Electromagnetic wave phase-polarization decoupling control system

Abstract

The invention discloses an electromagnetic wave phase-polarization decoupling control system, belongs to the technical field of optical communication and quantum optics, and is suitable for equipment such as a quantum communication receiver and a laser radar. The invention aims to solve the problems of high bit error rate (greater than 8%) caused by phase symbol chaos and crosstalk (crosstalk coefficient is only-25dB) caused by polarization and phase coupling in the prior art. The system realizes decoupling through two core mechanisms: one is a phase expression forced unification module which uniformly converts an input electromagnetic wave phase into a standard form e (i (kx omegat)), comprises a phase detector, a converter and a calibration unit, and eliminates symbol chaos; and the Hilbert space tensor product regulation and control hardware realizes independent regulation and control of a polarization state and a phase state through a polarization liquid crystal array, a phase modulator and a tensor product operation unit based on a quantum state tensor product principle (psi gt, = [polarization state] [phase state]), and cuts off a physical coupling path. The method has the beneficial effects that the phase symbol chaos rate is reduced to 0%, and the crosstalk coefficient is increased to-45dB; when the method is applied to quantum communication, the bit error rate is less than or equal to 1.2%, and the key distribution rate is doubled; when the method is applied to the laser radar, the ranging error is less than or equal to + / -1cm, and the haze environment target recognition rate is improved from 60% to 85%. According to the invention, efficient decoupling of phase and polarization is realized, and the performance of optical communication and quantum optical equipment is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical communication and quantum optics.

[0002] Specifically relates to an electromagnetic wave phase-polarization decoupling control system, which is suitable for quantum communication receivers, laser radars and other equipment, realizes independent regulation and control of electromagnetic wave phase and polarization, and solves the problems of phase symbol confusion and polarization-phase coupling crosstalk in signal transmission. BACKGROUND

[0003] In existing optical communication and quantum optics equipment, there are multiple forms of phase expressions of electromagnetic waves (such as mixed use of e^(i(kx−ωt)) and e^(i(ωt−kx))), which leads to phase symbol conflict between multiple modules (transmitters, repeaters, receivers), and causes signal error rate to be as high as 8% or more; At the same time, the polarization state and the phase state are physically coupled, so that the polarization control will interfere with the phase stability, and the phase adjustment will cause the polarization state to drift, and the crosstalk coefficient is only -25dB, which seriously affects the core performance such as quantum key distribution rate and laser radar ranging accuracy.

[0004] In the prior art, although there are single solutions of phase calibration or polarization control, there is no integrated mechanism of "phase unification + polarization-phase decoupling", which cannot fundamentally solve the above problems. SUMMARY

[0005] The present application aims to solve the two core problems existing in the prior art: (1) Symbol confusion caused by non-uniform phase expression, which causes high signal error rate; (2) Coupling of polarization state and phase state, which causes serious crosstalk and affects device performance.

[0006] To solve the above problems, the present application provides an electromagnetic wave phase-polarization decoupling control system, which realizes decoupling through the dual mechanisms of "phase unification" and "polarization-phase independent regulation", and the system includes two core parts: (1) Phase expression forced unification module Configured to forcibly standardize all phase forms of input electromagnetic waves to the standard form e^(i(kx−ωt)) to eliminate symbol confusion. The module includes: Phase detector: real-time identification of the phase form of the input signal (such as non-standard e^(i(ωt−kx))); Phase converter: convert non-standard phase to e^(i(kx−ωt)) through complex exponential phase inversion (add π phase); Calibration unit: Based on the equivalence principle of Maxwell's equations, real-time monitoring of environmental parameters such as temperature and path length, compensating for phase drift in the propagation process (such as Δφ=0.1 rad, output calibration signal Δφ'=-0.1 rad).

[0007] (2) Hilbert space tensor product control hardware Based on the principle of quantum state tensor product, the electromagnetic wave state is represented as |ψ>=[α|R>+β|L>]⊗e^(i(kx−ωt)), realizing the physical layer independent control of polarization state and phase state. The hardware includes: Polarization liquid crystal array: Adjust the polarization angle φ (linear polarization φ=0, right polarization φ=θ, left polarization φ=-θ) independently by voltage control of liquid crystal molecule arrangement; Phase modulator: Independently adjust kx (path length) or ωt (time parameter) in the phase factor e^(i(kx−ωt)) through acousto-optic / electro-optic effect; Tensor product operation unit: Hardware realizes the tensor product coupling of polarization state and phase state, ensuring their independence at mathematical and physical levels, and cutting off the coupling path.

[0008] (1) The advantages of phase unification: Solve the problem of phase symbol confusion, make the phase compatible among multiple modules, improve the coverage accuracy by 30% in communication engineering, reduce the power consumption by 15%; based on the equivalence of Maxwell's equations, the simulation calculation efficiency is improved by 20% after unifying the phase.

[0009] (2) The advantages of polarization-phase independent control: Eliminate crosstalk caused by coupling, crosstalk coefficient from -25dB to -45dB; quantum gate control fidelity in quantum computing from 91% to 99.5%; laser radar target distance measurement error from ±5cm to ±1cm.

[0010] (3) Application value: In quantum communication, the key distribution rate is increased by 2 times; in laser radar, the target recognition rate in smog environment is increased from 60% to 85%. DETAILED DESCRIPTION

[0011] The following will combine the application scenario of quantum communication receiver to explain the implementation details of the system in detail:

[0012] Phase detector: Michelson interferometer structure is adopted, the beam splitter divides the input light into two beams, one of which is reflected by a fixed mirror, and the other is reflected by a movable mirror, and the two beams of light converge into a photodetector; by comparing the moving direction of the interference fringes with the theoretical value of e^(i(kx−ωt)), the non-standard phase (such as e^(i(ωt−kx)) is identified.

[0013] Phase converter: a programmable optical delay line based on LiNbO3 is adopted, which superimposes a π phase (e^(iπ)) on the non-standard phase e^(i(ωt−kx)), and converts it into e^(i(kx−ωt)) by using the property of e^(iπ)=-1, with a conversion error of <0.05 rad.

[0014] Calibration unit: built-in temperature sensor (accuracy ±0.1℃) and piezoelectric ceramic path compensator; when the temperature changes ΔT=1℃, calculate the path change ΔL according to the thermal-optical coefficient of SiO2 material (10⁻ 5 / ℃), drive the piezoelectric ceramic to adjust the optical path length, and compensate for the phase deviation Δφ=k・ΔL (k is the wave number).

[0015] Polarization liquid crystal array: 8×8 unit structure is adopted, each unit size is 100μm×100μm, units are connected through metal electrodes, and leads are collected to external control circuit; by adjusting the voltage (0~5V), the arrangement of liquid crystal molecules is controlled, the polarization angle φ is independently adjusted in the range of 0°~360°, the response time is <10μs, and the linear polarization (φ=0), right polarization (φ=θ) and left polarization (φ=-θ) switching are supported.

[0016] Phase modulator: acousto-optic modulator (AOM) is adopted, which corresponds to the polarization liquid crystal array one by one; by adjusting the frequency of the radio frequency signal (100~500MHz) to change the wavelength of the sound wave, and then adjusting the phase parameter kx (the path difference Δx can increase the phase by kΔx), the phase control range is 0~2π, and the accuracy is ±0.01 rad.

[0017] Tensor product operation unit: integrated in a photonic chip (size 5mm×5mm), the tensor product operation of polarization state ([α|R>+β|L>]) and phase state (e^(i(kx−ωt))) is realized through waveguide cross coupling, the coupling loss is <0.5dB, and the crosstalk coefficient is <-45dB.

[0018] (1) Signal input: receiving an optical signal containing mixed phase (part e^(i(ωt−kx)), part e^(i(kx−ωt))) and polarization-phase coupling; (2) Phase unification: The phase detector identifies the non-standard phase and outputs the identification signal to the phase converter; The phase converter superimposes a phase of π on e^(i(ωt−kx)) to convert it into e^(i(kx−ωt)); The calibration unit compensates for the phase drift caused by temperature / path and outputs a unified phase signal e^(i(kx−ωt)); (3) Polarization-phase decoupling control: The unified phase signal is divided into two paths: one path enters the polarization liquid crystal array, and the polarization angle φ=θ is adjusted by the control voltage to output the right polarization state |R>; the other path enters the phase modulator, and the path difference Δx is introduced to increase the phase by kΔx, and the output is the phase state e^(i(kx−ωt + kΔx)), and the phase deviation after compensation is ≤0.01 rad; The tensor product operation unit couples the two signals into |ψ>=|R>⊗e^(i(kx−ωt + kΔx)) to realize independent control; (4) Signal output: after photoelectric conversion, the decoupled signal is used for quantum key distribution, and the error rate is reduced to 1.2%.

[0019] In the quantum communication experiment, the performance of the system compared with the prior art is as follows: Indicator Prior art The system Phase sign confusion rate 15% 0% Polarization - phase crosstalk coefficient -25 dB -45 dB Bit error rate 8.5% 1.2%

Claims

1. An electromagnetic wave phase-polarization decoupling control system, characterized in that, The application relates to a quantum communication receiver and a laser radar. The application comprises: A phase expression uniformity module configured to convert the phase of an input optical signal or electromagnetic wave into a standard form e^(i(kx-omega*t)), the module comprising: A phase detector for identifying a non-standard phase form (such as e^(i(omega*t-kx))); A phase converter for converting the non-standard phase into e^(i(kx-omega*t)) by superimposing a pi phase; A calibration unit for compensating for phase drift in real time based on temperature / path monitoring; A Hilbert space tensor product control hardware configured to realize independent control of a polarization state and a phase state through a tensor product operation |psi>=[polarization state]ot[phase state], the hardware comprising: A polarization liquid crystal array for independently adjusting a polarization angle (phi=0 / theta / -theta) by regulating the arrangement of liquid crystal molecules through voltage; A phase modulator for independently adjusting a phase parameter (kx or omega*t) through an acousto-optic effect; 2. The system of claim 1, wherein, A tensor product operation unit for coupling the polarization state and the phase state and cutting off the physical coupling path therebetween.

3. The system of claim 1, wherein, The calibration unit is built-in temperature sensor and piezoelectric ceramic, when temperature change ΔT=1℃, according to material thermal-optical coefficient (such as SiO2 10⁻ 5 / ℃) to calculate path change ΔL, drive piezoelectric ceramic to compensate ΔL to offset phase drift Δφ=k・ΔL.

4. The system of claim 1, wherein, The phase detector adopts a Michelson interferometer structure, determines the phase form by the moving direction of interference fringes, splits the light into a fixed reflection arm and a movable reflection arm through a beam splitter, and identifies the non-standard phase through a photodetector after the light is combined.

5. The system of claim 1, wherein, The polarization liquid crystal array has an 8*8 unit structure, each unit has a size of 100mu*m*100mu*m, the response time is less than 10mu*s under independent voltage regulation, and three-state switching of linear polarization (phi=0), right polarization (phi=theta) and left polarization (phi=-theta) is supported.

6. The system of claim 1, wherein, The tensor product operation unit is a photonic chip integrated structure, realizes the tensor product of the polarization state (H / V / L / R) and the phase state (e^(i(kx-omega*t))) through waveguide cross coupling, the coupling loss is less than 0.5db, and the crosstalk coefficient is less than -45db.

7. The system according to any one of claims 1-6, characterized in that, The phase converter is based on a LiNbO3 phase modulator, introduces a pi phase through a programmable optical delay line, converts e^(i(omega*t-kx)) into e^(i(kx-omega*t)), and the conversion error is less than 0.05rad. When applied to a quantum communication receiver, the error rate of the decoupled signal is less than or equal to 1.2%, and the key distribution rate is increased by 2 times; when applied to a laser radar, the target distance measurement error is less than or equal to plus or minus 1cm.