Apparatus and method for measuring atomic relaxation rates

Abstract

The application discloses a device and method for measuring atomic relaxation rate, which comprises a microwave unit for generating a microwave field, acting on an atomic cell to make atoms in the atomic cell produce a Rabi resonance; a laser unit for generating a laser beam to irradiate the atomic cell and use the laser beam to detect the Rabi resonance law of the atoms; a collection unit for collecting the laser beam after transmitting through the atomic cell and obtaining frequency information of the laser beam; and an upper computer for drawing the frequency information of the laser beam into a Rabi resonance curve of the atoms, solving the Rabi resonance curve of the atoms, and obtaining the atomic relaxation rate. The device and method for measuring the atomic relaxation rate disclosed by the application have higher accuracy.

Description

Technical Field

[0001] This invention relates to an apparatus and method for measuring atomic relaxation rate, belonging to the field of quantum precision measurement. Background Technology

[0002] As a core physical device in quantum precision measurement instruments such as atomic clocks, atomic magnetometers, and atomic gyroscopes, the performance of alkali metal atom gas cells directly restricts the measurement accuracy and sensitivity. Therefore, it is very important to select alkali metal gas cells with long-lived coherent atoms for use in quantum precision measurement instruments.

[0003] Alkali metal vapors typically contain alkali metal atoms and buffer gases. Their coherent atomic lifetimes can be characterized by atomic relaxation rate or relaxation time. The atomic relaxation mechanism includes collisions between atoms and the gas chamber wall, collisions between atoms, and collisions between atoms and the buffer gas. Accurate and rapid detection of the relaxation rate in the atomic gas chamber is of great significance in quantum precision measurement and quantum sensing applications.

[0004] A common method for detecting atomic relaxation rate involves the interaction of two laser beams with atoms. One beam acts as a pump light to polarize the atoms, while the other acts as a probe light to detect the degree of polarization of the polarized atoms. This method has a relatively complex optical path, consumes a lot of power, and is easily affected by external environmental factors. In addition, the measurement effect is related to the shape and size of the atomic gas cell being measured. For example, the surface of a small planar optical glass atomic gas cell can easily reflect some of the incident light, and the probe light can cause additional atomic relaxation problems, etc.

[0005] Therefore, it is necessary to conduct in-depth research on traditional atomic relaxation rate detection equipment and methods to solve the above problems and improve the efficiency and accuracy of detection. Summary of the Invention

[0006] To overcome the above problems, the inventors conducted in-depth research and designed a device for measuring atomic relaxation rate, the device comprising:

[0007] The microwave unit is used to generate a microwave field that acts on the atomic gas cell, causing the atoms in the atomic gas cell to produce Rabi resonance.

[0008] The laser unit is used to generate a laser beam to irradiate the atomic gas cell, and the laser beam is used to detect the Rabi resonance law of the atoms;

[0009] The acquisition unit is used to acquire the laser beam after it passes through the atomic gas cell and obtain the frequency information of the laser beam.

[0010] The host computer plots the frequency information of the laser beam into the Rabi resonance curve of the atom, calculates the Rabi resonance curve of the atom, and obtains the atomic relaxation rate.

[0011] In a preferred embodiment, the microwave unit includes a microwave source and an arbitrary waveform generator.

[0012] The arbitrary waveform generator provides a phase modulation signal to the microwave source, causing the microwaves output by the microwave source to be in a phase-modulated state.

[0013] The microwaves output from the microwave source act on the atomic gas cell, forming a microwave field that causes the alkali metal atoms in the ground state energy level to undergo Rabi resonance.

[0014] In a preferred embodiment, the microwave unit further includes a microwave resonant cavity for converting the microwaves output from the microwave source into a uniform microwave field, and the atomic gas chamber is disposed inside the microwave resonant cavity.

[0015] In a preferred embodiment, the microwave unit further includes a power amplifier placed between the microwave resonant cavity and the microwave source, which amplifies the microwaves output from the microwave source and feeds the amplified microwaves into the microwave resonant cavity.

[0016] In a preferred embodiment, the laser unit includes a frequency-stabilized laser for providing a laser beam of a preset frequency.

[0017] In a preferred embodiment, the acquisition unit includes a photodetector and a fast Fourier analyzer.

[0018] The photodetector is used to receive the laser beam after it passes through the atomic gas cell, convert the optical signal into an electrical signal, and transmit it to the fast Fourier transform analyzer.

[0019] The fast Fourier analyzer converts electrical signals into frequency signals to obtain the Rabi resonance amplitude of atoms.

[0020] In a preferred embodiment, the arbitrary waveform generator provides a phase modulation signal that causes the output power value of the microwave source to change periodically, and a set of Rabi resonance amplitudes is obtained for each cycle. The Rabi resonance amplitudes of multiple cycles are used to plot the Rabi resonance curve.

[0021] In a preferred embodiment, the host computer obtains the atomic relaxation rate by calculating the amplitude and full width at half maximum (FWHM) of the Rabi resonance curve.

[0022] In a preferred embodiment, the device further includes a temperature control unit for controlling the temperature of the atomic gas chamber so that the temperature inside the atomic gas chamber remains at a preset value.

[0023] The present invention also provides a method for measuring atomic relaxation rate, preferably implemented using the above-described apparatus, comprising the following steps:

[0024] A microwave field is generated by a microwave unit and acts on the atomic gas chamber;

[0025] A laser beam is generated by a laser unit to irradiate the atomic gas cell. The laser beam after passing through the atomic gas cell is collected by a collection unit to obtain the frequency information of the laser beam, which is used as the Rabi resonance amplitude.

[0026] Adjust the phase and power of the microwave field to obtain the corresponding Rabi resonance amplitude under different microwave fields, and plot the Rabi resonance curve.

[0027] Solve the Rabi resonance curve of the atom to obtain the atomic relaxation rate.

[0028] The beneficial effects of this invention include:

[0029] (1) Both microwaves and lasers interact with atoms. Microwaves are strongly coupled compared to lasers. If the microwave is in a closed microwave resonant cavity, it will be less affected by external interference and the Rabi resonance signal will have better signal-to-noise ratio. Therefore, the accuracy of this method for measuring the atomic relaxation rate based on the Rabi resonance principle will be higher.

[0030] (2) By placing the atomic gas cell in a closed heating environment, the temperature control is more precise and the effect is better, and the relaxation rate of the atomic gas cell under a certain temperature state can be evaluated in a true and accurate manner. Attached Figure Description

[0031] Figure 1 A schematic diagram of a device for measuring atomic relaxation rate according to a preferred embodiment of the present invention is shown.

[0032] Figure 2 This diagram illustrates a phase modulation signal provided by an arbitrary waveform generator to a microwave source according to a preferred embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0034] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0035] According to the present invention, an apparatus for measuring atomic relaxation rate is provided, such as... Figure 1 As shown, the device includes:

[0036] The microwave unit is used to generate a microwave field that acts on the atomic gas cell, causing the atoms in the atomic gas cell to produce Rabi resonance.

[0037] The laser unit is used to generate a laser beam to irradiate the atomic gas cell, and the laser beam is used to detect the Rabi resonance law of the atoms;

[0038] The acquisition unit is used to acquire the laser beam after it passes through the atomic gas cell and obtain the frequency information of the laser beam.

[0039] The host computer plots the frequency information of the laser beam into the Rabi resonance curve of the atom, calculates the Rabi resonance curve of the atom, and obtains the atomic relaxation rate.

[0040] In a preferred embodiment, the microwave unit includes a microwave source and an arbitrary waveform generator.

[0041] The arbitrary waveform generator provides a phase modulation signal to the microwave source, such as... Figure 2 As shown, the microwaves output by the microwave source are in a phase-modulated state. In this invention, a phase modulation is applied to the output microwave signal by an arbitrary waveform generator, causing a slight change in the frequency of the microwave field, i.e., forming a scanning microwave field. A set of signals is obtained through the interaction with atoms, thereby obtaining the Rabi resonance line shape.

[0042] The microwaves output from the microwave source act on the atomic gas cell, forming a scanning microwave field that causes the alkali metal atoms in the ground state energy level to undergo Rabi resonance.

[0043] In this invention, there are no special restrictions on the specific models of the microwave source and the arbitrary waveform generator. Those skilled in the art can choose any existing product model according to actual needs.

[0044] In a preferred embodiment, the microwave unit further includes a microwave resonant cavity for converting the microwaves output from the microwave source into a uniform microwave field, and the atomic gas chamber is disposed inside the microwave resonant cavity.

[0045] Furthermore, the microwave resonant cavity also serves as a magnetic shield, reducing interference from external magnetic fields.

[0046] The microwave resonant cavity is a commonly used resonant element. It is a medium region of arbitrary shape surrounded by conductive walls (or magnetic walls) in which electromagnetic oscillations can be formed. Its specific structure will not be described in detail in this invention.

[0047] In a preferred embodiment, a bracket is provided inside the microwave resonant cavity, and the atomic gas chamber is placed on the bracket. The bracket is made of a material that does not provide shielding for microwave propagation, such as glass or polytetrafluoroethylene (PTFE), preferably PTFE, which is easy to process.

[0048] Furthermore, an opening is provided on the microwave resonant cavity to allow the laser beam to enter and exit.

[0049] According to a preferred embodiment of the present invention, the microwave unit further includes a power amplifier, which is placed between the microwave resonant cavity and the microwave source to amplify the microwaves output from the microwave source and feed the amplified microwaves into the microwave resonant cavity.

[0050] According to a preferred embodiment of the present invention, the laser unit includes a frequency-stabilized laser for providing a laser beam of a preset frequency.

[0051] Preferably, the laser beam with the preset frequency refers to a laser beam whose output frequency can resonate with the intrinsic transition of the atom under test, thereby improving the accuracy of the measurement.

[0052] In a preferred embodiment, the laser unit further includes a collimating and expanding optical path, preferably a cage-type collimating and expanding optical path, for adjusting the beam spot size and improving measurement accuracy.

[0053] According to the present invention, the acquisition unit includes a photodetector and a fast Fourier analyzer.

[0054] The photodetector is used to receive the laser beam after it passes through the atomic gas cell, convert the optical signal into an electrical signal, and transmit it to the fast Fourier transform analyzer.

[0055] The fast Fourier analyzer converts electrical signals into frequency signals to obtain the Rabi resonance amplitude of atoms.

[0056] Furthermore, the arbitrary waveform generator provides a periodically changing phase modulation signal, causing the output power value of the microwave source to change periodically. Each cycle yields a set of Rabi resonance amplitudes, and the Rabi resonance amplitudes of multiple cycles are used to plot a Rabi resonance curve.

[0057] In a preferred embodiment, the Rabi resonance curve is plotted using a LabVIEW-based atomic relaxation rate analysis method.

[0058] According to the present invention, the host computer obtains the atomic relaxation rate by calculating the amplitude and full width at half maximum (FWHM) of the Rabi resonance curve.

[0059] The Rabi resonance curve of the solved atom can be expressed as:

[0060]

[0061] Where γ represents the atomic relaxation rate, ω FWHM This represents the full width at half maximum (FWHM) of the Rabi resonance curve.

[0062] In a preferred embodiment, the device further includes a temperature control unit for controlling the temperature of the atomic gas chamber to maintain a preset temperature. The specific preset value can be set by those skilled in the art based on the atoms to be measured and actual needs, and is not limited in this invention.

[0063] More preferably, the temperature control unit includes a heating coil and a temperature sensor.

[0064] The heating coil is located outside the microwave resonant cavity to provide heat to the air chamber inside the cavity.

[0065] The temperature sensor is located inside the atomic gas chamber, preferably near the center of the atomic gas chamber, to measure the temperature inside the atomic gas chamber.

[0066] The temperature control unit also includes a temperature control module, which adjusts the heat output of the heating coil based on the detection value of the temperature sensor to control the temperature inside the atomic gas chamber.

[0067] In this invention, there are no restrictions on the specific structure or model of the heating coil, temperature sensor, and temperature control module. Those skilled in the art can freely choose based on experience. Preferably, the temperature control module is any temperature control chip that adopts the KPI control method.

[0068] The present invention also provides a method for measuring atomic relaxation rate, preferably implemented using the above-described apparatus, comprising the following steps:

[0069] A microwave field is generated by a microwave unit and acts on the atomic gas chamber;

[0070] A laser beam is generated by a laser unit to irradiate the atomic gas cell. The laser beam after passing through the atomic gas cell is collected by a collection unit to obtain the frequency information of the laser beam, which is used as the Rabi resonance amplitude.

[0071] Adjust the phase of the microwave field to obtain the corresponding Rabi resonance amplitude under different microwave fields, and plot the Rabi resonance curve.

[0072] Solve the Rabi resonance curve of the atom to obtain the atomic relaxation rate.

[0073] Preferably, the method further includes the following steps:

[0074] Adjust the temperature of the atomic gas chamber to reach the preset value.

[0075] Preferably, the step of generating a laser beam to irradiate the atomic gas chamber via the laser unit includes the following sub-steps:

[0076] Adjust the frequency stabilizer so that the frequency of the output laser resonates with the intrinsic transition of atoms.

[0077] Adjust the collimating and expanding optical path and the position of the photodetector so that the optical path can be incident on the atomic gas cell and detected by the photodetector after being projected from the atomic gas cell;

[0078] Adjust the amplification factor of the photodetector so that the signal can be clearly extracted.

[0079] Preferably, adjusting the phase and power of the microwave field includes the following sub-steps:

[0080] Set the phase modulation signal of the arbitrary waveform generator, and the microwave field output by the microwave source changes periodically. In each cycle, the microwave will have a frequency perturbation under the phase modulation, which is used to interact with the atoms.

[0081] The modulation ratio of an arbitrary waveform generator is set. The modulation ratio adjusts the output amplitude. Generally, the modulation coefficient is set to 1 in the Agilent 8257D microwave source.

[0082] The output power of the microwave source is set. The specific setting value can be set by those skilled in the art according to actual needs, and the output power of the microwave source is kept constant during the measurement process.

[0083] According to the present invention, the electrical signal output by the photoelectric detector is obtained by using a Fourier fast analyzer. The resonance peaks are found within a set frequency range with the center frequency as the midpoint. The peak points of the resonance peaks are connected to obtain a set of Rabi resonance lines. Generally, the range is scanned up to 40 kHz. One point is detected every 1 kHz to obtain one resonance peak. The peak points of these 39 resonance peaks are connected to obtain a set of Rabi resonance lines.

[0084] In a preferred embodiment, the Rabi resonance curve of the solved atom can be expressed as:

[0085]

[0086] Where γ represents the atomic relaxation rate, ω FWHM This represents the full width at half maximum (FWHM) of the Rabi resonance curve.

[0087] Example

[0088] Example 1

[0089] The following apparatus was used to measure the temperature at 30℃, 40℃, 50℃, 60℃, and 70℃ respectively. 87 Rb atomic relaxation rate, 5mg 87 Rb atoms are placed in an atomic gas chamber filled with N2 inert gas. The device includes:

[0090] The microwave unit is used to generate a microwave field that acts on the atomic gas cell, causing the atoms in the atomic gas cell to produce Rabi resonance.

[0091] The laser unit is used to generate a laser beam to irradiate the atomic gas cell, and the laser beam is used to detect the Rabi resonance law of the atoms;

[0092] The acquisition unit is used to acquire the laser beam after it passes through the atomic gas cell and obtain the frequency information of the laser beam.

[0093] The host computer plots the frequency information of the laser beam into the Rabi resonance curve of the atom, calculates the Rabi resonance curve of the atom, and obtains the atomic relaxation rate.

[0094] The microwave unit includes a microwave source and an arbitrary waveform generator.

[0095] The arbitrary waveform generator provides a phase modulation signal to the microwave source, causing the microwaves output by the microwave source to be in a phase-modulated state.

[0096] The microwaves output from the microwave source act on the atomic gas cell, forming a microwave field that causes the alkali metal atoms in the ground state energy level to undergo Rabi resonance.

[0097] The microwave unit also includes a microwave resonant cavity, which is used to convert the microwaves output from the microwave source into a uniform microwave field, and the atomic gas chamber is disposed inside the microwave resonant cavity.

[0098] The microwave unit also includes a power amplifier, which is placed between the microwave resonant cavity and the microwave source to amplify the microwaves output from the microwave source and feed the amplified microwaves into the microwave resonant cavity.

[0099] The laser unit includes a frequency-stabilized laser for providing a laser beam of a preset frequency.

[0100] The acquisition unit includes a photodetector and a fast Fourier transform analyzer.

[0101] The photodetector is used to receive the laser beam after it passes through the atomic gas cell, convert the optical signal into an electrical signal, and transmit it to the fast Fourier transform analyzer.

[0102] The fast Fourier analyzer converts electrical signals into frequency signals to obtain the Rabi resonance amplitude of atoms.

[0103] The arbitrary waveform generator provides a phase modulation signal, causing the output power value of the microwave source to change periodically. Each cycle yields a set of Rabi resonance amplitudes, and the Rabi resonance amplitudes from multiple cycles are used to plot a Rabi resonance curve.

[0104] The host computer uses the amplitude and full width at half maximum (FWHM) of the Rabi resonance curve to calculate the atomic relaxation rate.

[0105] The device also includes a temperature control unit for controlling the temperature of the atomic gas chamber, so that the temperature inside the atomic gas chamber remains at a preset value.

[0106] The final measurement results are shown in Table 1.

[0107] Table 1

[0108]

[0109] Comparative Example 1

[0110] Using a traditional method, namely, using two laser beams to interact with atoms, one beam as a pump light to polarize the atoms, and the other beam as a probe light to detect the degree of polarization of the polarized atoms, the same atoms in Example 1 were measured, and the measurement results are shown in Table 2.

[0111] Table 2

[0112]

[0113]

[0114] As can be seen from Tables 1 and 2, the method in Example 1 can reduce measurement error by more than 20%.

[0115] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this invention, and are only for the convenience of describing this invention and simplifying the description, and 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 a limitation of this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0116] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0117] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present invention based on these embodiments, all of which fall within the scope of protection of the present invention.

Claims

1. An apparatus for measuring atomic relaxation rate, characterized in that, The device includes: The microwave unit is used to generate a microwave field that acts on the atomic gas cell, causing the atoms in the atomic gas cell to produce Rabi resonance. A laser unit is used to generate a laser beam to irradiate an atomic gas cell and to use the laser beam to detect the Rabi resonance law of atoms. The laser unit includes a collimating and expanding optical path for adjusting the size of the beam spot. The acquisition unit is used to acquire the laser beam after it passes through the atomic gas cell and obtain the frequency information of the laser beam. The host computer plots the frequency information of the laser beam into the Rabi resonance curve of the atom, solves the Rabi resonance curve of the atom, and obtains the atomic relaxation rate. The host computer uses the amplitude and full width at half maximum (FWHM) of the Rabi resonance curve to calculate the atomic relaxation rate. The Rabi resonance curve of the calculated atom is expressed as follows: ， in, Represents the atomic relaxation rate. This represents the full width at half maximum (FWHM) of the Rabi resonance curve; The microwave unit also includes a microwave resonant cavity, which is used to convert the microwaves output from the microwave source into a uniform microwave field, and the atomic gas chamber is disposed inside the microwave resonant cavity.

2. The apparatus for measuring atomic relaxation rate according to claim 1, characterized in that, The microwave unit includes a microwave source and an arbitrary waveform generator. The arbitrary waveform generator provides a phase modulation signal to the microwave source, causing the microwaves output by the microwave source to be in a phase-modulated state. The microwaves output from the microwave source act on the atomic gas cell, forming a microwave field that causes the alkali metal atoms in the ground state energy level to undergo Rabi resonance.

3. The apparatus for measuring atomic relaxation rate according to claim 1, characterized in that, The microwave unit also includes a power amplifier, which is placed between the microwave resonant cavity and the microwave source to amplify the microwaves output from the microwave source and feed the amplified microwaves into the microwave resonant cavity.

4. The apparatus for measuring atomic relaxation rate according to claim 1, characterized in that, The laser unit includes a frequency-stabilized laser for providing a laser beam of a preset frequency.

5. The apparatus for measuring atomic relaxation rate according to claim 1, characterized in that, The acquisition unit includes a photodetector and a fast Fourier transform analyzer. The photodetector is used to receive the laser beam after it passes through the atomic gas cell, convert the optical signal into an electrical signal, and transmit it to the fast Fourier transform analyzer. The fast Fourier analyzer converts electrical signals into frequency signals to obtain the Rabi resonance amplitude of atoms.

6. The apparatus for measuring atomic relaxation rate according to claim 2, characterized in that, The arbitrary waveform generator provides a phase modulation signal, causing the output power value of the microwave source to change periodically. Each cycle yields a set of Rabi resonance amplitudes, and the Rabi resonance amplitudes from multiple cycles are used to plot the Rabi resonance curve.

7. The apparatus for measuring atomic relaxation rate according to claim 1, characterized in that, The device also includes a temperature control unit for controlling the temperature of the atomic gas chamber, so that the temperature inside the atomic gas chamber remains at a preset value.

8. A method for measuring atomic relaxation rate, implemented using the apparatus described in any one of claims 1-7, characterized in that, Includes the following steps: A microwave field is generated by a microwave unit and acts on the atomic gas chamber; A laser beam is generated by a laser unit to irradiate the atomic gas cell. The laser beam after passing through the atomic gas cell is collected by a collection unit to obtain the frequency information of the laser beam, which is used as the Rabi resonance amplitude. Adjust the phase and power of the microwave field to obtain the corresponding Rabi resonance amplitude under different microwave fields, and plot the Rabi resonance curve. Solve the Rabi resonance curve of the atom to obtain the atomic relaxation rate; The Rabi resonance curve of the solved atom is expressed as: ， in, Represents the atomic relaxation rate. This represents the full width at half maximum (FWHM) of the Rabi resonance curve.

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