A polarization-entangled photon current sensor

Abstract

The present invention relates to a polarization-entangled photon current sensor, comprising an all-fiber polarization-entangled photon source, a high-potential sensing optical path, and a low-potential measuring optical path; the high-potential sensing optical path comprises an air-core photonic crystal fiber, a magnetic collecting ring, and a white screen; the low-potential measuring optical path comprises a collimating beam expander and a radial polarization grating; the all-fiber polarization-entangled photon source outputs two polarization-entangled photons, one of which enters the sensing optical path, passes through the air-core photonic crystal fiber, the light hole on the magnetic collecting ring, and the magneto-optical film, and is annihilated on the white screen; the other photon enters the measuring optical path, forms spatial light through the collimating beam expander, and then passes through the radial polarization grating for polarization analysis, converting the Faraday rotation angle into a synchronous translation of a fixed light spot. The light spot is positioned using an image sensor to obtain the Faraday rotation angle, thereby obtaining the current to be measured.

Description

Technical Field

[0001] The present invention belongs to the field of high-voltage current measurement, and in particular relates to a polarization entangled photon current sensor. Background Art

[0002] Flow sensors are important tools for "sensing" the operating status of power systems and are the basis for power system protection, control and metering. Their role is very important. However, existing current measurement technologies have several fundamental defects and can no longer meet the requirements of smart grid development. For example, electromagnetic current transformers have problems such as high insulation costs and leakage of insulating media such as insulating oil and insulating gas. Fiber Optical Current Transducers (FOCTs) have the advantages of reliable insulation, simple structure, maintenance-free, and environmentally friendly. Therefore, they are considered to be the ultimate development direction of power system current measurement. However, FOCTs have fundamental defects such as nonlinear measurement and optical power dependence, no harmonic measurement capability, and interference from stress line birefringence. Over the years, these problems have not been effectively solved.

[0003] Currently, quantum sensing technology is primarily used for weak magnetic field measurements, such as atomic magnetometers and quantum spatial magnetic field imaging. These technologies, with their advantages of high sensitivity, high resolution, and non-destructive measurement, have become a research hotspot in recent years. However, quantum sensing technology has not yet been applied to strong electromagnetic (current) measurement, and its application to high-voltage current measurement in power systems is a novel endeavor. Summary of the Invention

[0004] In view of this, an object of the present invention is to provide a polarization entangled photon current sensor to solve the above problems.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A polarization-entangled photon current sensor comprises an all-fiber polarization-entangled photon source, a high-potential sensing optical path, and a low-potential measuring optical path; the high-potential sensing optical path comprises an air-core photonic crystal fiber, a magnetic collecting ring, and a white screen; the low-potential measuring optical path comprises a collimating beam expander and a radial polarization grating; the all-fiber polarization-entangled photon source outputs two polarization-entangled photons, one of which enters the sensing optical path and, after passing through the air-core photonic crystal fiber, the light hole on the magnetic collecting ring, and the magneto-optical film, is annihilated on the white screen; the other photon enters the measuring optical path, forms spatial light through the collimating beam expander, and then, after being analyzed by the radial polarization grating, the Faraday rotation angle is converted into a synchronous translation of a fixed light spot. The light spot is positioned using an image sensor to obtain the Faraday rotation angle, thereby obtaining the current to be measured.

[0007] Furthermore, when the photons in the sensing light path pass through the magneto-optical film, the polarization plane thereof rotates, and the rotation angle is proportional to the current to be measured.

[0008] Furthermore, the rotation angle of the polarization plane of the photons in the measuring light path is the same as that of the photons in the sensing light path.

[0009] Furthermore, the Faraday rotation angle can be obtained by positioning the light spot using an image sensor, as follows:

[0010] The two-photon polarization entangled state generated by the all-fiber polarization entangled photon source is:

[0011]

[0012] Where H and V represent horizontal polarization and vertical polarization respectively. Represents the phase difference between horizontal polarization and vertical polarization;

[0013] Let one of the photons enter the sensing optical path, couple with the air-core photonic crystal fiber, and then pass through the magneto-optical film. Under the action of the magnetic field, the photon polarization entangled state obtains a new phase difference. Right now:

[0014]

[0015] Where β is the Faraday rotation angle, and the two-photon polarization entangled state becomes:

[0016]

[0017] When another photon enters the measurement optical path and passes through the radial polarization grating, it is equivalent to detecting the polarization state of the other photon. That is, there is a 50% probability of it being in the |H> state and a 50% probability of it being in the |V> state, that is:

[0018]

[0019] When the measurement optical path detects the |V> state, the phase at this time is directly measured through the radial polarization grating Right now:

[0020]

[0021] Combined with formula (2), β is obtained;

[0022] The Jones matrix of incident light passing through the radial polarization grating is expressed as:

[0023] G(x,y)=T[α(x,y)]G[κ(x,y)]T -1 [α(x,y)] (6)

[0024] Where T[α(x,y)] is the rotation matrix, α is the direction of the metal grid; G[κ(x,y)] is represented by a diagonal matrix:

[0025]

[0026] where t TM , t TE are the diffraction efficiencies of the transmitted components of the TM and TE waves, respectively; ξ is the phase difference between the two light waves;

[0027] Each metal grid unit of the radial polarization grating is described as a linear polarizer with the transmission axis perpendicular to α, and equation (6) is rewritten as:

[0028]

[0029] Assume that the angle between the direction of the incident light polarization plane and the x-axis of the system is If the amplitude is 1, the Jones matrix of the incident light vector is:

[0030]

[0031] After the incident light passes through the radial polarization grating, the Jones matrix of the outgoing light vector is:

[0032]

[0033] The expression of the emitted light intensity is:

[0034]

[0035] Order I out Taking the minimum value, we get:

[0036] α=φ (12)

[0037] Assuming the length of the grating is l, the range of the dark fringe translation is 0~l; assuming that when When the dark pattern center is on the 0° grid unit, the spot displacement Δx is related to The relationship satisfies:

[0038]

[0039] According to the above formula, we can get:

[0040]

[0041] The intensity distribution of the outgoing light after the radial polarization grating is obtained based on Matlab. The change of the spot can be synchronized with the change of the spot. Direct linear measurement of ; combined with formula (5), we can get β.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention solves the principle defect problem of FOCT and realizes polarization entangled photon current measurement based on the polarization entanglement characteristics of photons. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic structural diagram of the present invention;

[0045] Figure 2 is a schematic diagram of a radial polarization grating structure in one embodiment of the present invention;

[0046] Figure 3 The intensity distribution of the outgoing light after polarization analysis based on the radial polarization grating in one embodiment of the present invention;

[0047] In the figure: 1- all-fiber polarization entangled photon source, 2- air-core photonic crystal fiber, 3- magnetic collecting ring, 4- light hole, 5- magneto-optical film, 6- white screen, 7- collimating beam expander, 8- radial polarization grating, 9- output light spot of radial polarization grating analyzer. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0049] Please refer to Figure 1 The present invention provides a polarization entangled photon current sensor, comprising an all-fiber polarization entangled photon source, a high-potential sensing optical path and a low-potential measuring optical path; the high-potential sensing optical path comprises an air-core photonic crystal fiber, a magnetic collecting ring and a white screen; the low-potential measuring optical path comprises a collimating beam expander and a radial polarization grating; the all-fiber polarization entangled photon source outputs two polarization entangled photons, one of which enters the sensing optical path, and after passing through the air-core photonic crystal fiber, the light hole on the magnetic collecting ring and the magneto-optical film, is annihilated on the white screen; the other photon enters the measuring optical path, forms spatial light through the collimating beam expander, and then after passing through the radial polarization grating for polarization analysis, the Faraday rotation angle is converted into a synchronous translation of a fixed light spot. The Faraday rotation angle can be obtained by positioning the light spot using an image sensor, thereby obtaining the current to be measured.

[0050] In this embodiment, the polarization plane of photons in the sensing light path rotates when they pass through the magneto-optical film. This rotation angle is the Faraday rotation angle, and is proportional to the current being measured. Due to the properties of quantum entanglement, the polarization plane rotation angle of photons in the measuring light path is the same as that of photons in the sensing light path.

[0051] In this embodiment, the Faraday rotation angle can be obtained by positioning the light spot using an image sensor, as follows:

[0052] The two-photon polarization entangled state generated by the all-fiber polarization entangled photon source is:

[0053]

[0054] Where H and V represent horizontal polarization and vertical polarization respectively. Represents the phase difference between horizontal polarization and vertical polarization;

[0055] Let one of the photons enter the sensing optical path, couple with the air-core photonic crystal fiber, and then pass through the magneto-optical film. Under the action of the magnetic field, the photon polarization entangled state obtains a new phase difference. Right now:

[0056]

[0057] Where β is the Faraday rotation angle, and the two-photon polarization entangled state becomes:

[0058]

[0059] When another photon enters the measurement optical path and passes through the radial polarization grating, it is equivalent to detecting the polarization state of the other photon. That is, there is a 50% probability of it being in the |H> state and a 50% probability of it being in the |V> state, that is:

[0060]

[0061] When the measurement optical path detects the |V> state, the phase at this time can be directly measured by the radial polarization grating. Right now:

[0062]

[0063] Combined with formula (2), β is obtained.

[0064] The structure of the radial polarization grating is shown in the attached figure. Figure 2 As shown in the figure, the polarization analysis principle is as follows. The Jones matrix of the incident light passing through the radial polarization grating is expressed as:

[0065] G(x,y)=T[α(x,y)]G[κ(x,y)]T -1 [α(x,y)] (6)

[0066] Where T[α(x,y)] is the rotation matrix, α is the direction of the metal grid (which changes regularly between -50° and 50°). G[κ(x,y)] can be represented by a diagonal matrix:

[0067]

[0068] where t TM , tTE are the diffraction efficiencies (i.e., transmittances) of the TM and TE wave transmission components, respectively; ξ is the phase difference between the two light waves. Since the grating has a very high extinction ratio (t TE < <t TM ), t TE Therefore, each metal grid unit of the radial polarization grating is described as a linear polarizer with a transmission axis perpendicular to α, and equation (6) is rewritten as:

[0069]

[0070] Assume that the angle between the direction of the incident light polarization plane and the x-axis of the system is If the amplitude is 1, the Jones matrix of the incident light vector is:

[0071]

[0072] After the incident light passes through the radial polarization grating, the Jones matrix of the outgoing light vector is:

[0073]

[0074] The expression of the emitted light intensity is:

[0075]

[0076] Order I out Taking the minimum value, we get:

[0077] α=φ(12)

[0078] Therefore, when equation (12) is satisfied, the light intensity transmitted from the corresponding grid unit is the minimum value, and its location can be approximated as the center of the dark stripe. When the dark stripes are linearly translated along the grating unit, the grating direction of the radial polarization grating is α = -50° to 50°. The range of variation is 0°~100°; if the length of the grating is l, then the range of dark fringe translation is 0~l. When the dark pattern center is on the 0° grid unit, the spot displacement Δx is related to The relationship satisfies:

[0079]

[0080] According to the above formula, we can get:

[0081]

[0082] It can be seen that the radial polarization grating can achieve the polarization plane angle The linear measurement of the radial polarization grating is obtained based on Matlab. Figure 3 As shown. The change of the spot can be synchronized with the change of the spot. Direct linear measurement of . Combining with formula (5), we can get β.

[0083] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A polarization entangled photon current sensor, characterized in that: It includes an all-fiber polarization entangled photon source, a high-potential sensing optical path and a low-potential measuring optical path; the high-potential sensing optical path includes an air-core photonic crystal fiber, a magnetic collecting ring and a white screen; the low-potential measuring optical path includes a collimating beam expander and a radial polarization grating; the all-fiber polarization entangled photon source outputs two polarization entangled photons, one of which enters the sensing optical path and, after passing through the air-core photonic crystal fiber, the light hole on the magnetic collecting ring and the magneto-optical film, is annihilated on the white screen; the other photon enters the measuring optical path, forms spatial light through the collimating beam expander, and then, after being polarized by the radial polarization grating, the Faraday rotation angle is converted into a synchronous translation of a fixed light spot. The Faraday rotation angle can be obtained by positioning the light spot using an image sensor, thereby obtaining the current to be measured; When the photons in the sensing light path pass through the magneto-optical film, their polarization plane rotates, and the rotation angle is proportional to the current to be measured; The rotation angle of the polarization plane of the photons in the measuring light path is the same as that of the photons in the sensing light path.

2. The polarization entangled photon current sensor according to claim 1, characterized in that: The Faraday rotation angle can be obtained by positioning the light spot using an image sensor, as follows: The two-photon polarization entangled state generated by the all-fiber polarization entangled photon source is: Where H and V represent horizontal polarization and vertical polarization respectively. Represents the phase difference between horizontal polarization and vertical polarization; Let one of the photons enter the sensing optical path, couple with the air-core photonic crystal fiber, and then pass through the magneto-optical film. Under the action of the magnetic field, the photon polarization entangled state obtains a new phase difference. Right now: Where β is the Faraday rotation angle, and the two-photon polarization entangled state becomes: When another photon enters the measurement optical path and passes through the radial polarization grating, it is equivalent to detecting the polarization state of the other photon. That is, there is a 50% probability of it being in the |H> state and a 50% probability of it being in the |V> state, that is: When the measurement optical path detects the |V> state, the phase at this time is directly measured through the radial polarization grating Right now: Combined with formula (2), β is obtained; The Jones matrix of incident light passing through the radial polarization grating is expressed as: G(x,y)=T[α(x,y)]G[κ(x,y)]T -1 [α(x,y)] (6) Where T[α(x,y)] is the rotation matrix, α is the direction of the metal grid; G[κ(x,y)] is represented by a diagonal matrix: where t TM , t TE are the diffraction efficiencies of the transmitted components of TM and TE waves, respectively; ξ is the phase difference between the two light waves; Each metal grid unit of the radial polarization grating is described as a linear polarizer with the transmission axis perpendicular to α, and equation (6) is rewritten as: Assume that the angle between the direction of the incident light polarization plane and the x-axis of the system is If the amplitude is 1, the Jones matrix of the incident light vector is: After the incident light passes through the radial polarization grating, the Jones matrix of the outgoing light vector is: The expression of the emitted light intensity is: Order I out Taking the minimum value, we get: α=φ (12) Assuming the length of the grating is l, the range of the dark fringe translation is 0~l; assuming that when When the dark pattern center is on the 0° grid unit, the spot displacement Δx is related to The relationship satisfies: According to the above formula, we can get: The intensity distribution of the outgoing light after the radial polarization grating is obtained based on Matlab. The change of the spot can be synchronized with the change of the spot. Direct linear measurement of Combining with formula (5), we can get β.

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