Three-dimensional positioning system and positioning method based on quantum entangled photon pairs

Abstract

The present invention belongs to the field of quantum navigation and positioning technology, and specifically relates to a three-dimensional positioning system and positioning method based on quantum entangled photon pairs. The present invention uses a method based on Sagnac interferometer bidirectional pumping of PPKTP crystals to prepare entangled photon pairs. The signal light is transmitted to the target point to be measured through the measurement optical path and then reflected back to the local area. The absolute distance information of the target point to be measured is solved by the coincidence counting measurement method with the idle light. Based on the unique optical path structure design, by reading the horizontal rotation angle and pitch angle of the right-angle prism reflector, the angle between the propagation direction of the signal light beam and the coordinate axis can be obtained. In addition, combined with the absolute distance and azimuth information of the target point to be measured, three-dimensional high-precision positioning can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum navigation and positioning, and specifically relates to a three-dimensional positioning system and a positioning method based on quantum entangled photon pairs. Background Art

[0002] Distance measurement technology is the basis for positioning and navigating unknown targets. The distance measurement accuracy of the positioning system determines its positioning accuracy. Traditional distance measurement technologies, such as ultrasonic distance measurement, infrared distance measurement, and laser distance measurement, are based on classical physics, and their distance measurement accuracy is always limited by the standard quantum limit. In order to obtain higher positioning accuracy, it is necessary to seek a new distance measurement technology that can break through the standard quantum limit.

[0003] With the establishment of quantum theory, quantum mechanics has gradually penetrated into physical experiments, especially quantum theory and application technology based on quantum entanglement has developed rapidly. In 2001, the Giovannetti research group of the Massachusetts Institute of Technology proposed a new distance measurement method, namely quantum precision distance measurement, in the journal Nature. When a quantum light source with frequency entanglement and compression characteristics is used as the light source of the distance measurement system, the measurement accuracy can be improved by times. Where M represents the number of entangled pulses, and N represents the average number of photons in a pulse. This technology mainly uses the entanglement or compression characteristics of photons to achieve high-precision measurement of distance information, so that the measurement accuracy can break through the limitations of the standard quantum limit and reach the Heisenberg limit. Quantum precision ranging technology provides new technical support for achieving high-precision positioning.

[0004] At present, with the development of entangled light source preparation technology, entangled photon pairs with superior performance can be obtained based on spontaneous parametric down-conversion technology, which are called signal light and idle light. In the actual ranging process, the signal light is emitted to the target and then reflected back to the local area. The arrival time difference of the entangled photon pair is obtained by the coincidence counting measurement method with the idle light left in the local area, and then the distance information is solved based on the time difference.

[0005] For example, the Chinese invention patent with application number 202210383672X claims protection for a two-dimensional plane positioning system and method based on quantum entangled light. The system and method use the visible light beam emitted by the reference light source to coaxially transmit the signal photon to achieve fast and efficient coupling of quantum signals. Through the design of the optical path structure of the auxiliary positioning device, it is only necessary to rotate the right-angle prism reflector to achieve a 360-degree change in the ranging direction and the extraction of the azimuth. The distance and azimuth information from the target point to be measured can ultimately achieve high-precision positioning of the two-dimensional plane of quantum entangled light. However, the system and method can only achieve two-dimensional plane positioning. Most targets are targets located in three-dimensional space. From the current target positioning requirements, it is not enough to achieve only two-dimensional plane positioning. Only by achieving three-dimensional positioning of the target can the true position of the target be accurately known. Therefore, how to achieve high-precision three-dimensional positioning of the target based on quantum entangled light is an urgent problem to be solved. Summary of the invention

[0006] The purpose of the present invention is to provide a three-dimensional positioning system and positioning method based on quantum entangled photon pairs, so as to solve the problem that the existing technology can only achieve two-dimensional plane positioning of the target and cannot accurately achieve precise positioning of the target in three-dimensional space, so as to achieve high-precision three-dimensional positioning of space targets by integrating quantum measurement technology with traditional positioning technology.

[0007] In order to solve the above technical problems, the present invention provides a three-dimensional positioning system based on quantum entangled photon pairs, comprising an entangled light source, a first single-photon detector, a second single-photon detector, a coincidence measurement module, a coupler, an optical fiber circulator, an optical fiber collimator, a reflector, a right-angle prism reflector and a corner cube prism; the entangled light source is used to generate entangled photon pairs and divide them into idle light and signal light; the corner cube prism is arranged at a target point;

[0008] A first single-photon detector is arranged on the optical path of the idle light, and the idle light is used to be directly received by the first single-photon detector;

[0009] A coupler, a fiber circulator, a fiber collimator, a reflector, a right-angle prism reflector, a corner cube prism and a second single-photon detector are arranged on the optical path of the signal light, and the horizontal rotation angle and the pitch angle of the right-angle prism reflector are adjustable;

[0010] A coupler, a fiber circulator, a reflector, a right-angle prism reflector, a corner cube prism and a second single-photon detector are arranged on the optical path of the signal light, and the horizontal rotation angle and the pitch angle of the right-angle prism reflector are adjustable; when the actual positioning measurement of the target point is performed, the signal light is used to sequentially pass through the coupler, the fiber circulator, the fiber collimator, the reflector, the right-angle prism reflector and the corner cube prism, and then return to the right-angle corner cube reflector along the original path, and then sequentially pass through the reflector, the fiber collimator and the fiber circulator to be received by the second single-photon detector;

[0011] The coincidence measurement module is used to perform coincidence counting measurement to determine the actual measured optical path difference between the idle light and the signal light according to the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector during the actual positioning measurement process; and then use the actual measured optical path difference and the calibrated inherent optical path difference between the idle light and the signal light in the system to determine the absolute distance between the target point and the reflection point on the right-angle prism reflector, and perform three-dimensional positioning of the target point based on the absolute distance and the posture information of the right-angle prism reflector.

[0012] The beneficial effects are as follows: the present invention is provided with a right-angle prism reflector in the entire three-dimensional positioning system, and its horizontal rotation angle and pitch angle are adjustable. The direction of the signal light incident on the right-angle prism reflector is changed by changing its horizontal rotation angle and pitch angle, so that in the actual positioning measurement process, the signal light is reflected by the right-angle prism reflector to the corner prism set at the target point, and then returns along the original path through the corner prism, and then is received by the second single-photon detector, and the actual measured optical path difference between the idle light and the signal light is determined by performing a coincidence counting measurement according to the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector; and then the absolute distance between the target point and the reflection point on the right-angle prism reflector can be obtained by combining the actual measured optical path difference and the calibrated inherent optical path difference between the idle light and the signal light in the system, and the target point can be three-dimensionally positioned according to the absolute distance and the azimuth information of the right-angle prism reflector. Based on this unique optical path design, high-precision distance measurement and measurement of corresponding position information can be achieved, thereby achieving high-precision three-dimensional positioning.

[0013] Furthermore, when calibrating the inherent optical path difference between the idle light and the signal light in the system, the signal light is used to pass through the coupler, the fiber optic circulator, the fiber optic collimator, and the reflector in sequence to reach the right-angle prism reflector, and then return to the reflector along the original path, and then pass through the fiber optic collimator and the fiber optic circulator in sequence to be received by the second single-photon detector.

[0014] Furthermore, the absolute distance between the target point and the reflection point on the right-angle prism reflector is:

[0015] R OA =(L A -L0 ) / 2

[0016] In the formula, R OA L is the absolute distance between the target point A and the reflection point O on the right-angle prism reflector; A is the optical path difference obtained during the actual positioning measurement of target point A; L 0 is the inherent optical path difference between the idle light and the signal light in the system.

[0017] Further, according to the absolute distance R OA When the target point is positioned in three dimensions based on the position information of the right-angle prism reflector, α and β need to be determined based on the position information of the right-angle prism reflector. Point A' is the projection point of the target point A on the horizontal plane where point O is located. Then α is the angle between OA' and the x-axis in the coordinate system of the measurement system, and β is the angle between OA and OA'. The three-dimensional positioning result of the corresponding target point is:

[0018]

[0019] In the formula, (x A ,y A ,z A ) is the three-dimensional coordinate of the target point.

[0020] The beneficial effect is that by combining the horizontal rotation angle and pitch angle of the target point in a known coordinate system, corresponding to α and β, the target point can be positioned in three dimensions with high precision.

[0021] Furthermore, the three-dimensional positioning system also includes a turntable, and the fiber optic collimator, reflector and right-angle prism reflector are fixedly arranged on the turntable; and the right-angle prism reflector is rotated by the turntable to change the horizontal rotation angle of the right-angle prism reflector.

[0022] The beneficial effect is that the right-angle prism reflector can be rotated by using the turntable, which provides a new option for changing the emission direction of the signal light.

[0023] Furthermore, the optical fiber collimator and the optical fiber circulator are connected via a flexible optical fiber.

[0024] The beneficial effect is that the optical fiber collimator and the optical fiber circulator are connected via a flexible optical fiber, so that the optical fiber collimator can perform corresponding horizontal rotation.

[0025] In order to solve the above technical problems, the present invention also provides a three-dimensional positioning method based on quantum entangled photon pairs, comprising the following steps:

[0026] 1) Generate entangled photon pairs and separate them into idle light and signal light;

[0027] 2) When the actual positioning measurement of the target point to be measured is performed, the idle light generated is received by the first single-photon detector; the horizontal rotation angle and the pitch angle of the right-angle prism reflector are adjusted so that the generated signal light passes through the coupler, the fiber optic circulator, the fiber optic collimator, the reflector, the right-angle prism reflector and the corner cube mirror in sequence, and then returns to the right-angle prism reflector along the original path, and then passes through the reflector, the fiber optic collimator and the fiber optic circulator in sequence and is received by the second single-photon detector; a coincidence counting measurement is performed based on the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector to determine the actual measured optical path difference between the idle light and the signal light;

[0028] 3) Determine the absolute distance between the target point and the reflection point on the right-angle prism reflector by using the inherent optical path difference between the idle light and the signal light in the system measured during the calibration process and the actual measured optical path difference measured during the actual positioning measurement in step 2), and perform three-dimensional positioning of the target point based on the absolute distance and the posture information of the right-angle prism reflector.

[0029] The beneficial effects are as follows: by improving the horizontal rotation angle and pitch angle of the right-angle prism reflector, the direction of the signal light incident on the right-angle prism reflector is changed. In the actual positioning measurement process, the signal light returns through the corner prism, and combined with the arrival time of the idle light, the actual measured optical path difference between the idle light and the signal light can be obtained. Then, combined with the inherent optical path difference between the idle light and the signal light in the system measured during the calibration process, the absolute distance between the target point and the reflection point on the right-angle prism reflector can be obtained. According to the absolute distance and the posture information of the right-angle prism reflector, the target point can be located in three dimensions. Based on this unique optical path design, high-precision distance measurement and measurement of corresponding position information can be achieved, thereby achieving high-precision three-dimensional positioning.

[0030] Furthermore, the calibration process in step 3) includes: when calibrating the inherent optical path difference of the system, the idle light generated is received by the first single-photon detector; the reflecting surface of the right-angle prism reflector is adjusted so that the signal light passes through the coupler, the fiber optic circulator, the fiber optic collimator, and the reflector in sequence to reach the right-angle prism reflector, and then returns to the reflector along the original path, and then passes through the fiber optic collimator and the fiber optic circulator in sequence to be received by the second single-photon detector; and a coincidence counting measurement is performed based on the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector to determine the inherent optical path difference between the idle light and the signal light in the system.

[0031] Furthermore, the absolute distance between the target point and the reflection point on the right-angle prism reflector is:

[0032] R OA =(L A -L 0 ) / 2

[0033] In the formula, R OA L is the absolute distance between the target point A and the reflection point O on the right-angle prism reflector; A L is the optical path difference between the signal light and the idle light during the actual positioning measurement of the target point A; 0 It is the inherent optical path difference between the idle light and the signal light in the measurement system.

[0034] Furthermore, when the target point is three-dimensionally positioned according to the absolute distance and the posture information of the right-angle prism reflector, α and β need to be determined according to the posture information of the right-angle prism reflector. Point A' is the projection point of the target point A on the horizontal plane where point O is located. Then α is the angle between OA' and the x-axis in the coordinate system of the measurement system, and β is the angle between OA and OA'. The three-dimensional positioning result of the corresponding target point is:

[0035]

[0036] In the formula, (x A ,y A ,z A ) is the three-dimensional coordinate of the target point.

[0037] The beneficial effect is that by combining the horizontal rotation angle and pitch angle of the target point in a known coordinate system, corresponding to α and β, the target point can be positioned in three dimensions with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of preparing the quantum entangled photon pair of the present invention;

[0039] Figure 2 It is a schematic diagram of the principle of the three-dimensional positioning system based on quantum entangled photon pairs of the present invention;

[0040] Figure 3 It is a schematic diagram of the coordinate system of the present invention;

[0041] Figure 4 It is a schematic diagram of obtaining the horizontal rotation angle by means of a high-precision turntable according to the present invention;

[0042] Figure 5 It is a schematic diagram of target point coordinate measurement of the present invention.

[0043] Among them, 1-pump laser, 2-optical isolator, 3-1 / 4 wave plate, 4-first half-wave plate, 5-optical lens, 6-long wave pass dichroic mirror, 7-polarization beam splitter, 8-second half-wave plate, 9-first reflector, 10-second reflector, 11-first single photon detector, 12-time digital converter, 13-second single photon detector, 14-coupler, 15-fiber circulator, 16-fiber collimator, 17-third reflector, 18-right angle prism reflector, 19-corner prism, 20-coincidence measurement module. DETAILED DESCRIPTION

[0044] The present invention uses a photon pair with entangled characteristics to obtain the absolute distance between the target point and the measurement system by a coincidence counting measurement method. Through the optical path structure designed by the present invention, the angle between the target point to be measured and the coordinate axis of the coordinate system can be measured, so that the precise coordinate value of the target point in the known coordinate system can be solved. The present invention is further described in detail below in conjunction with the accompanying drawings.

[0045] Example of a three-dimensional positioning system based on quantum entangled photon pairs:

[0046] An embodiment of a three-dimensional positioning system based on quantum entangled photon pairs of the present invention has a structure as follows: Figure 2 As shown, Figure 2 Entangled light sources in Figure 1 Implementation. Figure 1 and Figure 2 The three-dimensional positioning system of the present invention is introduced in detail.

[0047] like Figure 1 As shown, the entangled light source includes a pump laser 1, and an optical isolator 2, a quarter wave plate 3, a first half wave plate 4 and an optical lens 5 are sequentially arranged on the optical path of the pump light (i.e., laser) emitted by the pump laser 1, so as to obtain 45° polarized light, which is incident on the Sagnac interferometer. Among them, the optical isolator 2 is mainly used to prevent the back-reflected light from interfering with or damaging the pump laser 1; the quarter wave plate 3 and the first half wave plate 4 are mainly used to adjust the polarization state of the pump light and the relative phase of different polarization components. The optical lens 5 is used to converge the pump light source so that its focus is located at the center of the PPKTP crystal.

[0048] The Sagnac interferometer includes a polarization beam splitter 7, a second half-wave plate 8, a periodically polarized crystal (PPKTP) and a plane mirror (including a first mirror 9 and a second mirror 10). The second half-wave plate 8 in the Sagnac interference ring is placed at a 45° direction to change the polarization direction of the polarized light beam. The horizontal polarization component in the pump light is transmitted at the polarization beam splitter 7, and then passes through the second half-wave plate 8 and the first mirror 9 to the PPKTP crystal and undergoes parametric down-conversion. The formed entangled photons reach the polarization beam splitter 7 through the second mirror 10, wherein the horizontal polarization component is transmitted and the vertical polarization component is reflected, and after reflection, it is transmitted at the long-wave pass dichroic mirror 6. The vertical polarization component in the pump light is reflected at the polarization beam splitter 7, and then passes through the second mirror 10 to the PPKTP crystal and undergoes parametric down-conversion. The formed entangled photons pass through the first reflector 9 and the second half-wave plate 8 and then reach the polarization beam splitter 7, wherein the horizontal polarization component is transmitted and then transmitted again at the long-wave pass dichroic mirror 6, and the vertical polarization component is reflected. Thus, the signal light and the idle light are finally obtained, and the finally obtained signal light and the idle light both contain the horizontal and vertical polarization components.

[0049] like Figure 2 As shown, in addition to the entangled light source, the entire three-dimensional positioning system also includes a first single-photon detector 11, a time-to-digital converter 12, a second single-photon detector 13, a coupler 14, a fiber circulator 15, a fiber collimator 16, a third reflector 17, a right-angle prism reflector 18, a corner prism 19 and a coincidence measurement module 20, and the fiber optic collimator 16 and the fiber optic circulator 15 are connected by a flexible optical fiber, so that the fiber optic collimator 16 can perform corresponding horizontal rotation.

[0050] The first single-photon detector 11 introduced above is arranged on the optical path of the idle light, and the idle light is directly coupled and received by the first single-photon detector 11 .

[0051] The above-mentioned coupler 14, fiber circulator 15, fiber collimator 16, fourth reflector 17, right-angle prism reflector 18, corner cube prism 19, and second single-photon detector 13 are arranged on the optical path of the signal light. Corner cube prism 19 is arranged at the target point. Among them, the horizontal rotation angle and pitch angle of right-angle prism reflector 18 can be adjusted, so as to realize the following two processes of the signal light: 1) when the inherent optical path difference of the system is calibrated, the reflection surface of right-angle prism reflector 18 is adjusted to the horizontal direction, and the signal light reaching the right-angle prism reflector after being reflected by the third reflector 17 directly returns along the original path; 2) when positioning the target point to be measured, by adjusting the horizontal rotation angle and pitch angle of right-angle prism reflector 18, the signal light reflected by the third reflector 17 is reflected by the right-angle prism reflector 18 to the center of corner cube prism 19, and returns to the original path after being reflected by corner cube prism 19. Regardless of which process is used, the final signal light passes through the third reflector 17 , the fiber collimator 16 , and the fiber circulator 15 , and is coupled and received by the second single-photon detector 13 .

[0052] The first single-photon detector 11 and the second single-photon detector 13 both transmit the collected electrical signals to the time-to-digital converter 12, which is used to record the arrival time sequence of the signal light and the idle light, and then determine the optical path difference between the idle light and the signal light by performing coincidence counting measurement through the coincidence measurement module 20. The target point can be measured according to the optical path difference.

[0053] Moreover, a turntable is also provided in the three-dimensional positioning system, and the third reflector 17 and the right-angle prism reflector 18 can be fixed on the turntable, so as to adjust the horizontal rotation angle of the right-angle prism reflector 18.

[0054] The entire measurement process of the three-dimensional positioning system is introduced below, that is, a three-dimensional positioning method based on quantum entangled photon pairs of the present invention.

[0055] In step 1, the pump light emitted by the pump laser 1 first enters the optical isolator 2 for protection, and then passes through the 1 / 4 wave plate 3, the first half-wave plate 4, the optical lens 5 and the long-wave pass dichroic mirror 6 to reach the Sagnac interferometer.

[0056] Step 2, the Sagnac interferometer is composed of a polarization beam splitter 7, a second half-wave plate 8, a periodically polarized crystal (PPKTP) and a plane mirror (including a first mirror 9 and a second mirror 10). By adjusting the 1 / 4 wave plate 3 and the first half-wave plate 4, the pump beam incident on the Sagnac interferometer is a 45° polarized light. The polarized light is divided into horizontal (H) and vertical (V) polarized lights of equal intensity by the polarization beam splitter 7. The two beams of light are reflected in the Sagnac ring and reach the PPKTP crystal, and parametric down conversion occurs, thereby generating entangled photon pairs. The signal light and the idle light contain horizontal and vertical polarized light components, respectively, and are in an entangled state.

[0057] Step three: the idle light is directly coupled and received by the first single-photon detector 11 at the measurement location and transmitted to the time-to-digital converter 12 .

[0058] In step 4, the signal light passes through the coupler 14 and enters the port ① of the fiber circulator 15, and then is output from the port ② of the fiber circulator 15. Subsequently, the signal light passes through the fiber collimator 16, the third reflector 17 and the right-angle prism reflector 18 respectively, and then is transmitted to the corner prism 19 of the target point.

[0059] Step five, the signal light reflected by the corner cube prism 19 is reflected along the original path to the port ② of the optical fiber circulator 15, and then output from the port ③ of the optical fiber circulator 15. Subsequently, the signal light is coupled and received by the second single-photon detector 13 and transmitted to the time digital converter 12.

[0060] Step six, establish a three-dimensional rectangular coordinate system, and define the reflection point of the signal light beam on the right-angle prism reflector 18 as the coordinate origin. Adjust the horizontal rotation angle and pitch angle of the right-angle prism reflector 18 to 0°. At this time, the angle between the reflection surface of the right-angle prism reflector 18 and the horizontal plane is 45°. Define the propagation direction of the signal light beam as the x-axis. The direction perpendicular to the x-axis in the horizontal plane is the y-axis, and the direction perpendicular to the x-axis and y-axis and upward is the z-axis. The right-angle prism reflector adjusts its horizontal rotation angle by rotating along the z-axis, and adjusts its pitch angle by rotating along the y-axis.

[0061] Step 7: calibrate the inherent optical path difference between the signal light and the idle light in the three-dimensional positioning system. Adjust the reflecting surface of the right-angle prism reflector 18 to the horizontal direction. Use the time-to-digital converter 12 to record the arrival time series of the signal light and the idle light respectively, and obtain the optical path difference L of the two beams by the coincidence counting measurement method. 0 , L 0 This is the inherent optical path difference between the signal light and the idle light in the measuring device. After the inherent optical path difference is calibrated, there is no need to recalibrate during the actual measurement process, even if the coordinates of the points to be measured at different locations are measured.

[0062] Step 8: During the actual positioning process, place the corner cube prism 19 at the target point A to be measured. The projection of point A in the xy plane is A'. By adjusting the horizontal rotation angle and pitch angle of the right-angle prism reflector 18, the signal light beam is irradiated on the center of the corner cube prism 19. At this time, the signal light is reflected back to the measuring device along the original path. At this time, the angle α between OA' and the x-axis and the angle β between OA and OA' are recorded.

[0063] Step 9: Obtain the optical path difference L between the signal light reflected at point A and the idle light by coincidence counting measurement A , then the distance between point A and point O is R OA =(L A -L 0 ) / 2.

[0064] Step 10, assume that the coordinate value of A is (x A ,y A ,z A ). The distance value R obtained by OA , and the angle values ​​α and β, the coordinate value of point A can be solved:

[0065]

[0066] The above method is applied to a specific example for description below.

[0067] Step 1, such as Figure 1 As shown, the 405 nm pump light emitted by the pump laser 1 first enters an optical isolator 2 for protection, and then the laser beam passes through a quarter wave plate 3, a first half wave plate 4, an optical lens 5 and a long-wave pass dichroic mirror 6 before reaching the Sagnac interferometer.

[0068] Step 2, the Sagnac interferometer is composed of a polarization beam splitter 7, a second half-wave plate 8, a periodically polarized crystal (PPKTP) and a plane mirror (including a first mirror 9 and a second mirror 10). The pump beam incident on the Sagnac interferometer is made to be 45° polarized light by adjusting the 1 / 4 wave plate 3 and the first half-wave plate 4. The second half-wave plate 8 in the Sagnac interference ring is placed at 45° to change the polarization direction of the polarized light beam. The horizontal polarization component in the pump light is transmitted at the polarization beam splitter 7, and then passes through the second half-wave plate 8 and the first mirror 9 to the PPKTP crystal and undergoes parametric down conversion. The formed entangled photons reach the polarization beam splitter 7 through the second mirror 10, where the horizontal polarization component is transmitted and the vertical polarization component is reflected. The vertical polarization component in the pump light is reflected at the polarization beam splitter 7, and then passes through the second mirror 10 to the PPKTP crystal and undergoes parametric down conversion. The formed entangled photons pass through the first reflector 9 and the second half-wave plate 8 and reach the polarization beam splitter 7, wherein the horizontal polarization component is transmitted and the vertical polarization component is reflected. Therefore, both the signal light and the idle light contain horizontal and vertical polarization components.

[0069] Step three, such as Figure 2 As shown, the idle light is directly coupled and received by the first single-photon detector 11 at the measurement location and transmits the electrical signal to the time-to-digital converter 12 .

[0070] In step 4, the signal light passes through the coupler 14 and enters the port ① of the fiber circulator 15, and then is output from the port ② of the fiber circulator 15. Subsequently, the signal light passes through the fiber collimator 16, the third reflector 17 and the right-angle prism reflector 18 respectively, and then is transmitted to the corner prism 19 of the target point.

[0071] Step five, the signal light reflected by the corner cube prism 19 is reflected along the original path to the port ② of the optical fiber circulator 15, and then output from the port ③ of the optical fiber circulator 15. Subsequently, the signal light is coupled and received by the second single-photon detector 13 and transmitted to the time digital converter 12.

[0072] Step 6: Figure 3 As shown, a three-dimensional rectangular coordinate system is established, and the reflection point of the signal light on the right-angle prism reflector 18 is defined as the coordinate origin. The horizontal rotation angle and the pitch angle of the right-angle prism reflector 18 are adjusted to the 0° direction. At this time, the angle between the reflection surface of the right-angle prism reflector 18 and the horizontal plane is 45°. The propagation direction of the signal light is defined as the x-axis. The direction perpendicular to the x-axis in the horizontal plane is the y-axis. The direction perpendicular to the x-axis and the y-axis and pointing upward is the z-axis direction. When the right-angle prism reflector 18 rotates along the z-axis, the propagation direction of the signal light beam in the horizontal plane can be changed. When the right-angle prism reflector 18 rotates along the y-axis, the pitch angle of the propagation direction of the signal light beam in the space can be changed, thereby realizing the three-dimensional positioning of the target point.

[0073] In order to obtain the horizontal rotation angle of the signal light, in addition to rotating the right-angle prism reflector 18 along the z-axis, it can also be achieved with the help of a high-precision turntable. Figure 4 As shown, the fiber collimator 16, the third reflector 17 and the right-angle prism reflector 18 are fixed on a high-precision turntable. The rotation axis of the turntable coincides with the z-axis of the coordinate system. Since the fiber collimator 16 and the fiber circulator 15 are connected by a flexible optical fiber, they can be rotated horizontally accordingly, thereby obtaining the horizontal rotation angle of the light beam.

[0074] Step seven, calibrate the inherent optical path difference of the system. Adjust the reflecting surface of the right-angle prism reflector 18 to the horizontal direction. The signal light first passes through the coupler 14 to enter the port ① of the fiber circulator 15, and then outputs from the port ② of the fiber circulator 15. Subsequently, the signal light passes through the fiber collimator 16, the third reflector 17 and the right-angle prism reflector 18 respectively, and then returns to the third reflector 17 along the original path. After that, the signal light is reflected along the original path to the port ② of the fiber circulator 15, and then outputs from the port ③ of the fiber circulator 15. Finally, the signal light is coupled and received by the second single-photon detector 13, and is transmitted to the time digital converter 12. The time digital converter 12 is used to record the arrival time series of the signal light and the idle light respectively, and the optical path difference L of the two beams of light is obtained by the coincidence counting measurement method. 0 , L 0 This is the inherent optical path difference between the signal light and the idle light inside the measuring device.

[0075] Step 8: Figure 5 As shown, the corner cube prism 19 is placed at the target point A to be measured. The projection point of point A in the xy plane is A'. The horizontal rotation angle and the pitch angle of the right-angle prism reflector 18 are adjusted so that the signal light is transmitted to the center of the corner cube prism 19. The signal light reflected by the corner cube prism 19 is reflected along the original path to the port ② of the optical fiber circulator 15, and then output from the port ③ of the optical fiber circulator 15. It is then coupled and received by the second single-photon detector 13, and the electrical signal is transmitted to the time digital converter 12. At this time, the angle α between OA' and the x-axis and the angle β between OA and OA' are recorded.

[0076] Step 9: Obtain the optical path difference L between the signal light reflected at point A and the idle light by coincidence counting measurement A , then the distance between point A and point O is R OA =(L A -L 0 ) / 2.

[0077] Step 10, assume that the coordinate value of A is (x A ,y A ,z A ). The distance value R obtained byOA , and the angle values ​​α and β, the coordinate value of point A can be solved:

[0078]

[0079] In summary, based on the method of bidirectionally pumping PPKTP crystals with Sagnac interferometer, entangled photon pairs are prepared. The signal light is transmitted to the target point to be measured through the measurement system and then reflected back to the local area. The absolute distance information of the target point to be measured is solved by the coincidence counting measurement method with the idle light. Based on the unique optical path structure design, the angle between the propagation direction of the signal light beam and the coordinate axis can be obtained by reading the horizontal rotation angle and pitch angle of the right-angle prism reflector. Finally, the absolute distance and azimuth information of the target point to be measured can be combined to achieve three-dimensional high-precision positioning.

[0080] Embodiment of a three-dimensional positioning method based on quantum entangled photon pairs:

[0081] The overall process of an embodiment of a three-dimensional positioning method based on quantum entangled photon pairs of the present invention is consistent with the three-dimensional positioning method based on quantum entangled photon pairs introduced in the embodiment of a three-dimensional positioning system based on quantum entangled photon pairs, which will not be repeated here.

Claims

1. A three-dimensional positioning system based on quantum entangled photon pairs, characterized in that: It includes an entangled light source, a first single-photon detector, a second single-photon detector, a coincidence measurement module, a coupler, an optical fiber circulator, an optical fiber collimator, a reflector, a right-angle prism reflector and a corner cube prism; the entangled light source is used to generate entangled photon pairs and separate them into idle light and signal light; the corner cube prism is arranged at a target point; A first single-photon detector is arranged on the optical path of the idle light, and the idle light is used to be directly received by the first single-photon detector; A coupler, a fiber circulator, a fiber collimator, a reflector, a right-angle prism reflector, a corner cube prism and a second single-photon detector are arranged on the optical path of the signal light, and the horizontal rotation angle and the pitch angle of the right-angle prism reflector are adjustable; when the actual positioning measurement of the target point is performed, the signal light is used to sequentially pass through the coupler, the fiber circulator, the fiber collimator, the reflector, the right-angle prism reflector and the corner cube prism, and then return to the right-angle corner cube reflector along the original path, and then sequentially pass through the reflector, the fiber collimator and the fiber circulator to be received by the second single-photon detector; The coincidence measurement module is used to perform coincidence counting measurement to determine the actual measured optical path difference between the idle light and the signal light according to the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector during the actual positioning measurement process; and then use the actual measured optical path difference and the calibrated inherent optical path difference between the idle light and the signal light in the system to determine the absolute distance between the target point and the reflection point on the right-angle prism reflector, and perform three-dimensional positioning of the target point based on the absolute distance and the posture information of the right-angle prism reflector.

2. The three-dimensional positioning system based on quantum entangled photon pairs according to claim 1, characterized in that: When calibrating the inherent optical path difference between the idle light and the signal light in the system, the signal light is used to pass through the coupler, the fiber circulator, the fiber collimator, the reflector in sequence to reach the right-angle prism reflector, and then return to the reflector along the original path, and then pass through the fiber collimator and the fiber circulator in sequence to be received by the second single-photon detector.

3. The three-dimensional positioning system based on quantum entangled photon pairs according to claim 2, characterized in that: The absolute distance between the target point and the reflection point on the right-angle prism reflector is: R OA =(L A -L0) / 2 In the formula, R OA L is the absolute distance between the target point A and the reflection point O on the right-angle prism reflector; A is the actual measured optical path difference obtained during the actual positioning measurement of target point A; L0 is the inherent optical path difference between the idle light and the signal light in the system.

4. The three-dimensional positioning system based on quantum entangled photon pairs according to claim 3 is characterized in that: When the target point is three-dimensionally positioned based on the absolute distance and the posture information of the right-angle prism reflector, α and β need to be determined based on the posture information of the right-angle prism reflector. Point A' is the projection point of the target point A on the horizontal plane where point O is located. Then α is the angle between OA' and the x-axis in the coordinate system of the measurement system, and β is the angle between OA and OA'. The three-dimensional positioning result of the corresponding target point is: In the formula, (x A ,y A ,z A ) is the three-dimensional coordinate of the target point.

5. The three-dimensional positioning system based on quantum entangled photon pairs according to claim 1, characterized in that: The three-dimensional positioning system also includes a turntable, and the fiber collimator, reflector and right-angle prism reflector are fixedly arranged on the turntable; and the right-angle prism reflector is rotated by the turntable to change the horizontal rotation angle of the right-angle prism reflector.

6. The three-dimensional positioning system based on quantum entangled photon pairs according to claim 1, characterized in that: The optical fiber collimator and the optical fiber circulator are connected via a flexible optical fiber.

7. A three-dimensional positioning method based on quantum entangled photon pairs, characterized in that: The steps include: 1) Generate entangled photon pairs and separate them into idle light and signal light; 2) When the actual positioning measurement of the target point to be measured is performed, the idle light generated is received by the first single-photon detector; the horizontal rotation angle and the pitch angle of the right-angle prism reflector are adjusted so that the generated signal light passes through the coupler, the fiber optic circulator, the fiber optic collimator, the reflector, the right-angle prism reflector and the corner cube mirror in sequence, and then returns to the right-angle prism reflector along the original path, and then passes through the reflector, the fiber optic collimator and the fiber optic circulator in sequence and is received by the second single-photon detector; a coincidence counting measurement is performed based on the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector to determine the actual measured optical path difference between the idle light and the signal light; 3) Determine the absolute distance between the target point and the reflection point on the right-angle prism reflector by using the inherent optical path difference between the idle light and the signal light in the system measured during the calibration process and the actual measured optical path difference measured during the actual positioning measurement in step 2), and perform three-dimensional positioning of the target point based on the absolute distance and the posture information of the right-angle prism reflector.

8. The three-dimensional positioning method based on quantum entangled photon pairs according to claim 7, characterized in that: The calibration process in step 3) includes: When the inherent optical path difference of the system is calibrated, the idle light generated is received by the first single-photon detector; the reflecting surface of the right-angle prism reflector is adjusted so that the signal light passes through the coupler, the fiber optic circulator, the fiber optic collimator, and the reflector in sequence to reach the right-angle prism reflector, and then returns to the reflector along the original path, and then passes through the fiber optic collimator and the fiber optic circulator in sequence to be received by the second single-photon detector; a coincidence counting measurement is performed based on the photon arrival time sequence detected by the first single-photon detector and the second single-photon detector to determine the inherent optical path difference between the idle light and the signal light in the system.

9. The three-dimensional positioning method based on quantum entangled photon pairs according to claim 8, characterized in that: The absolute distance between the target point and the reflection point on the right-angle prism reflector is: R OA =(L A -L0) / 2 In the formula, R OA L is the absolute distance between the target point A and the reflection point O on the right-angle prism reflector; A is the actual measured optical path difference obtained during the actual positioning measurement of target point A; L0 is the inherent optical path difference between the idle light and the signal light in the system.

10. The three-dimensional positioning method based on quantum entangled photon pairs according to claim 9, characterized in that: When the target point is three-dimensionally positioned according to the absolute distance and the posture information of the right-angle prism reflector, α and β need to be determined according to the posture information of the right-angle prism reflector. Point A' is the projection point of the target point A on the horizontal plane where point O is located. Then α is the angle between OA' and the x-axis in the coordinate system of the measurement system, and β is the angle between OA and OA'. The three-dimensional positioning result of the corresponding target point is: In the formula, (x A ,y A ,z A ) is the three-dimensional coordinate of the target point.

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