Method and system for probing atomic transitions in a cold atom microwave clock

Abstract

The application discloses a cold atom microwave clock atomic transition detection method and system, wherein the method comprises the following steps: using a single photodetector to measure the upper energy state signal 1 and the lower energy state signal 2 of the cold atom microwave clock atom in time; and obtaining the atomic transition probability according to the upper energy state signal 1 and the lower energy state signal 2. The application solves the problems of large volume, high cost and complex calibration caused by the fact that the traditional cold atom microwave clock needs two independent photodetectors to monitor the upper / lower energy state atoms, simplifies the existing cold atom detection module or technology, and improves the miniaturization ability and level of the cold atom microwave clock.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of atomic frequency standard, and particularly relates to a method and system for detecting atomic transition in a cold atom microwave clock. BACKGROUND

[0002] The frequency standard signal output by the cold atom microwave clock has high accuracy and long-term frequency stability, and plays an important role in time keeping, satellite navigation and positioning, time frequency comparison and precise measurement. At present, the development of cutting-edge technology is the miniaturization and engineering of the cold atom microwave clock, which requires the detection method or device of the cold atom quantum state to be simplified. Using a single photodetector instead of the traditional double photodetector is an important direction of simplification. In addition, the laser along the direction of the atomic group motion can be used as the cooling light in the cooling timing and as the detection light and detection heavy pumping light in the detection timing, which can also simplify the optical path. At present, the single photodetector is used to detect the quantum state of the cold atom, and the transition probability of the atom under the detection of the single photodetector is obtained . The microwave frequency f for exciting the atomic energy level transition is changed, and the corresponding atomic transition probability (f) under different frequencies is measured; when f is close to the atomic intrinsic transition frequency f0, the transition probability increases, forming a resonance curve; by finding the frequency point f max that makes the transition probability reach the maximum value, and locking the clock transition microwave frequency obtained by frequency multiplication and frequency synthesis of the local oscillator at f max , the frequency standard signal related to the atomic intrinsic transition frequency f0 can be output. However, under the condition of the single photodetector and only the detection light coinciding with the direction of the atomic motion trajectory, there is no method to obtain the normalized atomic transition probability in the cold atom microwave clock. SUMMARY

[0003] To solve the problems in the prior art, the application provides a method and system for detecting atomic transition in a cold atom microwave clock.

[0004] In a first aspect, a method for detecting atomic transition in a cold atom microwave clock is provided, comprising:

[0005] using a single photodetector to measure the upper energy state signal 1 and the lower energy state signal 2 of the atom in the cold atom microwave clock in time sharing mode;

[0006] obtaining the atomic transition probability from the upper energy state signal 1 and the lower energy state signal 2.

[0007] Optionally, the single photodetector is used to measure the upper energy state signal 1 and lower energy state signal 2, comprising:

[0008] when the atom passes through the single photodetector, the detection light is first turned on and lasts for a first preset time period T0 and then turned off, the upper energy state signal of the atom in the cold atom microwave cavity is measured using the single photodetector within the T0 time period 1; then the detection heavy pumping light is turned on and lasts for a second preset time period T1 and then turned off, the atom in the lower energy state is pumped to the upper energy state within the T1 time period; finally, the detection light is turned on again and lasts for a third preset time period T2 and then turned off, the lower energy state signal of the atom in the cold atom microwave cavity is measured using the single photodetector within the T2 time period 2.

[0009] Optionally, the atomic transition probability is obtained according to the upper energy state signal 1 and the lower energy state signal 2. The atomic transition probability is calculated by the following calculation formula:

[0010]

[0011] wherein, is a first constant coefficient, is a second constant coefficient.

[0012] In a second aspect, a cold atom microwave cavity atomic transition detection system is provided, which is used to implement the cold atom microwave cavity atomic transition detection method in the first aspect, and comprises:

[0013] an atomic fluorescence acquisition device, configured to acquire fluorescence emitted by the cold atom when the cold atom is detected by a detection light beam and output an electrical signal;

[0014] a signal analysis module, configured to separate the electrical signal output by the atomic fluorescence acquisition device into an upper energy state signal 1 and a lower energy state signal 2.

[0015] a transition probability calculation module, configured to calculate the transition probability 1 and the lower energy state signal 2 output by the signal analysis module.

[0016] Optionally, the system further comprises:

[0017] a timing control module, configured to turn on the detection light for first-step detection for a first preset time period, turn on the detection heavy pumping light for atomic state pumping for a second preset time period, and turn on the detection light for second-step detection for a third preset time period.

[0018] ​Optionally, the atomic fluorescence collection device is composed of a central lens, single photodetectors arranged on both sides of the lens, and a cold atom group movement area in a vacuum system; wherein the cold atom group movement area emits fluorescence when receiving probe light and detecting heavy pumping light.

[0019] In a third aspect, an electronic device is provided, which includes a memory, a processor, and a computer program stored in the memory and executable by the processor, and the processor implements the steps of the atomic transition detection method in the cold atom microwave clock in the first aspect when executing the computer program.

[0020] In a fourth aspect, a computer storage medium is provided, which stores a computer program, and the program implements the steps of the atomic transition detection method in the cold atom microwave clock in the first aspect when executed by a processor.

[0021] In a fifth aspect, a computer program product is provided, which includes a computer program or instructions, and the computer program or instructions implement the steps of the atomic transition detection method in the cold atom microwave clock in the first aspect when executed by a processor.

[0022] The technical solutions provided by some embodiments of the present application have at least the following beneficial effects:

[0023] The present application provides an atomic transition detection method and system in a cold atom microwave clock, wherein the method includes using a single photodetector to measure the upper energy state signal of the atom in the cold atom microwave clock 1 and the lower energy state signal 2 of the atom; and obtaining the atomic transition probability according to the upper energy state signal 1 and the lower energy state signal 2 of the atom. The present application solves the problems of large volume, high cost, and complex calibration caused by the need for two independent photodetectors to monitor the upper / lower energy state atoms in the traditional cold atom microwave clock, simplifies the existing detection module or technology of the cold atom, and improves the miniaturization capability and level of the cold atom microwave clock.

[0024] Other features and advantages of the present application will be set forth in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description and claims and the appended drawings.

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are described in detail as follows.

[0026] The advantages of the additional aspects of the present application will be partially set forth in the following description, partially will become apparent to those skilled in the art from the following description, or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the description of the embodiments of the present application or the prior art will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0028] Figure 1 Flow chart of the atomic transition detection method in the cold atom microwave clock shown in the embodiments of the present application;

[0029] Figure 2 Schematic diagram of the working principle of the atomic fluorescence acquisition device shown in the embodiments of the present application;

[0030] Figure 3 Schematic diagram of the upper energy state signal and the lower energy state signal of the cold atom in the microwave clock on the computer side shown in the embodiments of the present application;

[0031] Figure 4 Curve graph of the atomic transition probability in the microwave clock of the cold atom varying with the frequency of the input microwave shown in the embodiments of the present application;

[0032] Figure 5 Principle block diagram of the atomic transition detection system in the cold atom microwave clock shown in the embodiments of the present application.

[0033] Among them, 1-single photodetector, 2-lens, 3-cold atom group motion area, 4-cold atom group instantaneous position. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0035] The following description refers to the accompanying drawings. Unless otherwise indicated, like numbers in the different figures indicate the same or similar elements. The following example embodiments described in the example embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of methods and apparatuses consistent with some aspects of the present application as detailed in the appended claims.

[0036] In the description of the present application, it is understood that the terms "first", "second" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances. In addition, in the description of the present application, "a plurality of" means two or more, unless otherwise specified. The association relationship of the associated objects is described, which means that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0037] Embodiment one

[0038] The following will be combined with the attached Figure 1 A method for detecting atomic transition in a cold atom microwave cavity provided by the embodiment of the present application is described in detail.

[0039] A method for detecting atomic transition in a cold atom microwave cavity, comprising the following steps:

[0040] Step S1: using a single photodetector to measure the upper energy state signal of the cold atom microwave cavity atom in time 1 and the lower energy state signal 2;

[0041] Specifically, when the atom passes through the single photodetector, the detection light is first turned on and lasts for a first preset time period T0 and then turned off, the upper energy state signal of the cold atom microwave cavity atom is measured using the single photodetector within the T0 time 1;Then turn on the detection heavy pumping light and last for a second preset time period T1 and then turn off, pump the lower energy state atom to the upper energy state within the T1 time; Finally, turn on the detection light again and last for a third preset time period T2 and then turn off, measure the lower energy state signal of the cold atom microwave cavity atom using the single photodetector within the T2 time 2. The detection light and the detection heavy pumping light are usually generated by a semiconductor laser locked to the atomic energy level transition line.

[0042] Step S2: obtaining the atomic transition probability according to the upper energy state signal 1 and the lower energy state signal 2 .

[0043] In the detection stage of the cold atom microwave cavity, the atom is in two hyperfine sub-energy states of the ground state. According to the energy level, the two sub-energy levels are called upper energy state and lower energy state respectively; the ratio of the number of lower energy state atoms to the total number of atoms is called transition probability;

[0044] Specific to the embodiment, the first step detection is considered as the first preset time period T0 after the first opening of the detection light is closed, and the detection is performed within the first preset time period T0. Only the upper energy state atom emits fluorescence, and the fluorescence electrical signal is collected by the computer, and the output is the upper energy state signal 1. As a specific example Figure 3 The left side of the shadow area represents that the number of upper energy state atoms is proportional to the number of atoms, which is obtained by accumulating the voltage value in the window function and deducting the background value. The dashed line below is the background value, and the same applies below. At this step, the upper energy state atoms will disperse and partially lose;

[0045] The detection heavy pumping light is turned on and lasts for a second preset time period T1, and then is turned off. The lower energy state atoms are converted into upper energy state atoms under the action of the detection heavy pumping light within the second preset time period T1.

[0046] The detection light is turned on again and lasts for a third preset time period T2, and then is turned off. The second step detection is considered as the detection within the third preset time period T2. The atoms converted into upper energy state atoms under the action of the detection heavy pumping light and the upper energy state atoms that have not lost after the first step detection emit fluorescence together. The fluorescence signal is collected by the computer, and the output is the lower energy state signal 2. As a specific example Figure 3 The right side of the shadow area represents that the number of lower energy state atoms and the number of upper energy state atoms that have not lost are proportional to the sum of the number of atoms, which is obtained by accumulating the voltage value in the window function and deducting the background value.

[0047] In the specific implementation process, the number of upper energy state atoms is denoted as , and the number of lower energy state atoms is denoted as ,

[0048] The above physical parameters satisfy: ,

[0049] ;

[0050] Among them, , , are three constant coefficients;

[0051] In the specific implementation process, is the value of the fluorescence electrical signal after processing =1, 2) and the number of atoms emitting fluorescence. This value is eliminated in the final result and does not appear; is the ratio of the detection efficiency of the detector formed by the different positions of the cold atom group during the two detections. This value is near 1; is the proportion of the upper energy state atoms remaining in the cold atom group after the first detection. This value is generally between 0 and 0.5.​

[0052] From the above calculation relation of physical variables, the expression of atomic transition probability 1 and lower energy state signal 2 is calculated as follows:

[0053]

[0054] In the implementation process, the two parameters are adjusted according to the experimental results of scanning transition probability , so that the transition probability is between 0 and 1, and the value fluctuation of is minimized.

[0055]

[0056] The cooled atoms will undergo Ramsey transition in the excited microwave cavity. By scanning the microwave frequency in the microwave cavity, the calculated transition probability will appear Ramsey fringe pattern, as shown in Figure 4 , adjust the two parameters so that the transition probability forms a clear fringe pattern between 0 and 1; at this time, the average value μ and the standard deviation σ of are calculated, so that the value of σ / μ is minimized. At this time, the optimal value of , is obtained.

[0057] This method can be used as a general method for obtaining atomic probability in a single photodetector condition.

[0058] The present application uses a single photodetector to detect the quantum state of the cold atoms at different times, obtains a photoelectric signal, and then detects the ratio of the number of atoms in the lower energy state to the total number of atoms to obtain the transition probability of the atoms under the detection of the single photodetector, which solves the problems of large volume, high cost and complex calibration caused by the need for two independent photodetectors to monitor the upper / lower energy state atoms in the traditional cold atom microwave clock, simplifies the existing detection module or technology of cold atoms, and improves the miniaturization ability and level of the cold atom microwave clock.

[0059] Embodiment Two

[0060] The present application proposes a cold atom microwave clock atomic transition detection system for realizing the cold atom microwave clock atomic transition detection method of embodiment one, comprising:

[0061] ​​​​The atomic fluorescence acquisition device is used for acquiring fluorescence emitted by the cold atoms when the cold atoms are detected by a probe light beam and outputting an electric signal.

[0062] In the implementation process, the atomic fluorescence acquisition device is composed of a lens 2, single photodetectors 1 arranged on both sides of the lens 2, and a cold atom group motion region 3 in a vacuum system (i.e., the positions of the probe light and the probe heavy pumping light) as shown in the figure. Figure 2 The receiving surface of the single photodetector 1 is perpendicular to the axial direction of the lens 2. The principle process is as follows: the probe light beam irradiates the cold atom group at the cold atom group instantaneous position 4, and the cold atoms emit fluorescence. The fluorescence is collected by the lens 2 and focused on the photodetector, the single photodetector 1 generates an electric signal, and the fluorescence intensity signal is acquired by the computer after processing. Specifically, the probe light beam contains two lasers with different frequencies, i.e., the probe light and the probe heavy pumping light. The probe light irradiates the cold atom group, so that the upper energy state atoms in the cold atom group emit fluorescence, and the lower energy state atoms do not emit fluorescence. The probe heavy pumping light can convert the lower energy state atoms into the upper energy state atoms.

[0063] The signal analysis module is used for separating the electric signal output by the atomic fluorescence acquisition device into upper energy state signals 1 and lower energy state signals 2. 1 and the lower energy state signals 2.

[0064] The transition probability calculation module is used for calculating the transition probability according to the upper energy state signals 1 and the lower energy state signals 2 output by the signal analysis module. 1 and the lower energy state signals 2. ;

[0065] In a feasible implementation, as shown in the figure, the system further comprises: Figure 5

[0066] The timing control module is used for turning on the probe light for first-step detection for a first preset time period, turning on the probe heavy pumping light for atom state pumping for a second preset time period, and turning on the probe light for second-step detection for a third preset time period.

[0067] The cold atom microwave clock internal atom transition detection system provided by the embodiment is used for implementing the cold atom microwave clock internal atom transition detection method provided by the first embodiment, has the same technical features as the cold atom microwave clock internal atom transition detection method provided by the first embodiment, and can solve the same technical problems and achieve the same technical effects.

[0068] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, which will not be described herein.

[0069] Embodiment Three​​​

[0070] The embodiment also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable by the processor, and the processor implements the method according to any one of the embodiments of the present application when executing the computer program. The method is described in the foregoing function description, and will not be repeated here.

[0071] For example, it includes one or more processors, a storage device for storing one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors implement the method provided by the embodiments of the present application. The method is described in the foregoing function description, and will not be repeated here.

[0072] The electronic device also includes an input device and an output device; the processor, the storage device, the input device and the output device in the electronic device can be connected through a bus or other means.

[0073] Embodiment four

[0074] The present application provides a computer storage medium, which stores a computer program, and the program is executed by a processor to implement the steps of the atomic transition detection method in the cold atom microwave clock according to any one of the embodiments.

[0075] It can be understood that the storage medium includes: flash memory, hard disk, multimedia card, card memory (such as SD (Secure Digital Memory Card) or MDR (Memory Data Register), etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, magnetic disk, optical disk, server, APP (Application, the abbreviation of application software) application mall and other various media that can store program check codes.

[0076] Embodiment five

[0077] The embodiment provides a computer program product, including a computer program or instructions, and the computer program or instructions are executed by a processor to implement the atomic transition detection method in the cold atom microwave clock according to the embodiment one.

[0078] Based on such understanding, the technical solutions of the present application can be embodied in the form of a computer program product in essence or in the form of a part of the technical solutions or the part of the technical solutions that make contributions to the prior art.

[0079] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. The embodiments described above are merely for description, for example, the unit division is only a logical function division, and there can be another division manner in actual implementation; for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0080] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments.

[0081] In addition, each functional unit in the embodiments of the present application can be integrated in one processing unit, or each unit can exist physically as a separate unit, or two or more units can be integrated in one unit.

[0082] It should be noted that the flowcharts and block diagrams in the drawings show the possible implementation architectures, functions and operations of the system, method and computer program product according to the embodiments of the present application. In this regard, each block in the flowchart or block diagram can represent a module, program segment or part of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different orders than that shown in the drawings. For example, two consecutive blocks can actually be executed substantially in parallel, and sometimes in reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified functions or actions, or can be implemented by a combination of special-purpose hardware and computer instructions.

[0083] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present application, and are not intended to limit the technical solutions of the present application. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can make modifications or easy changes to the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features, within the technical scope disclosed by the present application. Such modifications, changes or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0084] The applicant of the present application has made a detailed description and explanation of the embodiments of the present application in combination with the drawings of the specification. However, those skilled in the art should understand that the above-described embodiments are only preferred embodiments of the present application, and the detailed description is only to help the reader better understand the spirit of the present application, and is not intended to limit the protection scope of the present application. On the contrary, any improvement or modification made on the basis of the spirit of the present application should fall within the protection scope of the present application.

Claims

1. A method for detecting atomic transitions within a cold atom microwave clock, characterized in that, The method comprises the following steps: Measuring upper state signals of atoms in a cold atom microwave clock using a single photodetector to measure the signals in time 1 and lower state signals 2; The upper energy state signal 1 and the lower energy state signal 2 are obtained ; The use of a single photodetector to measure the upper state signals of atoms in a cold atomic microwave clock on a time-sharing basis 1and lower state signals 2, comprising: Turning on the probe light and turning off after a first preset time period, measuring the signal of the upper energy state of the atoms in the cold atomic microwave clock using a single photodetector within the first preset time period 1; opening the detection heavy pumping light and closing after a second preset time period, and pumping the lower energy state atom to the upper energy state; turning off the probe light after a third preset time period, measuring a signal of a lower energy state of the atoms in the cold atomic microwave clock using the single photodetector during the third preset time period 2; The upper energy state signal 1 and the lower energy state signal 2 are used to obtain the atomic transition probability using the following calculation formula: wherein is the ratio of the detection efficiency of the detector for the two different positions of the cold atom cloud, is the proportion of atoms in the upper state that remain in the cold atom cloud after the first detection.

2. A system for detecting atomic transitions in a cold atom microwave clock, for implementing the method for detecting atomic transitions in a cold atom microwave clock according to claim 1, characterized in that, The method comprises the following steps: The atomic fluorescence acquisition device is used for acquiring the fluorescence emitted by the cold atom when it is detected by the detection light beam and outputting an electric signal. The signal analysis module is used for separating the electrical signal output by the atomic fluorescence acquisition device into the upper energy state signal and the lower energy state signal. 1 and 2. ​ A transition probability calculation module is configured to calculate the transition probability according to the upper energy state signal and the lower energy state signal output by the signal analysis module. 1 2 .

3. The cold atom microwave clock system of claim 2, wherein the atomic transition detection system is configured to detect the atomic transition of the cold atoms in the atomic cloud by detecting a change in the microwave signal. The method further comprises the following steps: The timing control module is used for opening the detection light for the first step detection for a first preset time period, opening the detection heavy pumping light for the atomic state pumping for a second preset time period, and opening the detection light for the second step detection for a third preset time period.

4. The cold atom microwave clock system of claim 2, wherein the atomic transition detection system is configured to detect a transition between the first and second energy levels of the first atomic species. The atomic fluorescence acquisition device is composed of a central lens, single photodetectors arranged on both sides of the lens, and a cold atom group movement area; wherein the cold atom group movement area is also the light beam position of the detection light and the detection heavy pumping light.

5. An electronic device, comprising: The computer program is stored in the memory and can be run on the processor, and the processor executes the computer program to realize the steps of the cold atom microwave clock internal atomic transition detection method in claim 1.

6. A computer storage medium having stored thereon a computer program, characterized in that The program is executed by the processor to realize the steps of the cold atom microwave clock internal atomic transition detection method in claim 1.

7. A computer program product comprising computer programs or instructions, characterized in that, The computer program or instructions are executed by the processor to realize the steps of the cold atom microwave clock internal atomic transition detection method in claim 1.

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