A rotation calibrator and angle measurement method based on quantum indefinite causal order

Abstract

A rotation calibrator and angle measurement method based on quantum indefinite causal order, the rotation calibrator comprising: a laser generating device adapted to generate a first polarized laser; a vortex wave plate adapted to respectively perform opposite orbital angular momentum raising and lowering operations on a left-handed circularly polarized laser portion and a right-handed circularly polarized laser portion in the first polarized laser, and output a second polarized laser; a rotating device, wherein the second polarized laser beam is deflected after passing through the rotating device in a first direction, and the deflected polarized laser beam passes through the rotating device in a second direction to obtain a third polarized laser; the rotating device comprising: a dove prism mechanism comprising a plurality of dove prism groups, arranged on a rotating platform to be measured; when the rotating platform to be measured rotates, each dove prism group is adapted to load the received polarized laser beam with the rotation angle of the rotating platform to be measured; and a detection device adapted to detect a fourth linearly polarized laser beam to obtain the rotation angle of the rotating platform.

Description

Technical Field

[0001] The present invention relates to the field of measurement, and in particular to a rotation calibrator and an angle measurement method based on quantum indefinite causal order. Background Art

[0002] In the fields of space exploration and precision machining, the requirements for geometric measurement, especially angle measurement, are becoming increasingly demanding. This is because accurate angle measurement is crucial for many scientific and technological applications. Angle, as a geometric quantity, is an important parameter for measuring rotational motion. By measuring angles, it is possible to infer topography and locate and calibrate the position of the rotary axes of high-precision machine tools. Current methods for angle measurement include photoelectric autocollimation, circular grating measurement, and laser interferometry, but these methods all have numerous limitations.

[0003] The photoelectric autocollimator measurement method involves directing a parallel light beam onto a plane mirror. When the mirror rotates, the parallel beam is reflected back at twice the angle. The rotation angle is then inferred by detecting the change in the position of the parallel beam on the detector. The photoelectric autocollimation method can achieve highly accurate angle measurement, but its accuracy is directly related to the optical path length. Therefore, a long optical path is often required and the measurement range is significantly limited. Currently, the measurement accuracy of related autocollimators is 10 milliarcseconds, and the measurement range is only between ±150 milliarcseconds.

[0004] The circular grating measurement method utilizes two overlapping gratings, one with its lines angled slightly relative to the other. The angle is measured by the shifting light and dark patterns of the moiré fringes formed by the two gratings as they rotate. While this method offers a wide measurement range, high-line-count circular gratings are expensive and subject to installation errors such as eccentricity and indexing errors, requiring more complex reading methods to minimize these errors.

[0005] Laser interferometry is a method of splitting a coherent laser beam into two beams using a beam splitter. The beams are then incident on two corner cubes placed on the same rotating stage and reflected by the two corner cubes before interfering at the beam splitter. When the rotating stage rotates, the position of the corner cubes changes, causing the optical path lengths of the two laser beams to differ, resulting in changes in the brightness of the interference. The angle measurement range of the relevant multi-beam laser interferometer is ±500μrad, and the resolution is 0.03μrad. It can be seen that although the measurement accuracy of the laser interferometry method is high, it has certain limitations on the measurement range. It is also necessary to know the distance between the two corner cubes accurately before measurement to reduce deviations. In addition, the interference measurement itself is also susceptible to environmental interference.

[0006] Therefore, it is difficult for the above-mentioned measurement methods to simultaneously achieve the characteristics of high precision, large range, easy reading, and resistance to environmental interference. Summary of the Invention

[0007] In view of the above problems, the present invention provides a rotation calibration instrument and angle measurement method based on quantum indefinite causal order.

[0008] As a first aspect of the present invention, a rotation calibrator based on quantum indefinite causal order is provided, comprising:

[0009] a laser generating device adapted to generate a first polarized laser;

[0010] a vortex wave plate adapted to perform opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first polarized laser, respectively, and output a second polarized laser;

[0011] A rotating device, wherein the second polarized laser beam is redirected after passing through the rotating device in a first direction, and the redirected polarized laser beam passes through the rotating device in a second direction to obtain a third polarized laser beam; the first direction is antiparallel to the second direction, and the rotating device comprises:

[0012] A dove prism mechanism includes a plurality of dove prism groups, some of which are disposed on a rotating platform to be measured; when the rotating platform to be measured rotates, each of the dove prism groups is adapted to load the received polarized laser light with the rotation angle of the rotating platform to be measured, thereby applying a rotation operation to the spatial mode of the received polarized laser light;

[0013] wherein the third polarized laser is incident on the vortex wave plate along the second direction, and the vortex wave plate performs opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the third polarized laser, respectively, to obtain a fourth polarized laser; the left-handed circularly polarized laser portion of the fourth polarized laser has the same orbital angular momentum as the left-handed circularly polarized laser portion in the first polarized laser, and the right-handed circularly polarized laser portion of the fourth polarized laser has the same orbital angular momentum as the right-handed circularly polarized laser portion in the first polarized laser;

[0014] The detection device is adapted to detect the fourth linearly polarized laser to obtain the rotation angle of the rotating stage.

[0015] According to an embodiment of the present invention, each Dove prism group includes:

[0016] A first dovetail prism is mounted on the rotating stage to be measured and rotates along with the rotating stage to be measured, and the first dovetail prism performs a rotation operation on the spatial mode of the received polarized laser light;

[0017] A second Dove prism is arranged on the rotating table to be measured and does not contact the rotating table. The second Dove prism is suitable for correcting the spatial mode of the polarized laser output by the first Dove prism in the same group and then transmitting it to the next Dove prism group; wherein the polarized laser beam corrected by the second Dove prism has the same spatial mode as the polarized laser beam input to the first Dove prism.

[0018] According to an embodiment of the present invention, the rotating device further comprises:

[0019] A first Faraday rotator and a second Faraday rotator are arranged at both ends of the Dove prism mechanism along the optical path. The first Faraday rotator and the second Faraday sensor are adapted to ensure that the polarization phases of the polarized laser light input to the Dove prism mechanism along the first direction and the polarized laser light output from the Dove prism mechanism along the second direction meet preset conditions.

[0020] According to an embodiment of the present invention, the first Faraday rotator, the second Faraday rotator and the Dove prism group constitute an adjustment unit;

[0021] The rotating device also includes:

[0022] A first quarter wave plate and a second quarter wave plate are provided along the optical path, wherein the first quarter wave plate and the second quarter wave plate are provided at two ends of the first adjustment unit respectively.

[0023] The first quarter-wave plate and the second quarter-wave plate are adapted to ensure that the polarization phases of the second polarized laser light and the third polarized laser light have the same mirror image.

[0024] According to an embodiment of the present invention, the rotating device further comprises:

[0025] The hollow roof prism is adapted to deflect a light beam of polarized laser light passing through the rotating device along a first direction.

[0026] According to an embodiment of the present invention, the laser generating device includes:

[0027] A laser, adapted to generate an initial laser;

[0028] a beam splitter, adapted to split the initial laser into two paths;

[0029] The polarization beam splitter is adapted to convert one path of the initial laser light into the first polarized laser light; and is adapted to split the fourth polarized laser light into a first probe sub-laser and a second probe sub-laser with perpendicular polarization directions.

[0030] The detection device comprises:

[0031] a first photodetector, adapted to detect the first detection sub-laser;

[0032] A second photodetector is used to detect the second detection sub-laser

[0033] The adjustable attenuation plate is arranged between the polarization beam splitter and the first photodetector and is suitable for adjusting the power of the first detection sub-laser.

[0034] According to an embodiment of the present invention, the rotation angle of the rotating stage is obtained by the following expression:

[0035] P=sin 2 (4N1N2θ)

[0036]

[0037] Wherein, θ represents the rotation angle, P represents the projection probability, N1 represents the order of the vortex wave plate, N2 represents the number of the Dove prism groups, ν1 represents the number of photons detected by the polarization beam splitter, ν2 represents the number of photons detected by the beam splitter, η1 represents the detection efficiency of the polarization beam splitter, and η2 represents the detection efficiency of the beam splitter.

[0038] According to an embodiment of the present invention, the rotation calibrator further includes:

[0039] The filtering device is suitable for filtering the first linearly polarized laser light emitted by the laser generating device, and is also suitable for filtering the detection polarized laser light.

[0040] The filtering device comprises:

[0041] A first lens, a second lens, and a hole-shaped structure located at the focal points of the first lens and the second lens.

[0042] According to an embodiment of the present invention, there is also provided an angle measurement method, using the above-mentioned rotation calibration instrument, the method comprising:

[0043] generating a first polarized laser beam using a laser generating device;

[0044] Using a vortex wave plate, the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first linearly polarized laser light are subjected to opposite orbital angular momentum raising and lowering operations, respectively, and output second polarized laser light;

[0045] The second polarized laser light is incident on the rotating device along a first direction. After the second polarized laser light passes through the rotating device along the first direction, the beam is deflected, and the deflected polarized laser light passes through the rotating device along a second direction to obtain a third polarized laser light. When the rotating stage to be measured rotates, the Dove prism assembly is used to load the received polarized laser light with the rotation angle of the rotating stage to be measured, so as to apply a rotation operation to the spatial mode of the received polarized laser light.

[0046] Using the vortex wave plate, respectively, the left-handed circularly polarized laser and the right-handed circularly polarized laser in the third linearly polarized laser are subjected to opposite orbital angular momentum raising and lowering operations to obtain a fourth polarized laser;

[0047] The fourth polarized laser light is detected by a detection device to obtain the rotation angle of the rotating stage.

[0048] According to an embodiment of the present invention, before performing the angle measurement, the method further comprises calibrating the rotation calibrator.

[0049] According to an embodiment of the present invention, a vortex wave plate is used to apply different angular momentum lifting operations to polarized lasers with different spin directions in the transmitted polarized lasers, and a Dove prism group is used to load the received polarized lasers with the rotation angle of the rotating stage to be measured, thereby realizing the loading of the rotation operation and the lifting operation of the orbital angular momentum onto the polarized laser for detecting the rotation angle of the rotating stage to be measured, thereby realizing the measurement of the rotation angle of the rotating stage to be measured using the quantum indefinite causal order.

[0050] According to an embodiment of the present invention, when measuring the rotation angle of a rotating stage using quantum indefinite causal order, each application of orbital angular momentum increases or decreases the polarization components of the same polarized laser beam, and the different polarization components of the same polarized laser beam are not spatially separated. Therefore, the measurement system of this embodiment of the present invention is less susceptible to environmental influences. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of an optical path of a quantum indefinite causal order rotation calibrator provided in an embodiment of the present invention is shown;

[0052] Figure 2 A data graph showing how the probability of polarization projection measurement varies with the rotation angle of the rotating stage to be measured, provided by an embodiment of the present invention;

[0053] Figure 3 The polarization image of the vortex wave plate provided by the embodiment of the present invention is shown.

[0054] Description of Reference Numerals

[0055] 1 Laser generating device

[0056] 11 Laser

[0057] 12 beam splitters

[0058] 13 Polarization beam splitter

[0059] 2 Vortex wave plates

[0060] 3 Rotating device

[0061] 31 Dove Prism Mechanism

[0062] 311 Dove prism set

[0063] 3111 First Prism

[0064] 3112 Second Prism

[0065] 32 First Faraday Rotator

[0066] 33 Second Faraday Rotator

[0067] 34 First quarter wave plate

[0068] 35 second quarter wave plate

[0069] 4 Detection device

[0070] 5 Rotary table to be tested

[0071] 51 First Photodetector

[0072] 52 second photodetector

[0073] 53 adjustable attenuation plate

[0074] 6 Filtering device

[0075] 61 First lens

[0076] 62 Second lens

[0077] 63 porous structure

[0078] 7Hollow Roof Prisms DETAILED DESCRIPTION

[0079] In the process of realizing the present invention, it was found that the method of measuring using quantum indefinite causal order is a new measurement method in the field of quantum information. In the method of measuring using quantum indefinite causal order, two types of operations are prepared into a superposition state with different causal orders, and the parameter information is extracted by reading the control bits of the causal order. When the number of two types of operations is the same, the number of operations of the two types is continuously stacked N, and the uncertainty of the measurement parameter will increase with 1 / N. 2 Reduced, the measurement accuracy can be greatly improved.

[0080] In angle measurement, since angle and orbital angular momentum are a pair of non-commutative physical quantities, the two operations within the quantum indefinite causal order structure correspond to physical rotation and orbital angular momentum increase and decrease operations, respectively. Because these two operations are non-commutative, there exists an angle-dependent geometric phase difference between different causal orders, allowing the angle to be read in the measurement of the control bit. Furthermore, the measurement method utilizing the quantum indefinite causal order does not require the initial system quantum state, so even deviations in the initial spatial distribution of photons will not affect the final result. Using photon polarization as the control bit effectively avoids environmental interference with the interference results, and the reading method is simple and direct.

[0081] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0082] Figure 1 A schematic diagram of the optical path of a rotation calibrator provided according to an embodiment of the present invention is shown.

[0083] like Figure 1 As shown, the rotation calibration instrument includes: a laser generating device 1, a vortex wave plate 2, a rotating device 3 and a detection device 4.

[0084] The laser generating device 1 is adapted to generate a first polarized laser beam. The first polarized laser beam can be, for example, a horizontally linearly polarized laser beam, which is a superposition of a left-handed circularly polarized laser beam portion and a right-handed circularly polarized laser beam portion. The vortex wave plate 2 is adapted to perform opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser beam portion and the right-handed circularly polarized laser beam portion of the first linearly polarized laser beam, respectively, and output a second polarized laser beam.

[0085] After the second polarized laser beam passes through the rotating device 3 in the first direction, it is redirected. The redirected polarized laser beam then passes through the rotating device in the second direction, producing a third polarized laser beam. The first direction is antiparallel to the second direction. The rotating device 3 includes a dove prism mechanism 31, which comprises multiple dove prism groups 311, partially disposed on the rotating stage 5 to be measured. When the rotating stage 5 to be measured rotates, each dove prism group 311 is adapted to apply the rotation angle of the rotating stage 5 to the received polarized laser beam, thereby applying a rotational operation to the spatial mode of the received polarized laser beam. The third polarized laser beam is incident on the vortex wave plate 2 in the second direction. The vortex wave plate 2 performs opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser beam portion and the right-handed circularly polarized laser beam portion of the third linearly polarized laser beam, respectively, to produce a fourth polarized laser beam. The left-handed circularly polarized laser beam portion of the fourth polarized laser beam has the same orbital angular momentum as the left-handed circularly polarized laser beam portion of the first polarized laser beam, and the right-handed circularly polarized laser beam portion of the fourth polarized laser beam has the same orbital angular momentum as the right-handed circularly polarized laser beam portion of the first polarized laser beam. The detection device 4 is adapted to detect the fourth linearly polarized laser light to obtain the rotation angle of the rotating stage.

[0086] According to an embodiment of the present invention, different angular momentum lifting operations are applied to polarized lasers with different spin directions in the transmitted polarized lasers through the vortex wave plate 2, and the Dove prism group 311 is used to load the rotation angle of the rotating stage 5 to be measured onto the received polarized lasers, thereby realizing the loading of the rotation operation and the lifting operation of the orbital angular momentum onto the polarized laser for detecting the rotation angle of the rotating stage to be measured, and realizing the measurement of the rotation angle of the rotating stage 5 to be measured using the quantum indefinite causal order.

[0087] According to an embodiment of the present invention, when measuring the rotation angle of a rotating stage using quantum indefinite causal order, each application of orbital angular momentum increases or decreases the polarization components of the same polarized laser beam, and the different polarization components of the same polarized laser beam are not spatially separated. Therefore, the measurement system of this embodiment of the present invention is less susceptible to environmental influences.

[0088] According to an embodiment of the present invention, a laser generating device 1 includes a laser 11, a beam splitter 12, and a polarization beam splitter 13. Laser 11 is configured to generate an initial laser beam having a narrow linewidth and a Gaussian distribution. Beam splitter 12 is configured to split the initial laser beam into two paths. Polarization beam splitter 13 is configured to convert one path of the initial laser beam into a first polarization laser beam.

[0089] According to an embodiment of the present invention, the vortex wave plate 2 is suitable for performing opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser part and the right-handed circularly polarized laser part in the first linearly polarized laser, that is, the vortex wave plate 2 generates orbital angular momentum vortex beams of +N1 and -N1 orders for the left-handed circularly polarized laser part and the right-handed circularly polarized laser part, respectively, and the orbital angular momentum vortex beams of +N1 and -N1 orders maintain their coherent properties, where N1 is an arbitrary integer.

[0090] According to an embodiment of the present invention, the number of dove prism groups can be, for example, N2, and each dove prism group 31 includes: a first dove prism 3111 and a second dove prism 3112. The first dove prism 311 is mounted on the rotating stage 5 to be measured and rotates with the rotating stage 5 to be measured. The first dove prism 311 performs a rotation operation on the spatial mode of the received polarized laser. The second dove prism 312 is set on the rotating stage but does not contact the rotating stage 5 to be measured. The second dove prism 312 is suitable for correcting the spatial mode of the polarized laser output by the first dove prism 311 of the same group and then transmitting it to the next dove prism group 31, thereby ensuring that the polarized laser beam output by this group does not produce a mirror flip. When each dove prism is placed, it is necessary to ensure that the polarized laser beam passing through it does not undergo a significant deflection.

[0091] According to an embodiment of the present invention, the rotation device 3 further includes a first Faraday rotator 32 and a second Faraday rotator 33 disposed along the optical path at both ends of the dove prism mechanism 31. Polarized laser light output from the first Faraday rotator 32 is input to the dove prism mechanism 31, and polarized laser light output from the dove prism mechanism 31 is input to the second Faraday rotator 33. The first Faraday rotator 32 and the second Faraday rotator 33 cooperate with each other to ensure that the polarization phases of the polarized laser light input to the dove prism mechanism 31 along a first direction and the polarized laser light output from the dove prism mechanism 31 along a second direction meet a predetermined condition. For example, the predetermined condition may be to ensure that the polarization angles of the polarized laser light input to the dove prism mechanism 31 along the first direction and the polarized laser light output from the dove prism mechanism 31 along the second direction differ by 90 degrees.

[0092] According to an embodiment of the present invention, the first Faraday rotator 32, the second Faraday rotator 33, and the prism mechanism 31 constitute an adjustment unit. The rotation device 3 also includes a first quarter-wave plate 34 and a second quarter-wave plate 35 arranged along the optical path, and the first quarter-wave plate 34 and the second quarter-wave plate 35 are respectively arranged at both ends of the adjustment unit. The first quarter-wave plate 34 is used to receive the second polarized laser light, convert the polarization state of the second polarized laser light, and then input it into the first Faraday rotator 32. The second quarter-wave plate 35 receives the polarized laser light output by the second Faraday rotator 33. The first quarter-wave plate 34 and the second quarter-wave plate 35 are used to change the state of the transmitted polarized laser light, and their working principle is as follows: the first quarter-wave plate 34 and the second quarter-wave plate 35 are used to convert the polarized laser light including two circularly polarized laser light superimposed into the polarized laser light including two linearly polarized laser light superimposed, or convert the polarized laser light including two linearly polarized laser light superimposed into the polarized laser light including two circularly polarized laser light superimposed. The first quarter wave plate 34 and the second quarter wave plate 35 cooperate with each other to ensure that the polarization phases of the second polarized laser light and the third polarized laser light differ by 180°, that is, to ensure that the polarization phases of the second polarized laser light and the third polarized laser light have the same mirror image.

[0093] According to an embodiment of the present invention, the rotating device 3 further includes a hollow roof prism 7, which is adapted to deflect the polarized laser beam passing through the rotating device 3 along the first direction.

[0094] According to an embodiment of the present invention, the fast axis angle of the second quarter-wave plate 35 disposed near the hollow roof prism is always parallel to the two reflecting surfaces of the hollow roof prism 34 .

[0095] According to an embodiment of the present invention, the polarization beam splitter 13 is further adapted to split the fourth polarized laser light into a first probe sub-laser light and a second probe sub-laser light with polarization directions perpendicular to each other.

[0096] According to an embodiment of the present invention, the detection device 5 includes: a first photodetector 51 , a second photodetector 52 and an adjustable attenuation plate 53 .

[0097] The first photodetector 51 is adapted to detect the first detection sub-laser. The second photodetector is adapted to detect the second detection sub-laser. The adjustable attenuator 53 is disposed between the polarization beam splitter 51 and the first photodetector 52 and is adapted to adjust the power of the first detection sub-laser.

[0098] According to an embodiment of the present invention, the system further includes a filtering device 6 adapted to filter the first linearly polarized laser light emitted by the laser generating device and also adapted to filter the detection polarized laser light. The filtering device 6 includes a first lens 61, a second lens 62, and an aperture structure 63 (e.g., a pinhole) located at the focal points of the first lens 61 and the second lens 62.

[0099] According to an embodiment of the present invention, when the vortex wave plate 2 performs opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first polarized laser light, it also simultaneously converts the left-handed circularly polarized laser light in the first linearly polarized laser light into the right-handed circularly polarized laser light, and converts the right-handed circularly polarized laser light in the first linearly polarized laser light into the left-handed circularly polarized laser light. Therefore, the second polarized laser light output after the first polarized laser light passes through the vortex wave plate 2 also includes a superposition of the two circularly polarized laser lights, and the left-handed circularly polarized laser light portion of the second polarized laser light corresponds to the right-handed circularly polarized laser light portion in the first polarized laser light, and the right-handed circularly polarized laser light portion of the second polarized laser light corresponds to the left-handed circularly polarized laser light portion in the first polarized laser light. The third polarized laser light transmitted along the second direction also includes a superposition of the two circularly polarized laser lights, and the left-handed circularly polarized laser light portion of the third polarized laser light corresponds to the right-handed circularly polarized laser light portion in the first polarized laser light, and the right-handed circularly polarized laser light portion of the third polarized laser light corresponds to the left-handed circularly polarized laser light portion in the first polarized laser light. When the third polarized laser beam passes through the vortex wave plate 2, the vortex wave plate 2 performs an angular momentum-increasing operation on the left-handed circularly polarized laser beam portion of the third linearly polarized laser beam, converting the left-handed circularly polarized laser beam portion of the third linearly polarized laser beam into right-handed circularly polarized laser beam. The vortex wave plate 2 then performs an angular momentum-decreasing operation on the right-handed circularly polarized laser beam portion of the third linearly polarized laser beam, converting the right-handed circularly polarized laser beam portion of the third linearly polarized laser beam into left-handed circularly polarized laser beam, and ultimately outputs a fourth polarized laser beam. Therefore, after two angular momentum conversion operations, the left-handed circularly polarized laser beam portion of the fourth polarized laser beam has the same angular momentum as the left-handed circularly polarized laser beam portion of the first polarized laser beam, and the right-handed circularly polarized laser beam portion of the fourth polarized laser beam has the same angular momentum as the right-handed circularly polarized laser beam portion of the first polarized laser beam.

[0100] The following describes how different operations are applied to polarized laser light during angle detection. In the angle measurement device according to an embodiment of the present invention, the left-handed circularly polarized laser light portion of the first polarized laser light first undergoes an orbital angular momentum increase operation, which can be expressed as formula (1).

[0101]

[0102] Secondly, after the rotation operation, it can be expressed as formula (2).

[0103]

[0104] Finally, the operation of orbital angular momentum decreasing can be expressed as formula (3).

[0105]

[0106] In formula (1) to formula (3), represents the orbital angular momentum increase operation, l represents the orbital angular momentum quantum number, represents the azimuth operator, represents the orbital angular momentum operator.

[0107] For the right-handed circularly polarized laser in the first polarized laser, it first experiences a decrease in orbital angular momentum. operation, and then the rotation operation Finally, the orbital angular momentum rises operation.

[0108] Therefore, after the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first polarized laser light undergo orbital angular momentum operation and rotation operation respectively, the total operation they undergo can be expressed as formula (4).

[0109]

[0110] Where |L> represents the polarization state of left-handed circularly polarized laser; |R> represents the vibration state of right-handed circularly polarized true laser; the default value of l is 1.

[0111] When the first polarized laser beam is incident with the horizontal linear polarization |H>, it is in a superposition state of two circular polarizations and two causal orders. When the spatial mode of the photon is represented by |ψ>, the final state after passing through the device, namely the fourth polarized laser beam, can be expressed as Equation (5).

[0112]

[0113] According to formula (5), the information of the rotation angle of the measuring turntable can be obtained.

[0114] According to an embodiment of the present invention, the rotation angle of the rotating stage is obtained by the following expression:

[0115] P=sin 2 (4N1N2θ) (6)

[0116]

[0117] Where θ represents the rotation angle, P represents the projection probability, N1 represents the order of the vortex wave plate, N2 represents the number of Dove prism groups, v1 represents the number of photons detected by the polarization beam splitter, v2 represents the number of photons detected by the beam splitter, η1 represents the detection efficiency of the polarization beam splitter, and η2 represents the detection efficiency of the beam splitter.

[0118] Combine Figure 1 As a second aspect of the present invention, a method for measuring an angle is further provided, using the above-mentioned rotation calibrator, the method comprising: operations S1 to S5.

[0119] In operation S1, a laser generating device 1 generates a first polarized laser.

[0120] In operation S2, a vortex wave plate is used to perform opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first linearly polarized laser, and outputs a second polarized laser;

[0121] In operation S3, a second polarized laser beam is incident on the rotating device along a first direction. After the second polarized laser beam passes through the rotating device along the first direction, the beam is redirected, and the redirected polarized laser beam passes through the rotating device along a second direction to obtain a third polarized laser beam. When the rotating stage to be measured rotates, a Dove prism assembly is used to load the received polarized laser beam with the rotation angle of the rotating stage to be measured, thereby applying a rotation operation to the spatial mode of the received polarized laser beam.

[0122] In operation S4, the vortex wave plate 2 is used to perform opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser and the right-handed circularly polarized laser in the third linearly polarized laser to obtain a fourth polarized laser.

[0123] In operation S5 , the fourth polarized laser light is detected by the detection device 4 to obtain the rotation angle of the rotating stage.

[0124] According to an embodiment of the present invention, before formally performing the angle measurement, the method further includes calibrating the rotation calibrator (ie, correcting or setting it to zero).

[0125] The calibration method is to stop the rotating stage 5 to be measured and rotate the first quarter wave plate 34 in front of the vortex wave plate 2 to minimize the light intensity emitted by the polarization beam splitter. The calibrated quarter wave plate needs to be fixed during the measurement process.

[0126] During angle detection, the first photodetector and the second photodetector simultaneously detect the light intensity emitted from the polarization beam splitter (PBS) and the reflective end of the beam splitter (BS). The attenuation plate is placed at the reflective end of the PBS to keep the photon collection efficiency of the reflective ends of the PBS and BS roughly balanced.

[0127] The following combination Figure 1 Specific embodiments are listed to illustrate the angle detection method of the present invention.

[0128] Step A: The laser 11 is a 795nm narrow linewidth semiconductor laser. After the generated initial laser beam passes through the beam splitter 2 and the polarization beam splitter 3, its polarization is prepared to be horizontal polarization, thereby obtaining the first polarized laser.

[0129] Step B: After the first polarized laser passes through the optical spatial filter device 6 consisting of a first lens 61 with a focal length of 75 mm, a pinhole with a diameter of 200 μm, and a second lens 62 with a diameter of 150 mm, the spatial mode of the polarized beam becomes a better Gaussian mode and is expanded to twice its original value.

[0130] Step C: Under the action of the vortex wave plate 2, the spatial mode of the left-handed circularly polarized laser portion of the filtered first polarized laser is converted into a +N1-order vortex beam, and the polarization is changed to right-handed circularly polarized laser. Similarly, the spatial mode of the right-handed circularly polarized portion of the first polarized laser is converted into a -N1-order vortex beam, and the polarization is changed to left-handed circularly polarized laser, thereby obtaining the second polarized laser.

[0131] Step D: After the second polarized laser passes through the first quarter wave plate 34 and the first Faraday rotator 32, the superposition of the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion is converted into +45 ° Linear polarized laser part and -45 ° Superposition of linearly polarized laser parts.

[0132] Step E: The dove prism mechanism 31 consists of N2 dove prism groups, each with two dove prisms. Only the first dove prism 3111 in each group applies the same rotation angle to the transmitted polarized laser light, thereby rotating the spatial mode of the beam. The total internal reflection property of the dove prism affects the polarization during this process, making the output polarization unknown.

[0133] Step E: The polarized laser light output from the Dove prism is transmitted to the hollow roof prism 7 after passing through the second Faraday rotator 33 and the second quarter wave plate 35. After being reflected in the hollow roof prism 7, it is reflected back along the original path. The polarized laser light output from the second quarter wave plate 35 along the second direction is rotated by 90 degrees relative to the polarized laser light input to the second quarter wave plate 35 along the first direction. ° Unlike an ordinary plane reflector, the laser beam reflected by the hollow roof prism 7 does not undergo mirror flipping, thereby maintaining the same spatial mode of the polarized laser beam before and after reflection by the hollow roof prism 7 .

[0134] Step F: The spatial mode of the polarized laser light output from the second Faraday rotator 33 along the second direction is rotated again by the Dove prism mechanism 31, and then passes through the first Faraday rotator 32 and the first quarter wave plate 34, and its polarization state is changed from +45 ° Linear polarized laser part and -45 ° The superposition of the linearly polarized laser light components is restored to the superposition of the left-handed circularly polarized laser light components and the right-handed circularly polarized laser light components, thereby obtaining a third linearly polarized laser light component. Passing through the Dove prism mechanism 31 twice (in both the first and second directions) naturally cancels out the effect of the Dove prism mechanism 31 on polarization.

[0135] Step G: The vortex wave plate 3 restores the order of the +N1-order and -N1-order vortex beams in the third linearly polarized laser back to the zero order, and the rotation angle of the spatial mode is encoded in the phase between left-handed circular polarization and right-handed circular polarization to obtain the fourth linearly polarized laser.

[0136] Step H: After the fourth linearly polarized laser passes through the filter system 6 composed of the first lens 61 , the pinhole, and the second lens 62 , the high-frequency spatial noise is filtered out, leaving the low-frequency signal portion.

[0137] Step I: The beam splitter 12 has a splitting ratio of 50 / 50. The filtered fourth polarized laser light passes through the polarization beam splitter 3 and is divided into a vertical polarization portion and a horizontal polarization portion. The polarized laser light of the vertical polarization portion is directly reflected and enters the first photodetector 51 through the adjustable attenuation plate 53. The polarized laser light of the horizontal polarization portion is directly transmitted into the beam splitter 12 and partially reflected to the second photodetector 52. The first photodetector 51 and the second photodetector 52 respectively detect the number of photons of the input polarized laser light. The adjustable attenuation plate 53 is adjusted so that the detection efficiency of the two photodetectors is roughly balanced.

[0138] In the above method, before performing angle detection, the angle detection device needs to be calibrated, and the angle of the Dove prism mechanism 31 before rotation is defined as 0. ° At this point, if the additional phase difference is completely canceled, the polarization states of the polarized laser light input to the first quarter-wave plate 34 along the first direction and the polarized laser light output from the second quarter-wave plate 35 along the second direction should remain unchanged. Therefore, by rotating the first quarter-wave plate 34 so that the light intensity detected at the reflective end of the polarization beam splitter 13 is minimum, it can be considered that the additional phase difference has been canceled, and the above-mentioned device has been successfully calibrated. The rotation angle of the calibrated quarter-wave plate 34 needs to be fixed before measuring the rotation angle.

[0139] Figure 2 A data graph showing how the polarization projection measurement probability provided by an embodiment of the present invention varies with the rotation angle of the rotating stage to be measured is shown.

[0140] Figure 2 There are seven parts (a) to (g), which correspond to the curves of the change between the projection probability of vertical polarization and the rotation angle when using different orders of vortex wave plates 2 and different numbers of Dove prism groups 311. Among them, N1 is the order of the vortex wave plate used, and N2 is the number of Dove prism groups. Figure 2 As shown, the measured change in the polarization angle of the light beam is proportional to the product of N1 and N2.

[0141] Figure 3 The polarization image of the vortex wave plate provided by the embodiment of the present invention is shown.

[0142] Figure 3 There are seven parts (a) to (g), which are the patterns of vortex wave plates 2 with order N1 equal to 1, 2, 3, 4, 5, 6 and 128, respectively, obtained by projecting the incident horizontally polarized light beam onto the horizontal polarization. Figure 3 It can be seen that the light beams in the seven parts (a)-(g) present clear petal-like patterns of 2, 4, 6, 8, 10, 12 and 256 petals, respectively, corresponding to the superposition of ±1, ±2, ±3, ±4, ±5, ±6 and ±128 orders of orbital angular momentum, indicating that the vortex wave plate 2 can better apply the required orbital angular momentum operation.

[0143] The embodiments of the present invention have higher accuracy among current angle measurement methods, and the reading method relies only on polarization measurement, which is easier. The designed round-trip collinear optical path is not easily affected by environmental interference and is more stable than a general interferometer. At the same time, a compensation method is also provided to eliminate most system deviations, so it has a wider range of application scenarios.

[0144] The above specific embodiments further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rotation calibrator based on quantum indefinite causal order, comprising: a laser generating device adapted to generate a first polarized laser; a vortex wave plate adapted to perform opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first polarized laser, respectively, and output a second polarized laser; A rotating device, wherein the second polarized laser beam is redirected after passing through the rotating device in a first direction, and the redirected polarized laser beam passes through the rotating device in a second direction to obtain a third polarized laser beam; the first direction is antiparallel to the second direction, and the rotating device comprises: A dove prism mechanism includes a plurality of dove prism groups, some of which are disposed on a rotating platform to be measured; when the rotating platform to be measured rotates, each of the dove prism groups is adapted to load the received polarized laser light with the rotation angle of the rotating platform to be measured, thereby applying a rotation operation to the spatial mode of the received polarized laser light; wherein the third polarized laser is incident on the vortex wave plate along the second direction, and the vortex wave plate performs opposite orbital angular momentum raising and lowering operations on the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the third polarized laser, respectively, to obtain a fourth polarized laser; the left-handed circularly polarized laser portion of the fourth polarized laser has the same orbital angular momentum as the left-handed circularly polarized laser portion in the first polarized laser, and the right-handed circularly polarized laser portion of the fourth polarized laser has the same orbital angular momentum as the right-handed circularly polarized laser portion in the first polarized laser; The detection device is adapted to detect the fourth polarized laser light to obtain the rotation angle of the rotating stage.

2. The rotation aligner according to claim 1, wherein: Each Dove prism set includes: A first dovetail prism is mounted on the rotating stage to be measured and rotates along with the rotating stage to be measured, and the first dovetail prism performs a rotation operation on the spatial mode of the received polarized laser light; A second Dove prism is arranged on the rotating table to be measured and does not contact the rotating table. The second Dove prism is suitable for correcting the spatial mode of the polarized laser output by the first Dove prism in the same group and then transmitting it to the next Dove prism group; wherein the polarized laser beam corrected by the second Dove prism has the same spatial mode as the polarized laser beam input to the first Dove prism.

3. The rotation aligner according to claim 1, wherein: The rotating device also includes: A first Faraday rotator and a second Faraday rotator are arranged at both ends of the Dove prism mechanism along the optical path, and the first Faraday rotator and the second Faraday rotator are adapted to ensure that the polarization phases of the polarized laser light input to the Dove prism mechanism along the first direction and the polarized laser light output from the Dove prism mechanism along the second direction meet preset conditions.

4. The rotation aligner according to claim 3, wherein: The first Faraday rotator, the second Faraday rotator and the Dove prism mechanism constitute an adjustment unit; The rotating device also includes: A first quarter wave plate and a second quarter wave plate are arranged along the optical path, wherein the first quarter wave plate and the second quarter wave plate are respectively arranged at two ends of the adjustment unit, The first quarter-wave plate and the second quarter-wave plate are adapted to ensure that the polarization phases of the second polarized laser light and the third polarized laser light have the same mirror image.

5. The rotation aligner according to claim 1, wherein: The rotating device also includes: The hollow roof prism is adapted to deflect a light beam of polarized laser light passing through the rotating device along a first direction.

6. The rotation aligner according to claim 1, wherein: The laser generating device comprises: A laser, adapted to generate an initial laser; a beam splitter, adapted to split the initial laser into two paths; A polarization beam splitter, adapted to convert one path of the initial laser light into the first polarized laser light; and adapted to split the fourth polarized laser light into a first probe sub-laser and a second probe sub-laser with perpendicular polarization directions; The detection device comprises: a first photodetector, adapted to detect the first detection sub-laser; a second photodetector, adapted to detect the second detection sub-laser; The adjustable attenuation plate is arranged between the polarization beam splitter and the first photodetector and is suitable for adjusting the power of the first detection sub-laser.

7. The rotation aligner according to claim 6, wherein: The rotation angle of the rotating stage is obtained by the following expression: in, represents the rotation angle, P represents the projection probability, represents the order of the vortex wave plate, represents the number of the Dove prism groups, represents the number of photons detected by the polarization beam splitter and represents the number of photons detected by the beam splitter, represents the detection efficiency of the polarization beam splitter, represents the detection efficiency of the beam splitter.

8. The rotation aligner according to claim 1, further comprising: a filter device adapted to filter the first polarized laser light emitted by the laser generating device and also adapted to filter the fourth polarized laser light; The filtering device comprises: A first lens, a second lens, and a hole-shaped structure located at the focal points of the first lens and the second lens.

9. A method for measuring an angle, using the rotation calibrator according to any one of claims 1 to 8, the method comprising: generating a first polarized laser beam using a laser generating device; Using a vortex wave plate, the left-handed circularly polarized laser portion and the right-handed circularly polarized laser portion in the first polarized laser light are subjected to opposite orbital angular momentum raising and lowering operations, respectively, and output second polarized laser light; The second polarized laser light is incident on the rotating device along a first direction. After the second polarized laser light passes through the rotating device along the first direction, the beam is deflected, and the deflected polarized laser light passes through the rotating device along a second direction to obtain a third polarized laser light. When the rotating stage to be measured rotates, the Dove prism assembly is used to load the received polarized laser light with the rotation angle of the rotating stage to be measured, so as to apply a rotation operation to the spatial mode of the received polarized laser light. Using the vortex wave plate, respectively, the left-handed circularly polarized laser and the right-handed circularly polarized laser in the third polarized laser are subjected to opposite orbital angular momentum raising and lowering operations to obtain a fourth polarized laser; The fourth polarized laser light is detected by a detection device to obtain the rotation angle of the rotating stage.

10. The angle measurement method according to claim 9, wherein: Before performing the angle measurement, the method further includes calibrating the rotation collimator.

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