, generating entangled photon pairs, specifically signal photons and idler photon pairs with wavelengths of 1560 nm each.

[0041] S4. Construction of entangled states and accumulation of intensity: Utilizing the waveguide's support for both TE0 and TE1 modes and the orthogonal distribution of their electric fields, the entangled photon pairs generated in step S3 are coupled to the TE0 and TE1 modes respectively, so that the intensity of the signal photon and idler photon can be continuously accumulated as the waveguide transmission distance increases, while maintaining their polarization entanglement characteristics.

[0042] S5. Output of entangled photon pairs: Signal photons and idler photons in polarization entanglement states are output from the waveguide corresponding to the two different mode channels TE0 and TE1, respectively.

[0043] Example 2

[0044] Based on the two-dimensional material entangled photon preparation scheme based on periodic trench structure constructed in Example 1, this embodiment explores the physical mechanism of the periodic trench structure in achieving quasi-phase matching and improving nonlinear conversion efficiency by introducing systematic simulation analysis and experimental verification, and performs quantitative analysis and optimization verification of key structural parameters.

[0045] S1. Waveguide Structure Fabrication and Simulation Model Establishment

[0046] Based on the optimized parameters of Example 1, a complete waveguide structure simulation model was established. This model strictly follows the physical parameters of Example 1: a silicon dioxide substrate with a surface roughness of less than 1 nanometer and a thickness of more than 1 micrometer is used; the waveguide layer is a rhombic stacked molybdenum disulfide with a height of 400 nanometers; the width of the non-trench region is 800 nanometers; the trench period is 680 nanometers; the trench ratio is 15%; and the trench depth is 120 nanometers.

[0047] To conduct comparative analysis, three reference models were established simultaneously:

[0048] (a) Grooveless straight waveguide model: Except for not including periodic groove structures, the other parameters are completely consistent with those of Example 1;

[0049] (b) Non-optimal trench ratio model: The trench ratio r is set to 5% (corresponding to trench width W1 = 760 nm), and the other parameters are kept the same as in Example 1;

[0050] (c) Non-optimal trench ratio model: The trench ratio r is set to 10% (corresponding to trench width W1 = 720 nm), and the other parameters are kept the same as in Example 1.

[0051] S2. Systematic Simulation Verification and Analysis

[0052] The model was systematically analyzed for optical properties using professional Lumerical MODE simulation software: the modal refractive index distribution of the structure in Example 1 was extracted (corresponding to the attached...). Figure 7 a) Simulation results show that the periodic trench structure achieves regular modulation of the effective refractive index of the TE0 and TE1 modes by changing the geometric configuration of the waveguide cross-section. Specifically, the periodic trenches, through alternating waveguide widths, form a periodically modulated equivalent refractive index distribution in space. This result clearly confirms that the periodic trench structure possesses the ability to precisely control the waveguide mode characteristics, laying the physical foundation for the realization of the quasi-phase-matching effect.

[0053] S3 Quasi-phase-matching effect verification

[0054] Simulation results of the grooveless straight waveguide model show (corresponding to) Figure 7 d) Its normalized amplitude exhibits a regular oscillation with a period of approximately 680 nanometers due to phase mismatch, and the amplitude shows no increasing trend. This confirms that phase mismatch is the dominant factor restricting the nonlinear efficiency of the grooveless structure, which contrasts sharply with the "oscillation growth" brought about by the grooved structure in Example 1. This demonstrates the core mechanism by which periodic grooves compensate for phase mismatch and transform ineffective oscillations into effective nonlinear growth.

[0055] Performance comparison of different groove ratios (corresponding appendix) Figure 7 (b) and (c) When the trench ratio increases from 5% to 15%, the normalized amplitude oscillation increases to 160 over a transmission distance of 100 micrometers; however, as the trench ratio continues to increase, the normalized amplitude decreases. This data clearly shows that the system performance is optimized at r = 15%, which is completely consistent with the parameter selection in Example 1.

[0056] Normalized amplitude variation with transmission distance (corresponding appendix) Figure 7 b) and 7c) show that, under the preferred parameters (r = 15%), the normalized amplitude exhibits typical oscillatory growth characteristics, steadily increasing from 0 to approximately 160 over a transmission distance of 100 micrometers. This behavior is direct evidence of the nonlinear efficiency coherent accumulation achieved by the quasi-phase matching effect.

[0057] S4 trench ratio optimization criticality verification

[0058] Simulation results of the non-optimal trench ratio model show that although the structure theoretically still possesses a certain quasi-phase matching capability, the mode distortion and loss caused by the abrupt change in waveguide structure reduce system performance, leading to a significant decrease in nonlinear conversion efficiency. This result physically confirms that the parameter selection in Example 1, which strictly limits the trench ratio to the range of 0%-20% and preferably selects 15%, has sufficient scientific basis, providing clear parameter boundaries for device optimization design.

[0059] This implementation aims to fully reveal the core role of periodic trench structures in achieving quasi-phase matching and improving nonlinear conversion efficiency from a physical mechanism perspective through systematic simulation analysis and experimental verification. It also quantitatively verifies the optimization boundaries of key structural parameters, providing solid theoretical support and experimental evidence for the technical solution of Example 1. All results consistently demonstrate that the parameter combination used in Example 1 achieves optimal performance within the stated design space.

[0060] It should be understood that the embodiments disclosed in this invention are illustrative of the principles of the invention, and the foregoing embodiments should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and variations to the embodiments without departing from the spirit and essence of the invention. These modifications and variations, including the use of equivalents or alternative features, all fall within the scope defined by the appended claims.

Claims

1. A method for preparing highly efficient entangled photon pairs based on rhombic stacked two-dimensional materials, characterized in that: Includes the following steps, S1. Prepare a substrate and fabricate a two-dimensional material periodic trench waveguide layer on the substrate. The two-dimensional material thin film waveguide extends along the light propagation direction Z-axis, and its cross-section is rectangular. It is etched with periodically arranged rectangular trenches along the Z-axis direction to form a waveguide structure with alternating wide and narrow regions. The width of the wide region is W0, the width of the narrow region is W1, and the trench period is Λ. S2. Provide a 780 nm laser as a pump source, adjust the polarization of the pump light to linear polarization in the x-direction, and then couple the adjusted pump light into the TEO mode of the two-dimensional material periodic trench waveguide layer; S3. The pump light is propagated in a two-dimensional material periodic trench waveguide layer. The quasi-phase matching effect generated by the periodic trench structure is used to compensate for the phase mismatch between the pump light and the downconversion light. The spontaneous parametric downconversion process is realized through the second-order nonlinear optical effect of the two-dimensional material, generating polarization-entangled signal photons and idler photon pairs. S4. By utilizing the mode characteristics of a two-dimensional material periodic trench waveguide layer, signal photons and idler photons are coupled to the TE0 mode and TE1 mode, respectively, so that the intensity of signal photons and idler photons can be continuously accumulated as the waveguide transmission distance increases, while maintaining their polarization entanglement characteristics. S5. Signal photons and idler photons in polarization entanglement states are output from two different mode channels of the two-dimensional material periodic trench waveguide layer.

2. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S1, the substrate material is silicon dioxide, and the surface roughness of the substrate is less than 1 nanometer to 5 nanometers.

3. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S1, the thickness of the substrate is greater than 1 micrometer.

4. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S1, the two-dimensional material is a transition metal sulfide with a non-centrosymmetric crystal structure. The transition metal sulfide is rhombic stacked molybdenum disulfide with point group D. 3h .

5. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S1, the height of the two-dimensional material periodic trench waveguide layer is H, and the value of H ranges from 300 nanometers to 500 nanometers.

6. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S1, the value of W0 ranges from 600 nm to 1000 nm; Λ is determined by the formula Λ=2π / |Δk|, where Δk is the difference in propagation constants between the pump light TE0 mode, the signal light TE0 mode, and the idler light TE1 mode.

7. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S1, the groove ratio is r, r = W1 / W0, and the value of r ranges from 0% to 20%.

8. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S2, the pump light is coupled either through end-face coupling or grating coupling.

9. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S3, the wavelengths of both the signal photon and the idler photon pair are 1560 nanometers.

10. The method for preparing efficient entangled photon pairs based on rhomboid stacked two-dimensional materials as described in claim 1, characterized in that: In step S4, the polarization entanglement state is |Ψ> represents the total quantum state of the entangled photon pair, and |x> and |z> represent photons polarized along the x and z directions, respectively; the performance of the entangled photon pair is verified by coincidence counting measurements.

Images