CN115236681A - Three-dimensional positioning system and positioning method based on quantum entangled photon pair - Google Patents
Three-dimensional positioning system and positioning method based on quantum entangled photon pair Download PDFInfo
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- CN115236681A CN115236681A CN202210833111.5A CN202210833111A CN115236681A CN 115236681 A CN115236681 A CN 115236681A CN 202210833111 A CN202210833111 A CN 202210833111A CN 115236681 A CN115236681 A CN 115236681A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4818—Constructional features, e.g. arrangements of optical elements using optical fibres
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Abstract
The invention belongs to the technical field of quantum navigation positioning, and particularly relates to a three-dimensional positioning system and a positioning method based on quantum entangled photon pairs. The invention utilizes a method based on a Sagnac interferometer bidirectional pumping PPKTP crystal to prepare an entangled photon pair, signal light is transmitted to a target point to be measured through a measuring light path and then reflected back to the local, and absolute distance information of the target point to be measured is calculated with idle light through a coincidence counting measurement method. Based on the unique light path structure design, the included angle between the propagation direction of the signal light beam and the coordinate axis can be obtained by reading the horizontal rotation angle and the pitch angle of the right-angle prism reflector. And then the absolute distance and azimuth angle information of the target point to be detected are combined to realize three-dimensional high-precision positioning.
Description
Technical Field
The invention belongs to the technical field of quantum navigation positioning, and particularly relates to a three-dimensional positioning system and a positioning method based on quantum entangled photon pairs.
Background
The distance measurement technology is the basis for realizing the positioning and navigation of unknown target objects, and the positioning accuracy is determined by the distance measurement accuracy of a positioning system. Traditional distance measurement technologies, such as ultrasonic distance measurement, infrared distance measurement, laser distance measurement and the like, are distance measurement technologies based on classical physics, and the distance measurement precision of the traditional distance measurement technologies is always limited by standard quantum limits. In order to obtain higher positioning accuracy, a novel distance measurement technology capable of breaking through the standard quantum limit must be sought.
With the establishment of quantum theory, quantum mechanics is gradually deepened into physical experiments, and particularly, the quantum theory and application technology based on quantum entanglement are rapidly developed. In 2001, a new distance measurement method, namely quantum precision distance measurement, was proposed by the national institute of science and technology, giovannetti research group in Nature. When a quantum light source having frequency entanglement and compression characteristics is employed as a light source of a distance measuring system, measurement accuracy can be improved
And (4) doubling. Where M represents the number of entangled pulses and N represents the average number of photons in a pulse. The technology mainly utilizes the entanglement or compression characteristic of photons to realize high-precision measurement of distance information, so that the measurement precision can break through the limit of standard quantum limit and reach the Heisenberg limit. The quantum precision distance measurement technology provides a new technical support for realizing high-precision positioning.
Currently, with the development of the entangled light source preparation technology, entangled photon pairs with superior performance can be obtained based on a spontaneous parameter down-conversion technology, which are respectively called signal light and idle light. In the actual ranging process, signal light is emitted to a target to be measured and then reflected back to the local, the arrival time difference of the entangled photon pair is obtained through a coincidence counting measurement method with idle light left in the local, and then distance information is solved according to the time difference.
For example, chinese patent application No. 202210383672X claims a two-dimensional planar positioning system and method based on quantum entangled light, the system and method achieve fast and efficient coupling of quantum signals by means of coaxial transmission of visible light beams emitted by a reference light source and signal photons, and through an optical path structure design of an auxiliary positioning device, 360-degree conversion of a distance measurement direction and extraction of an azimuth angle can be achieved only by rotating a right-angle prism reflector therein, and high-precision positioning of a two-dimensional plane of quantum entangled light can be finally achieved by using distance and azimuth angle information with a target point to be measured. However, the system and method can only realize two-dimensional plane positioning. Most targets are targets located in a three-dimensional space, and from the view of the current target positioning requirement, only two-dimensional plane positioning is not enough, and the real position of the target can be accurately known only by realizing three-dimensional positioning of the target. Therefore, how to realize high-precision three-dimensional positioning of the target based on quantum entanglement light is an urgent problem to be solved.
Disclosure of Invention
The invention aims to provide a three-dimensional positioning system and a positioning method based on quantum entangled photon pairs, which are used for solving the problem that the prior art can not accurately realize the precise positioning of a target in a three-dimensional space only by realizing the two-dimensional plane positioning of the target, and realize the high-precision three-dimensional positioning of the space target by realizing the fusion of a quantum measurement technology and a traditional positioning technology.
In order to solve the technical problems, the invention provides a three-dimensional positioning system based on quantum entangled photon pairs, which comprises 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 prism, wherein the entangled light source is connected with the first single photon detector and the second single photon detector; the entanglement light source is used for generating entanglement photon pairs and dividing the entanglement photon pairs into idle light and signal light; the corner cube is disposed at a target point;
a first single-photon detector is arranged on the light path of the idle light, and the idle light is directly received by the first single-photon detector;
a coupler, an optical fiber circulator, an optical fiber collimator, a reflector, a right-angle prism reflector, a corner 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;
a coupler, an optical fiber circulator, a reflector, a right-angle prism reflector, a corner prism and a second single photon detector are arranged on the light path of the signal light, and the horizontal rotation angle and the pitch angle of the right-angle prism reflector can be adjusted; when the actual positioning measurement is carried out on a target point, signal light is used for returning to the right-angle prism reflector along the original path after sequentially passing through the coupler, the optical fiber circulator, the optical fiber collimator, the reflector, the right-angle prism reflector and the corner prism, and then is received by the second single photon detector after sequentially passing through the reflector, the optical fiber collimator and the optical fiber circulator;
the coincidence measurement module is used for performing coincidence counting measurement according to the photon arrival time sequences detected by the first single-photon detector and the second single-photon detector in the actual positioning measurement process to determine the actual measurement optical path difference between idle light and signal light; and determining the absolute distance between the target point and the reflecting point on the right-angle prism reflector by using the actually measured optical path difference and the inherent optical path difference between idle light and signal light in the calibrated system, and carrying out three-dimensional positioning on the target point according to the absolute distance and the pose information of the right-angle prism reflector.
The beneficial effects are as follows: the whole three-dimensional positioning system is provided with a right-angle prism reflector, the horizontal rotation angle and the pitch angle of the right-angle prism reflector are adjustable, and the direction of signal light incident to the right-angle prism reflector is changed by changing the horizontal rotation angle and the pitch angle of the right-angle prism reflector, so that the signal light is reflected to a corner prism arranged at a target point through the right-angle prism reflector in the actual positioning and measuring process, then returns along the original path through the corner prism and is received by a second single photon detector, and the coincidence counting measurement is carried out according to the photon arrival time sequence detected by a first single photon detector and a second single photon detector to determine the actual measurement optical path difference between idle light and the signal light; and then the actual measured optical path difference and the calibrated inherent optical path difference between idle light and signal light in the system are combined to obtain the absolute distance between the target point and the reflecting point on the right-angle prism reflector, and the target point can be positioned in three dimensions according to the absolute distance and the azimuth angle information of the right-angle prism reflector. Based on the unique light path design, high-precision distance measurement and measurement of corresponding position information can be realized, and high-precision three-dimensional positioning is further realized.
Further, when the inherent optical path difference between idle light and signal light in the system is calibrated, the signal light is used for sequentially passing through the coupler, the optical fiber circulator, the optical fiber collimator and the reflector to reach the right-angle prism reflector, then returning to the reflector along the original path, and further sequentially passing through the optical fiber collimator and the optical fiber circulator to be received by the second single photon detector.
Further, the absolute distance between the target point and the reflection point on the right-angle prism mirror is as follows:
R OA ＝(L A -L 0 )/2
in the formula, R OA The absolute distance between the target point A and a reflection point O on the right-angle prism reflector; l is a radical of an alcohol A The optical path difference obtained in the actual positioning measurement process of the target point A is obtained; l is 0 Is the inherent path difference between the idle light and the signal light in the system.
Further, according to the absolute distance R OA When the pose information of the rectangular prism reflector is used for three-dimensionally positioning the target point, alpha and beta are determined according to the pose information of the rectangular prism reflector, if a point A ' is a projection point of the target point A on a horizontal plane where a point O is located, alpha is an included angle between OA ' and an x axis in a coordinate system of a measuring system, and beta is an included angle between OA and OA '; the three-dimensional positioning result of the corresponding target point is as follows:
in the formula (x) A ,y A ,z A ) Is the three-dimensional coordinates of the target point.
The beneficial effects are as follows: the target point can be positioned in three dimensions with high precision by combining the horizontal rotation angle and the pitch angle of the target point in the known coordinate system, corresponding to alpha and beta.
Furthermore, the three-dimensional positioning system also comprises a rotary table, and the optical fiber collimator, the reflecting mirror and the right-angle prism reflecting mirror are fixedly arranged on the rotary table; and the rotation of the right-angle prism reflector is realized through the rotary table so as to change the horizontal rotation angle of the right-angle prism reflector.
The beneficial effects are as follows: the rotation of the right-angle prism reflector can be realized by utilizing the rotary table, and a new choice is provided for changing the emission direction of the signal light.
Further, the optical fiber collimator and the optical fiber circulator are connected through a flexible optical fiber.
The beneficial effects are as follows: the optical fiber collimator and the optical fiber circulator are connected through a flexible optical fiber, so that the optical fiber collimator can perform corresponding horizontal rotation.
In order to solve the technical problem, the invention also provides a three-dimensional positioning method based on quantum entangled photon pairs, which comprises the following steps:
1) Generating entangled photon pairs and dividing the entangled photon pairs into idle light and signal light;
2) When the actual positioning measurement is carried out on a target point to be measured, generated idle light is received by the first single-photon detector; adjusting the horizontal rotation angle and the pitching angle of the right-angle prism reflector, so that the generated signal light sequentially passes through the coupler, the optical fiber circulator, the optical fiber collimator, the reflector, the right-angle prism reflector and the corner prism, then returns to the right-angle prism reflector along the original path, and further sequentially passes through the reflector, the optical fiber collimator and the optical fiber circulator and is received by the second single photon detector; performing coincidence counting measurement according to the photon arrival time sequences detected by the first single-photon detector and the second single-photon detector to determine the actual measurement optical path difference of the idle light and the signal light;
3) And (3) determining 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 idle light and signal light in the system measured in the calibration process and the actually measured optical path difference measured in the actual positioning measurement process in the step 2), and carrying out three-dimensional positioning on the target point according to the absolute distance and the pose information of the right-angle prism reflector.
The beneficial effects are as follows: the direction of signal light incident to the right-angle prism reflector is changed by improving the horizontal rotation angle and the pitch angle of the right-angle prism reflector, the signal light returns through the corner prism in the actual positioning measurement process, the actual measurement optical path difference between the idle light and the signal light can be obtained by combining the arrival time of the idle light, the absolute distance between a target point and a reflection point on the right-angle prism reflector can be obtained by combining the inherent optical path difference between the idle light and the signal light in the system measured in the calibration process, and the target point can be positioned in three dimensions according to the absolute distance and the pose information of the right-angle prism reflector. Based on the unique light path design, high-precision distance measurement and measurement of corresponding position information can be realized, and high-precision three-dimensional positioning is further realized.
Further, the calibration process in step 3) includes: when the inherent optical path difference of the system is calibrated, the generated idle light is received by the first single-photon detector; adjusting the reflecting surface of the right-angle prism reflector to enable the signal light to reach the right-angle prism reflector through the coupler, the optical fiber circulator, the optical fiber collimator and the reflector in sequence, then returning to the reflector along the original path, and further being received by the second single photon detector after passing through the optical fiber collimator and the optical fiber circulator in sequence; and performing coincidence counting measurement according to the photon arrival time sequences detected by the first single-photon detector and the second single-photon detector to determine the inherent optical path difference between idle light and signal light in the system.
Further, the absolute distance between the target point and the reflection point on the right-angle prism mirror is as follows:
R OA ＝(L A -L 0 )/2
in the formula, R OA The absolute distance between a target point A and a reflecting point O on the right-angle prism reflector is shown; l is A Actually positioning the difference between the signal light and the idle optical path in the measurement process for the target point A; l is a radical of an alcohol 0 The inherent optical path difference between the idle light and the signal light in the system is measured.
Further, when the target point is three-dimensionally positioned according to the absolute distance and the pose information of the right-angle prism reflector, alpha and beta are determined according to the pose information of the right-angle prism reflector, a point A ' is a projection point of the target point A on a horizontal plane where a point O is located, alpha is an included angle between OA ' and an x axis in a coordinate system of the measuring system, and beta is an included angle between OA and OA '; the three-dimensional positioning result of the corresponding target point is as follows:
in the formula (x) A ,y A ,z A ) Is the three-dimensional coordinates of the target point.
The beneficial effects are as follows: in combination with the horizontal rotation angle and the pitch angle of the target point in the known coordinate system, corresponding to α and β, a highly accurate three-dimensional positioning of the target point is possible.
Drawings
FIG. 1 is a schematic illustration of quantum entangled photon pair preparation according to the present invention;
FIG. 2 is a schematic diagram of the principle of the quantum entangled photon pair-based three-dimensional positioning system of the present invention;
FIG. 3 is a schematic of the coordinate system of the present invention;
FIG. 4 is a schematic view of the present invention for obtaining horizontal rotation angles with a high precision turntable;
FIG. 5 is a schematic view of the coordinate measurement of a target point according to the present invention.
The device comprises a 1-pump laser, a 2-optical isolator, a 3-1/4 wave plate, a 4-first half wave plate, a 5-optical lens, a 6-long wave pass dichroic mirror, a 7-polarization beam splitter, an 8-second half wave plate, a 9-first reflector, a 10-second reflector, an 11-first single-photon detector, a 12-time digital converter, a 13-second single-photon detector, a 14-coupler, a 15-optical fiber circulator, a 16-optical fiber collimator, a 17-third reflector, an 18-right-angle prism reflector, a 19-angle corner prism and a 20-coincidence measurement module.
Detailed Description
The invention utilizes photon pairs with entanglement characteristics to obtain the absolute distance between a target point and a measurement system by a coincidence counting measurement method. The optical path structure designed by the invention can measure the included angle between the target point to be measured and the coordinate axis of the coordinate system, thereby solving the accurate coordinate value of the target point in the known coordinate system. The present invention will be described in further detail with reference to the accompanying drawings.
The embodiment of the three-dimensional positioning system based on quantum entangled photon pairs comprises:
the invention relates to a three-dimensional positioning system embodiment based on quantum entangled photon pairs, the structure of which is shown in fig. 2, and an entangled light source in fig. 2 is realized by using fig. 1. The three-dimensional positioning system of the present invention will be described in detail with reference to fig. 1 and 2.
As shown in fig. 1, the entanglement light source includes a pump laser 1, and an optical isolator 2, a 1/4 wave plate 3, a first half-wave plate 4 and an optical lens 5 are sequentially disposed on an optical path of pump light (i.e., laser light) emitted from the pump laser 1, so as to obtain 45 ° polarized light, and the 45 ° polarized light is incident to the Sagnac interferometer. The optical isolator 2 is mainly used for preventing back reflection light from interfering or damaging the pump laser 1; the 1/4 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 the 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.
The Sagnac interferometer includes a polarizing beam splitter 7, a second half-wave plate 8, a periodically poled crystal (PPKTP), and a planar mirror (including a first mirror 9 and a second mirror 10). A second half-wave plate 8 within the Sagnac interferometric ring is placed at 45 to change the polarization direction of the polarized beam. The horizontal polarization component in the pump light is transmitted at the polarization beam splitter 7, then passes through the second half-wave plate 8 and the first reflector 9, then is transmitted to the PPKTP crystal, and undergoes parametric down-conversion. The formed entangled photons reach the polarizing beam splitter 7 via a second mirror 10, wherein the horizontal polarization component is transmitted and the vertical polarization component is reflected and transmitted at the long-wave-pass dichroic mirror 6 after reflection. The vertical polarization component in the pump light is reflected by the polarization beam splitter 7, passes through the second reflector 10, is transmitted to the PPKTP crystal, and undergoes parameter down-conversion. The formed entangled photons pass through a first mirror 9 and a second half-wave plate 8 and then reach a polarization beam splitter 7, wherein horizontal polarization components are transmitted and then transmitted again at a long-wave-pass dichroic mirror 6, and vertical polarization components are reflected. Thereby finally obtaining signal light and idle light, and the signal light and the idle light finally obtained both contain horizontal and vertical polarization components.
As shown in fig. 2, besides the entanglement light source, the whole three-dimensional positioning system further 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 mirror 17, a right-angle prism mirror 18, a corner cube 19 and a coincidence measurement module 20, and the fiber collimator 16 and the fiber circulator 15 are connected by a flexible fiber, so that the fiber collimator 16 can perform corresponding horizontal rotation.
The first single-photon detector 11 described above is arranged on the light path of the idle light, and the idle light is directly coupled and received by the first single-photon detector 11.
The coupler 14, the optical fiber circulator 15, the optical fiber collimator 16, the fourth mirror 17, the rectangular prism mirror 18, the corner cube 19, and the second single-photon detector 13 described above are disposed on the optical path of the signal light. The corner cube 19 is disposed at the target point. Wherein, the horizontal rotation angle and the pitch angle of the rectangular prism reflector 18 can be adjusted, thereby realizing the following two processes of the signal light: 1) When the inherent optical path difference of the system is calibrated, the reflecting surface of the 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 the target point to be measured is positioned, the horizontal rotation angle and the pitch angle of the rectangular prism reflector 18 are adjusted, so that the signal light reflected by the third reflector 17 is reflected to the center of the corner prism 19 through the rectangular prism reflector 18, and returns back to the original path after being reflected by the corner prism 19. In any process, the final signal light passes through the third reflector 17, the optical fiber collimator 16 and the optical fiber circulator 15, and is coupled and received by the second single-photon detector 13.
The first single-photon detector 11 and the second single-photon detector 13 transmit the collected electric signals to the time-to-digital converter 12, the time-to-digital converter 12 is configured to record the arrival time sequence of the signal light and the idle light, and further perform coincidence counting measurement by the coincidence measurement module 20 to determine the optical path difference between the idle light and the signal light. The target point can be measured according to the optical path difference.
Further, a turntable is provided in the three-dimensional positioning system, and the third reflecting mirror 17 and the right-angle prism reflecting mirror 18 may be fixed to the turntable, thereby achieving adjustment of the horizontal rotation angle of the right-angle prism reflecting mirror 18.
The whole measurement process of the three-dimensional positioning system is described below, namely the three-dimensional positioning method based on quantum entangled photon pairs.
Firstly, pump light emitted by a pump laser 1 enters an optical isolator 2 for protection, and then passes through a 1/4 wave plate 3, a first half wave plate 4, an optical lens 5 and a long-wave pass dichroic mirror 6 to reach the Sagnac interferometer.
And step two, the Sagnac interferometer consists of a polarization beam splitter 7, a second half-wave plate 8, a periodic polarization crystal (PPKTP) and a plane mirror (comprising a first mirror 9 and a second mirror 10). The pump beam incident to the Sagnac interferometer is made to be 45 ° polarized by adjusting the 1/4 wave plate 3 and the first half wave plate 4. The polarized light is divided into polarized light in the horizontal (H) and vertical (V) directions having equal intensity by the polarization beam splitter 7. The two beams of light respectively reach the PPKTP crystal through reflection in the Sagnac ring and are transformed under parameters, and then entangled photon pairs are generated. The signal light and the idle light respectively contain horizontal and vertical polarized light components and are in an entangled state.
And step three, directly coupling and receiving the idle light by the first single-photon detector 11 at the measurement local and transmitting the idle light into the time-to-digital converter 12.
And step four, the signal light enters the port (1) of the optical fiber circulator 15 through the coupler 14 and then is output from the port (2) of the optical fiber circulator 15, and then the signal light passes through the optical 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.
Step five, the signal light reflected by the corner cube 19 is reflected to the port (2) of the fiber circulator 15 along the original path, and then is output from the port (3) of the fiber circulator 15, and then the signal light is coupled and received by the second single-photon detector 13 and is transmitted to the time-to-digital converter 12.
And step six, establishing a three-dimensional rectangular coordinate system, and defining a reflection point of the signal beam on the rectangular prism reflector 18 as a coordinate origin. The horizontal rotation angle and the pitch angle of the right-angle prism reflector 18 are both adjusted to 0 degree, and the included angle between the reflecting surface of the right-angle prism reflector 18 and the horizontal plane is 45 degrees. The propagation direction of the signal beam is defined as the x-axis. The direction perpendicular to the x axis in the horizontal plane is the y axis, and the directions perpendicular to the x axis and the y axis and upward are the z axis directions. The rectangular prism mirror adjusts its horizontal rotation angle by rotating along the z-axis, and adjusts its pitch angle by rotating along the y-axis.
And seventhly, calibrating the inherent optical path difference of the signal light and the idle light in the three-dimensional positioning system. The reflecting surface of the rectangular prism mirror 18 is adjusted to the horizontal direction. The time-to-digital converter 12 is used to record the arrival time sequence of the signal light and the idle light respectively, and the optical path difference L of the two beams of light is obtained by coincidence counting measurement 0 ，L 0 Namely the inherent optical path difference of the signal light and the idle light in the measuring device. After the inherent optical path difference is calibrated, in the actual measurement process, even if the coordinates of the points to be measured at different positions are measured, the calibration is not needed again.
Step eight, in the actual positioning process, the corner cube 19 is placed on the target point a to be measured. The projection of the point A in the xy plane is A'. By adjusting the horizontal rotation angle and the pitch angle of the rectangular prism mirror 18, the signal beam is irradiated on the center of the rectangular prism 19, and the signal beam is reflected back to the measuring apparatus along the original path. The angle α between OA 'and x-axis and the angle β between OA and OA' are recorded.
Step nine, obtaining the optical path difference L between the signal light reflected by the point A and the idle light by a coincidence counting measurement method A The distance between the point A and the point O is R OA ＝(L A -L 0 )/2。
Step ten, assuming that the coordinate value of A is (x) A ,y A ,z A ). By obtaining a distance value R OA And the angle values α and β, the coordinate values of point a can be solved:
the following description will be made by applying the above method to a specific example.
Firstly, as shown in fig. 1, 405nm pump light emitted by a pump laser 1 firstly enters an optical isolator 2 for protection, and then laser beams pass through a 1/4 wave plate 3, a first half wave plate 4, an optical lens 5 and a long-wave pass dichroic mirror 6 and then reach a Sagnac interferometer.
And step two, the Sagnac interferometer consists of a polarization beam splitter 7, a second half-wave plate 8, a periodic polarization crystal (PPKTP) and a plane mirror (comprising a first mirror 9 and a second mirror 10). The pump beam incident to the Sagnac interferometer is made to be 45 ° polarized by adjusting the 1/4 wave plate 3 and the first half wave plate 4. A second half-wave plate 8 within the Sagnac interferometric ring is placed at 45 to change the polarization direction of the polarized beam. The horizontal polarization component in the pump light is transmitted at the polarization beam splitter 7, then passes through the second half-wave plate 8 and the first reflector 9, then is transmitted to the PPKTP crystal, and undergoes parametric down-conversion. The entangled photons formed reach the polarizing beam splitter 7 via a second mirror 10, in which the horizontal polarization component is transmitted and the vertical polarization component is reflected. The vertical polarization component in the pump light is reflected by the polarization beam splitter 7, transmitted to the PPKTP crystal through the second reflecting mirror 10, and subjected to parameter down-conversion. The formed entangled photons pass through a first mirror 9 and a second half-wave plate 8 and reach the polarizing beam splitter 7, wherein the horizontal polarization component is transmitted and the vertical polarization component is reflected. Thus, both the signal light and the idle light contain both horizontal and vertical polarization components.
And step three, as shown in fig. 2, the idle light is directly coupled and received by the first single-photon detector 11 at the measurement local and transmits the electric signal to the time-to-digital converter 12.
And step four, the signal light enters the port (1) of the optical fiber circulator 15 through the coupler 14 and then is output from the port (2) of the optical fiber circulator 15, and then the signal light passes through the optical 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.
Step five, the signal light reflected by the corner cube 19 is reflected to the port (2) of the fiber circulator 15 along the original path, and then is output from the port (3) of the fiber circulator 15, and then the signal light is coupled and received by the second single-photon detector 13 and is transmitted to the time-to-digital converter 12.
Step six, as shown in fig. 3, a three-dimensional rectangular coordinate system is established, and a reflection point of the signal light on the rectangular prism reflector 18 is defined as a coordinate origin. The horizontal rotation angle and the pitch angle of the rectangular prism reflector 18 are both adjusted to 0 degree, and at the moment, the included angle between the reflecting surface of the rectangular prism reflector 18 and the horizontal plane is 45 degrees. 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 upward is the z-axis direction. The direction of propagation of the signal beam in the horizontal plane can be changed when the right angle prism mirror 18 is rotated along the z-axis. When the right-angle prism reflector 18 rotates along the y-axis, the pitch angle of the signal beam in the propagation direction in the space can be changed, and then the three-dimensional positioning of the target point is realized.
For acquiring the horizontal rotation angle of the signal light, it is possible to realize by means of a high-precision turn table in addition to by rotating the right-angle prism mirror 18 along the z-axis. As shown in fig. 4, the fiber collimator 16, the third mirror 17, and the right-angle prism mirror 18 are fixed on a high-precision turret. The axis of rotation of the turntable coincides with the z-axis of the coordinate system. Due to the connection between the fiber collimator 16 and the fiber circulator 15 via the flexible fiber, a corresponding horizontal rotation can be performed, and thus a horizontal rotation angle of the light beam can be obtained.
And step seven, calibrating the inherent optical path difference of the system. The reflecting surface of the right-angle prism reflector 18 is adjusted to the horizontal direction. The signal light first enters port (1) of the fiber circulator 15 via the coupler 14 and then is output from port (2) of the fiber circulator 15. Then, the signal light passes through the fiber collimator 16, the third mirror 17, and the right-angle prism mirror 18, and returns to the third mirror 17 along the original path. Then, the signal light is reflected to the port (2) of the fiber circulator 15 along the original path, and then output 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 into a time-to-digital converterA transducer 12. The time-to-digital converter 12 is used to record the arrival time sequence of the signal light and the idle light respectively, and the optical path difference L of the two beams of light is obtained by coincidence counting measurement 0 ，L 0 Namely the inherent optical path difference of the signal light and the idle light in the measuring device.
Step eight, as shown in fig. 5, the corner cube 19 is placed on the target point a to be measured. The projection point of the point A in the xy plane is A'. The horizontal rotation angle and the pitch angle of the rectangular prism reflector 18 are adjusted so that the signal light is transmitted to the center of the corner cube 19. The signal light reflected by the corner cube 19 is reflected to the port (2) of the fiber circulator 15 along the original path, and then output from the port (3) of the fiber circulator 15. And then coupled and received by the second single-photon detector 13 and transmits the electrical signal to the time-to-digital converter 12. The angle α between OA 'and x-axis and the angle β between OA and OA' are recorded.
Step nine, obtaining the optical path difference L between the signal light reflected by the point A and the idle light by a coincidence counting measurement method A The distance between the point A and the point O is R OA ＝(L A -L 0 )/2。
Step ten, assuming that the coordinate value of A is (x) A ,y A ,z A ). By obtaining a distance value R OA And the angle values α and β, the coordinate values of point a can be solved:
in summary, the entangled photon pair is prepared by the method of bidirectionally pumping the PPKTP crystal based on the Sagnac interferometer, the signal light is transmitted to the target point to be measured through the measurement system and then reflected back to the local, and the absolute distance information of the target point to be measured is solved by the idle light and the measurement method of coincidence counting. Based on the unique light path structure design, the included angle between the propagation direction of the signal beam and the coordinate axis can be obtained by reading the horizontal rotation angle and the pitch angle of the rectangular prism reflector. And finally, the absolute distance and azimuth angle information of the target point to be detected are combined to realize three-dimensional high-precision positioning.
The embodiment of the three-dimensional positioning method based on quantum entangled photon pairs comprises the following steps:
in the embodiment of the three-dimensional positioning method based on the quantum entangled photon pair, the whole process is the same as that of the three-dimensional positioning method based on the quantum entangled photon pair introduced in the embodiment of the three-dimensional positioning system based on the quantum entangled photon pair, and the description is omitted here.
Claims (10)
1. A three-dimensional positioning system based on quantum entangled photon pairs is characterized by 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 prism; the entanglement light source is used for generating entanglement photon pairs and dividing the entanglement photon pairs into idle light and signal light; the corner cube is disposed at a target point;
a first single-photon detector is arranged on an optical path of the idle light, and the idle light is directly received by the first single-photon detector;
a coupler, an optical fiber circulator, an optical fiber collimator, a reflector, a right-angle prism reflector, a corner 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 is carried out on a target point, signal light is used for returning to the right-angle prism reflector along the original path after sequentially passing through the coupler, the optical fiber circulator, the optical fiber collimator, the reflector, the right-angle prism reflector and the corner prism, and then is received by the second single photon detector after sequentially passing through the reflector, the optical fiber collimator and the optical fiber circulator;
the coincidence measurement module is used for performing coincidence counting measurement according to photon arrival time sequences detected by the first single-photon detector and the second single-photon detector in an actual positioning measurement process to determine an actual measurement optical path difference between idle light and signal light; and determining the absolute distance between the target point and the reflecting point on the right-angle prism reflector by using the actually measured optical path difference and the inherent optical path difference between idle light and signal light in the calibrated system, and carrying out three-dimensional positioning on the target point according to the absolute distance and the pose information of the right-angle prism reflector.
2. The quantum entangled photon pair based three-dimensional positioning system according to claim 1, wherein 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, and the mirror in sequence to reach the right-angle prism mirror, then return to the mirror 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 quantum entangled photon pair based three-dimensional positioning system according to claim 2, wherein the absolute distance between the target point and the reflection point on the right-angle prism mirror is:
R OA ＝(L A -L 0 )/2
in the formula, R OA The absolute distance between a target point A and a reflecting point O on the right-angle prism reflector is shown; l is A Actually positioning the actual measurement optical path difference obtained in the measurement process for the target point A; l is 0 Is the inherent path difference between the idle light and the signal light in the system.
4. The three-dimensional positioning system based on quantum entangled photon pair according to claim 3, characterized in that when the target point is three-dimensionally positioned according to the absolute distance and the pose information of the rectangular prism reflector, α and β are determined according to the pose information of the rectangular prism reflector, where the point A ' is the projection point of the target point A on the horizontal plane where the point O is located, α is the included angle between OA ' and the x axis in the coordinate system of the measurement system, and β is the included angle between OA and OA '; the three-dimensional positioning result of the corresponding target point is as follows:
wherein (x) A ,y A ,z A ) Are the three-dimensional coordinates of the target point.
5. The quantum entangled photon pair-based three-dimensional positioning system according to claim 1, further comprising a turntable, on which the fiber collimator, the mirror and the right-angle prism mirror are fixedly disposed; and the rotation of the right-angle prism reflector is realized through the turntable so as to change the horizontal rotation angle of the right-angle prism reflector.
6. The quantum entangled photon pair based three-dimensional positioning system of claim 1, wherein the fiber collimator and the fiber circulator are connected by a flexible fiber.
7. A three-dimensional positioning method based on quantum entangled photon pairs is characterized by comprising the following steps:
1) Generating entangled photon pairs and dividing the entangled photon pairs into idle light and signal light;
2) When the actual positioning measurement is carried out on a target point to be measured, generated idle light is received by the first single-photon detector; adjusting the horizontal rotation angle and the pitching angle of the right-angle prism reflector to enable the generated signal light to sequentially pass through the coupler, the optical fiber circulator, the optical fiber collimator, the reflector, the right-angle prism reflector and the corner prism, then return to the right-angle prism reflector along the original path, and then sequentially pass through the reflector, the optical fiber collimator and the optical fiber circulator to be received by the second single photon detector; performing coincidence counting measurement according to the photon arrival time sequences detected by the first single-photon detector and the second single-photon detector to determine the actual measurement optical path difference of the idle light and the signal light;
3) And (3) determining 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 idle light and signal light in the system measured in the calibration process and the actually measured optical path difference measured in the actual positioning measurement process in the step 2), and carrying out three-dimensional positioning on the target point according to the absolute distance and the pose information of the right-angle prism reflector.
8. The quantum entangled photon pair-based three-dimensional positioning method according to claim 7, wherein the calibration process in step 3) comprises:
when the inherent optical path difference of the system is calibrated, generated idle light is received by the first single-photon detector; adjusting a reflecting surface of the right-angle prism reflector to enable the signal light to reach the right-angle prism reflector through the coupler, the optical fiber circulator, the optical fiber collimator and the reflector in sequence, then returning to the reflector along the original path, and then being received by the second single photon detector after passing through the optical fiber collimator and the optical fiber circulator in sequence; and performing coincidence counting measurement according to the photon arrival time sequences detected by the first single-photon detector and the second single-photon detector to determine the inherent optical path difference between idle light and signal light in the system.
9. The quantum entangled photon pair based three-dimensional positioning method according to claim 8, wherein the absolute distance between the target point and the reflection point on the right-angle prism mirror is as follows:
R OA ＝(L A -L 0 )/2
in the formula, R OA The absolute distance between the target point A and a reflection point O on the right-angle prism reflector; l is A Actually positioning the actual measurement optical path difference obtained in the measurement process for the target point A; l is a radical of an alcohol 0 Is the inherent path difference between the idle light and the signal light in the system.
10. The quantum entangled photon pair-based three-dimensional positioning method according to claim 9, wherein when the target point is three-dimensionally positioned according to the absolute distance and the pose information of the rectangular prism reflector, α and β are determined according to the pose information of the rectangular prism reflector, where the point a ' is a projection point of the target point a on a horizontal plane where the point O is located, α is an included angle between OA ' and an x axis in a coordinate system of the measurement system, and β is an included angle between OA and OA '; the three-dimensional positioning result of the corresponding target point is as follows:
wherein (x) A ,y A ,z A ) Is the three-dimensional coordinates of the target point.
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