System for detecting quantum entanglement and device for teaching quantum entanglement

Abstract

This application provides a quantum entanglement detection system and a quantum entanglement teaching device, relating to the field of quantum information science and technology. The quantum entanglement detection system, designed by combining a light source, polarization adjustment components, parametric down-conversion components, filtering and detection components, and counting and processing components, can achieve simple and efficient detection of optical quantum entanglement. The system boasts advantages such as simple structure, low cost, and ease of implementation. According to Heisenberg's uncertainty principle, the time width of a photon is inversely proportional to its spectral bandwidth. By using a first narrowband filter and a second narrowband filter to stretch and expand the time widths of the first and second photons, the entanglement correlation between them is enhanced. Compared to using a compensating crystal, this further reduces the cost of the quantum entanglement detection system, facilitating its application in quantum entanglement teaching devices and filling the current gap in quantum entanglement teaching practice.

Description

Specification 1 A Quantum Entanglement Detection System and Quantum Entanglement Teaching Equipment Technical Field This application relates to the field of quantum information science and technology, and more specifically, to a quantum entanglement detection system and quantum entanglement teaching equipment. Background Art Quantum mechanics is the cornerstone of modern physics, and its concepts such as quantum superposition and quantum entanglement have profoundly changed human understanding of nature. However, these concepts are highly abstract and contradict traditional macroscopic world experience, making it difficult for students to develop an intuitive understanding during the teaching process. Experimental demonstration is a key means to resolve this teaching difficulty. Revealing abstract principles through intuitive phenomena can effectively improve teaching effectiveness and students' learning interest. Currently, there are some industrialized teaching devices on the market for demonstrating advanced quantum phenomena such as quantum entanglement. These devices are usually built based on sophisticated optical platforms, single-photon sources, high-precision time-to-digital converters, and other specialized components, and can completely realize classical experiments such as the Bell inequality test to verify the nonlocality of quantum mechanics. However, such solutions have significant limitations: their system structure is complex, they have high requirements for the operating environment (such as darkrooms and shockproof conditions), and most importantly, the purchase and maintenance costs are extremely high. This makes it difficult for most secondary schools and regular universities' physics laboratories to undertake such work, resulting in quantum physics experimental teaching often remaining at the stage of theoretical explanation and video demonstration, severely lacking hands-on practice. The high cost has become one of the main obstacles to the popularization of cutting-edge quantum mechanics knowledge and the cultivation of innovative talents. Therefore, there is an urgent need to develop a low-cost, easy-to-implement, and simple-to-operate teaching kit that can effectively demonstrate core quantum phenomena (especially quantum entanglement) to lower the threshold for schools to offer related experimental courses and fill the gap in current teaching practice. In view of this, this application provides a quantum entanglement detection system and quantum entanglement teaching equipment, effectively solving the technical problems existing in the prior art. The quantum entanglement detection system is simple in composition, low in cost, and easy to implement for detecting quantum entanglement, so as to be better applied in quantum entanglement teaching equipment, thereby filling the current gap in quantum entanglement teaching practice. To achieve the above objectives, the technical solution provided in this application is as follows: A quantum entanglement detection system, comprising: a light source for generating a pump beam; a polarization adjustment component disposed on the transmission optical path of the pump beam for adjusting the pump beam into a superposition state pump beam with horizontal and vertical polarization superimposed, the superposition state pump beam comprising multiple superposition state pump photons; a parametric down-conversion component disposed on the transmission optical path of the superposition state pump beam for converting the superposition state pump photons into polarization-entangled first photons and second photons through a spontaneous parametric down-conversion process; and a first filtering and detection component disposed on the transmission optical path of the first photons for filtering and detecting the first photons to obtain and output a first electrical signal, comprising at least a first polarizer, a first narrowband filter, and a first single-photon detector arranged sequentially;A second filtering and detection component, disposed on the transmission optical path of the second photon, is used to filter and detect the second photon, obtain and output a second electrical signal, and includes at least a second polarizer, a second narrowband filter and a second single-photon detector arranged sequentially; a counting and processing component, electrically connected to the first filtering and detection component and the second filtering and detection component respectively, is used to perform coincidence counting on the first electrical signal and the second electrical signal to obtain a coincidence count value, and is also used to determine whether the first photon and the second photon are in a quantum entangled state based on the coincidence count value under at least four different polarization settings; wherein, the first narrowband filter is also used to stretch the time width of the first photon, and the second narrowband filter is also used to stretch the time width of the second photon to enhance the entanglement correlation between the first photon and the second photon. Optionally, the quantum entanglement detection system further includes: an aperture, disposed on the transmission optical path of the pump beam and located between the light source and the polarization adjustment component, for spatial filtering of the pump beam. Optionally, the quantum entanglement detection system further includes: a first reflector disposed on the transmission optical path of the pump beam and located between the aperture and the polarization adjustment component, for deflecting the pump beam to a first preset direction. Optionally, the quantum entanglement detection system further includes: a second reflector disposed on the transmission optical path of the first photon and located between the parametric down-conversion component and the first polarizer, for guiding the first photon to the incident surface of the first polarizer; and / or, a third reflector disposed on the transmission optical path of the second photon and located between the parametric down-conversion component and the second polarizer, for guiding the second photon to the incident surface of the second polarizer. Optionally, the first filtering detection component further includes a first coupler and a first optical fiber. The first coupler is disposed on the output optical path of the first narrowband filter, and the first coupler is connected to the first single-photon detector via the first optical fiber. The first coupler is used to couple the first photon stretched by the first narrowband filter to the first optical fiber. The first single-photon detector is used to detect the stretched first photon, obtain and output the first electrical signal. Optionally, the second filtering and detection component further includes a second coupler and a second optical fiber. The second coupler is disposed in the output optical path of the second narrowband filter, and the second coupler is connected to the second single-photon detector via the second optical fiber. The second coupler is used to couple the second photon, stretched by the second narrowband filter, to the second optical fiber. The second single-photon detector is used to detect the stretched second photon, obtain and output the second electrical signal. Optionally, the counting and processing component includes:A coincidence counter, electrically connected to the first single-photon detector and the second single-photon detector respectively, is used to count the coincidence of the first electrical signal and the second electrical signal to obtain the coincidence count value. A host computer, electrically connected to the coincidence counter, is used to determine whether the first photon and the second photon are in a quantum entangled state based on the coincidence count value under at least four different polarization settings. Optionally, the polarization adjustment component includes a half-wave plate, which is disposed in the transmission optical path of the pump beam and located between the light source and the parametric down-conversion component. Optionally, the parametric down-conversion component includes a paired type I low-temperature phase barium metaborate crystal, which is disposed in the transmission optical path of the superimposed state pump beam and located between the polarization adjustment component and the first filtering detection component, and also between the polarization adjustment component and the second filtering detection component. Based on the same inventive concept, this application also provides a quantum entanglement teaching device, which includes the above-mentioned quantum entanglement detection system. Compared with existing technologies, the technical solution provided in this application has at least the following advantages: HK 30134894 A Specification 3 This application provides a quantum entanglement detection system and a quantum entanglement teaching device. In this application, a quantum entanglement detection system is designed by combining a light source, a polarization adjustment component, a parametric down-conversion component, a first filter detection component, a second filter detection component, and a counting processing component. This system can simply and efficiently realize the detection of optical quantum entanglement, and it has advantages such as simple structure, low cost, and ease of implementation. Furthermore, according to the Heisenberg uncertainty principle, the time width of a photon is inversely proportional to its spectral bandwidth. Therefore, this application uses a first narrowband filter and a second narrowband filter to stretch and expand the time width of the first and second photons, thereby enhancing the entanglement correlation between them. Compared with using a compensation crystal, the narrowband filter can further reduce the cost of the quantum entanglement detection system, making it easier to apply in quantum entanglement teaching devices and filling the current gap in quantum entanglement teaching practice. Brief Description of the Drawings To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. Figure 1 is a schematic diagram of the structure of a quantum entanglement detection system provided in an embodiment of this application; Figure 2 is a schematic diagram of the structure of another quantum entanglement detection system provided in an embodiment of this application; Figure 3 is a schematic diagram of the structure of yet another quantum entanglement detection system provided in an embodiment of this application; Figure 4Figure 5 is a schematic diagram of another quantum entanglement detection system provided in an embodiment of this application; Reference numerals: 100 – Light source; 200 – Polarization adjustment component, 210 – Half-wave plate; 300 – Parametric down-conversion component, 310 – Paired type I low-temperature phase barium borate crystal or paired type II low-temperature phase barium borate crystal; 410 – First polarizer, 420 – Second polarizer; 510 – First narrowband filter, 520 – Second narrowband filter; 610 – First coupler, 620 – Second coupler; 710 – First single-photon detector, 720 – Second single-photon detector; 800 – Counting processing component, 810 – Coincidence counter, 820 – Host computer; 910 – Aperture, 920 – First reflector, 931 – Second reflector, 932 – Third reflector. The specific embodiments of this application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. As mentioned in the background art, quantum mechanics is the cornerstone of modern physics, and its concepts such as quantum superposition and quantum entanglement have profoundly changed human understanding of nature. However, these concepts are highly abstract and contradict the experience of the traditional macroscopic world, making it difficult for students to establish an intuitive understanding during the teaching process. Experimental demonstration is a key means to resolve this teaching difficulty. HK 30134894 A Specification 4 reveals abstract principles through intuitive phenomena, which can effectively improve teaching effectiveness and students' learning interest. At present, there are some industrialized teaching devices on the market for demonstrating advanced quantum phenomena such as quantum entanglement. These devices are usually built based on professional components such as precision optical platforms, single-photon sources, and high-precision time-to-digital converters, and can completely realize classical experiments such as Bell's inequality test to verify the nonlocality of quantum mechanics. However, such solutions have significant limitations: their systems are complex, require specific environmental conditions (such as darkrooms and shockproof environments), and, most importantly, are extremely expensive to purchase and maintain. This makes them unsuitable for most secondary schools and regular universities' physics laboratories, resulting in quantum physics experimental teaching often remaining at the stage of theoretical explanation and video demonstrations, severely lacking hands-on practice. The high cost has become one of the main obstacles to the popularization of cutting-edge quantum mechanics knowledge and the cultivation of innovative talents. Therefore, there is an urgent need to develop a low-cost, easy-to-implement, and simple-to-operate teaching kit that can effectively demonstrate core quantum phenomena (especially quantum entanglement) to lower the threshold for schools to offer related experimental courses and fill the gap in current teaching practice.Based on this, embodiments of this application provide a quantum entanglement detection system and a quantum entanglement teaching device, effectively solving the technical problems existing in the prior art. The quantum entanglement detection system has a simple structure, low cost, and is easy to implement for detecting quantum entanglement, so as to be better applied in quantum entanglement teaching devices, thereby filling the current gap in quantum entanglement teaching practice. To achieve the above objectives, the technical solutions provided by embodiments of this application are as follows, and the technical solutions provided by embodiments of this application are described in detail with reference to Figures 1 to 5. Referring to Figure 1, it is a schematic diagram of the structure of a quantum entanglement detection system provided by an embodiment of this application, in which the dashed lines indicate the optical path. The quantum entanglement detection system provided in this application includes: a light source 100 for generating a pump beam; a polarization adjustment component 200 disposed on the transmission optical path of the pump beam, the polarization adjustment component 200 for adjusting the pump beam into a superposition state pump beam with horizontal and vertical polarization superimposed, the superposition state pump beam including multiple superposition state pump photons; a parametric down-conversion component 300 disposed on the transmission optical path of the superposition state pump beam, the parametric down-conversion component 300 for converting the superposition state pump photons into polarization-entangled first photons and second photons through a spontaneous parametric down-conversion process; and a first filtering and detection component disposed on the transmission optical path of the first photon, the first filtering and detection component for filtering and detecting the first photon to obtain and output a first electrical signal, the first filtering and detection component including at least a first polarizer 410, a first narrowband filter 510 and a first single-photon detector 710 sequentially disposed on the transmission optical path of the first photon; The second filtering and detection component is disposed on the transmission optical path of the second photon. The second filtering and detection component is used to filter and detect the second photon, obtain and output a second electrical signal. The second filtering and detection component includes at least a second polarizer 420, a second narrowband filter 520, and a second single-photon detector 720 sequentially disposed on the transmission optical path of the second photon. The first narrowband filter 510 is further used to stretch the time width of the first photon, and the second narrowband filter 520 is further used to stretch the time width of the second photon, thereby enhancing the entanglement between the first and second photons. A counting and processing component 800 is electrically connected to the first and second filtering and detection components, respectively. The counting and processing component 800 is used to perform coincidence counting on the first and second electrical signals to obtain a coincidence count value, and is also used to determine whether the first and second photons are in a quantum entangled state based on the coincidence count values ​​under at least four different polarization settings. As can be seen from the above, the technical solution provided in this application embodiment only uses the light source 100, polarization adjustment component 200, and HK...30134894 A Specification 5 The simple optical devices—parameter down-conversion component 300, first filter detection component, second filter detection component, and counting processing component 800—design a quantum entanglement detection system, achieving the purpose of quantum entanglement detection. This gives the quantum entanglement detection system advantages such as simple structure, low cost, and ease of implementation. Furthermore, this application embodiment uses a first narrowband filter 510 and a second narrowband filter 520 to stretch photons in time based on the Heisenberg uncertainty principle, thereby enhancing the entanglement correlation between the first and second photons. Compared to using a compensating crystal, the narrowband filter can further reduce the cost of the quantum entanglement detection system, facilitating its better application in quantum entanglement teaching equipment and filling the current gap in quantum entanglement teaching practice. The quantum entanglement detection system provided in this application embodiment achieves quantum entanglement detection by generating entangled photon pairs. Specifically, the working process of the quantum entanglement detection system provided in this application embodiment is as follows: S1. After the quantum entanglement detection system is ready, the light source 100 is first turned on, so that the light source 100 generates a pump beam. In some embodiments, the light source 100 provided in this application embodiment may include a laser, that is, the pump beam output by the light source 100 is a laser. It should be noted that the pump beam provided in this application embodiment can be a laser of any wavelength and corresponding color; after determining the wavelength and color of the laser, the polarization adjustment component 200, parametric down-conversion component 300, polarizer, narrowband filter, single-photon detector, etc. used in the optical path all need to be matched and adjusted accordingly according to the parameters of the laser. In order to make the principle of the quantum entanglement detection system clearer, the following technical content of this application will be described using a 405nm blue laser as an example. S2. The pump beam is transmitted to the polarization adjustment component 200, which is adjusted to an appropriate angle so that the pump beam is in a superimposed state of horizontal and vertical polarization, thereby outputting a superimposed pump beam (i.e., outputting a |H⟩+|V⟩ pump beam, where H represents horizontal polarization and V represents vertical polarization). In some embodiments, the polarization adjustment component 200 provided in this application includes a half-wave plate 210, wherein the half-wave plate 210 is disposed in the transmission optical path of the pump beam and is located between the light source 100 and the parametric down-conversion component 300. For example, when the pump beam is a 405nm wavelength blue laser, the adapted half-wave plate 210 is a 405nm half-wave plate; the half-wave plate 210 is rotated by a set angle (e.g., 22.5 degrees) with the transmission optical path of the pump beam as the axis, so that the blue laser is in a superimposed state of horizontal and vertical polarization, and the half-wave plate 210 outputs a superimposed state of |H⟩+|V⟩ laser.S3. The superimposed pump beam is transmitted to the parametric down-conversion component 300. After the spontaneous parametric down-conversion process of the parametric down-conversion component 300, the superimposed pump beam is converted into polarization-entangled first and second photons, that is, entangled photon pairs in the state of |HH⟩+|VV⟩ are obtained. In some embodiments, the parametric down-conversion component 300 provided in this application includes a paired type I low-temperature phase barium metaborate crystal 310 (i.e., β-BaB₂O₄ crystal), wherein the paired type I low-temperature phase barium metaborate crystal 310 is disposed in the transmission optical path of the superimposed pump beam and is located between the polarization adjustment component 200 and the first filter detection component, and also between the polarization adjustment component 200 and the second filter detection component; that is, the paired type I low-temperature phase barium metaborate crystal 310 is located between the polarization adjustment component 200 and the first polarizer 410, and also between the polarization adjustment component 200 and the second polarizer 420. The half-wave plate 210 outputs a laser in a superposition state |H⟩+|V⟩. The paired type I low-temperature barium borate crystal 310 includes two type I low-temperature barium borate crystals with their optical axes orthogonally arranged. Photons pass through the two type I low-temperature barium borate crystals one after the other. On one type I low-temperature barium borate crystal, a |HH⟩ photon pair is generated, and on the other type I low-temperature barium borate crystal, a |VV⟩ photon pair is generated. After being processed by the paired type I low-temperature barium borate crystal 310, an entangled photon pair in the state |HH⟩+|VV⟩ is generated, which is two 810nm laser beams. In some embodiments, the parametric down-conversion component 300 provided in this application includes a paired type II low-temperature phase barium metaborate crystal 310 (i.e., β-BaB₂O₄ crystal), wherein the paired type II low-temperature phase barium metaborate crystal 310 is disposed in the transmission optical path of the superimposed pump beam and is located between the polarization adjustment component 200 and the first filter detection component, and also between the polarization adjustment component 200 and the second filter detection component; that is, the paired type II low-temperature phase barium metaborate crystal 310 is located between the polarization adjustment component 200 and the first polarizer 410, and also between the polarization adjustment component 200 and the second polarizer 420. The half-wave plate 210 (HK 30134894 A) outputs a laser in a superposition state of |H⟩+|V⟩. The paired type II low-temperature barium borate crystal 310 comprises two type II low-temperature barium borate crystals orthogonally arranged on their optical axes. Photons pass sequentially through the two type II low-temperature barium borate crystals. One type II low-temperature barium borate crystal generates a |HV⟩ photon pair, and the other type II low-temperature barium borate crystal generates a |VH⟩ photon pair. After being processed by the paired type II low-temperature barium borate crystal 310, entangled photon pairs in the state of |HV⟩+|VH⟩ are generated, i.e., two 810nm laser beams. S4, Parametric Down-Conversion ComponentThe parametric down-conversion assembly 300 transmits a first photon to a first filtering and detection component, such as transmitting the first photon first to a first polarizer 410, and then passing through a first narrowband filter 510 before being detected by a first single-photon detector 710, which outputs a first electrical signal; and the parametric down-conversion assembly 300 transmits a second photon to a second filtering and detection component, such as transmitting the second photon first to a second polarizer 420, and then passing through a second narrowband filter 520 before being detected by a second single-photon detector 720, which outputs a second electrical signal. In some embodiments, the paired type I low-temperature barium metaborate crystal 310 provided in this application modulates the laser of the superposition state |H⟩+|V⟩ into two 810nm lasers. One laser is transmitted to a first filtering and detection assembly composed of at least a first polarizer 410, a first narrowband filter 510, and a first single-photon detector 710, and the other laser is transmitted to a second filtering and detection assembly composed of at least a second polarizer 420, a second narrowband filter 520, and a second single-photon detector 720. The first narrowband filter 510 and the second narrowband filter 520 are both matched as 810nm narrowband filters. Referring to Figure 2, which is a schematic diagram of another quantum entanglement detection system provided in an embodiment of this application, the first filtering and detection component provided in this embodiment of the application further includes a first coupler 610 and a first optical fiber (not shown in the figure). The first coupler 610 is disposed in the outgoing optical path of the first narrowband filter 510, and the first coupler 610 is connected to the first single-photon detector 710 through the first optical fiber. The first coupler 610 is used to couple the first photon stretched by the first narrowband filter 510 to the first optical fiber. The first single-photon detector 710 is used to detect the stretched first photon, obtain and output a first electrical signal. Furthermore, the second filtering and detection component provided in this application embodiment also includes a second coupler 620 and a second optical fiber (not shown in the accompanying drawings). The second coupler 620 is disposed in the outgoing optical path of the second narrowband filter 520, and the second coupler 620 is connected to the second single-photon detector 720 through the second optical fiber. The second coupler 620 is used to couple the second photon stretched by the second narrowband filter 520 to the second optical fiber. The second single-photon detector 720 is used to detect the stretched second photon, obtain and output a second electrical signal. It is understood that in other optional embodiments of this application, in order to simplify the structure, the optical fiber coupling structure based on the coupler and the optical fiber may not be adopted, but the outgoing photon of the first narrowband filter 510 or the second narrowband filter 520 can be directly...By directly optically coupling the outgoing light path of the narrowband filter to the photosensitive surface of the single-photon detector, a free-space optical path is formed. This results in fewer optical components and higher design flexibility, but also higher requirements for optical path alignment. The appropriate optical path can be flexibly selected based on actual needs. It should be noted that in the quantum entanglement detection system provided in this application embodiment, for the parametric down-conversion component 300 composed of two crystals, such as paired type I or paired type II low-temperature barium borate crystals, photons must pass through both crystals sequentially, generating a corresponding photon pair on each crystal. Since the two photon pairs are generated from different crystals, there is a time difference in their generation times, resulting in a relative delay or time difference when the two photon pairs arrive at the filter detection component. Assume that this time difference causes a spatial distance of 30 micrometers. In this embodiment, a narrowband filter is placed before the single-photon detector to limit the bandwidth. According to the uncertainty principle, this stretches the photon wave packet, broadening it in the time domain, i.e., stretching the time width or spatial length of the photon. Taking a narrowband filter with a full width at half maximum (FWHM) of 810 nm as an example, the spatial length of the photon wave packet becomes Lc≈(810nm)² / 10nm≈65 micrometers. 65 micrometers is greater than 30 micrometers, naturally covering the 30-micrometer gap caused by the inconsistent generation times of the two pairs of photons in the paired Type I or Type II low-temperature barium borate crystal 310. The first and second photon wave packets overlap at least partially, prolonging the photon coherence time and thus preserving photon entanglement. Here, the photon wave packet is the probability amplitude distribution of a single photon in space and time, describing "the probability of finding this photon at a certain time and location". It should be noted that "Lc≈(810nm)² / 10nm≈65 micrometers" originates from the application of the uncertainty principle in time and frequency: The derivation steps are as follows: 1. There is an approximate relationship between the frequency bandwidth and the time width of a photon: ; Δt is the time width (coherence time) of the photon (or photon wave packet), and Δv is the frequency bandwidth of the photon (or photon wave packet). 2. Convert the frequency bandwidth to the wavelength width: . 3. Substitute into the formula to obtain the time width: . 4. Convert the time width to the spatial length: ; where Lc is the coherence length (spatial length) of the photon wave packet, λ is the center wavelength of the photon wave packet, and Δλ is the wavelength width of the photon wave packet (i.e., the wavelength range of the narrowband filter). S5. Finally, the counting processing component 800 obtains the first electrical signal output by the first filtering detection component and the second electrical signal output by the second filtering detection component. That is, the counting processing component 800 acquires the first electrical signal output by the first single-photon detector 710, and acquires the signal from the second single-photon detector 720.The output second electrical signal is then used to perform a coincidence count on the first and second electrical signals to obtain a coincidence count value. Based on the coincidence count values ​​under at least four different polarization conditions, it is determined whether the first and second photons are in an entangled state. Optionally, the counting processing component 800 provided in this embodiment can determine the quantum entanglement of the first and second photons using the CHSH (Clauser-Horne-Shimony-Holt) inequality. As shown in Figure 2, the counting processing component 800 provided in this embodiment includes: a coincidence counter 810, which is electrically connected to the first single-photon detector 710 and the second single-photon detector 720 respectively. The coincidence counter 810 is used to perform a coincidence count on the first and second electrical signals to obtain a coincidence count value; and a host computer 820, which is electrically connected to the coincidence counter 810. The host computer 820 is used to determine whether the first and second photons are in a quantum entangled state based on the coincidence count values ​​under at least four different polarization conditions. Based on this, by adjusting the angle between the first polarizer 410 and the second polarizer 420, the coincidence counter 810 acquires coincidence count values ​​under different angles (different polarization settings). Then, the host computer 820 determines the quantum entanglement status based on the coincidence count values ​​and the CHSH inequality. Table 1 shows the coincidence count values ​​acquired by the coincidence counter 810 under different angles between the first polarizer 410 and the second polarizer 420, as provided in this embodiment. The angle between the substrates of the first polarizer 410 and the second polarizer 420 is 22.5 degrees or a multiple of 22.5 degrees, which is to theoretically obtain the maximum violation of the CHSH inequality S value (i.e., to prove the nonlocality of quantum mechanics). In Table 1, α is the orientation angle of the first polarizer 410, β is the orientation angle of the second polarizer 420, and the remaining values ​​are the coincidence count values ​​of the coincidence counter 810 every 10 seconds. β α 0 degrees 90 degrees 45 degrees 135 degrees 22.5 degrees 1750 419 1723 420 112.5 degrees 396 1899 452 1740 67.5 degrees 393 1647 1643 410 157.5 degrees 1710 475 405 1704 Table 1 CHSH Inequality S value calculation process, first calculate the correlation function E(α, β): ; N represents the coincidence count value, ⊥ represents the orthogonal angle of the current angle (i.e., plus 90 degrees). For example, if α = 22.5 degrees, then α⊥ = 112.5 degrees; Finally, through the formulaCombining the four correlation functions S = E(α, β) − E(α, β') + E(α', β) + E(α', β') (where α' represents α + 45 degrees and β' represents β + 45 degrees) yields the CHSH inequality S value. If |S| > 2, it proves that the experimental results violate the classic Bell inequality. Based on the coincidence counts shown in Table 1, taking α=0 and β=22.5 as examples, the corresponding four correlation functions and the S-values ​​of the CHSH inequality are as follows: E(0, 22.5)=(1750+1899-396-419) / (1750+1899+396+419)=0.6349; E(0, 67.5)=(393+475-1647-1710) / (393+475+1647+1710)= -0.5891; E(45, 22.5)= (1723+1740-420-452) / (1723+1740+420+452)=0.5977; E(45, 67.5)= (1643+1704-410-405) / (1643+1704+410+405)=0.6084; S=E(0, 22.5)-E(0, 67.5)+E(45, 22.5)+E(45, 67.5)= 0.6349+0.5891+0.5977+0.6084=2.4301>2; This proves that the quantum entanglement detection system provided in this application embodiment can experimentally obtain a CHSH inequality S value greater than 2, which successfully violates the CHSH inequality under the classical physical limit, clearly supports quantum mechanics, negates the local hidden variable theory, and does not require the use of a compensation crystal and a high-precision time-to-digital converter, making the quantum entanglement detection system have advantages such as simple structure, low cost, and ease of implementation. In order to improve the performance and applicability of the quantum entanglement detection system, the structure of the quantum entanglement detection system can also be optimized in this application embodiment. Referring to Figure 3, which is a schematic diagram of another quantum entanglement detection system provided in this application embodiment, the quantum entanglement detection system provided in this application embodiment further includes: an aperture 910, which is disposed in the transmission optical path of the pump beam, and a polarization adjustment component 200 is disposed in the output optical path of the aperture 910, that is, the aperture 910 is located between the light source 100 and the polarization adjustment component 200, and the aperture 910 is used to perform spatial filtering on the pump beam. When the polarization adjustment component 200 provided in this application embodiment includes a half-wave plate 210, the half-wave plate 210 is disposed in the output optical path of the aperture 910, and the beam profile of the pump beam is controlled by the aperture 910 to optimize the performance of the quantum entanglement detection system. Optionally, the aperture 910 provided in this application embodiment...A small aperture stop can be used, with the aperture diameter of stop 910 being 1-12mm, specifically 4mm, 6mm, 8mm, etc., and this application does not impose specific limitations. Referring to Figure 4 in the specification of HK 30134894 A, this is a schematic diagram of another quantum entanglement detection system provided in an embodiment of this application. The quantum entanglement detection system provided in this embodiment further includes: a first reflector 920, which is disposed on the transmission optical path of the pump beam and on the output optical path of stop 910. A polarization adjustment component 200 is disposed on the output optical path of the first reflector 920, meaning the first reflector 920 is located between stop 910 and polarization adjustment component 200. The first reflector 920 is used to refract the pump beam to a first preset direction. When the polarization adjustment component 200 provided in this application embodiment includes a half-wave plate 210, the half-wave plate 210 is disposed on the outgoing optical path of the first reflector 920, thereby expanding the optical path design range and improving the applicable scenarios of the quantum entanglement detection system. Referring to Figure 5, which is a structural schematic diagram of another quantum entanglement detection system provided in this application embodiment, the quantum entanglement detection system provided in this application embodiment further includes: a second reflector 931, which is disposed on the transmission optical path of the first photon, and the second reflector 931 is located between the parametric down-conversion component 300 and the first polarizer 410. The second reflector 931 is used to guide the first photon to the incident surface of the first polarizer 410. When the parametric down-conversion component 300 provided in this application embodiment includes a paired type I low-temperature barium metaborate crystal (or a paired type II low-temperature barium metaborate crystal) 310, the second reflector 931 is located between the paired type I low-temperature barium metaborate crystal (or the paired type II low-temperature barium metaborate crystal) 310 and the first polarizer 410. And / or, the quantum entanglement detection system provided in this application embodiment further includes: a third reflector 932, which is disposed in the transmission optical path of the second photon, and the second reflector 931 is located between the parametric down-conversion component 300 and the second polarizer 420. The third reflector 932 is used to guide the second photon to the incident surface of the second polarizer 420. When the parametric down-conversion component 300 provided in this application embodiment includes a paired type I low-temperature barium metaborate crystal (or a paired type II low-temperature barium metaborate crystal) 310, the third reflector 932 is located between the paired type I low-temperature barium metaborate crystal (or a paired type II low-temperature barium metaborate crystal) 310 and the second polarizer 420. The quantum entanglement detection system provided in this application embodiment may include only the second reflector 931, or only the third reflector 932, or both.The second reflector 931 and the third reflector 932 need to be specifically designed according to the actual application. By selecting and designing the second reflector 931 and the third reflector 932 in the optical path, the range of optical path design can be expanded, and the applicable scenarios of the quantum entanglement detection system can be improved. Based on the same inventive concept, this application also provides a quantum entanglement teaching device, which includes the quantum entanglement detection system provided in any of the above embodiments. Optionally, the quantum entanglement detection system provided in this application can be fixedly installed on an optical breadboard, and this application does not impose specific limitations on this. In summary, this application provides a quantum entanglement detection system and a quantum entanglement teaching device. In this application, the quantum entanglement detection system is designed by combining a light source, a polarization adjustment component, a parametric down-conversion component, a first filtering detection component, a second filtering detection component, and a counting processing component. This design can simply and efficiently realize optical quantum entanglement detection, and the quantum entanglement detection system has the advantages of simple structure, low cost, and ease of implementation. Meanwhile, according to the Heisenberg uncertainty principle, the time width of a photon is inversely proportional to its spectral bandwidth. Therefore, this application uses a first narrowband filter and a second narrowband filter to stretch and expand the time width of the first photon and the second photon, thereby enhancing the entanglement between the first photon and the second photon. Compared with the method of using a compensation crystal, the narrowband filter can further reduce the cost of the quantum entanglement detection system, so as to better apply it to quantum entanglement teaching equipment, thereby filling the current gap in quantum entanglement teaching practice. In the description of the embodiments of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of 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, and therefore should not be construed as a limitation of this application. HK 30134894 A Specification 10 Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the embodiments of this application, unless otherwise expressly specified and limited, such as the terms "installation," "connection," or "linking,"The term "fixed" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal connection of two components or the interaction between two components, unless otherwise explicitly defined. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. In the embodiments of this application, unless otherwise explicitly specified and defined, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature. In the embodiments of this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in this specification. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application. HK 30134894 A Claim 1 1. A quantum entanglement detection system, characterized in that it comprises: a light source for generating a pump beam; a polarization adjustment component disposed on the transmission optical path of the pump beam for adjusting the pump beam into a superposition state pump beam with horizontal and vertical polarization superimposed, the superposition state pump beam comprising a plurality of superposition state pump photons; a parametric down-conversion component disposed on the transmission optical path of the superposition state pump beam for converting the superposition state pump photons into polarization-entangled first photons and second photons through a spontaneous parametric down-conversion process; a first filtering detection component disposed on the transmission optical path of the first photon for filtering and detecting the first photon, obtaining and outputting a first electrical signal, comprising at least a first polarizer, a first narrowband filter and a first single-polarizer arranged sequentially.A photon detector; a second filtering detection component, disposed in the transmission optical path of the second photon, for filtering and detecting the second photon, obtaining and outputting a second electrical signal, comprising at least a second polarizer, a second narrowband filter and a second single-photon detector arranged sequentially; a counting processing component, electrically connected to the first filtering detection component and the second filtering detection component respectively, for performing coincidence counting on the first electrical signal and the second electrical signal to obtain a coincidence count value, and further for determining whether the first photon and the second photon are in a quantum entangled state based on the coincidence count value under at least four different polarization settings; wherein, the first narrowband filter is further used to stretch the time width of the first photon, and the second narrowband filter is further used to stretch the time width of the second photon to enhance the entanglement correlation between the first photon and the second photon. 2. The quantum entanglement detection system according to claim 1, wherein the quantum entanglement detection system further comprises: an aperture, disposed in the transmission optical path of the pump beam and located between the light source and the polarization adjustment component, for spatial filtering of the pump beam. 3. The quantum entanglement detection system according to claim 2, characterized in that the quantum entanglement detection system further comprises: a first reflector, disposed in the transmission optical path of the pump beam and located between the aperture and the polarization adjustment component, for refracting the pump beam to a first preset direction. 4. The quantum entanglement detection system according to claim 3, characterized in that the quantum entanglement detection system further comprises: a second reflector, disposed in the transmission optical path of the first photon and located between the parametric down-conversion component and the first polarizer, for guiding the first photon to the incident surface of the first polarizer; and / or, a third reflector, disposed in the transmission optical path of the second photon and located between the parametric down-conversion component and the second polarizer, for guiding the second photon to the incident surface of the second polarizer. 5. The quantum entanglement detection system according to claim 1, characterized in that the first filtering and detection component further includes a first coupler and a first optical fiber, the first coupler is disposed in the output optical path of the first narrowband filter, and the first coupler is connected to the first single-photon detector through the first optical fiber, the first coupler is used to couple the first photon stretched by the first narrowband filter to the first optical fiber, and the first single-photon detector is used to detect the stretched first photon, obtain and output the first electrical signal. 6. The quantum entanglement detection system according to claim 5, characterized in that the second filtering and detection component further includes a second coupler and a second optical fiber, the second coupler is disposed in the output optical path of the second ... single-photon detector is connected to the first single-photon detector through the first optical fiber, the first single-photon detector is used to detect the stretched first photon, obtain and output the first electrical signal. 6. The quantum entanglement detection system according to claim 5, characterized in that the second filtering and detection component further includes a second coupler and a second optical fiber, the second coupler is disposed in the output optical path of the second narrowband filter, and the first single-photon detector is connected to the first single-photon detector through the first optical fiber, and the first single-photon detector is connected to the first single-photon detector through the first optical fiber, the first single-photon detector is used to detect the stretched first photon, obtain and output the first electrical signal. 6. The quantum entanglement detection system according to claim 5,The second coupler is connected to the second single-photon detector via a second optical fiber. The second coupler is used to couple the second photon, stretched by the second narrowband filter, to the second optical fiber. The second single-photon detector is used to detect the stretched second photon, obtain and output the second electrical signal. 7. The quantum entanglement detection system according to claim 1, wherein the counting processing component comprises: a coincidence counter, electrically connected to the first single-photon detector and the second single-photon detector respectively, used to perform coincidence counting on the first electrical signal and the second electrical signal to obtain the coincidence count value; a host computer, electrically connected to the coincidence counter, used to determine whether the first photon and the second photon are in a quantum entangled state based on the coincidence count value under at least four different polarization settings. 8. The quantum entanglement detection system according to any one of claims 1-7, wherein the polarization adjustment component comprises a half-wave plate, the half-wave plate being disposed on the transmission optical path of the pump beam and located between the light source and the parametric down-conversion component. 9. The quantum entanglement detection system according to any one of claims 1-7, characterized in that the parametric down-conversion component comprises a paired type I low-temperature phase barium metaborate crystal, the paired type I low-temperature phase barium metaborate crystal being disposed in the transmission optical path of the superposition state pump beam, and located between the polarization adjustment component and the first filtering detection component, and also located between the polarization adjustment component and the second filtering detection component. 10. A quantum entanglement teaching device, characterized in that the quantum entanglement teaching device comprises the quantum entanglement detection system according to any one of claims 1-9. HK 30134894 A Instruction Manual, Figure 1: 100 Light Source Polarization Adjustment Component, Parametric Down-Conversion Component, First Polarizer, First Narrow-Band Filter, Second Polarizer, Second Narrow-Band Filter, First Single-Photon Detector, Second Single-Photon Detector, Counting Processing Component, 200 210 300 310 410 420 520 510 710 720 800. Figure 1: 100 Light Source Polarization Adjustment Component, Parametric Down-Conversion Component, First Polarizer, First Narrow-Band Filter, Second Polarizer, Second Narrow-Band Filter, First Coupler, Second Coupler, First Single-Photon Detector, Second Single-Photon Detector, Counting Processing Component, Coincidence Counter, Host Computer, 200 210 300 310 410 420 520 510 610 710 620 720 800 810 820. Figure 2: HK 30134894 A Instruction Manual, Figure 2: 100. The first parametric downconversion component of the light source polarization adjustment componentPolarizer First Narrow Band Filter Second Polarizer Second Narrow Band Filter First Coupler Second Coupler First Single Photon Detector Second Single Photon Detector Counting Processing Component Conformance Counter Host Computer 200 210 300 310 410 420 520 510 610 710 620 720 800 810 820 910 Figure 3 100 Light Source Polarization Adjustment Component Parametric Down-Conversion Component First Polarizer First Narrow Band Filter Second Polarizer Second Narrow Band Filter First Coupler Second Coupler First Single Photon Detector Second Single Photon Detector Counting Processing Component Conformance Counter Host Computer 200 210 300 310 420 520 610 710 620 720 800 810 820 910 920 410 510 Figure 4 HK 30134894 A Figure 3 in the instruction manual shows the following components: 100 Light source polarization adjustment component, parametric down-conversion component, 200, 210, 300, 310, 910, 920, first polarizer, first narrowband filter, first coupler, first single-photon detector, 610, 710, 410, 510, second polarizer, second narrowband filter, second coupler, second single-photon detector, 420, 520, 620, 720, counting processing component, coincidence counter, host computer, 800, 810, 820, 931, 932. Figure 5 shows HK 30134894 A.