BD-based single-photon interference teaching experiment device

Abstract

The utility model relates to the technical field of quantum information and quantum optics, and provides a BD-based single-photon interference teaching experiment device, which comprises an entanglement source for generating single photons, a collimator and a BD-based single-photon interference light path for realizing single-photon interference, the BD-based single-photon interference light path comprises a first half-wave plate, a quarter-wave plate, a polarization plate, a first reflector, a first BD, a second BD, a second half-wave plate and a polarization splitting prism which are sequentially arranged along the light path, the light path is divided into two light paths through the polarization splitting prism, one light path enters a first single-photon detector through the second reflector, and the other light path enters a second single-photon detector through the fourth reflector. And the other light path enters the second single-photon detector through the third reflecting mirror. In the single photon interference teaching experiment device, the BD is adopted to replace a Mach-Zehnder interferometer and other devices, so that the number of optical elements is reduced, and the optical adjustment difficulty of the original Mach-Zehnder interferometer and other devices is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of quantum information and quantum optics, in particular to a single-photon interference teaching experiment device based on BD. Background Art

[0002] The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] According to quantum mechanics, the energy of a beam of light is composed of many basic energy units, each of which is a photon. A single photon is indivisible, meaning it has particle properties. However, quantum mechanics teaches that matter exhibits a wave-particle duality. Single-photon interference experiments offer a deeper understanding of this wave-particle duality. In the first chapter of his classic work, Principles of Quantum Mechanics, Paul Dirac discussed the quantum mechanical description of photon interference: "Each photon interferes only with itself." Single-photon interference is a crucial concept in quantum information applications, particularly in quantum computing and quantum communication, where it holds significant practical applications, such as quantum bit manipulation and quantum entanglement. Single-photon interference can be achieved using interferometers such as the Michelson interferometer and the Mach-Zehnder interferometer. However, due to the extremely low energy of single photons and the invisible optical path, the optical path adjustment requirements are extremely demanding, making it difficult to teach.

[0004] Currently, most existing single-photon interference teaching methods rely solely on classical demonstrations, which fail to fully demonstrate the properties of single photons. Alternatively, complex optical paths are used on optical platforms to achieve single-photon interference. However, due to the extremely low energy of single photons and the invisible optical path, the optical path adjustment requirements are extremely stringent. This leads to drawbacks such as large system size, numerous components, high experimental environment requirements, and low integration. Furthermore, debugging the optical path is often very complex, resulting in low student success rates and long debugging times. This makes it difficult to apply this method to teaching demonstrations and the teaching difficulty is excessive. Virtual simulation experiments are completed using a mouse under ideal experimental conditions, preventing students from hands-on operation. This can lead to a lack of understanding of real quantum experiments and an inability to master the standard operation and usage of the various components used in quantum experiments. Utility Model Content

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the utility model provides a single-photon interference teaching experimental device based on BD. In the single-photon interference teaching experimental device, the utility model adopts BD (a combination of a polarization splitter prism and a reflector) to replace devices such as Mach-Zehnder interferometers, which not only reduces the number of optical components, but also reduces the optical adjustment difficulty of devices such as Mach-Zehnder interferometers, making it easier for students with less quantum-related knowledge to learn and understand.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] The utility model provides a single-photon interference teaching experiment device based on BD.

[0008] A BD-based single-photon interference teaching experimental device comprises: an entangled source for generating single photons, a collimator, and a BD-based single-photon interference optical path for realizing single-photon interference;

[0009] The BD-based single-photon interference optical path includes: a first half-wave plate, a quarter-wave plate, a polarization plate, a first reflector, a first BD, a second BD, a second half-wave plate, and a polarization beam splitter prism arranged in sequence along the optical path. The optical path is divided into two optical paths by the polarization beam splitter prism. One optical path enters the first single-photon detector through the second reflector, and the other optical path enters the second single-photon detector through the third reflector.

[0010] Furthermore, the entanglement source is connected to a third single-photon detector.

[0011] Furthermore, the combination of the first BD6 and the second BD7 is equivalent to a Mach-Zehnder interferometer.

[0012] Furthermore, the optical path difference between the two paths of the Mach-Zehnder interferometer is changed by adjusting the first BD6 and the second BD7.

[0013] Furthermore, the first half-wave plate and the quarter-wave plate are combined to generate 45° polarized light.

[0014] Furthermore, the first reflector, the second reflector and the third reflector are all used to change the propagation direction of light.

[0015] Furthermore, the first single-photon detector, the second single-photon detector and the third single-photon detector are used for single-photon detection to convert the optical signal of the single photon into an electrical signal.

[0016] Furthermore, the collimator is used to connect the single photons generated by the entangled source to the BD-based single-photon interference optical path.

[0017] Furthermore, the first single-photon detector, the second single-photon detector and the third single-photon detector are all connected to a coincidence measurement system for performing coincidence measurement on the photons detected by the first single-photon detector, the second single-photon detector and the third single-photon detector.

[0018] Furthermore, the coincidence measurement system is connected to a host computer.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The utility model integrates the optical path while ensuring the experimental effect. The system designed by the utility model is small in size and has low requirements on the experimental environment. It does not require an optical platform or a darkroom environment, and an ordinary laboratory can meet the requirements.

[0021] The simple optical path of this new device makes it easier for students with limited quantum knowledge to understand single-photon interference phenomena. This makes it more suitable for teaching. With the development of science and technology, quantum science knowledge is gradually being incorporated into secondary school education, making quantum knowledge more accessible. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention.

[0023] Figure 1 This is an optical structure diagram of the BD-based single-photon interference teaching experimental device shown in the present invention;

[0024] Figure 2 This is a diagram showing experimental data of the teaching software of the present invention showing the changing trend of P1 with optical path difference;

[0025] Figure 3 This is a diagram showing experimental data of the teaching software of the present invention showing the changing trend of P2 with optical path difference;

[0026] Among them, 1. collimator, 2. first half-wave plate, 3. quarter-wave plate, 4. polarizer, 5. first reflector, 6. first BD, 7. second BD, 8. second half-wave plate, 9. polarization beam splitter, 10. second reflector, 11. first single-photon detector, 12. third reflector, 13. second single-photon detector, 14. third single-photon detector. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] Explanation of terms:

[0030] Beam Displacer (BD): A device that splits an input polarized beam into two spatially separated beams that propagate in parallel with orthogonal polarizations. The BD used in this embodiment can be understood as a combination of a polarization beam splitter (PBS) and a reflector. This device can reduce the difficulty of optical adjustment in devices such as Mach-Zehnder interferometers, and can relatively easily achieve changes in the optical path difference by adjusting the rotation of the BD.

[0031] An entangled source can be used as a single photon source. It generates entangled photon pairs through a spontaneous parametric down-conversion process. Polarization detection is performed on one of the photons (called the signal light), thereby "declaring" its twin photon (called the idler light) to be a single photon.

[0032] like Figure 1 As shown, this embodiment provides a BD-based single-photon interference teaching experiment device, including: an entangled source for generating single photons, and a BD-based single-photon interference optical path for realizing single-photon interference. The BD-based single-photon interference optical path includes: a collimator 1, a first half-wave plate (HWP) 2, a quarter-wave plate (QWP) 3, a polarizer 4, a first reflector 5, a first BD 6, a second BD 7, a second half-wave plate 8, and a polarization beam splitter (PBS) 9 arranged in sequence along the optical path. The polarization beam splitter 9 splits the optical path into two paths. One optical path enters a first single-photon detector 11 through a second reflector 10, and the other optical path enters a second single-photon detector through a third reflector 12. The entangled source is connected to a third single-photon detector 14.

[0033] The entanglement source uses the spontaneous parametric down-conversion process of the nonlinear crystal to generate single photons, which are connected to the BD-based single-photon interference optical path through a fiber coupler.

[0034] The first single-photon detector 11 , the second single-photon detector 13 and the third single-photon detector 14 are used for single-photon detection, and convert the optical signal of the single-photon interference experiment result into an electrical signal.

[0035] The first single-photon detector 11, the second single-photon detector 13 and the third single-photon detector 14 are all connected to a coincidence measurement system, which is used to perform coincidence measurement on the photons detected by the first single-photon detector 11, the second single-photon detector 13 and the third single-photon detector 14, and to count the events in which photons are detected simultaneously in two or three optical fibers.

[0036] The coincidence measurement system and the BD-based single-photon interference teaching experimental device are both connected to a host computer for collecting experimental results and performing data processing on the experimental results to meet teaching needs.

[0037] In some embodiments, the collimator 1 is used to connect the 810 nm single photons generated by the entangled source into the BD-based single-photon interference optical path.

[0038] In some embodiments, the combination of the first half-wave plate 2 and the quarter-wave plate 3 can achieve any polarization state. In this experiment, the angles of the two need to be adjusted to make it 45° polarized light. The polarizer 4 can ensure that the output light is 45° polarized light.

[0039] In some embodiments, the first reflector 5 , the second reflector 10 , and the third reflector 12 are all used to change the propagation direction of light.

[0040] In some embodiments, the combination of the first BD6 and the second BD7 is equivalent to a Mach-Zehnder interferometer, wherein the second BD7 can slightly change the optical path difference between the two paths of the interferometer by manually adjusting the rotation of the prism frame.

[0041] In some embodiments, the polarization beam splitter prism 9 is configured to transmit the horizontally polarized light (H light) component of the incident light and reflect the vertically polarized light (V light) component.

[0042] In some embodiments, the first single-photon detector 11, the second single-photon detector 13 and the third single-photon detector 14 are used to couple the incident parallel light into the optical fiber at its end as much as possible. The single-photon detector detects the photons in the optical fiber and records the time when the photons are detected.

[0043] The working principle of the BD-based single-photon interference teaching experimental device described in this utility model is:

[0044] (1) Turn on the entanglement source and observe whether the optical path is normal. The entanglement source uses the parametric down-conversion process to prepare single photons. For a single photon polarized in the H or V direction on a certain light propagation path, the quantum state |H> or |V> can be used to describe this single photon.

[0045] (2) Adjust the angles of the first half-wave plate 2 and the quarter-wave plate 3 to maximize the number of photons passing through the polarization plate (45°) 4. The quantum state at this time is |H> + |V>.

[0046] (3) After passing through the first BD6 and the second BD7, the H light component is transmitted, while the V light component continues to propagate after two reflections. The first BD6 and the second BD7 are rotated in the same direction, and the values ​​detected by the first single-photon detector 11 and the second single-photon detector 13 are observed at this time. The value of the first single-photon detector 11 is calculated to be P1, and the value of the second single-photon detector 13 is calculated to be P2. When the number of photons detected by the first single-photon detector 11 is the maximum, the optical path difference is an integer multiple of the wavelength.

[0047] (4) Record the counts C12 of the simultaneous responses of the first single-photon detector 11 and the third single-photon detector 14, and the counts C13 of the simultaneous responses of the second single-photon detector 13 and the third single-photon detector 14. Use C12 and C13 to calculate the probability of photons being output from the two exits:

[0048]

[0049] (5) Gradually increase the optical path difference, repeat the previous step each time and record the data, and draw a graph with the step value as the horizontal axis and P1 and P2 as the vertical axis.

[0050] like Figure 2 、 Figure 3 The figure shows the variation trend of P1 and P2 with optical path difference. Each point in the figure represents the actual measured data value, and the curve is fitted by each data point. As can be seen from the figure, P1 and P2 change with the change of optical path difference, and their variation trend follows a cosine curve. When the P1 value is maximum, P2 is minimum, and when the P1 value is maximum, P2 is minimum.

[0051] It is not difficult to understand that when photons pass through the polarization beam splitter prism 9, the reflected path accumulates more than the transmitted path. The phase of the |V> light accumulates π more phase than the |H> light after passing through the first BD6 and the second BD7. The second half-wave plate 8 is used to adjust the polarization directions of the two beams to be consistent, and the interference between the two beams is canceled. When the optical path difference is 0 or an integer multiple of the wavelength, the peaks and troughs of the two waves are superimposed, and the troughs and peaks are superimposed, which leads to the cancellation of the wave oscillations. Theoretically, the values ​​of P1 and P2 are zero, and the light intensity is the lowest at this time; when the optical path difference is half of the wavelength, the peaks and peaks of the two waves are superimposed, and the troughs and troughs are superimposed, which leads to the constructive oscillation of the waves, and the light intensity is the highest at this time.

[0052] Therefore, it can be explained that at this time, the single photon underwent a wave-like interference phenomenon.

[0053] In the disclosed embodiments, the utility model utilizes BD to realize single-photon interference, which simplifies the difficulty of experimental operation, makes the experimental operation simple, and facilitates teaching.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A BD-based single-photon interference teaching experimental device, characterized in that: include: An entangled source and collimator for generating single photons, and a BD-based single-photon interferometer optical path for achieving single-photon interference; The BD-based single-photon interference optical path includes: a first half-wave plate, a quarter-wave plate, a polarization plate, a first reflector, a first BD, a second BD, a second half-wave plate, and a polarization beam splitter prism arranged in sequence along the optical path. The optical path is divided into two optical paths by the polarization beam splitter prism. One optical path enters the first single-photon detector through the second reflector, and the other optical path enters the second single-photon detector through the third reflector.

2. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The entanglement source is connected to a third single-photon detector.

3. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The combination of the first BD and the second BD is equivalent to a Mach-Zehnder interferometer.

4. The BD-based single-photon interference teaching experimental device according to claim 3 is characterized in that: By adjusting the first BD and the second BD, the optical path difference between the two paths of the Mach-Zehnder interferometer is changed.

5. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The first half-wave plate and the quarter-wave plate are combined to generate 45° polarized light.

6. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The first reflector, the second reflector and the third reflector are all used to change the propagation direction of light.

7. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The first single-photon detector, the second single-photon detector and the third single-photon detector are used for single-photon detection and convert the optical signal of the single photon into an electrical signal.

8. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The collimator is used to connect the single photons generated by the entangled source to the BD-based single-photon interference optical path.

9. The BD-based single-photon interference teaching experimental device according to claim 1 is characterized in that: The first single-photon detector, the second single-photon detector and the third single-photon detector are all connected to a coincidence measurement system for performing coincidence measurement on the photons detected by the first single-photon detector, the second single-photon detector and the third single-photon detector.

10. The BD-based single-photon interference teaching experimental device according to claim 9, characterized in that: The compliance measurement system is connected to a host computer.

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