An experimental teaching demonstration device and method for verifying quantum superposition principle and application thereof

Abstract

The application discloses an experimental teaching demonstration device for verifying a quantum superposition state principle, comprising 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 an optical path. The application also discloses an undergraduate experimental teaching demonstration method for verifying the quantum superposition state principle, wherein a superposition state is formed by using a vertical polarization state and a horizontal polarization state, the relative phase of the horizontal polarization state and the vertical polarization state is changed, and the change of the photon polarization state is observed, so that the quantum superposition state principle demonstration is realized, and the method has wide application value.

Description

Technical Field

[0001] This invention relates to the fields of quantum physics and optical measurement technology, and in particular to an experimental teaching demonstration device, demonstration method and application for verifying the principle of quantum superposition. Background Technology

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

[0003]

[0004] It can be seen that the probability distribution of a superposition state is not the sum of the probabilities of the original two wave functions, but rather an interfering probability. This means that the states of a quantum system are not simply combinations of independent states, but exist in phase relationships, leading to quantum interference. Therefore, quantum superposition embodies the fundamental difference between quantum mechanics and classical physics, revealing the probabilistic and nondeterministic nature of the microscopic world, making this transition difficult for students educated in classical physics to adapt to. Simultaneously, when observing a particle in a superposition state, the wave function instantly collapses from one superposition state to one of the definite states; this process is random and unpredictable. Therefore, we usually cannot directly "see" a quantum system in a superposition state, making it difficult for students to grasp the changes in the quantum state before and after measurement. Furthermore, although the superposition principle has been verified through the double-slit experiment, quantum delayed-choice experiment, and quantum erasure experiment, these experiments typically require complex equipment and stringent experimental conditions, making it difficult for students to conduct them personally. Therefore, designing superposition experimental devices and demonstration methods suitable for undergraduate teaching is of profound significance for students to deeply understand the essence of the quantum world, develop quantum technology, and explore the fundamental laws of nature. Summary of the Invention

[0005] To address the lack of suitable demonstration devices for teaching in existing technologies, this invention provides an experimental teaching demonstration method and device for verifying the principle of quantum superposition. It aims to combine the fundamental theories of quantum mechanics with experiments, helping students understand the concept of superposition in quantum mechanics and enabling undergraduates to gain a deeper understanding of the fundamental concepts of quantum mechanics.

[0006] To achieve the above objectives, this invention proposes an experimental teaching demonstration device for verifying the principle of quantum superposition, comprising: a coherent light source, an attenuator, a polarizer, a first λ / 2 waveplate, a λ / 4 waveplate, a second λ / 2 waveplate, a polarization beam splitter, a photon counter, and a pulse counter arranged sequentially along the optical path; wherein,

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

[0008] The attenuator is used to change the light intensity of the coherent light source, reducing the light intensity to the pW level to obtain incident light at the single photon level.

[0009] The polarizer is used to convert the coherent optical field into horizontally linearly polarized light and output it.

[0010] The first λ / 2 waveplate is used to adjust and control the polarization direction of the horizontally linearly polarized light by changing the optical axis direction, thereby achieving the superposition of vertically polarized light and horizontally polarized light in any proportion.

[0011] The λ / 4 waveplate is used to change the relative phase of horizontally polarized light and vertically polarized light. When the fast axis of the λ / 4 waveplate is vertical, the horizontally polarized light propagates along the slow axis in the λ / 4 waveplate, changing only the phase of the horizontally polarized light by π / 2. When the fast axis of the λ / 4 waveplate is horizontal, the vertically polarized light propagates along the slow axis in the λ / 4 waveplate, changing only the phase of the vertically polarized light by π / 2.

[0012] In one specific implementation, the λ / 4 waveplate is fixedly mounted on an optical rotating stage, which is used to change the relative phase of horizontally polarized light and vertically polarized light. By rotating the optical rotating stage, the λ / 4 waveplate is rotated along the optical axis, which changes the thickness of the horizontally polarized light passing through the λ / 4 waveplate, thereby controlling and changing the phase difference between the horizontally polarized light and the vertically polarized light.

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

[0014] The polarization beam splitter is used to combine two optical signals with a relative phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 waveplate, respectively. After the beam is combined, the two arms of the polarization beam splitter emit optical signals in the horizontal polarization direction and the vertical polarization direction, respectively.

[0015] The optical signals emitted from the polarization beam splitter enter the first photon counter and the second photon counter respectively, and are counted by the first pulse counter and the second pulse counter;

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

[0017] The first pulse counter is used to count voltage pulse signals and observe the distribution of photons.

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

[0019] The second pulse counter is used to count voltage pulse signals and observe the distribution of photons.

[0020] A linear superposition state consisting of a vertical polarization state |H> and a horizontal polarization state |V> is prepared by the coherent light source, the polarizer, and the first λ / 2 waveplate. c1 and c2 control the ratio of horizontally and vertically polarized light with respect to the first λ / 2 waveplate; relative phase The phase relationship between the two polarized lights was controlled.

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

[0022] Based on the above apparatus, this invention proposes an experimental teaching demonstration method for verifying the principle of quantum superposition. It utilizes the fact that linearly polarized photons are a superposition of horizontal and vertical polarization states to conduct experimental demonstrations. Light emitted from a coherent source is attenuated by an attenuator to obtain a single-photon horizontal source. After passing through a polarizer, this single-photon source is in a horizontally linearly polarized state. Under the action of a first λ / 2 waveplate, the originally horizontally polarized single-photon source is placed in a linear superposition of the horizontal polarization state |V> and the vertical polarization state |H>. Here, c1 and c2 are related to the rotation angle of the first λ / 2 waveplate. That is, when the angle between the incoming horizontally polarized light and the fast axis of the first λ / 2 waveplate is θ, the linearly polarized light will rotate through an angle of 2θ. At this time, c1 = cos2θ and c2 = sin2θ, thus controlling the ratio of horizontally polarized light to vertically polarized light. Relative phase An optical rotating stage is used to rotate a λ / 4 waveplate, changing the relative phase of horizontally and vertically polarized light and controlling the phase relationship between the two types of polarized light. A second λ / 2 waveplate is adjusted to control the polarization direction of the light output from the λ / 4 waveplate. When the angle between the polarization direction and the fast axis of the waveplate is 45°, both the original horizontally and vertically polarized light can be projected in the horizontal and vertical polarization directions, respectively, and each direction consists of two beams of light with a phase difference. After passing through a polarization beam splitter, the probability density of the quantum state is measured. When the phase is stable, the probability density of the quantum state satisfies the interference condition. When the phase is unstable, the probability density of the quantum state does not satisfy the interference condition. This allows for an experimental demonstration of the principle of quantum superposition.

[0023] The specific steps include the following:

[0024] Step 1: Construct and utilize a coherent light source, a polarizer, and a first λ / 2 waveplate 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 beamsplitter behind the first λ / 2 waveplate. Rotate the first λ / 2 waveplate to change the vibration direction of the incident linearly polarized light and its angle with the fast axis. Record the beam splitting ratio of the polarization beamsplitter at different angles to obtain the probability of the occurrence of the horizontal polarization state |V> and the vertical polarization state |H>. Then, insert an attenuator after the coherent light source, and place a first photon counter, a first pulse counter, a second photon counter, and a second pulse counter after the polarization beamsplitter. Measure the number of photons at different angles of the previously calibrated first λ / 2 waveplate. After recording, adjust the first λ / 2 waveplate to make the beam splitting ratio of the polarization beamsplitter 50:50, and remove the attenuator, the first photon counter, the first pulse counter, the second photon counter, and the second pulse counter.

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

[0027] Step 4: Adjust the second λ / 2 waveplate. When the angle between the polarization direction and the fast axis of the second λ / 2 waveplate is 45°, both the original horizontally polarized light and the original vertically polarized light will have projections in the horizontal and vertical polarization directions, and two light signals with a phase difference will be generated in the horizontal and vertical polarization directions.

[0028] Step 5: Use an optical rotary stage to control the λ / 4 waveplate to rotate along its optical axis, thereby changing the relative phase of the horizontally polarized light and the vertically polarized light. The light intensity detected after the polarization beam splitter is recorded point by point along with the rotation angle θ of the optical rotating stage at that time. This is used to calibrate the relationship between the rotation angle θ of the λ / 4 waveplate and the change in phase. The phase corresponding to the rotation angle θ at the point of 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 point of minimum light intensity is π.

[0029] Step Six: Insert an attenuator after the coherent light source, and place the first photon counter, first pulse counter, second photon counter, and second pulse counter after the polarization beam splitter. Use a light-shielding plate to block the light path in front of the first λ / 2 waveplate. Record the dark count generated by the photon counters within 1 second multiple times and calculate the average value. Due to environmental noise and electronic noise, the photon counters can still record pulse signals even without actual optical signal input; this is called the dark count. This step is used to measure the dark count value per unit time. Subsequent data acquisitions should all be subtracted from the dark count generated within the corresponding time period.

[0030] Step 7: Fix the first λ / 2 waveplate 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 and second pulse counters within 1 second at different rotation angles of the optical rotating stage. Then change the angle of the first λ / 2 waveplate and repeat the above experiment.

[0031] Step 8: When the optical rotary stage rotates randomly, rotate the second λ / 2 waveplate and record the counts of the first pulse counter and the second pulse counter at each point.

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

[0033] Steps three through seven are used to apply different phases to the superposition state, i.e. The probability distribution of the superposition state was measured after the first and second photon counters.

[0034] Step eight is used to prepare a mixed-state superposition that breaks the state of instability, even if Phase in It becomes a high-frequency random phase, at which point the measurement results will lose 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 teaching experiments and demonstrations of the quantum superposition principle.

[0036] The beneficial effects of this invention include: This invention designs an undergraduate teaching demonstration device to verify the principle of quantum superposition. Utilizing components such as a polarizer, a λ / 2 waveplate, and a λ / 4 waveplate, it generates a linear superposition of horizontally and vertically polarized states. By precisely adjusting the relative phase, the interference characteristics of quantum superposition are visually demonstrated. This device is simple to operate, does not rely on complex equipment or stringent experimental conditions, and is suitable for teaching environments. By adjusting the polarization ratio and phase relationship, the formation and disappearance of quantum interference patterns can be observed, leading to a deeper understanding of superposition and interference phenomena in quantum mechanics. On the one hand, it can deepen students' understanding of the fundamental physical concepts of superposition in quantum mechanics; on the other hand, it can help students learn about cutting-edge science and technology, thus helping to cultivate students' scientific literacy.

[0037] By using intuitive optical elements and devices, such as polarizers, λ / 2 waveplates, and λ / 4 waveplates, students can directly participate in the experimental operations, adjusting various parameters and observing the results, thus increasing the fun and interactivity of learning. This direct participation not only cultivates students' experimental skills but also improves their ability to connect theory with practice, enabling them to link abstract quantum mechanics theories with concrete experimental phenomena. Furthermore, the experiment encourages students to explore different combinations of polarization states and phase relationships, stimulating their curiosity and exploratory desire, and helping to cultivate their innovative thinking and problem-solving abilities. The device is simple in design and easy to operate, requiring no complex equipment or stringent experimental conditions, making quantum physics more accessible and lowering the learning threshold for students. Moreover, this device is not only suitable for teaching but can also serve as a preliminary research tool, helping students begin research activities at the undergraduate level and laying a foundation for future research work. Because it uses a low-power light source and simple optical elements, the entire experimental process is safe and harmless, suitable for use in a classroom environment. The device has a simple structure, is easy to maintain, and can also be easily modified or have new functions added in the future according to teaching needs. In summary, the demonstration device of this invention not only helps students understand and master the principle of quantum superposition, but also has multifaceted educational significance and practical value. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of an experimental teaching demonstration device for verifying the principle of quantum superposition proposed in this invention.

[0040] Figure 2This is a flowchart of an experimental teaching demonstration method for verifying the principle of quantum superposition proposed in this invention.

[0041] Figure 1 In the diagram, 1-coherent light source, 2-attenuator, 3-polarizer, 4-first λ / 2 waveplate, 5-λ / 4 waveplate, 6-optical rotating stage, 7-second λ / 2 waveplate, 8-polarization beam splitter, 9-first photon counter, 10-first pulse counter, 11-second photon counter, and 12-second pulse counter. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0043] This invention provides an undergraduate experimental teaching demonstration device for verifying the principle of quantum superposition. A linear superposition state consisting of a vertically polarized state |H> and a horizontally polarized state |V> is prepared using a coherent light source 1, a polarizer 3, and a first λ / 2 waveplate 4. Here, c1 and c2 are related to the rotation angle of the first λ / 2 waveplate 4. Relative phase The superposition is generated by rotating a λ / 4 waveplate 5 around the optical axis under the control of an optical rotating stage 6. The distribution of photons is observed by a second λ / 2 waveplate 7, a polarization beam splitter 8, a photon counter, and a 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 exhibits interference characteristics. Conversely, if the relative phase is uncertain, the interference pattern will disappear. Based on this demonstration device, this invention also provides an undergraduate experimental teaching demonstration method for verifying the principle of quantum superposition. By using a vertical polarization state and a horizontal polarization state to form a superposition state, changing the relative phase of the horizontal polarization state and the vertical polarization state, and observing the change in the photon polarization state, the principle of quantum superposition is demonstrated.

[0044] This invention provides an experimental teaching demonstration device for verifying the principle of quantum superposition. For example... Figure 1 As shown, it specifically includes:

[0045] The optical path is sequentially arranged as follows: a coherent light source 1, an attenuator 2, a polarizer 3, a first λ / 2 waveplate 4, a λ / 4 waveplate 5 (fixed on an optical rotating stage 6), a second λ / 2 waveplate 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] The coherent light source 1 is used to generate a monochromatic frequency-stabilized coherent light field;

[0047] The attenuator 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 at the single photon level.

[0048] The polarizer 3 is used to output horizontally linearly polarized light of the aforementioned coherent optical field;

[0049] The first λ / 2 waveplate 4 is used to adjust the polarization direction of the horizontally linearly polarized light, thereby achieving the superposition of vertically polarized light and horizontally polarized light in any proportion;

[0050] The λ / 4 waveplate 5 is used to change the relative phase of horizontally polarized light and vertically polarized light. When the fast axis of the λ / 4 waveplate 5 is vertical, it only changes the phase of the horizontal component of the polarized light; when the fast axis of the λ / 4 waveplate 5 is horizontal, it only changes the phase of the vertical component of the polarized light.

[0051] The optical rotating stage 6 is used to change the relative phase of horizontally polarized light and vertically polarized light. By rotating the optical rotating stage, the λ / 4 waveplate 5 is rotated along the optical axis, which can change the thickness of the coherent light passing through the λ / 4 waveplate 5 and control the change in the phase value of the horizontal component of the polarized light.

[0052] The second λ / 2 waveplate 7 is used to adjust the polarization direction of the output light from the λ / 4 waveplate 5. When the angle between the polarization direction and the fast axis of the second λ / 2 waveplate 7 is 45°, both the horizontally polarized light and the vertically polarized light output from the λ / 4 waveplate 5 are rotated by 45°. At this time, both the original horizontally polarized light and the original vertically polarized light can be projected in the horizontal and vertical polarization directions, and both the horizontal and vertical polarization directions are composed of two light signals with a phase difference.

[0053] The polarization beam splitter 8 is used to combine two optical signals with a phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 waveplate 7, respectively. After the beam is combined, 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.

[0054] The first photon counter 9 is used to convert weak light signals into electrical pulse signals;

[0055] The first pulse counter 10 is used to count voltage pulse signals and observe the distribution of photons.

[0056] The second photon counter 11 is used to convert weak light signals into electrical pulse signals;

[0057] The second pulse counter 12 is used to count voltage pulse signals and observe the distribution of photons.

[0058] The second aspect of the present invention provides an experimental teaching demonstration method for verifying the principle of quantum superposition. Linearly polarized photons are generated by a coherent light source 1, an attenuator 2, a polarizer 3, and a first λ / 2 waveplate 4. The phases of the horizontal and vertical polarization states in the linearly polarized photons are changed by a λ / 4 waveplate 5 and an optical rotating stage 6. The probability amplitudes of the horizontal and vertical polarization states are measured by a second λ / 2 waveplate 7, a polarization beam splitter 8, a photon counter, and a pulse counter.

[0059] like Figure 2 As shown, the specific steps are as follows:

[0060] Step 1: Construct and utilize coherent light source 1, polarizer 3, and first λ / 2 waveplate 4 to obtain a linear superposition state Ψ at the single-photon level, which is formed by the superposition of horizontal polarization state |V> and vertical polarization state |H>.

[0061] Step 2: Place a polarization beam splitter 8 behind the first λ / 2 waveplate 4, rotate the first λ / 2 waveplate 4, and record the beam splitting ratio of the incident linearly polarized light after passing through the polarization beam splitter 8 at different angles of the first λ / 2 waveplate 4. By rotating the first λ / 2 waveplate 4, a linear superposition state Ψ composed of horizontally polarized states |V> and vertically polarized states |H> with different ratios can be obtained. Then, insert an attenuator 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. Measure the number of photons at different angles of the previously calibrated first λ / 2 waveplate 4. After recording, adjust the first λ / 2 waveplate 4 so that the beam splitting ratio of the polarization beam splitter 8 is 50:50, and remove the attenuator 2, the first photon counter 9, the first pulse counter 10, the second photon counter 11, and the second pulse counter 12.

[0062] Step 3: Insert a λ / 4 waveplate 5 and a second λ / 2 waveplate 7 between the first λ / 2 waveplate 4 and the polarization beam splitter 8 to complete the optical path construction.

[0063] Step 4: Adjust the second λ / 2 waveplate 7. When the angle between the polarization direction and the fast axis of the second λ / 2 waveplate 7 is 45°, both the original horizontally polarized light and the original vertically polarized light can be projected in the horizontal and vertical polarization directions, and two light signals with phase difference are generated in the horizontal and vertical polarization directions.

[0064] Step 5: Use the optical rotating stage 6 to rotate the λ / 4 waveplate 5, thereby changing the relative phase of the horizontally polarized light and the vertically polarized light. The intensity of the light detected after the polarization beam splitter 8 is recorded point by point, along with the rotation angle θ of the optical rotating stage 6 at that moment. This is used to calibrate the relationship between the rotation angle θ of the λ / 4 waveplate 5 and the change in phase. The phase corresponding to the rotation angle θ at the point of 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 point of minimum light intensity is π.

[0065] Step Six: Insert attenuator 2 after coherent light source 1, and place first photon counter 9, first pulse counter 10, second photon counter 11, and second pulse counter 12 after polarization beam splitter 8. Use a light shield to block the light path in front of first λ / 2 waveplate 4. Record the dark count generated by the photon counters within 1 second multiple times and calculate the average value. Due to environmental noise and electronic noise, the photon counters can still record pulse signals even without actual light signal input; this is called dark counting. This step is used to measure the dark count value per unit time. Subsequent data acquisitions should all be subtracted from the dark count generated within the corresponding time period.

[0066] Step 7: Fix the first λ / 2 waveplate 4 at a certain angle. 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. Measure 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 stage 6. Then change the angle of the first λ / 2 waveplate 4 and repeat the above experiment.

[0067] Step 8: When the optical rotary stage 6 rotates randomly, rotate the second λ / 2 waveplate 7 and record the counts of the first pulse counter 10 and the second pulse counter 12 at each point.

[0068] This invention demonstrates the measurement process of quantum superposition through experiments, leading students to perceive the quantum world. The device is simple and easy to operate, which helps students deepen their understanding of the basic concepts of quantum mechanics through experiments.

[0069] The specific embodiments of the present invention have been described in detail above, but they are merely 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 to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

[0070] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. An experimental teaching demonstration device for verifying the principle of quantum superposition, characterized in that, The demonstration device includes: a coherent light source (1), an attenuator (2), a polarizer (3), a first λ / 2 waveplate (4), a λ / 4 waveplate (5), a second λ / 2 waveplate (7), a polarization beam splitter (8), a photon counter, and a pulse counter, arranged sequentially along the optical path; wherein, The coherent light source (1) is used to generate a monochromatic frequency-stabilized coherent light field; The attenuator (2) is used to change the light intensity of the coherent light source to obtain incident light at the level of a single photon. The polarizer (3) is used to convert the coherent optical field into horizontally linearly polarized light and output it. The first λ / 2 waveplate (4) is used to adjust the polarization direction of the horizontally linearly polarized light; The λ / 4 waveplate (5) is used to change the relative phase of horizontally polarized light and vertically polarized light; The second λ / 2 waveplate (7) is used to adjust the polarization direction of the output light of the λ / 4 waveplate (5); The polarization beam splitter (8) is used to combine two optical signals with a relative phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 waveplate (7), and then output the optical signals in the horizontal polarization direction and the vertical polarization direction respectively after combining. The photon counter is used to convert photon signals into single electrical pulse signals; The pulse counter is used to count voltage pulse signals and observe the distribution of photons. A linear superposition state consisting of a vertical polarization state |H> and a horizontal polarization state |V> is prepared by the coherent light source (1), the polarizer (3), and the first λ / 2 waveplate (4). c1 and c2, along with the first λ / 2 waveplate, control the ratio of horizontally and vertically polarized light; relative phase Control the phase relationship between the two polarized lights; c1 = cos2θ, c2 = sin2θ, where θ is the angle between the horizontal linearly polarized light and the fast axis of the first λ / 2 waveplate (4).

2. The demonstration device as described in claim 1, characterized in that, The λ / 4 waveplate (5) is fixedly mounted on the optical rotating stage (6). The optical rotating stage (6) can rotatably adjust the angle of the λ / 4 waveplate (5), thereby changing the phase difference between the horizontally polarized light and the vertically polarized light after the horizontally linearly polarized light is decomposed by the λ / 4 waveplate (5).

3. The demonstration device as described in 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 it; The second photon counter (11) and the second pulse counter (12) convert the photon signal into a single pulse signal and count it.

4. The demonstration device as described in claim 1, characterized in that, The second λ / 2 waveplate (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.

5. 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 1-4. After the photon is adjusted to a horizontal polarization state by the polarizer (3), the ratio of horizontally polarized light to vertically polarized light is controlled by rotating the first λ / 2 waveplate (4) to construct a linear superposition state of horizontal and vertical polarization states. The relative phase of horizontally polarized light and vertically polarized light is adjusted by rotating the λ / 4 waveplate (5), and the polarization direction of the output light of the λ / 4 waveplate (5) is adjusted by the second λ / 2 waveplate (7). Then, the polarization state is projected and measured by combining optical devices to finally verify the interference characteristics of the quantum superposition state.

6. The demonstration method as described in claim 5, characterized in that, The demonstration method specifically includes the following steps: Step 1: Construct and utilize a coherent light source (1), a polarizer (3), and a first λ / 2 waveplate (4) 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>. Step 2: Place a polarization beam splitter (8) behind the first λ / 2 waveplate (4), rotate the first λ / 2 waveplate (4) to change the vibration direction of the incident ray polarized light and its angle with the fast axis, and record the beam splitting ratio of the polarization beam splitter (8) at different angles to obtain the probability of the occurrence of the horizontal polarization state |V> and the vertical polarization state |H>. Then, insert an attenuator (2) behind 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) behind the polarization beam splitter (8) to measure the number of photons at different angles of the previously calibrated first λ / 2 waveplate (4). After recording, adjust the first λ / 2 waveplate (4) so ​​that the beam splitting ratio of the polarization beam splitter (8) is 50:50, and remove the attenuator (2), the first photon counter (9), the first pulse counter (10), the second photon counter (11), and the second pulse counter (12). Step 3: Insert a λ / 4 waveplate (5) and a second λ / 2 waveplate (7) between the first λ / 2 waveplate (4) and the polarization beam splitter (8) to complete the optical path construction; Step 4: Adjust the second λ / 2 waveplate (7). When the angle between the polarization direction and the fast axis of the second λ / 2 waveplate 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 light signals with phase difference are generated in the horizontal polarization direction and the vertical polarization direction. Step 5: Use the optical rotating stage (6) to control the λ / 4 waveplate (4) to rotate along its optical axis, thereby changing 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 to calibrate the relationship between the rotation angle θ of the λ / 4 waveplate (5) and the change of phase. Step 6: Insert an attenuator (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 waveplate (4), record the dark count generated by the photon counter within 1 second multiple times, and calculate the average value. Step 7: Fix the first λ / 2 waveplate (4) at a certain angle. After the light signal passes through the polarization beam splitter (8), it is received by the first photon counter (9) and the second photon counter (11) respectively. Measure the count of the first pulse counter (10) and the second pulse counter (12) within 1 second at different rotation angles of the optical rotating stage (6). Then change the angle of the first λ / 2 waveplate (4) and repeat the above experiment. Step 8: When the optical rotary stage (6) rotates randomly, rotate the second λ / 2 waveplate (7) and record the counts of the first pulse counter (10) and the second pulse counter (12) at each point.

7. The application of the demonstration device as described in any one of claims 1-4, or the demonstration method as described in claim 5 or 6, in the teaching experiment demonstration of the quantum superposition principle.

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