Quantum weak measurement system and method based on polarization maintaining coupler splitting

Abstract

A quantum weak measurement system and method based on polarization maintaining coupler light splitting, the system comprises a SLD light source, an optical isolator, a polarization maintaining coupler, a solution pool to be measured, a standard solution pool, a mirror and a spectrometer; the SLD light source emits a laser beam, the laser beam passes through the optical isolator and is divided into two light beams by the polarization maintaining coupler for pre-selection. The light beams of the measurement arm and the reference arm pass through the solution pool to be measured and the standard solution pool respectively, are reflected by the first and second mirrors, pass through the solution pool to be measured and the standard solution pool again to introduce a phase difference, and finally return to the polarization maintaining coupler for post-selection. The coupled outgoing light is received by the spectrometer and subjected to center wavelength analysis. The present application can reduce the interference of the environment (such as stray light, particle scattering, etc.) on the system, and the detection is more accurate and sensitive. By using the polarization maintaining coupler, the input signal is separated or coupled at a very high ratio, so that the light intensity projected to the post-selection state tends to zero to realize the orthogonality of the pre-selection state and the post-selection state. Compared with the polarization perpendicular method, the present system has a higher extinction ratio and a more significant weak value amplification effect.

Description

Technical Field

[0001] This invention relates to the field of biomedical detection based on optical phase, and more particularly to a quantum weak measurement system and method based on polarization-maintaining coupler spectroscopy. Background Technology

[0002] With economic development and technological progress, people's living standards have improved significantly, leading to increased attention on the detection of trace biomolecules (such as human papillomavirus, hepatitis virus, and staphylococcus). High-precision detection of these substances is not only crucial for clinical medicine but also plays a significant role in disease prevention and human health diagnosis. However, most existing physiological solution detection instruments are specific and specialized, unable to detect concentrations in other types of solutions. Furthermore, ordinary biological detectors struggle to achieve high sensitivity for physiological solutions with low detection limits. Therefore, designing a universal, high-precision, and high-sensitivity biological solution concentration detection device holds great promise. Summary of the Invention

[0003] To overcome the above problems, the present invention provides a quantum weak measurement system and method based on polarization-maintaining coupler spectroscopy.

[0004] The first aspect of the present invention provides a quantum weak measurement system based on polarization-maintaining coupler spectroscopy, comprising an SLD light source (1), an optical isolator (2), a polarization-maintaining coupler (3), a solution cell to be measured (4), a standard solution cell (5), a first mirror (6), a second mirror (7), and a spectrometer (8); wherein the polarization-maintaining coupler (3) has a first port, a second port, a third port, and a fourth port;

[0005] The laser beam emitted by the SLD light source (1) enters the first port of the polarization-maintaining coupler (3) after passing through the optical isolator (2). The polarization-maintaining coupler (3) performs pre-selection and splits the incident laser beam into two beams, which are output from the second port and the third port of the polarization-maintaining coupler (3) respectively. The beam output from the second port is used as the reference arm beam, and the beam output from the third port is used as the measurement arm beam.

[0006] The measuring arm beam and the reference arm beam exit through the test solution cell (4) and the standard solution cell (5) respectively, generating a phase difference; the measuring arm beam exits after passing through the test solution cell (4), and the exited light is reflected by the first reflecting mirror (6) and returns to the third port of the polarization-maintaining coupler (3) after passing through the test solution cell (4); the reference arm beam exits after passing through the standard solution cell (5), and the exited light is reflected by the second reflecting mirror (7) and returns to the second port of the polarization-maintaining coupler (3) after passing through the standard solution cell (5); that is, the measuring arm beam and the reference arm beam exit through the test solution cell (4) and the standard solution cell (5) respectively, generating a phase difference; After passing through the liquid pool (5), the light is reflected by the first reflector (6) and the second reflector (7), and then returns to the polarization-maintaining coupler (3) after passing through the test solution pool (4) and the standard solution pool (5) for post-selection. At the same time, the measurement arm beam and the reference arm beam returning to the polarization-maintaining coupler (3) are coupled to the fourth port. The light emitted from the fourth port is received by the spectrometer (8) and the center wavelength is analyzed. The center wavelength shift of the measured spectrum is analyzed, and the refractive index difference of the solution is solved in reverse. Then, the refractive index of the solution in the measurement arm is obtained. Based on the relationship between the solution concentration and the refractive index, the solution concentration is detected.

[0007] Furthermore, the laser beam emitted by the SLD light source (1) is a broadband light with a center wavelength of 830nm and a bandwidth of ≥20nm.

[0008] A second aspect of the present invention provides a measurement method for a quantum weak measurement system based on polarization-maintaining coupler spectroscopy, comprising the following steps:

[0009] Step 1, define the path state through the first port, the second port, and the fourth port as follows: The path state through the first port, the third port, and the fourth port is The splitting ratios of the two paths, from port 1 to port 2 and from port 1 to port 3, are a. 2 :b 2 The splitting ratio of the two paths from the second port to the fourth port and from the third port to the fourth port is b. 2 :a 2 Meanwhile, a 2 +b 2 ≈1;

[0010] Step 2, passing the beam through the first port as a pre-selection, the system's pre-selection state can then be represented as:

[0011]

[0012] System operators:

[0013]

[0014] The phase difference introduced between the system reference arm and the measuring arm is:

[0015]

[0016] Where λ0 is the center wavelength of the laser, l is the longitudinal length of the liquid cell, Δn is the refractive index difference of the solution on the reference arm and the measuring arm, and x is the unavoidable initial phase difference of the system.

[0017] Step 3, the beam passes through the fourth port for post-selection, and the post-selection state of the system is:

[0018]

[0019] Based on the definition of weak values, the weak values ​​are obtained:

[0020]

[0021] By using weak measurement theory and substituting the system phase difference, the shift in the spectral center wavelength is obtained:

[0022]

[0023] Where Δλ is the laser bandwidth.

[0024] The beneficial effects of this invention are:

[0025] 1. Since the propagation of light in the system is almost entirely completed in the optical fiber, the interference of the environment (such as stray light, particle scattering, etc.) on the system can be reduced, and the small phase change detection method realized by the present invention has high sensitivity.

[0026] 2. For systems with high splitting ratios, the orthogonality of the front and rear selected states can also be achieved by making the light intensity projection approach zero. This system uses polarization-maintaining fiber to stabilize the polarization information of the beam, and can also disregard polarization and analyze the front and rear selected states based solely on the splitting ratio of the fiber coupler.

[0027] 3. Fiber optic sensing system designs can be integrated, and efficient cabling can improve space utilization. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the present invention.

[0029] Figure 2 This is a schematic diagram of the bias-maintaining coupler in this invention.

[0030] Figure 3 This is a schematic diagram of the working range of the system in this invention. The detection of optical phase is most sensitive at the bi-peak position.

[0031] Explanation of reference numerals in the attached diagram: 1. SLD light source; 2. Isolator; 3. Polarization maintaining coupler; 4. Test solution cell; 5. Standard solution cell; 6. First reflecting mirror; 7. Second reflecting mirror; 8. Spectrometer. Detailed Implementation

[0032] The technical solution of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] Example 1

[0036] See attached document Figure 1-3 A quantum weak measurement system based on polarization-maintaining coupler spectroscopy is proposed. According to the weak measurement principle, by selecting appropriate pre- and post-selection states within the weak measurement system, the output pointer state contains a weak value with an amplification factor. The measurand can be obtained by relating the weak value to the measurand. The system includes an SLD light source 1, an optical isolator 2, a polarization-maintaining coupler 3, a solution cell for the measurand 4, a standard solution cell 5, a first mirror 6, a second mirror 7, and a spectrometer 8. The polarization-maintaining coupler 3 has a first port, a second port, a third port, and a fourth port.

[0037] The laser beam emitted by the SLD light source 1 enters the first port of the polarization-maintaining coupler 3 after passing through the optical isolator 2. The polarization-maintaining coupler 3 performs pre-selection and splits the incident laser beam into two beams, which are output from the second port and the third port of the polarization-maintaining coupler 3, respectively. The beam output from the second port is called the reference arm beam, and the beam output from the third port is called the measurement arm beam.

[0038] The measuring arm beam and the reference arm beam exit through the test solution cell 4 and the standard solution cell 5, respectively, generating a phase difference. After passing through the test solution cell 4, the measuring arm beam exits and is reflected by the first reflecting mirror 6, returning to the third port of the polarization-maintaining coupler 3. The reference arm beam exits through the standard solution cell 5 and is reflected by the second reflecting mirror 7, returning to the second port of the polarization-maintaining coupler 3. That is, after passing through the test solution cell 4 and the standard solution cell 5, the measuring arm beam and the reference arm beam are reflected by the first reflecting mirror 6 and the second reflecting mirror 7, respectively, and then return to the polarization-maintaining coupler 3 for post-selection. At the same time, the measuring arm beam and the reference arm beam returning to the polarization-maintaining coupler 3 are coupled to the fourth port. The light emitted from the fourth port is received by the spectrometer 8 and the center wavelength is analyzed. The center wavelength shift of the measured spectrum is analyzed, and the refractive index difference of the solution is calculated in reverse to obtain the refractive index of the measuring arm solution. Based on the relationship between solution concentration and refractive index, the solution concentration is detected.

[0039] In the embodiments of the present invention, the laser beam emitted by the SLD light source 1 is a broadband light with a center wavelength of 830nm and a bandwidth of ≥20nm. The laser beam passing through the optical isolator 2 can effectively reduce the influence of reflected light in the polarization maintaining coupler 3 on the light source.

[0040] In embodiments of the present invention, the quantum weak measurement system based on polarization-maintaining coupler spectroscopy is in a dual-path reflection state; the polarization-maintaining coupler is a high-splitting-ratio polarization-maintaining coupler. The preparation of the selected states before and after the measurement is accomplished through the polarization-maintaining coupler. The function of this system is to perform highly sensitive detection of the concentration of the solution within the measurement arm.

[0041] Example 2

[0042] The measurement method for a quantum weak measurement system based on polarization-maintaining coupler spectroscopy includes the following steps:

[0043] Step 1, define the path state through the first port, the second port, and the fourth port as follows: The path state through the first port, the third port, and the fourth port is The splitting ratios of the two paths, from port 1 to port 2 and from port 1 to port 3, are a. 2 :b 2The splitting ratio of the two paths from the second port to the fourth port and from the third port to the fourth port is b. 2 :a 2 Meanwhile, a 2 +b 2 ≈1;

[0044] Step 2, passing the beam through the first port as a pre-selection, the system's pre-selection state can then be represented as:

[0045]

[0046] System operators:

[0047]

[0048] The phase difference introduced between the system reference arm and the measuring arm is:

[0049]

[0050] Where λ0 is the center wavelength of the laser, l is the longitudinal length of the liquid cell, Δn is the refractive index difference of the solution on the reference arm and the measuring arm, and x is the unavoidable initial phase difference of the system.

[0051] Step 3, the beam passes through the fourth port for post-selection, and the post-selection state of the system is:

[0052]

[0053] Based on the definition of weak values, the weak values ​​are obtained:

[0054]

[0055] By using weak measurement theory and substituting the system phase difference, the shift in the spectral center wavelength is obtained:

[0056]

[0057] Where Δλ is the laser bandwidth.

[0058] Therefore, by measuring the shift in the center wavelength of the spectrum through spectral analysis, the refractive index difference of the solution can be calculated in reverse, and the refractive index of the solution in the measuring arm can be obtained. Based on the relationship between solution concentration and refractive index, the solution concentration can be detected with high precision.

[0059] This invention designs a quantum weak measurement system based on polarization-maintaining coupler spectroscopy. According to the principle of weak value amplification, a phase difference is introduced between the two arms after the polarization-maintaining coupler spectroscopy, causing a slight perturbation to the system. Since the phase delay is caused by the concentration change, the relationship between the shift of the center wavelength of the emitted spectrum and the phase difference can be used to detect the concentration of biological solutions.

[0060] Weak value is defined as Where |ψ i > and |ψ f > represents the before and after selected states of the system, and A is the observable operator of the system evolution. In previous weak measurement work, the before and after selected states were made to tend towards orthogonality by adjusting two polarizers, thereby amplifying the weak value, which can be the optical path correlation quantity mentioned above. This is a method that utilizes polarization information for orthogonality. This invention proposes to achieve orthogonality of the before and after selected states by making the light intensity projection tend to zero. By using a high splitting ratio fiber polarization-maintaining coupler, the light intensity projected onto the after selected state tends to zero, achieving "orthogonality" of the before and after selected states under the optical amplitude degree of freedom, obtaining a larger weak value, and thus realizing the application of weak measurement in the amplified measurement of the phase difference between two paths.

[0061] This invention constructs a dual-optical-path reflective weak measurement system. Quantum weak measurement is a high-precision signal detection technology that has emerged in recent years and has received widespread attention and application due to its unique advantages in signal amplification. Compared with traditional biological solution detection techniques, quantum weak measurement has high sensitivity, wide applicability, and does not consume raw materials. Compared with linear common-path systems, the dual-optical-path weak measurement system can increase the degree of freedom in optical path adjustment and facilitate coupling. The fiber optic sensing-based design can reduce the interference of the environment (such as stray light, particle scattering, etc.) on the system compared with ordinary weak measurement systems, resulting in more accurate and sensitive detection. By using a polarization-maintaining coupler, the input signal is separated or coupled at a very high ratio, so that the light intensity projected onto the post-selected state approaches zero, achieving orthogonality between the pre- and post-selected states. Compared with the method of perpendicular polarization, this system has a higher extinction ratio and a more significant weak value amplification effect.

[0062] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A quantum weak measurement system based on polarization-maintaining coupler spectral splitting, characterized in that: The system includes an SLD light source (1), an optical isolator (2), a polarization-maintaining coupler (3), a solution cell to be tested (4), a standard solution cell (5), a first reflector (6), a second reflector (7), and a spectrometer (8). The polarization-maintaining coupler (3) has a first port, a second port, a third port, and a fourth port. The polarization-maintaining coupler (3) is a high-split-ratio fiber polarization-maintaining coupler. It achieves orthogonality between the front and rear selected states by making the light intensity projection approach zero. The high-split-ratio polarization-maintaining coupler (3) makes the light intensity projected onto the rear selected state approach zero, thereby achieving "orthogonality" between the front and rear selected states under the degree of freedom of light amplitude, thus realizing weak measurement. The laser beam emitted by the SLD light source (1) enters the first port of the polarization-maintaining coupler (3) after passing through the optical isolator (2). The polarization-maintaining coupler (3) performs pre-selection and splits the incident laser beam into two beams, which are output from the second port and the third port of the polarization-maintaining coupler (3) respectively. The beam output from the second port is used as the reference arm beam, and the beam output from the third port is used as the measurement arm beam. The measuring arm beam and the reference arm beam exit through the test solution cell (4) and the standard solution cell (5) respectively, generating a phase difference; the measuring arm beam exits after passing through the test solution cell (4), and the exited light is reflected by the first reflector (6) and returns to the third port of the polarization-maintaining coupler (3) after passing through the test solution cell (4); the reference arm beam exits after passing through the standard solution cell (5), and the exited light is reflected by the second reflector (7) and returns to the second port of the polarization-maintaining coupler (3) after passing through the standard solution cell (5); that is, the measuring arm beam and the reference arm beam exit through the test solution cell (4) and the standard solution cell (5) respectively, generating a phase difference; the measuring arm beam exits after passing through the test solution cell (4) and the standard solution cell (5), generating a phase difference; the measuring arm beam exits after passing through the test solution cell (4) and the standard solution cell (5), generating a phase difference. After passing through the liquid pool (5), the light is reflected by the first reflector (6) and the second reflector (7), and then returns to the polarization-maintaining coupler (3) after passing through the test solution pool (4) and the standard solution pool (5) for post-selection. At the same time, the measurement arm beam and the reference arm beam returning to the polarization-maintaining coupler (3) are coupled to the fourth port. The light emitted from the fourth port is received by the spectrometer (8) and the center wavelength is analyzed. The center wavelength shift of the measured spectrum is analyzed, and the refractive index difference of the solution is solved in reverse. Then, the refractive index of the measurement arm solution is obtained. Based on the relationship between the solution concentration and the refractive index, the solution concentration is detected.

2. The quantum weak measurement system based on polarization-maintaining coupler spectroscopy as described in claim 1, characterized in that: The laser beam emitted by the SLD light source (1) is a broadband light with a center wavelength of 830nm and a bandwidth of ≥20nm.

3. A measurement method based on the quantum weak measurement system using a polarization-maintaining coupler as described in claim 1 or 2, characterized in that, Includes the following steps: Step 1, define the path state through the first port, the second port, and the fourth port as follows: The path state through the first port, the third port, and the fourth port is The splitting ratios of the two paths, from port 1 to port 2 and from port 1 to port 3, are: The splitting ratios of the two paths from the second port to the fourth port and from the third port to the fourth port are: ;at the same time ; The splitting ratio is high, and the orthogonality of the preceding and following selection states is achieved by making the light intensity projection approach zero; Step 2, passing the beam through the first port as a pre-selection, then the system's pre-selection state is represented as: （1） System operators: （2） The phase difference introduced between the system reference arm and the measuring arm is: （3） in The center wavelength of the laser. Let be the longitudinal length of the liquid pool. The difference in refractive index of the solutions on the reference arm and the measuring arm, This is the unavoidable initial phase difference of the system; Step 3, the beam passes through the fourth port for post-selection, and the post-selection state of the system is: （4） Based on the definition of weak values, the weak values ​​are obtained: （5） By using weak measurement theory and substituting the system phase difference, the shift in the spectral center wavelength is obtained: （6） in This refers to the laser bandwidth.

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