Polarization control system and method for quantum communication

Abstract

The invention provides a polarization control system and method for quantum communication. The polarization control system comprises a Kuder optical path, an electric encoder, a half-wave plate and a control panel, the Kuder optical path is connected with the half-wave plate optical path, and the electric encoder is arranged in the Kuder optical path and electrically connected with the half-wave plate and the control panel; the Kuder light path is used for transmitting polarized light to the half-wave plate; the half-wave plate is used for correcting the polarization direction of the polarized light through rotation; the electric encoder is used for measuring the orientation and the pitching angle of the Kuder optical path and sending feedback information to the control panel; and the control panel controls the half-wave plate to rotate through the feedback information. The requirement for the light beam polarization state in quantum communication can be met, the signal receiving rate is increased, the transmission efficiency is improved, and the system is simple in structure.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication technology, and in particular to a polarization control system and method for quantum communication. Background Art

[0002] In quantum communication, polarized light is most commonly used as a coding method. Changes in polarization state will lead to an increase in the system bit error rate, which in turn affects the communication code rate and security. That is, the polarization performance of polarized light will directly affect the communication performance of the quantum communication system. The Coode optical path can separate the turntable from the optical cabin, which not only enables the device to have a stable optical cabin, but also has good maneuverability. In terms of target tracking, it can effectively improve the tracking accuracy. Therefore, using the Coode optical path structure in quantum communication can help improve the signal reception rate and increase the transmission efficiency. However, due to the defects of the Coode optical path's own structure, the use of the Coode optical path in quantum communication is limited.

[0003] Therefore, there is an urgent need for a simple and mature Kuder optical path structure that can be used in quantum communication to improve the signal reception rate and increase the transmission efficiency. Summary of the invention

[0004] Based on this, it is necessary to provide a polarization control system and method for quantum communication to address the above technical problems.

[0005] A polarization control system for quantum communication, comprising: a Coode optical path, an electric encoder, a half wave plate and a control board; the Coode optical path is connected to the half wave plate optical path, the electric encoder is arranged in the Coode optical path, and is electrically connected to the half wave plate and the control board; the Coode optical path is used to transmit polarized light to the half wave plate; the half wave plate is used to correct the polarization direction of the polarized light by rotation; the electric encoder is used to measure the azimuth and pitch angle of the Coode optical path, and send feedback information to the control board; the control board controls the rotation of the half wave plate through the feedback information.

[0006] In some embodiments, the Coode optical path adopts a primary imaging form, an afocal imaging form or a secondary imaging form.

[0007] A polarization control method for quantum communication is implemented by using a polarization control system for quantum communication as described above, and comprises the following steps: emitting polarized light to a Coode optical path, and transmitting the light beam through the Coode optical path; measuring the azimuth and elevation angle of the light beam in the Coode optical path by an electric encoder, obtaining feedback information, and transmitting the feedback information to a control board; analyzing the feedback information by using the control board, obtaining a rotation angle, and controlling a half wave plate to rotate according to the rotation angle; the Coode optical path transmits the polarized light to the half wave plate, and the polarization direction of the polarized light is corrected by the rotated half wave plate.

[0008] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: by connecting the Coode optical path with the half wave plate optical path, an electric encoder is arranged in the Coode optical path and is electrically connected to the half wave plate and a control board; the Coode optical path is used to transmit polarized light to the half wave plate; the half wave plate is used to correct the polarization direction of the polarized light by rotation; the electric encoder measures the azimuth and pitch angle of the Coode optical path, and sends feedback information to the control board, and the half wave plate is controlled to rotate by the control board to achieve correction of the polarization direction of the polarized light, and by adding the electric encoder, the azimuth and pitch angle in the Coode optical path are fed back, and then the half wave plate is controlled to rotate to correct the polarization direction of the light beam, thereby solving the problem of the polarization characteristics of the light beam being affected by spatial rotation, meeting the requirements for the polarization state of the light beam in quantum communication, improving the signal reception rate, increasing the transmission efficiency, and the system structure is simple, which is convenient for equipment modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The figure is a schematic diagram of the structure of a polarization control system for quantum communication in one embodiment.

[0010] Figure 2 1 is a diagram showing the optical path structure of the secondary imaging Kuder optical path in one embodiment.

[0011] Figure 3 FIG. 4 is a schematic diagram of a half wave plate in one embodiment.

[0012] Figure 4 The figure is a flow chart of a polarization control method for quantum communication in one embodiment. DETAILED DESCRIPTION

[0013] Before describing the specific embodiments of the present invention, the overall concept of the present invention is described as follows:

[0014] The present invention is mainly developed based on the quantum communication process. At present, due to the structural defects of the Coode optical path itself, when applied to polarization control, polarized light passing through the Coode optical path will produce phase delay, causing polarization state degradation and signal quality reduction.

[0015] Therefore, the present invention proposes a polarization control system for quantum communication, which connects the Coode optical path with the half wave plate optical path, and the electric encoder is arranged in the Coode optical path, and is electrically connected to the half wave plate and the control board; the Coode optical path is used to transmit polarized light to the half wave plate; the half wave plate is used to correct the polarization direction of the polarized light by rotation; the electric encoder measures the azimuth and pitch angle of the Coode optical path, and sends feedback information to the control board, and the half wave plate is controlled to rotate by the control board to realize the correction of the polarization direction of the polarized light, and by adding the electric encoder, the azimuth and pitch angle in the Coode optical path are fed back, and then the half wave plate is controlled to rotate to correct the polarization direction of the light beam, which solves the problem of affecting the polarization characteristics of the light beam due to spatial rotation, meets the requirements of the polarization state of the light beam in quantum communication, improves the signal reception rate, increases the transmission efficiency, and the system structure is simple, the technology is mature, and it is easy to carry out equipment transformation.

[0016] After introducing the overall concept of the present invention, in order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail by specific implementation methods in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] In one embodiment, Figure 1 As shown, a polarization control system for quantum communication is provided, comprising: a Coode optical path 10, an electric encoder 20, a half wave plate 30 and a control board (not shown in the figure), wherein the Coode optical path 10 is optically connected to the half wave plate 30, and the electric encoder 20 is arranged in the Coode optical path 10, and is electrically connected to the half wave plate 30 and the control board; the Coode optical path 10 is used to transmit polarized light to the half wave plate 30; the half wave plate 30 is used to correct the polarization direction of the polarized light by rotation; the electric encoder 20 is used to measure the azimuth and pitch angles of the Coode optical path 10, and send feedback information to the control board; the control board controls the rotation of the half wave plate 30 according to the feedback information.

[0018] In this embodiment, the Coode optical path 10 is connected to the half wave plate 30 optical path, and the electric encoder 20 is arranged in the Coode optical path 10, and is electrically connected to the half wave plate 30 and the control board; the Coode optical path 10 is used to transmit polarized light to the half wave plate 30; the electric encoder 20 measures the azimuth and pitch angle of the Coode optical path, and sends feedback information to the control board, and the half wave plate 30 is controlled to rotate by the control board to achieve correction of the polarization direction of the polarized light. By adding the electric encoder 20, the azimuth and pitch angle in the Coode optical path 10 are fed back, and the half wave plate 30 is controlled to rotate to correct the polarization direction of the light beam, which solves the problem of affecting the polarization characteristics of the light beam due to spatial rotation, meets the requirements for the polarization state of the light beam in quantum communication, improves the signal reception rate, increases the transmission efficiency, and has a simple system structure, which is convenient for equipment modification.

[0019] The polarization of light refers to the loss of symmetry in the spatial distribution of the electric vector vibration of the light wave with respect to the propagation direction of the light.

[0020] Specifically, after the polarized light is incident, the light beam is reflected in the Kuder optical path 10. At the same time, the electric encoder 20 measures the reflection azimuth and pitch angle of the light beam and feeds back the information to the control board in real time. The control board calculates the rotation angle of the half wave plate 30 based on the feedback information, and controls the half wave plate 30 to rotate, thereby ensuring the fidelity requirements for the polarization state of the light beam in quantum communication.

[0021] Among them, the imaging forms of the Coode optical path include primary imaging form, afocal image form and secondary imaging form. The primary imaging form is that the cassette objective lens and the Coode optical path share the same focal length, and a convergent light beam is emitted from the end of the structure. The afocal image form is parallel light entering and parallel light exiting, and the primary and secondary mirrors work together to reduce the beam. The secondary imaging form is that the cassette objective lens has a primary image plane. After passing through the primary image plane, the light beam is collimated into parallel light by the secondary collimator, and then introduced into the subsequent optical path through the Coode mirror. Since the secondary imaging form can delay the exit pupil while ensuring the optical quality, thereby reducing the distance from the exit pupil to the final image plane, which is conducive to reducing the optical aperture of the subsequent optical path, the secondary imaging form is more frequently used.

[0022] Taking the secondary imaging Kude optical path as an example, the optical path structure is as follows Figure 2 As shown, the light beam first passes through the cassette objective lens, and then is reflected by Coode 1 mirror, Coode 2 mirror, Coode 3 mirror and Coode 4 mirror in sequence, and then is collimated by a collimator, and finally passes through a 1 / 2 wave plate to achieve polarization state restoration.

[0023] Among them, the half wave plate is a birefringent crystal with a certain thickness. When the normally incident light passes through, the phase difference between the ordinary light (o light) and the extraordinary light (e light) is equal to π or an odd multiple thereof.

[0024] Specifically, the half-wave plate is also called a half-wave plate. Its main material is quartz crystal. It uses the principle of birefringence to change the polarization state of the incident light beam. When linear polarized light is incident vertically on the crystal, and the direction of the optical axis is parallel to the surface of the crystal, due to the birefringence effect, the incident linear polarized light will be decomposed into mutually perpendicular o light and e light, with refractive indices of n0 and n2 respectively. e , then after passing through a wafer with a thickness of d, the phase difference δ=(2m+1)π, where m is an integer. If the vibration plane of the incident linear polarized light forms an angle α with the optical axis, after passing through the half-wave plate, the vibration plane of the linear polarized light rotates by 2α, as Figure 3 shown.

[0025] When polarization control is performed, polarized light is incident as a collimated beam, and then exits after passing through the Coode optical path, and the polarization of the beam is maintained and transmitted. In the Coode optical path, the light is introduced into the Coode optical path by a reflector, and the propagation path of the light is transformed by reflection through a multi-faceted high-precision reflector, so that the light can be sent to the predetermined direction after passing through the Coode mirror.

[0026] In quantum communication, it is necessary to change the propagation direction of the outgoing light beam in real time and keep the optical path aligned, so the Coode optical path is needed to complete the deflection of the optical path. The Coode optical path is a light-guiding optical path that can turn the light beam to rotate with the axis system. The laser beam passing through the Coode optical path can be free from the influence of the rotation of the turntable and emit in the predetermined direction. However, the polarized light in quantum communication will produce phase delay after passing through the traditional Coode optical path, causing the polarization state to degenerate and the signal transmission quality to decrease.

[0027] The present invention combines an electric encoder and a half wave plate, and adds a Coode optical path structure that can control the polarization state to the equipment used in the field of quantum communication, which not only meets the requirements for the polarization state of the light beam in quantum communication, but also improves the signal reception rate and increases the transmission efficiency; an electric encoder is added to the Coode optical path to feedback the orientation and pitch angle in the Coode optical path, and then the electric half wave plate is controlled to rotate to correct the polarization direction of the light beam, thereby solving the problem of the polarization characteristics of the light beam being affected by spatial rotation.

[0028] The azimuth and pitch angles of the Kuder optical path are measured by an electric encoder and sent to the control board. The control board changes the fast axis direction of the half-wave plate based on the feedback information, thereby controlling the polarization state of the light, thereby effectively restoring the polarization direction of the light beam, meeting the requirements for the polarization state of the light beam in quantum communication, improving the signal reception rate, increasing the transmission efficiency, and helping to promote the development of quantum communication.

[0029] In one embodiment, Figure 4 As shown, a polarization control method for quantum communication is also provided, which is implemented by using the above-mentioned polarization control system for quantum communication, and includes the following steps:

[0030] Step S210, emitting polarized light to the Coode optical path, and transmitting the light beam through the Coode optical path.

[0031] Step S220, using an electric encoder to measure the azimuth and pitch angle of the light beam in the Kude optical path, obtain feedback information, and transmit it to the control board.

[0032] Step S230, analyzing the feedback information through the control board to obtain a rotation angle, and controlling the half wave plate to rotate according to the rotation angle.

[0033] In step S240, the Coode optical path transmits the polarized light to the half wave plate, and the polarization direction of the polarized light is corrected by the rotated half wave plate.

[0034] In this embodiment, polarized light is emitted to the Coode optical path, and the light beam is transmitted through the Coode optical path. At the same time, an electric encoder is used to measure the azimuth and pitch angle of the light beam in the Coode optical path, and feedback information is obtained and transmitted to the control board. The rotation angle is obtained by analysis of the control board, and the rotation of the half wave plate is controlled. After the Coode optical path transmits the polarized light to the half wave plate, the polarization angle of the polarized light is corrected by the rotated half wave plate, thereby effectively restoring the polarization direction of the light beam, meeting the requirements for the polarization state of the light beam in quantum communication, improving the signal reception rate, and increasing the transmission efficiency.

[0035] The above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A polarization control system for quantum communication, characterized in that: include: Kuder optical path, electric encoder, half wave plate and control board; The Coode optical path is connected to the half-wave plate optical path, and the electric encoder is arranged in the Coode optical path and is electrically connected to the half-wave plate and the control board; The Coode optical path is used to transmit polarized light to the half wave plate; The half wave plate is used to correct the polarization direction of polarized light by rotation; The electric encoder is used to measure the azimuth and pitch angle of the Kude optical path and send feedback information to the control board; The control board controls the rotation of the half wave plate according to the feedback information.

2. A polarization control system for quantum communication according to claim 1, characterized in that: The Coode optical path adopts a primary imaging form, an afocal imaging form or a secondary imaging form.

3. A polarization control method for quantum communication, characterized in that: The method is implemented by using a polarization control system for quantum communication as claimed in any one of claims 1 to 2, comprising the following steps: emitting polarized light to a Coode optical path, and transmitting the light beam through the Coode optical path; An electric encoder is used to measure the azimuth and pitch angle of the light beam in the Kude optical path, and feedback information is obtained and transmitted to the control board; Analyzing the feedback information through a control panel to obtain a rotation angle, and controlling the half wave plate to rotate according to the rotation angle; The Coode optical path transmits the polarized light to the half wave plate, and the polarization direction of the polarized light is corrected by the rotated half wave plate.

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