Experiment teaching demonstration device for verifying quantum superposition principle, demonstration method and application

Abstract

The invention discloses an experiment teaching demonstration device for verifying a quantum superposition state principle. The experiment teaching demonstration device comprises a coherent light source, an attenuation sheet, a polarizer, a first lambda / 2 wave plate, a lambda / 4 wave plate, a second lambda / 2 wave plate, a polarization beam splitter, a photon counter and a pulse counter which are sequentially arranged along a light path. The invention further discloses an undergraduate experiment teaching demonstration method for verifying the quantum superposition state principle, the vertical polarization state and the horizontal polarization state are used for forming the superposition state, the relative phase of the horizontal polarization state and the vertical polarization state is changed, the change of the photon polarization state is observed, the quantum superposition state principle demonstration is achieved, and the undergraduate experiment teaching demonstration method has wide application value.

Description

Technical Field

[0001] The present invention relates to the field of quantum physics and optical measurement technology, and in particular to an experimental teaching demonstration device, a demonstration method and an application for verifying the quantum superposition principle. Background Art

[0002] In quantum mechanics, the state of a particle is uncertain and exists in the form of probability. This probabilistic description allows the particle to be in a superposition of multiple states. The state of a quantum system is described by a wave function, and the square of the wave function |Ψ| 2 is the probability density of the system being in a particular state. If a quantum system is in a linear superposition state of state |Ψ1> and state |Ψ2> The probability density of this quantum state is

[0003]

[0004] It can be seen that the probability distribution of the superposition state is not the sum of the probabilities of the original two wave functions, but a probabilistic interference occurs. This means that the state of the quantum system is not just a simple combination of independent states, but there is a phase relationship between them, which leads to the phenomenon of quantum interference. Therefore, the quantum superposition state reflects the fundamental difference between quantum mechanics and classical physics, reveals the probabilistic and non-deterministic nature of the microscopic world, and makes it difficult for students who have received classical physics education to adapt to this change. At the same time, when a particle in a superposition state is observed, the wave function will instantly collapse from a superposition state to one of the determined states. This process is random and unpredictable. Therefore, we usually cannot directly "see" a quantum system in a superposition state, which makes it difficult for students to grasp the changes in quantum states before and after measurement. In addition, although the superposition principle has been verified by double-slit experiments, quantum delayed choice experiments, and quantum eraser experiments, these experiments usually require complex equipment and harsh experimental conditions, and students usually have little chance to conduct these experiments in person. Therefore, designing superposition state experimental devices and demonstration methods suitable for undergraduate teaching has far-reaching significance for students to deeply understand the nature of the quantum world, develop quantum technology, and explore the basic laws of nature. Summary of the invention

[0005] In order to solve the problem that there is no suitable teaching demonstration device in the prior art, the present invention provides an experimental teaching demonstration method and a demonstration device for verifying the principle of quantum superposition, which aims to combine the basic physical theory of quantum mechanics with experiments, help students understand the concept of superposition in quantum mechanics, and enable undergraduates to have a deeper understanding of the basic concepts of quantum mechanics.

[0006] In order to achieve the above-mentioned object, the present invention proposes an experimental teaching demonstration device for verifying the principle of quantum superposition, comprising: a coherent light source, an attenuation plate, a polarizer, a first λ / 2 wave plate, a λ / 4 wave plate, a second λ / 2 wave plate, a polarization beam splitter, a photon counter and a pulse counter arranged in sequence along the optical path; wherein,

[0007] The coherent light source is used to generate a monochromatic frequency-stable coherent light field;

[0008] The attenuation plate is used to change the light intensity of the coherent light source, reduce the light intensity to the pW level, and obtain incident light at the single photon level;

[0009] The polarizer is used to convert the coherent light field into horizontal linear polarized light and output it;

[0010] The first λ / 2 wave plate is used to adjust and control the polarization direction of the horizontal linear polarized light by changing the direction of the optical axis, thereby realizing the superposition of vertical polarized light and horizontal polarized light in any proportion;

[0011] The λ / 4 wave plate is used to change the relative phase of horizontal polarized light and vertical polarized light. When the fast axis of the λ / 4 wave plate is in the vertical direction, the horizontal polarized light propagates along the slow axis direction in the λ / 4 wave plate, and only the phase of the horizontal polarized light is changed by π / 2; when the fast axis of the λ / 4 wave plate is in the horizontal direction, the vertical polarized light propagates along the slow axis direction in the λ / 4 wave plate, and only the phase of the vertical polarized light is changed by π / 2;

[0012] In a specific implementation process, the λ / 4 wave plate is fixedly mounted on an optical rotating platform, and the optical rotating platform is used to change the relative phase of the horizontal polarized light and the vertical polarized light. By rotating the optical rotating platform, the λ / 4 wave plate is rotated along the optical axis, so that the thickness of the horizontal linear polarized light passing through the λ / 4 wave plate can be changed, and the phase difference between the horizontal polarized light and the vertical polarized light can be controlled and changed;

[0013] The second λ / 2 wave plate is used to adjust the polarization direction of the light output by the λ / 4 wave plate. When the angle between the polarization direction of the light output by the λ / 4 wave plate and the fast axis of the second λ / 2 wave plate is 45°, the horizontal polarized light and the vertical polarized light output by the λ / 4 wave plate are both rotated by 45°; at this time, both the original horizontal polarized light and the original vertical polarized light can be projected in the horizontal polarization direction and the vertical polarization direction, and the horizontal polarization direction and the vertical polarization direction are composed of two light fields with the same phase difference;

[0014] The polarization beam splitter is used to respectively realize the combination of two optical signals with relative phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 wave plate, and after the combination, the two arms of the polarization beam splitter respectively emit optical signals in the horizontal polarization direction and the vertical polarization direction;

[0015] The optical signal emitted by the polarization beam splitter enters the first photon counter and the second photon counter respectively, and is counted by the first pulse counter and the second pulse counter;

[0016] The first photon counter is used to convert a weak photon signal into a single electrical pulse signal;

[0017] The first pulse counter is used for counting voltage pulse signals and observing the distribution of photons.

[0018] The second photon counter is used to convert a weak photon signal into a single electrical pulse signal;

[0019] The second pulse counter is used for counting voltage pulse signals and observing the distribution of photons.

[0020] The coherent light source, the polarizer, and the first λ / 2 wave plate are used to prepare a linear superposition state consisting of a vertical polarization state |H> and a horizontal polarization state |V> c1 and c2 and the first λ / 2 wave plate control the ratio of horizontal and vertical polarized light; relative phase The phase relationship between the two polarized lights is controlled.

[0021] The second λ / 2 wave plate, the polarization beam splitter, the photon counter and the pulse counter complete the probability amplitude measurement of the horizontal polarization state and the vertical polarization state.

[0022] Based on the above device, the present invention proposes an experimental teaching demonstration method for verifying the principle of quantum superposition state, which uses the linear polarization photon to be a superposition state of horizontal polarization state and vertical polarization state to carry out experimental demonstration. The light emitted by the coherent light source is attenuated by the attenuation plate to obtain a single photon horizontal light source. After passing through the polarizer, the single photon source is in a horizontal linear polarization state. Under the action of the first λ / 2 wave plate, the single photon source originally in horizontal polarization is in a linear superposition state of horizontal polarization state |V> and vertical polarization state |H>. Here c1 and c2 are related to the rotation angle of the first λ / 2 wave plate, that is, when the angle between the incoming horizontal linear polarized light and the fast axis of the first λ / 2 wave plate is θ, the linear polarized light will rotate through an angle of 2θ. At this time, c1 = cos2θ, c2 = sin2θ, thereby controlling the ratio of horizontal polarized light to vertical polarized light. Relative phase The λ / 4 wave plate is driven to rotate by an optical rotating table to change the relative phase of the horizontal polarized light and the vertical polarized light and control the phase relationship between the two polarized lights. The second λ / 2 wave plate is adjusted to adjust and control the polarization direction of the output light of the λ / 4 wave plate. When the angle between the polarization direction and the fast axis of the wave plate is 45°, the original horizontal polarized light and the original vertical polarized light can be projected in the horizontal polarization direction and the vertical polarization direction, and the horizontal polarization direction and the vertical polarization direction are composed of two beams of light signals with phase difference. The probability density of the quantum state is measured after passing through the polarization beam splitter. When the phase is stable, the probability density of the quantum state meets the interference condition. When the phase is unstable, the probability density of the quantum state does not meet the interference condition. In this way, the experimental teaching demonstration of the principle of quantum superposition can be completed.

[0023] The specific steps include the following:

[0024] Step 1: Build and use a coherent light source, a polarizer, and a first λ / 2 wave plate to obtain a linear superposition state Ψ at the single-photon level, which is formed by the superposition of the horizontal polarization state |V> and the vertical polarization state |H>.

[0025] Step 2: Place a polarization beam splitter behind the first λ / 2 wave plate, rotate the first λ / 2 wave plate, change the vibration direction of the incident linear polarized light and its angle with the fast axis, record the splitting ratio of the polarization beam splitter at different angles, and obtain the probability of the horizontal polarization state |V> and the vertical polarization state |H>, then insert an attenuation plate behind the coherent light source, and place the first photon counter, the first pulse counter, the second photon counter and the second pulse counter behind the polarization beam splitter, and measure the number of photons at different angles of the first λ / 2 wave plate calibrated previously; after the recording is completed, adjust the first λ / 2 wave plate so that the splitting ratio of the polarization beam splitter is 50:50, and remove the attenuation plate, the first photon counter, the first pulse counter, the second photon counter and the second pulse counter;

[0026] Step 3: Insert the λ / 4 wave plate and the second λ / 2 wave plate between the first λ / 2 wave plate and the polarization beam splitter to complete the optical path construction.

[0027] Step 4: Adjust the second λ / 2 wave plate. When the angle between the polarization direction and the fast axis of the second λ / 2 wave plate is 45°, the original horizontally polarized light and the original vertically polarized light are projected in the horizontal polarization direction and the vertical polarization direction, and two optical signals with phase difference are generated in the horizontal polarization direction and the vertical polarization direction.

[0028] Step 5: Use an optical rotating stage to control the λ / 4 wave plate to rotate along its optical axis to change the relative phase of the horizontally polarized light and the vertically polarized light. The light intensity detected after the polarization beam splitter and the rotation angle θ of the optical rotating stage at this time are recorded point by point to calibrate the relationship between the rotation angle θ of the λ / 4 wave plate and the changed phase. The phase corresponding to the rotation angle θ at the maximum light intensity is 0, the phase corresponding to the rotation angle θ at half the light intensity is π / 2, and the phase corresponding to the weakest light intensity is π.

[0029] Step 6: Insert the attenuation plate after the coherent light source, and place the first photon counter, the first pulse counter, the second photon counter and the second pulse counter after the polarization beam splitter. Use the light shielding plate to block the light path in front of the first λ / 2 wave plate, and record the dark counts generated by the photon counter within 1s multiple times and calculate the average value. Due to environmental noise and electronic noise, the photon counter can still record the pulse signal without the actual light signal input, which is called dark count. This step is used to measure the dark count value per unit time. The subsequent collected data must subtract the dark count generated in the corresponding time.

[0030] Step 7: Fix the first λ / 2 wave plate at a certain angle. After the optical signal passes through the polarization beam splitter, it is received by the first photon counter and the second photon counter respectively. Measure the counts of the first pulse counter and the second pulse counter within 1s at different rotation angles of the optical rotating stage. Then change the angle of the first λ / 2 wave plate and repeat the above experiment.

[0031] Step 8: When the optical rotating stage rotates randomly, the second λ / 2 wave plate is rotated and the counts of the first pulse counter and the second pulse counter are recorded point by point.

[0032] Steps 1 and 2 are used to prepare a superposition state Ψ=c1|V>+c2|H> and measure it. The experimental results verify that the superposition state satisfies characteristics.

[0033] Steps 3 to 7 are used to impose different phases on the superposition state, i.e. And measure the probability distribution of the superposition state after the first photon counter and the second photon counter

[0034] Step eight is used to prepare a mixed state that destroys the superposition state, even if Phase It becomes a high-frequency random phase, and the measurement result loses the probability density distribution characteristics of the superposition state.

[0035] The present invention also provides the application of the above-mentioned demonstration device or the above-mentioned demonstration method in the teaching experiment demonstration of quantum superposition principle, etc.

[0036] The beneficial effects of the present invention include: the present invention designs an undergraduate teaching demonstration device for verifying the principle of quantum superposition state, uses polarizers, λ / 2 wave plates, λ / 4 wave plates and other components to generate linear superposition states of horizontal polarization states and vertical polarization states, and intuitively displays the interference characteristics of quantum superposition states by precisely adjusting the relative phase. The device is easy to operate, does not rely on complex equipment or harsh experimental conditions, and is suitable for teaching environments. By adjusting the polarization state ratio and phase relationship, the formation and disappearance of quantum interference patterns can be observed, and the superposition state and interference phenomenon in quantum mechanics can be deeply understood. On the one hand, it can deepen students' understanding of the basic physical concepts of superposition states in quantum mechanics, and on the other hand, it can help students understand cutting-edge science and technology and help cultivate students' scientific literacy.

[0037] By using intuitive optical components and equipment, such as polarizers, λ / 2 wave plates, λ / 4 wave plates, etc., students can directly participate in the experimental operation, adjust various parameters and observe the results, thereby increasing the interest and interactivity of learning. This direct participation not only cultivates students' experimental skills, but also improves their ability to link theory with practice, enabling students to link abstract quantum mechanics theory with specific experimental phenomena. In addition, during the experiment, students are encouraged to explore different polarization state combinations and phase relationships, which stimulates their curiosity and desire to explore, and helps to cultivate students' innovative thinking and problem-solving skills. The device is simple in design and easy to operate. It does not require complex equipment or harsh experimental conditions, making the study of quantum physics more approachable and lowering the learning threshold for students. At the same time, this device is not only suitable for teaching, but also can be used as a preliminary scientific research tool to help students start to engage in scientific research activities at the undergraduate stage and lay the foundation for future scientific research work. Due to the use of low-power light sources and simple optical components, the entire experimental process is safe and harmless, and is suitable for use in a classroom environment. The device has a simple structure and is easy to maintain, and it is also convenient to add new functions or improve existing parts according to teaching needs in the future. In summary, the demonstration device of the present invention not only helps students understand and master the principle of quantum superposition, but also has many educational significances and practical values. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 It is a schematic diagram of an experimental teaching demonstration device for verifying the principle of quantum superposition state proposed by the present invention.

[0040] Figure 2The present invention provides a flow chart of an experimental teaching demonstration method for verifying the principle of quantum superposition.

[0041] Figure 1 In it, 1-coherent light source, 2-attenuation plate, 3-polarizer, 4-first λ / 2 wave plate, 5-λ / 4 wave plate, 6-optical rotating table, 7-second λ / 2 wave plate, 8-polarization beam splitter, 9-first photon counter, 10-first pulse counter, 11-second photon counter and 12-second pulse counter. DETAILED DESCRIPTION

[0042] The present invention is further described in detail with reference to the following specific examples and drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0043] The present invention provides an undergraduate experimental teaching demonstration device for verifying the principle of quantum superposition state. A linear superposition state consisting of a vertical polarization state |H> and a horizontal polarization state |V> is prepared by a coherent light source 1, a polarizer 3, and a first λ / 2 wave plate 4. Here c1 and c2 are related to the rotation angle of the first λ / 2 wave plate 4. Relative phase The λ / 4 wave plate 5 is controlled by the optical rotating table 6 to rotate around the optical axis. The distribution of photons is observed by the second λ / 2 wave plate 7, the polarization beam splitter 8, the photon counter and the pulse counter. When the horizontal polarization state |V> and the vertical polarization state |H> have a definite relative phase, the probability density of this superposition state shows interference characteristics. On the contrary, if the relative phase is uncertain, the interference pattern will disappear. Based on the demonstration device, the present invention also provides an undergraduate experimental teaching demonstration method for verifying the principle of quantum superposition state, which uses the vertical polarization state and the horizontal polarization state to form a superposition state, changes the relative phase of the horizontal polarization state and the vertical polarization state, observes the change of the polarization state of the photon, and realizes the demonstration of the principle of quantum superposition state.

[0044] The present invention provides an experimental teaching demonstration device for verifying the principle of quantum superposition. Figure 1 As shown, specifically including:

[0045] Arranged in sequence along the optical path are a coherent light source 1, an attenuation plate 2, a polarizer 3, a first λ / 2 wave plate 4, a λ / 4 wave plate 5 (fixedly mounted on an optical rotating table 6), a second λ / 2 wave plate 7, a polarization beam splitter 8, a photon counter (including a first photon counter 9 and a second photon counter 11), and a pulse counter (including a first pulse counter 10 and a second pulse counter 12).

[0046] in,

[0047] The coherent light source 1 is used to generate a monochromatic frequency-stable coherent light field;

[0048] The attenuation plate 2 is used to change the light intensity of the coherent light source, reduce the light intensity to the pW level, and obtain incident light of the single photon level;

[0049] The polarizer 3 is used to output the horizontal linear polarized light of the coherent light field;

[0050] The first λ / 2 wave plate 4 is used to adjust the polarization direction of the horizontal linear polarized light, so as to achieve the superposition of vertical polarized light and horizontal polarized light in any proportion;

[0051] The λ / 4 wave plate 5 is used to change the relative phase of the horizontal polarized light and the vertical polarized light. When the fast axis of the λ / 4 wave plate 5 is in the vertical direction, only the phase of the horizontal component of the polarized light is changed; when the fast axis of the λ / 4 wave plate 5 is in the horizontal direction, only the phase of the vertical component of the polarized light is changed;

[0052] The optical rotating stage 6 is used to change the relative phase of the horizontal polarized light and the vertical polarized light. By rotating the optical rotating stage, the λ / 4 wave plate 5 is rotated along the optical axis, so that the thickness of the coherent light passing through the λ / 4 wave plate 5 can be changed, and the phase value of the horizontal component of the polarized light can be controlled and changed;

[0053] The second λ / 2 wave plate 7 is used to adjust the polarization direction of the light output by the λ / 4 wave plate 5. When the angle between the polarization direction and the fast axis of the second λ / 2 wave plate 7 is 45°, the horizontal polarized light and the vertical polarized light output by the λ / 4 wave plate 5 are both rotated by 45°. At this time, both the original horizontal polarized light and the original vertical polarized light can be projected in the horizontal polarization direction and the vertical polarization direction, and the horizontal polarization direction and the vertical polarization direction are composed of two light signals with phase difference;

[0054] The polarization beam splitter 8 is used to realize the combination of two optical signals with phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 wave plate 7, and after the combination, the two arms of the polarization beam splitter 8 emit optical signals in the horizontal polarization direction and the vertical polarization direction respectively; the emitted optical signals enter the first photon counter 9 and the second photon counter 11 respectively, and are counted by the first pulse counter 10 and the second pulse counter 12;

[0055] The first photon counter 9 is used to convert weak light signals into electrical pulse signals;

[0056] The first pulse counter 10 is used for counting voltage pulse signals and observing the distribution of photons.

[0057] The second photon counter 11 is used to convert a weak light signal into an electrical pulse signal;

[0058] The second pulse counter 12 is used for counting voltage pulse signals and observing the distribution of photons.

[0059] The second aspect of the present invention provides an experimental teaching demonstration method for verifying the principle of quantum superposition. A coherent light source 1, an attenuation plate 2, a polarizer 3, and a first λ / 2 wave plate 4 generate linearly polarized photons. A λ / 4 wave plate 5 and an optical rotating table 6 change the phases of the horizontal polarization state and the vertical polarization state in the linearly polarized photons. A second λ / 2 wave plate 7, a polarization beam splitter 8, a photon counter, and a pulse counter complete the probability amplitude measurement of the horizontal polarization state and the vertical polarization state.

[0060] like Figure 2 As shown, the specific steps are as follows:

[0061] Step 1: Build and use a coherent light source 1, a polarizer 3, and a first λ / 2 wave plate 4 to obtain a linear superposition state Ψ formed by superposition of a horizontal polarization state |V> and a vertical polarization state |H> at a single-photon level.

[0062] Step 2: Place a polarization beam splitter 8 behind the first λ / 2 wave plate 4, rotate the first λ / 2 wave plate 4, and record the splitting ratio of the incident linear polarized light after passing through the polarization beam splitter 8 at different angles of the first λ / 2 wave plate 4. The linear superposition state Ψ composed of horizontal polarization states |V> and vertical polarization states |H> in different proportions can be obtained by rotating the first λ / 2 wave plate 4. Then, insert the attenuation plate 2 behind the coherent light source 1, and place the first photon counter 9, the first pulse counter 10, the second photon counter 11 and the second pulse counter 12 behind the polarization beam splitter 8 to measure the number of photons at different angles of the first λ / 2 wave plate 4 calibrated before. After the recording is completed, adjust the first λ / 2 wave plate 4 so that the splitting ratio of the polarization beam splitter 8 is 50:50, and remove the attenuation plate 2, the first photon counter 9, the first pulse counter 10, the second photon counter 11 and the second pulse counter 12.

[0063] Step 3: Insert the λ / 4 wave plate 5 and the second λ / 2 wave plate 7 between the first λ / 2 wave plate 4 and the polarization beam splitter 8 to complete the optical path construction.

[0064] Step 4: Adjust the second λ / 2 wave plate 7. When the angle between the polarization direction and the fast axis of the second λ / 2 wave plate 7 is 45°, the original horizontally polarized light and the original vertically polarized light can be projected in the horizontal polarization direction and the vertical polarization direction, and two light signals with phase difference are generated in the horizontal polarization direction and the vertical polarization direction.

[0065] Step 5: Use the optical rotating platform 6 to drive the λ / 4 wave plate 5 to rotate and change the relative phase of the horizontally polarized light and the vertically polarized light The light intensity detected after the polarization beam splitter 8 and the rotation angle θ of the optical rotating stage 6 at this time are recorded point by point, which is used to calibrate the relationship between the rotation angle θ and the phase change of the λ / 4 wave plate 5. The phase corresponding to the rotation angle θ at the maximum light intensity is 0, the phase corresponding to the rotation angle θ at half the light intensity is π / 2, and the phase corresponding to the weakest light intensity is π.

[0066] Step 6: Insert the attenuation plate 2 after the coherent light source 1, and place the first photon counter 9, the first pulse counter 10, the second photon counter 11 and the second pulse counter 12 after the polarization beam splitter 8. Use a light shield to block the light path in front of the first λ / 2 wave plate 4, and record the dark counts generated by the photon counter within 1s for many times and calculate the average value. Due to environmental noise and electronic noise, the photon counter can still record the pulse signal without the actual light signal input, which is called dark count. This step is used to measure the dark count value per unit time. The subsequent collected data must subtract the dark count generated in the corresponding time.

[0067] Step 7: Fix the first λ / 2 wave plate 4 at a certain angle, and after the optical signal passes through the polarization beam splitter, it is received by the first photon counter 9 and the second photon counter 10 respectively, and the counts of the first pulse counter 11 and the second pulse counter 12 within 1 second at different rotation angles of the optical rotating stage 6 are measured. Then change the angle of the first λ / 2 wave plate 4 and repeat the above experiment.

[0068] Step 8: When the optical rotating stage 6 rotates randomly, the second λ / 2 wave plate 7 is rotated and the counts of the first pulse counter 11 and the second pulse counter 12 are recorded point by point.

[0069] The present invention demonstrates the measurement process of quantum superposition state through experiments, leading students to perceive the quantum world. The device is simple and easy to operate, which is conducive to students deepening their understanding of the basic concepts of quantum mechanics through experiments.

[0070] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

[0071] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the present invention, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the attached claims.

Claims

1. An experimental teaching demonstration device for verifying the principle of quantum superposition, characterized in that: The demonstration device comprises: a coherent light source (1), an attenuation plate (2), a polarizer (3), a first λ / 2 wave plate (4), a λ / 4 wave plate (5), a second λ / 2 wave plate (7), a polarization beam splitter (8), a photon counter and a pulse counter, which are arranged in sequence along the optical path; wherein: The coherent light source (1) is used to generate a monochromatic frequency-stable coherent light field; The attenuation plate (2) is used to change the light intensity of the coherent light source to obtain incident light of the single photon order; The polarizer (3) is used to convert the coherent light field into horizontal linear polarized light and output it; The first λ / 2 wave plate (4) is used to adjust the polarization direction of the horizontal linear polarized light; The λ / 4 wave plate (5) is used to change the relative phase of the horizontally polarized light and the vertically polarized light; The second λ / 2 wave plate (7) is used to adjust the polarization direction of the light output by the λ / 4 wave plate (5); The polarization beam splitter (8) is used to respectively realize the combination of two optical signals with relative phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 wave plate (7), and then respectively emit the optical signals in the horizontal polarization direction and the vertical polarization direction after the combination; The photon counter is used to convert the photon signal into a single electrical pulse signal; The pulse counter is used for counting voltage pulse signals and observing the distribution of photons.

2. The demonstration device according to claim 1, characterized in that: The λ / 4 wave plate (5) is fixedly mounted on an optical rotating platform (6), and the optical rotating platform (6) is capable of rotatably adjusting the angle of the λ / 4 wave plate (5), thereby changing the phase difference between the horizontally polarized light and the vertically polarized light after the horizontally polarized light is decomposed by the λ / 4 wave plate (5).

3. The demonstration device according to claim 1, characterized in that: The first photon counter (9) and the first pulse counter (10) convert the photon signal into a single electrical pulse signal and count them; The second photon counter (11) and the second pulse counter (12) convert the photon signal into a single pulse signal and perform counting.

4. The demonstration device according to claim 1, characterized in that: The coherent light source (1), the polarizer (3) and the first λ / 2 wave plate (4) are used to prepare a linear superposition state consisting of a vertical polarization state |H> and a horizontal polarization state |V> c1 and c2 and the first λ / 2 wave plate control the ratio of horizontal and vertical polarized light; Relative Phase The phase relationship between the two polarized lights is controlled; c1=cos2θ, c2=sin2θ, θ is the angle between the horizontal linear polarized light and the fast axis of the first λ / 2 wave plate (4).

5. The demonstration device according to claim 1, characterized in that: The second λ / 2 wave plate (7), the polarization beam splitter (8), the photon counter and the pulse counter complete the probability amplitude measurement of the horizontal polarization state and the vertical polarization state.

6. An experimental teaching demonstration method for verifying the principle of quantum superposition, characterized in that: The demonstration method is based on the demonstration device as described in any one of claims 1 to 6. After adjusting the photons to a horizontal polarization state through a polarizer (3), the ratio of horizontal polarized light to vertical polarized light is controlled by a first λ / 2 wave plate (4) to construct a linear superposition state of the horizontal polarization state and the vertical polarization state; the relative phase of the horizontal polarized light and the vertical polarized light is adjusted by rotating a λ / 4 wave plate (5), and the polarization direction of the output light of the λ / 4 wave plate (5) is controlled by a second λ / 2 wave plate (7); then, the polarization state is projected and measured in combination with an optical device, and finally the interference characteristics of the quantum superposition state are verified.

7. The demonstration method according to claim 6, characterized in that: The demonstration method specifically comprises the following steps: Step 1: construct and use a coherent light source (1), a polarizer (3), and a first λ / 2 wave plate (4) to obtain a linear superposition state Ψ formed by superposition of a horizontal polarization state |V> and a vertical polarization state |H> at a single-photon level; Step 2: placing a polarization beam splitter (8) behind the first λ / 2 wave plate (4), rotating the first λ / 2 wave plate (4), changing the vibration direction of the incident linear polarized light and its angle with the fast axis, recording the splitting ratio of the polarization beam splitter (8) at different angles, thereby obtaining the probability of the horizontal polarization state |V> and the vertical polarization state |H> appearing, then inserting an attenuation plate (2) behind the coherent light source (1), and placing a first photon counter (9), a first pulse counter (10), a second photon counter (11) and a second pulse counter (12) behind the polarization beam splitter (8), and measuring the number of photons at different angles of the first λ / 2 wave plate (4) calibrated previously; after recording, adjusting the first λ / 2 wave plate (4) so ​​that the splitting ratio of the polarization beam splitter (8) is 50:50, and removing the attenuation plate (2), the first photon counter (9), the first pulse counter (10), the second photon counter (11) and the second pulse counter (12); Step 3: inserting the λ / 4 wave plate (5) and the second λ / 2 wave plate (7) between the first λ / 2 wave plate (4) and the polarization beam splitter (8) to complete the optical path construction; Step 4: adjusting the second λ / 2 wave plate (7), when the angle between the polarization direction and the fast axis of the second λ / 2 wave plate is 45°, the original horizontally polarized light and the original vertically polarized light are projected in the horizontal polarization direction and the vertical polarization direction, and two optical signals with a phase difference are generated in the horizontal polarization direction and the vertical polarization direction; Step 5: Use the optical rotating platform (6) to control the λ / 4 wave plate (4) to rotate along its optical axis to change the relative phase of the horizontally polarized light and the vertically polarized light. The light intensity detected after the polarization beam splitter (8) and the rotation angle θ of the optical rotating stage (6) at that time are recorded point by point, and used to calibrate the relationship between the rotation angle θ of the λ / 4 wave plate (5) and the changed phase; Step 6: insert an attenuation plate (2) after the coherent light source (1), and place a first photon counter (9), a first pulse counter (10), a second photon counter (11) and a second pulse counter (12) after the polarization beam splitter (8), use a light shielding plate to block the light path in front of the first λ / 2 wave plate (4), record the dark counts generated by the photon counters within 1 second multiple times and calculate the average value; Step 7: The first λ / 2 wave plate (4) is fixed at a certain angle, and the optical signal is received by the first photon counter (9) and the second photon counter (11) respectively after passing through the polarization beam splitter (8), and the counts of the first pulse counter (10) and the second pulse counter (12) within 1 second at different rotation angles of the optical rotating table (6); then the angle of the first λ / 2 wave plate (4) is changed, and the above experiment is repeated; Step 8: When the optical rotating platform (6) rotates randomly, the second λ / 2 wave plate (7) is rotated and the counts of the first pulse counter (11) and the second pulse counter (12) are recorded point by point.

8. Application of the demonstration device as described in any one of claims 1 to 5, or the demonstration method as described in claim 6 or 7 in the teaching experiment demonstration of quantum superposition principle.

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