Alkali metal atomic polarizability stability control method based on data fusion

Abstract

An alkali metal atomic polarizability stability control method based on data fusion is beneficial to bringing about the advantages of interference resistance and strong robustness by additionally using a photoelectric detector on the basis of an original optical pumping system, and is characterized by comprising the following steps: step 1, arranging an NPBS on an optical path of a pumping light input side of a glass atomic gas chamber in an optical pumping device, the reflection side of the NPBS is connected with the PD1, the transmission side of the NPBS is connected with the PD2 through the glass atomic gas chamber, the PD1 and the PD2 are respectively connected with the upper computer through the data acquisition module, and the upper computer is connected with the LCVR; 2, reflected light information is collected through the PD1, and transmitted light information is collected through the PD2; 3, constructing a system transfer equation containing a random item to carry out different spatial data fusion; step 4, fusing data at different time; and step 5, adjusting the control voltage of the LCVR through the upper computer according to the error information of the pumping rate sensed by the alkali metal atoms, stabilizing the atomic pumping rate in real time, and further stabilizing the polarizability.

Description

Technical Field

[0001] The invention relates to the field of quantum measurement technology, in particular to a method for stabilizing polarizability of alkali metal atoms based on data fusion. Background Art

[0002] With the development of new theories and technologies in the quantum field, various scientific instruments based on quantum effects are constantly and significantly breaking through the measurement limits of traditional instruments. As a new generation of precision measurement instruments, quantum instruments based on the optical pumping process have incomparable advantages in performance indicators compared to traditional instruments and are an important development direction for high-precision measurement in the future.

[0003] The stability of atomic polarizability is a prerequisite for the atomic spin measurement device to achieve precise measurement. The fluctuation of atomic polarizability is greatly affected by light power and is an important factor affecting polarizability fluctuation. When the traditional power stabilization scheme based on the spectrometer is used for a long time, it is impossible to distinguish whether it is the laser fluctuation or the temperature of the spectrometer, resulting in the change of the splitting ratio. The scheme of the present invention utilizes the original device of the optical pumping system and uses an additional photodetector, which has the advantages of strong anti-interference and robustness. Summary of the invention

[0004] Aiming at the need for long-term anti-interference and stable control of the polarizability of alkali metal atoms, the present invention proposes a stable control method of the polarizability of alkali metal atoms based on data fusion. By using an additional photodetector on the basis of the original optical pumping system, it is beneficial to bring the advantages of strong anti-interference and robustness.

[0005] The technical solution of the present invention is as follows:

[0006] A method for stabilizing polarizability of alkali metal atoms based on data fusion, characterized in that it comprises the following steps:

[0007] Step 1, a depolarizing beam splitter prism NPBS is arranged on the optical path of the pump light input side of the glass atom gas chamber in the optical pumping device, the reflection side of the depolarizing beam splitter prism NPBS is connected to the first photodetector PD1, the transmission side of the depolarizing beam splitter prism NPBS is connected to the second photodetector PD2 through the glass atom gas chamber, PD1 and PD2 are respectively connected to the host computer through the data acquisition module, and the host computer is connected to the liquid crystal variable phase retarder LCVR:

[0008] Step 2, using a data acquisition module to collect reflected light information from the NPBS through PD1, and to collect transmitted light information from the glass atomic gas cell through PD2;

[0009] Step 3, construct a system transfer equation containing random terms, and use a host computer to perform different spatial data fusion on the reflected light information and the transmitted light information. The system transfer equation containing random terms is as follows:

[0010] X k =H k x k +G k υ k ,

[0011]

[0012] x k =[P pd1 , P pd2 ,ΔI] T ,

[0013] Where X k is the pump rate vector, H k is the first transfer matrix, x k is the optical power vector, G k is the second transfer matrix, υ k is a random noise vector, k is the time instant, is the optical power information after data fusion at different optical detection points at time k, C k is the matrix used to estimate the fusion information at time k, P pd1 is the optical power information detected by PD1, P pd2 is the optical power information detected by PD2, ΔI is the pump rate loss caused by atomic absorption, and T is the transposition operator;

[0014] Step 4: Fusion of data at different times is performed using the following equation:

[0015]

[0016] in is the pump rate or corresponding optical power obtained at time k, is the pump rate or corresponding optical power estimated at time k-1, A k It is the matrix used to estimate the fusion information at time k, i.e., the data fusion factor;

[0017] Step 5, using the error information of the pumping rate felt by the alkali metal atoms, the control voltage of the LCVR is adjusted through the PID module of the host computer to achieve the purpose of stabilizing the atomic pumping rate in real time when the optical pumping system is operating, and then stabilizing the polarizability.

[0018] Step 5 includes the following formula:

[0019]

[0020]

[0021] where e k is the error at time k, R p is the reference value of the pumping rate felt by the atoms, u k is the control voltage applied to the LCVR at time k, K P is the proportional coefficient in PID, K I is the integral coefficient in PID, i is the serial number, e is i is the i-th error value, K D is the differential coefficient in PID, e k-1 is the error at time k-1, u k-1 is the control voltage applied to the LCVR at time k-1.

[0022] Step 3 includes the following formula:

[0023]

[0024] C k =[1-κ,κ,0],

[0025] Where α is the conversion coefficient between optical power and pump rate, β is the transmittance of the glass cell, β is defined as the ratio of the outgoing light power to the incident light power, γ is the splitting ratio of the splitter, and γ is defined as the ratio of the main light power to the branch light power.

[0026] The technical effects of the present invention are as follows: the present invention provides a stable control method of alkali metal atomic polarizability based on data fusion, which can bring the advantages of strong anti-interference and robustness.

[0027] The advantages of the present invention compared with the prior art are:

[0028] The present invention constructs a system transfer model, and then obtains the pumping rate felt by the alkali metal atoms in real time through a real-time recursive relationship, and then adjusts the control voltage of the LCVR, which can achieve long-term stability of the polarizability of the alkali metal atoms and has the advantages of small size and online non-destructive measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of an optical pumping device involved in implementing a method for stabilizing the polarizability of alkali metal atoms based on data fusion of the present invention. Figure 1It includes a laser (such as a distributed feedback laser, Distributed Feedback Laser, DFB), a polarizing beamsplitter prism PBS (Polarizing Beamsplitter), a liquid crystal variable phase retarder LCVR (Liquid Crystal Variable Retarder), a depolarizing beamsplitter prism NPBS (Non-polarizing Beamsplitter), a first photodetector PD1 (Photoelectric Detector), a second photodetector PD2, a three-axis magnetic field coil located between NPBS and PD2, and a glass atomic gas chamber located in the three-axis magnetic field coil, PD1 is connected to a data acquisition module, and the data acquisition module is connected to LCVR through a host computer (the host computer has a built-in PID module, PID, Proportional Integral Derivative, proportional, integral, differential).

[0030] Figure 2 The present invention is a schematic diagram of an atomic polarizability estimation process based on data fusion involved in implementing a method for stabilizing alkali metal atomic polarizability based on data fusion of the present invention. Figure 2 The method comprises the steps of: step 1, the data acquisition module acquires the reflected light information from the NPBS through PD1, and acquires the transmitted light information from the glass atom gas chamber through PD2; step 2, the host computer performs different spatial data fusion on the reflected light information and the transmitted light information, and X k =H k x k +G k υ k , X k is the pump rate vector, H k is the first transfer matrix, x k is the optical power vector, x k =[P pd1 , P pd2 ,ΔI] T , P pd1 is the optical power information detected by PD1, P pd2 is the optical power information detected by PD2, ΔI is the pump rate loss caused by atomic absorption, T is the transposition operator, G k is the second transfer matrix, υ k is a random noise vector, k is the time instant, is the optical power information after data fusion at different optical detection points at time k, C k is a matrix used to estimate the fusion information at time k; Step 3, the host computer fuses the reflected light information and the transmitted light information at different times, is the pump rate or corresponding optical power obtained at time k, is the pump rate or corresponding optical power estimated at time k-1, A k It is the matrix used to estimate the fusion information at time k, namely the data fusion factor.

[0031] Figure 3 It is a flow chart of a method for stabilizing polarizability of alkali metal atoms based on data fusion according to the present invention. Figure 3 The process includes step 1, the data acquisition module collects the reflected light information from the NPBS through PD1, and collects the transmitted light information from the glass atomic gas chamber through PD2; step 2, calculates Step 3, calculate e k , e k is the error at time k; Step 4, calculate u k ,u k is the control voltage applied to the LCVR; u k After applying to LCVR, return to step 1 and repeat the cycle. DETAILED DESCRIPTION

[0032] Below is the attached figure ( Figure 1-Figure 3 ) and Examples illustrate the present invention.

[0033] Figure 1 It is a schematic diagram of the structure of an optical pumping device involved in implementing a method for stabilizing the polarizability of alkali metal atoms based on data fusion of the present invention. Figure 2 The present invention is a schematic diagram of an atomic polarizability estimation process based on data fusion involved in implementing a method for stabilizing alkali metal atomic polarizability based on data fusion of the present invention. Figure 3 The figure is a flow chart of a method for stabilizing the polarizability of alkali metal atoms based on data fusion according to the present invention. Figures 1 to 3 As shown, a method for stable control of polarizability of alkali metal atoms based on data fusion includes the following steps: Step 1, a depolarizing beam splitter prism NPBS is arranged on the optical path of the pump light input side of the glass atom gas chamber in the optical pumping device, the reflection side of the depolarizing beam splitter prism NPBS is connected to the first photodetector PD1, and the transmission side of the depolarizing beam splitter prism NPBS is connected to the second photodetector PD2 through the glass atom gas chamber, PD1 and PD2 are respectively connected to the host computer through the data acquisition module, and the host computer is connected to the liquid crystal variable phase retarder LCVR; Step 2, using the data acquisition module to collect reflected light information from NPBS through PD1, and collecting transmitted light information from the glass atom gas chamber through PD2; Step 3, constructing a system transfer equation containing random terms, and using the host computer to perform different spatial data fusion on the reflected light information and the transmitted light information, and the system transfer equation containing random terms is as follows:

[0034] X k =H k x k +G k υ k ,

[0035]

[0036] x k =[P pd1 , P pd2 ,ΔI] T ,

[0037] Where X k is the pump rate vector, H k is the first transfer matrix, x k is the optical power vector, G k is the second transfer matrix, υ k is a random noise vector, k is the time instant, is the optical power information after data fusion at different optical detection points at time k, C k is the matrix used to estimate the fusion information at time k, P pd1 is the optical power information detected by PD1, P pd2 is the optical power information detected by PD2, ΔI is the pump rate loss caused by atomic absorption, and T is the transposition operator;

[0038] Step 4: Fusion of data at different times is performed using the following equation:

[0039]

[0040] in is the pump rate or corresponding optical power obtained at time k, is the pump rate or corresponding optical power estimated at time k-1, A k It is the matrix used to estimate the fusion information at time k, i.e., the data fusion factor;

[0041] Step 5, using the error information of the pumping rate felt by the alkali metal atoms, the control voltage of the LCVR is adjusted through the PID module of the host computer to achieve the purpose of stabilizing the atomic pumping rate in real time when the optical pumping system is operating, and then stabilizing the polarizability.

[0042] Step 5 includes the following formula:

[0043]

[0044] where e k is the error at time k, R p is the reference value of the pumping rate felt by the atoms, uk is the control voltage applied to the LCVR at time k, K P is the proportional coefficient in PID, K I is the integral coefficient in PID, i is the serial number, e is i is the i-th error value, K D is the differential coefficient in PID, e k-1 is the error at time k-1, u k-1 is the control voltage applied to the LCVR at time k-1.

[0045] Step 3 includes the following formula:

[0046]

[0047] C k =[1-κ,κ,0],

[0048] Where α is the conversion coefficient between optical power and pump rate, β is the transmittance of the glass cell, β is defined as the ratio of the outgoing light power to the incident light power, γ is the splitting ratio of the splitter, and γ is defined as the ratio of the main light power to the branch light power.

[0049] The present invention discloses a method for stabilizing the polarizability of alkali metal atoms based on data fusion, and provides a feasible solution for real-time stabilization of the polarizability of alkali metal atoms in the direction of pumping laser in an optical pumping system. The present invention takes the polarizability of alkali metal atoms in the optical pumping system as the research object, and aims at the requirement that the polarizability of alkali metal atoms in the atomic gas chamber needs to be stable for a long time. First, a system transfer equation containing random terms at different optical power detection points is established, and then the data at the past and present moments of different detection points are fused by the data fusion method to obtain the final optical power information. Since the pumping rate felt by the atom has a functional relationship with the optical power, the relaxation rate of the atom is almost unchanged when the temperature is stable, and the atomic polarizability can be estimated in real time according to the optical power information after data fusion. The obtained real-time atomic polarizability is compared with the polarizability reference value to obtain the error amount. The PID method is used to control the driving voltage of the liquid crystal variable phase retarder (LCVR), which can stabilize the optical pumping rate and thus stabilize the polarizability of the alkali metal atoms. The stabilization method of the present invention is a real-time non-destructive polarizability stabilization control method, which ensures the long-term stability and anti-interference of the polarizability of the alkali metal atoms.

[0050] A data fusion-based alkali metal atomic polarizability stable control method includes a distributed feedback laser (DFB), a liquid crystal variable phase retarder (LCVR), a polarizing beamsplitter (PBS), a depolarizing beamsplitter (NPBS), a quarter-wave plate, an oven device, a glass atomic gas chamber, a photoelectric detector (PD), a three-axis magnetic field coil, a data acquisition module, a host computer module, and a function generator.

[0051] Step 1: Construct a system transfer equation containing random terms, and measure and identify the parameters. Adjust the frequency of the DFB pumping laser to the operating frequency, use an oven and a heating film to heat the atomic gas chamber to the working state, and give appropriate excitation to the three-dimensional magnetic compensation coil so that the atomic gas chamber is not disturbed by the external magnetic field. From the composition of the pumping system, according to factors such as the refraction of the gas chamber and the characteristics of the spectrometer, derive the relationship between different light detection points and the pumping rate, and write it as a transfer equation with random noise terms to facilitate data processing in step 2;

[0052] Step 2: Based on the data fusion method, the pump rate felt by the atoms is estimated in real time. Based on step 1, the pump rate information at different time and space points is integrated using covariance prediction and recursive algorithms to estimate the real pump rate felt by the atoms in real time.

[0053] Step 3: Utilize the real-time alkali metal atom pumping rate of step 2, and obtain the error information of the pumping rate felt by the alkali metal atoms by subtracting it from the set value of the alkali metal atom pumping rate. Adjust the control voltage of the LCVR through the PID module of the host computer to achieve the purpose of stabilizing the atomic pumping rate in real time when the optical pumping system is operating, and then stabilize the polarizability.

[0054] The atomic gas chamber is a glass gas chamber widely used in the field of quantum measurement. Considering the optical loss caused by the atomic gas chamber wall and the optical power loss caused by light absorption, it is defined that before the pump light enters the gas chamber, the first photodetector is marked with PD1 to detect the branch optical power information obtained by the spectrometer. After the pump light exits the gas chamber, the photodetector that detects the output optical power information is PD2.

[0055] In the step 1, based on the measurement and identification of system parameters, the transfer equation X between different measurement points and the optical pumping rate actually felt by the atoms is obtained. k =H k x k +Gk υ k Among them, X k is the pump rate vector and k refers to the time. Define the k moment, and deduce the pumping rates from the detection information of PD1 and PD2 as is the pump rate from PD1 and PD2, ΔI is the pump rate loss caused by atomic absorption, and α is the conversion coefficient of optical power and pump rate, from optical power to pump. β is the transmittance of the glass gas cell, that is, the ratio of the output light power to the incident light power. γ is the splitting ratio of the splitter, defined as the ratio of the main light power to the branch light power. H k and G k is the transfer matrix, which contains the above three parameters. k is the optical power vector, P pd1 and P pd2 are the optical power information detected by PD1 and PD2, respectively, k =[P pd1 , P pd2 , ΔI] T υ k is a random noise vector.

[0056] The optical power information after data fusion at different light detection points at time k is: The k in the upper right corner represents the k moment, Where k is the data fusion factor, which is obtained in real time according to the recursive algorithm. The pump rate obtained at time k is The estimated pump rate at time k-1 is Among them A k is the data fusion factor.

[0057] refer to Figure 1 The light emitted by the distributed feedback laser passes through the power stabilization module composed of PBS and LCVR, and is divided into two beams through NPBS. One beam is detected by PD1, and the other beam of linear polarized light passes through a quarter-wave plate and becomes circularly polarized pump light, which enters the atomic gas chamber. The optical power of the light emitted from the atomic gas chamber is detected by PD2. The incident light and the output light power pass through the data acquisition module and enter the host computer for data processing. The host computer obtains the fluctuation of the pump rate felt by the atoms inside the gas chamber through calculation, and adjusts the liquid crystal control voltage through the PID method to stabilize the polarization rate.

[0058] refer to Figure 2 The atomic polarizability estimation process based on data fusion, P pd1 is the optical power detected by PD1, and the pump rate information inferred from PD1 is

[0059]

[0060] Where Rp1(t) represents the real-time pump rate information, α is the conversion coefficient between optical power and pump rate. β is the transmittance of the glass gas cell, which is defined as the ratio of the outgoing light power to the incident light power. γ is the splitting ratio of the splitter, which is defined as the ratio of the main light power to the branch light power. ω1(t) is the noise of the measured PD detector, It indicates the average optical power sensed by detector PD1 during the system identification process.

[0061] The pump rate information inferred from PD2 is as follows:

[0062]

[0063] Where Rp2(t) represents the real-time pump rate information. Ψ(I) is the noise introduced by light absorption, It indicates the average optical power sensed by detector PD1 during the system identification process.

[0064] The transfer equation X contains random terms k =H k x k +G k υ k .in

[0065]

[0066] X k is the pump rate vector, x k is the optical power vector x k =[P pd1 , P pd2 , ΔI] T υ k is a random noise vector, and are the discrete forms of ω1(t) and Ψ(I), respectively. Define Q k Yes k The variance matrix of E(υ T υ)=Q k .

[0067] The optical power information after position data fusion is: Combining the system equations, we can get the following formula:

[0068] X k =H k x k +G k υ k ,

[0069]

[0070] Among them, C k =[1-κ,κ,0]. The optical power after time data fusion is

[0071] In the actual estimation process,

[0072]

[0073] P k =(1-A k ) k-1

[0074]

[0075] Among them, A k , P k , C k is the matrix used to estimate the fusion information at time k. k-1 is the matrix at time k-1, used to update P k and A k .

[0076] refer to Figure 3 The atomic polarizability stability control process uses the system parameters obtained by system identification and measurement as prior information, and integrates the real-time PD1 and PD2 information to obtain The error at time k is defined as e k , R p is the reference value of the pump rate felt by the atoms. k is the control voltage applied to the LCVR, e k-1 is the error at time k-1, K P , K I , K D is the PID parameter, K P is the proportionality coefficient, K I is the differential coefficient, K D is the differential coefficient.

[0077]

[0078] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A method for stable control of polarizability of alkali metal atoms based on data fusion, characterized in that: The following steps are involved: Step 1, a depolarizing beam splitter prism NPBS is arranged on the optical path of the pump light input side of the glass atom gas chamber in the optical pumping device, the reflection side of the depolarizing beam splitter prism NPBS is connected to the first photodetector PD1, the transmission side of the depolarizing beam splitter prism NPBS is connected to the second photodetector PD2 through the glass atom gas chamber, PD1 and PD2 are respectively connected to a host computer through a data acquisition module, and the host computer is connected to a liquid crystal variable phase retarder LCVR; Step 2, using a data acquisition module to collect reflected light information from the NPBS through PD1, and to collect transmitted light information from the glass atomic gas cell through PD2; Step 3, construct a system transfer equation containing random terms, and use a host computer to perform different spatial data fusion on the reflected light information and the transmitted light information. The system transfer equation containing random terms is as follows: X k =H k x k +G k υ k , x k =[P pd1 ,P pd2 ,ΔI] T , Where X k is the pump rate vector, H k is the first transfer matrix, x k is the optical power vector, G k is the second transfer matrix, υ k is a random noise vector, k is the time instant, is the optical power information after data fusion at different optical detection points at time k, C k is the matrix used to estimate the fusion information at time k, P pd1 is the optical power information detected by PD1, P pd2 is the optical power information detected by PD2, ΔI is the pump rate loss caused by atomic absorption, and T is the transposition operator; Step 4: Fusion of data at different times is performed using the following equation: in is the pump rate or corresponding optical power obtained at time k, is the pump rate or corresponding optical power estimated at time k-1, A k It is the matrix used to estimate the fusion information at time k, i.e., the data fusion factor; Step 5, using the error information of the pumping rate felt by the alkali metal atoms, the control voltage of the LCVR is adjusted through the PID module of the host computer to achieve the purpose of stabilizing the atomic pumping rate in real time when the optical pumping system is operating, and then stabilizing the polarizability.

2. The method for stabilizing polarizability of alkali metal atoms based on data fusion according to claim 1, characterized in that: Step 5 includes the following formula: where e k is the error at time k, R p is the reference value of the pumping rate felt by the atoms, u k is the control voltage applied to the LCVR at time k, K P is the proportional coefficient in PID, K I is the integral coefficient in PID, i is the serial number, e is i is the i-th error value, K D is the differential coefficient in PID, e k-1 is the error at time k-1, u k-1 is the control voltage applied to the LCVR at time k-1.

3. The method for stabilizing polarizability of alkali metal atoms based on data fusion according to claim 1, characterized in that: Step 3 includes the following formula: C k =[1-k,k,0], Where α is the conversion coefficient between optical power and pump rate, β is the transmittance of the glass cell, β is defined as the ratio of the outgoing light power to the incident light power, γ is the splitting ratio of the splitter, and γ is defined as the ratio of the main light power to the branch light power.

Images