Bias weak measurement method and system based on push-pull phase modulator

Abstract

The invention provides a bias weak measurement method and system based on a push-pull type phase modulator, and the method comprises the steps: defining an initial state of the system through a pre-selection operation, introducing an initial bias phase through the push-pull type phase modulator for pre-coupling, enabling the system and a to-be-measured parameter to complete weak coupling, and obtaining a weak measurement result. Screening a target final-state optical signal through a post-selection operation; after the post selection is completed, processing the input final-state optical signal through a spectrum dichotomy module, and measuring the output optical signal to obtain a measurement value to be measured; and data processing is carried out on the measured value, a current to-be-measured phase and a corresponding offset phase are solved, an offset phase signal is negated and superposed with an initial offset phase to obtain a feedback phase, and the push-pull phase modulator is controlled by applying voltage to generate a corresponding phase. The technical problems that in existing bias weak measurement, the initial phase regulation and control precision is insufficient, and the closed-loop noise suppression capacity is limited are solved.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and more specifically, to a method and system for measuring bias weakness based on a push-pull phase modulator. Background Technology

[0002] In the field of high-precision measurement, weak measurement technology, as an emerging measurement method, has attracted widespread attention due to its ability to break through the sensitivity limits of traditional measurements. The basic principle of this technology is to introduce weak coupling between the system under test and the probe, thereby converting weak signals into significant changes in observable physical quantities of the probe (such as light intensity, phase, and frequency) through post-selection operations without significantly perturbing the system under test. Leveraging this advantage, weak measurement has been widely applied in cutting-edge fields such as quantum measurement, precision sensing, and optical detection.

[0003] Building upon standard weak measurement, researchers proposed a bias weak measurement scheme. This scheme enhances the response to weak signals by introducing a bias delay into the system and further expands the dynamic range of the measurement by combining it with closed-loop control technology. Although bias weak measurement demonstrates significant advantages in improving measurement sensitivity, existing technologies still face key technical challenges in practical application. First, birefringent crystals are commonly used to achieve initial bias phase modulation, but this method is limited by the physical properties of the crystal itself, resulting in limited modulation accuracy and making it difficult to achieve flexible and controllable adjustment of the initial bias phase. Second, in the closed-loop control process, stepped-wave signal modulation is often used to improve response speed, but this type of modulation is prone to signal overshoot or overflow, introducing significant impulse noise and ultimately affecting the measurement accuracy and stability of the system.

[0004] To address the aforementioned issues, existing research has proposed improved solutions. For example, Chinese Patent Application No. CN202511084012.1 discloses a method and system for compensating for weak measurements in a high-sensitivity range with zero-position calibration. This method acquires four-channel light intensity data under zero-input conditions, corrects the selected state using polarization intensity differences, and further calculates the time delay introduced by channel loss differences. Based on this, a phase modulator is used to introduce a compensating phase during the pre-coupling stage to correct the system's asymmetric loss and ensure the measurement system operates in the high-sensitivity range. However, the dynamic adjustment capability of this scheme during the compensation process still needs improvement, and further refinement is required for precise control of the initial phase and closed-loop noise suppression.

[0005] In summary, achieving high-precision control of the bias phase and effectively suppressing noise generated during closed-loop control remain the core technical bottlenecks in the practical application of current bias measurement technology. Therefore, more optimized solutions are urgently needed to further improve the sensitivity and stability of the measurement system. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for measuring bias weakness based on a push-pull phase modulator.

[0007] According to one aspect of the present invention, a method for measuring bias weakness based on a push-pull phase modulator includes: The bias weak measurement steps are as follows: the initial state of the system is defined through a pre-selection operation, and the initial bias phase is introduced through a push-pull phase modulator. Pre-coupling is performed to connect the system with the parameter to be measured. After completing the weak coupling, the target final state optical signal is selected and filtered through the subsequent operation. Spectral binary detection steps: After the selection is completed, the input final state optical signal is processed by the spectral binary module, and the optical signal output by the spectral binary module is measured to obtain the measurement value containing the measurement. Closed-loop control steps: Process the acquired measured values ​​containing the measurand to calculate the current measurand and its corresponding offset phase. The offset phase signal is inverted and superimposed with the initial offset phase to obtain the feedback phase. Based on the feedback phase, the corresponding phase is generated by applying a voltage to the push-pull phase modulator.

[0008] Preferably, the pre-selection in the bias weak measurement step is as follows: set the angle between the optical axis of the polarizer and the 1 / 2 wave plate and the horizontal direction to 45°, and split the incident light into horizontally polarized light and vertically polarized light of the same intensity.

[0009] Preferably, the pre-coupling in the bias weak measurement step is specifically as follows: an initial bias phase is introduced between the horizontally polarized light and the vertically polarized light using a push-pull phase modulator. .

[0010] Preferably, the post-selection in the bias weak measurement step is as follows: the system to be measured and the parameter to be measured. After completing the weak coupling, set the angle between the coupling result and the optical axis and the horizontal direction to be... 1 / 4 wave plate and polarizer, Choose the angle later.

[0011] Preferably, the spectral bisection detection step includes: performing spectral bisection processing on the output optical signal to obtain the intensity value of the high-frequency component of the signal light. The intensity value of the low-frequency part .

[0012] Preferably, the closed-loop control step includes: processing the signal detected by spectral bisection using a weak measurement method to obtain a normalized amplitude intensity. ; Using normalized amplitude intensity and to be measured Relationship

[0013] In the formula, For spectral width, The center frequency of the initial spectrum, Indicates the offset delay. Choose the angle later.

[0014] Solve for the measured value at this time and the corresponding system offset phase , satisfy:

[0015] The offset phase signal is inverted and superimposed with the initial offset phase to form the feedback phase. The feedback phase is applied to the push-pull phase modulator.

[0016] According to another aspect of the present invention, a bias weak measurement system based on a push-pull phase modulator includes: The bias weak measurement steps are as follows: the initial state of the system is defined through a pre-selection operation, and the initial bias phase is introduced through a push-pull phase modulator. Pre-coupling is performed to connect the system with the parameter to be measured. After completing the weak coupling, the target final state optical signal is selected and filtered through the subsequent operation. Spectral binary detection steps: After the selection is completed, the input final state optical signal is processed by the spectral binary module, and the optical signal output by the spectral binary module is measured to obtain the measurement value containing the measurement. Closed-loop control steps: Process the acquired measured values ​​containing the measurand to calculate the current measurand and its corresponding offset phase. The offset phase signal is inverted and superimposed with the initial offset phase to obtain the feedback phase. Based on the feedback phase, the corresponding phase is generated by applying a voltage to the push-pull phase modulator.

[0017] Preferably, the pre-coupling in the bias weak measurement step is specifically as follows: an initial bias phase is introduced between the horizontally polarized light and the vertically polarized light using a push-pull phase modulator. .

[0018] Preferably, the post-selection in the bias weak measurement step is as follows: the system to be measured and the parameter to be measured. After completing the weak coupling, set the angle between the coupling result and the optical axis and the horizontal direction to be... 1 / 4 wave plate and polarizer, Choose the angle later.

[0019] Preferably, the spectral bisection detection step includes: performing spectral bisection processing on the output optical signal to obtain the intensity value of the high-frequency component of the signal light. The intensity value of the low-frequency part .

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The optical path structure is significantly simplified, and the system is easier to build. This invention uses a push-pull phase modulator to replace the birefringent crystal in the traditional solution, achieving direct modulation of the initial bias phase without relying on precise angle matching of complex optical components. The optical path structure is effectively simplified, the number of components is reduced, and the overall stability and maintainability of the system are significantly improved. At the same time, it is easy to deploy in compact or integrated optical platforms.

[0021] 2. Strong bias phase adjustability enables high-precision bias control. The push-pull structure can achieve continuous, fast, and wide dynamic range phase adjustment through voltage control. Compared with the inherent fixed birefringence of crystals, its bias phase adjustment has high precision, good repeatability, and is easy to calibrate and maintain long-term stability in experimental and engineering applications, which helps to improve the sensitivity and adjustability of bias weak measurement.

[0022] 3. Closed-loop control noise is significantly reduced, improving system measurement performance. The push-pull phase modulator supports a larger phase adjustment, resulting in a smaller step wave amplitude required for closed-loop control, thus effectively reducing the frequency of step wave overflow. Overflow-induced pulse noise is significantly reduced, improving the system's signal-to-noise ratio. The dynamic range and stability of weak closed-loop measurements are enhanced, making it suitable for continuous, long-term, and highly repeatable practical measurement tasks.

[0023] 4. The sensitivity and reliability of weak measurements are comprehensively improved. Through optical path optimization, enhanced phase adjustability, and closed-loop noise suppression, this invention can map the micro-delay or phase change to be measured onto observable measurements with higher gain, while maintaining system operation within the linear high-sensitivity range. Overall measurement accuracy, repeatability, and anti-interference capabilities are all enhanced, enabling weak bias measurements to move from experimental verification to engineering applications.

[0024] 5. By applying an initial bias phase, it simplifies the optical path layout and enables convenient adjustment of the initial bias phase. Simultaneously, it is compatible with closed-loop designs, utilizing the characteristics of a push-pull structure to achieve a larger adjustable phase under the same stepped wave height conditions, effectively mitigating the acceleration stepped wave overflow phenomenon and reducing pulse noise caused by overflow. Attached Figure Description

[0025] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram illustrating the principle of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0027] For ease of understanding, the terms or concepts involved in this application are explained below: (1) Weak measurement: A quantum measurement method that achieves high-sensitivity detection of weak physical quantities through weak coupling between the system and the probe, and has the characteristic of not significantly disturbing the system.

[0028] (2) Pre-selection and post-selection: In weak measurement, pre-selection refers to pre-setting the initial quantum state of the system, while post-selection refers to selecting a specific final state after coupling measurement. The combination of the two can significantly amplify small physical effects.

[0029] (3) Push-pull phase modulator: an electro-optic modulator that achieves high-precision, linearly adjustable phase control by applying opposite voltages to two electrodes and is suitable for optical signal modulation.

[0030] (4) Bias weak measurement: Based on standard weak measurement, an initial bias phase is introduced to improve the response sensitivity to changes in target parameters. It is often used to improve the dynamic range and noise immunity of the measurement system.

[0031] (5) Spectral binary detection: By dividing and analyzing the spectrum of the incident light signal, light intensity information reflecting the change of the measured parameter can be extracted, thereby improving the resolution and processing efficiency of the signal.

[0032] (6) Closed-loop control: A control method that feeds back the system output signal to the input for dynamic adjustment. It is used to maintain stable system operation and suppress interference. It is widely used in automatic control and precision measurement systems.

[0033] (7) Feedback phase: The phase signal generated in the closed-loop control is used to adjust the system input. It achieves dynamic compensation and error correction by superimposing it with the initial bias phase.

[0034] (8) Phase modulation accuracy: refers to the ability and precision of adjusting the phase of the optical signal in the system, which directly affects the measurement sensitivity and system stability.

[0035] Example 1: A bias-based weak measurement method based on a push-pull phase modulator is disclosed. This method achieves initial bias phase application and closed-loop compensation control in bias-based weak measurement using a push-pull phase modulator. First, a polarizer and a half-wave plate are used for pre-selection to prepare the input light into horizontal and vertical polarization states of equal intensity. Then, an adjustable bias phase is introduced between the two orthogonal polarizations as pre-coupling, enabling weak coupling between the system and the parameter to be measured. After the evolved state is projected by a post-selection module, the output light enters a spectral bisection detection module. The normalized light intensity difference is calculated by comparing the intensities of high-frequency and low-frequency signals. Based on the linear relationship between the light intensity difference, the time delay to be measured, and the system offset phase, the current time delay estimate and the corresponding offset phase are calculated. The offset phase is inverted and superimposed with the initial bias phase to generate a feedback phase. The push-pull phase modulator compensates for the system phase offset in real time, keeping the measurement within the linear high-sensitivity range and effectively suppressing noise caused by stepped wave overflow, thus improving the accuracy and stability of the weak measurement.

[0036] The following is combined with Figure 1 and Figure 2 The following is a detailed explanation of each step of the method: The bias weak measurement steps are as follows: the initial state of the system is defined through a pre-selection operation, and the initial bias phase is introduced through a push-pull phase modulator. Pre-coupling is performed to connect the system with the parameter to be measured. After completing the weak coupling, select the final state optical signal of the target through the subsequent selection operation.

[0037] Specifically, the pre-selection in the bias weak measurement step is as follows: set the angle between the optical axis of the polarizer and the 1 / 2 wave plate and the horizontal direction to 45°, and split the incident light into horizontally polarized light and vertically polarized light of the same intensity.

[0038] Specifically, the pre-coupling in the bias weak measurement step is as follows: an initial bias phase is introduced between the horizontally polarized light and the vertically polarized light using a push-pull phase modulator. .

[0039] Specifically, the post-selection in the bias weak measurement step is as follows: the system to be measured and the parameter to be measured. After completing the weak coupling, set the angle between the coupling result and the optical axis and the horizontal direction to be... 1 / 4 wave plate and polarizer, Choose the angle later.

[0040] Spectral binary detection steps: After the selection is completed, the input final-state optical signal is processed by the spectral binary module, and the optical signal output by the spectral binary module is measured to obtain the measurement value containing the value to be measured.

[0041] It should be noted that the spectral bisection detection step includes: performing spectral bisection processing on the output optical signal to obtain the intensity value of the high-frequency part of the signal light. The intensity value of the low-frequency part .

[0042] Closed-loop control steps: Process the acquired measured values ​​containing the measurand to calculate the current measurand and its corresponding offset phase. The offset phase signal is inverted and superimposed with the initial offset phase to obtain the feedback phase. Based on the feedback phase, the corresponding phase is generated by applying a voltage to the push-pull phase modulator.

[0043] It should be noted that the closed-loop control steps specifically include: The signal detected by spectral bisection is processed using a weak measurement method to obtain the normalized amplitude intensity. .

[0044] Using normalized amplitude intensity and to be measured The relationship between them:

[0045] In the formula, For spectral width, The center frequency of the initial spectrum, Indicates the offset delay. Choose the angle later.

[0046] Solve for the measured value at this time and the corresponding system offset phase , satisfy:

[0047] The offset phase signal is inverted and superimposed with the initial offset phase to form the feedback phase. The feedback phase is applied to the push-pull phase modulator.

[0048] The present invention also provides a bias weak measurement system based on a push-pull phase modulator. The bias weak measurement system based on a push-pull phase modulator can be implemented by executing the process steps of the bias weak measurement method based on a push-pull phase modulator. That is, those skilled in the art can understand the bias weak measurement method based on a push-pull phase modulator as a preferred embodiment of the bias weak measurement system based on a push-pull phase modulator.

[0049] Example 2: The following describes the estimation of time delay parameters using the offset weak measurement method and system based on a push-pull phase modulator provided by this invention: The offset weak measurement technique converts the measured micro-delay into a system phase offset, amplifies it, and achieves real-time measurement and phase offset compensation through closed-loop control. The push-pull phase modulator simplifies the optical path layout, enables rapid and accurate adjustment of the initial offset phase, reduces pulse noise caused by overflow, and improves the measurement accuracy of the offset weak measurement system.

[0050] The mathematical model of the system is established as follows: pointer initial state is , representing the spectral state of light. Let the wave function represent the spectral distribution of the pointer light. The center frequency of the initial spectrum, For spectral width, Representing angular frequency:

[0051] During the pre-selection process, the pointer light is modulated as follows:

[0052] That is, the pre-selection state is ,in and These represent the horizontal and vertical polarization states, respectively. Indicates the bias delay and initial bias phase. satisfy: The composite quantum state of the system and probe after pre-selection can be represented as follows: In weak interactions, the interaction between the system and the pointer can be represented by a unitary operator.

[0053] in, This corresponds to the Stokes polarization operator. This represents the actual measured time delay.

[0054] In the post-selection process, the evolved quantum state is projected onto a pre-defined post-selection state that is approximately orthogonal to the pre-selection state.

[0055] in It is the post-selection angle, which is related to the offset phase. satisfy The relationship. Weak values ​​can be calculated:

[0056] Therefore, when the current selection and the subsequent selection are nearly perpendicular, the calculated weak value of the bias weak measurement will be very large. After the subsequent selection, the final state of the pointer state can be represented as...

[0057] Accordingly, its spectral distribution can be calculated using the following formula.

[0058] A wavelength division multiplexer (WDM) is used, whose operating frequency covers the bandwidth of the light source and whose center frequency is equal to the center frequency of the light source. The WDM is used to process the acquired signal light at its center frequency. Using the dividing point as the reference point, the high-frequency band is reflected and the low-frequency band is transmitted. Two photodetectors are used to receive the reflected and transmitted light respectively to obtain two light intensities. , Using light intensity contrast as the observation index, we obtained

[0059] Delay and system offset phase The following relationship exists:

[0060] At that time, Yan At very low speeds, light intensity contrast and latency and light intensity contrast and system offset phase A linear mathematical relationship can be approximated as existing: , , These are coefficient values, which can be obtained through specific experimental calibration. The time delay to be measured is easily obtained. and system offset phase .

[0061] For the calculated offset phase Perform an inversion operation and compare it with the initial bias phase. The result is obtained by superposition. The feedback phase is applied to the push-pull phase modulator to cancel the phase offset introduced by the time delay of the test in the previous measurement cycle, so as to keep the system response within the high sensitivity linear range.

[0062] The maximum adjustment range of the push-pull phase modulator is nearly doubled compared to that of the traditional phase modulator, which reduces the stepped wave overflow frequency by 50% to 70%, reduces the pulse noise power caused by overflow by more than 50%, and improves the system signal-to-noise ratio by 3 to 5 dB.

[0063] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0064] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for measuring bias weakness based on a push-pull phase modulator, characterized in that, include: The bias weak measurement steps are as follows: the initial state of the system is defined through a pre-selection operation, and the initial bias phase is introduced through a push-pull phase modulator. Pre-coupling is performed to connect the system with the parameter to be measured. After completing the weak coupling, the target final state optical signal is selected and filtered through the subsequent operation. Spectral binary detection steps: After the selection is completed, the input final state optical signal is processed by the spectral binary module, and the optical signal output by the spectral binary module is measured to obtain the measurement value containing the measurement. Closed-loop control steps: Process the acquired measured values ​​containing the measurand to calculate the current measurand and its corresponding offset phase. The offset phase signal is inverted and superimposed with the initial offset phase to obtain the feedback phase. Based on the feedback phase, the corresponding phase is generated by applying a voltage to the push-pull phase modulator.

2. The method according to claim 1, characterized in that, The specific pre-selection step in the bias weak measurement process is as follows: By setting the angle between the optical axis of the polarizer and the half-wave plate and the horizontal direction to 45°, the incident light is split into horizontally polarized light and vertically polarized light of equal intensity.

3. The method according to claim 1, characterized in that, The pre-coupling in the bias weak measurement step is as follows: An initial bias phase is introduced between horizontally polarized light and vertically polarized light using a push-pull phase modulator. .

4. The method according to claim 1, characterized in that, The specific post-selection in the bias weak measurement step is as follows: System to be tested and parameters to be tested After completing the weak coupling, set the angle between the coupling result and the optical axis and the horizontal direction to be... 1 / 4 wave plate and polarizer, Choose the angle later.

5. The method according to claim 1, characterized in that, The spectral dichotomy detection step includes: By performing spectral bisection on the output optical signal, the intensity value of the high-frequency component of the signal light is obtained. The intensity value of the low-frequency part is .

6. The method according to claim 1, characterized in that, The closed-loop control steps include: The signal detected by spectral bisection is processed using a weak measurement method to obtain the normalized amplitude intensity. ; Using normalized amplitude intensity and to be measured The relationship between them: In the formula, For spectral width, The center frequency of the initial spectrum, Indicates the offset delay. For later selection angle; Solve for the measured value at this time and the corresponding system offset phase , satisfy: The offset phase signal is inverted and superimposed with the initial offset phase to form the feedback phase. The feedback phase is applied to the push-pull phase modulator.

7. A bias weak measurement system based on a push-pull phase modulator, characterized in that, include: The bias weak measurement module defines the system's initial state through a pre-selection operation and introduces the initial bias phase through a push-pull phase modulator. Pre-coupling is performed to connect the system with the parameter to be measured. After completing the weak coupling, the target final state optical signal is selected and filtered through the subsequent operation. Spectral Dividing Detection Module: After the selection is completed, the input final-state optical signal is processed by the spectral dividing module, and the optical signal output by the spectral dividing module is measured to obtain the measurement value containing the measurement. Closed-loop control module: Processes the acquired measurement values ​​containing the measurand to calculate the current measurand and its corresponding offset phase. The offset phase signal is inverted and superimposed with the initial offset phase to obtain the feedback phase. Based on the feedback phase, the corresponding phase is generated by applying a voltage to the push-pull phase modulator.

8. The system according to claim 1, characterized in that, The pre-coupling in the bias weak measurement module is specifically as follows: An initial bias phase is introduced between horizontally polarized light and vertically polarized light using a push-pull phase modulator. .

9. The system according to claim 1, characterized in that, The specific post-selection in the bias weak measurement module is as follows: System to be tested and parameters to be tested After completing the weak coupling, set the angle between the coupling result and the optical axis and the horizontal direction to be... 1 / 4 wave plate and polarizer, Choose the angle later.

10. The system according to claim 1, characterized in that, The spectral binary detection module includes: By performing spectral bisection on the output optical signal, the intensity value of the high-frequency component of the signal light is obtained. The intensity value of the low-frequency part is .

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