A method for lossless spin flipping of nuclear spins in a SERF inertial measurement device

Abstract

The application provides a SERF inertial measurement device nuclear spin lossless flip method, relates to the technical field of quantum precision measurement and inertial navigation, and lossless inverts the nuclear spin polarization direction by applying a specific radio frequency magnetic field to the SERF inertial measurement device. The frequency and amplitude of the applied radio frequency magnetic field change over time, so that the effective magnetic field experienced by the nuclear spin in the rotating coordinate system changes slowly from initially parallel to the polarization direction to the opposite polarization direction, thereby realizing lossless inversion of the nuclear spin polarization direction. The application has important significance for realizing online rapid measurement of nuclear polarization rate, developing a new type of inertial measurement output scheme and further suppressing system slow drift error.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement and inertial navigation technology, and in particular to a method for non-destructive nuclear spin flipping in a SERF inertial measurement device. Background Technology

[0002] Atomic inertial measurement devices based on the SERF spin-free exchange relaxation effect are powerful tools for cutting-edge physics research, providing technical means for research such as dark matter detection, strange interaction force measurement and CPT symmetry breaking verification.

[0003] In the SERF atomic spin inertial measurement device, nuclear spins serve as long-lived quantum memory carriers, and the periodic and precise flipping of their polarization directions is crucial for suppressing slow drift errors. However, existing methods that directly apply strong resonant pulsed magnetic fields for flipping have significant limitations: on the one hand, the non-adiabatic nature of the pulsed magnetic field significantly exacerbates the relaxation rate of the atomic system, leading to rapid decay of nuclear spin polarization and shortening of coherence time; on the other hand, the incompleteness and uncontrollability of the flipping process introduce additional measurement noise and system errors, severely restricting the achievement of the device's limiting sensitivity and the improvement of its long-term stability.

[0004] Therefore, a method for non-destructive nuclear spin flipping in a SERF inertial measurement device is needed to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for non-destructive nuclear spin reversal in a SERF inertial measurement device, which achieves efficient, rapid and controllable reversal of the nuclear spin polarization direction without introducing significant relaxation or disrupting the SERF's self-compensation working state.

[0006] To achieve the above objectives, the present invention provides a method for non-destructive nuclear spin flipping in a SERF inertial measurement device, comprising the following steps:

[0007] S1, Heating the atomic gas chamber to establish a high-temperature, weak magnetic environment: [This involves] introducing K-Rb-... 21 The atomic gas cell of Ne's SERF inertial measurement unit is placed in a demagnetized magnetic shielded barrel, and the gas cell is heated to the working temperature by an oven with heating coils.

[0008] S2: Apply circularly polarized pump-polarized alkali metal electron spin and inert gas nuclear spin along the Z-axis;

[0009] S3: After the optical pumping process in S2 reaches a steady state, triaxial magnetic compensation is performed, and the SERF self-compensation working state is entered.

[0010] S4: Perform lossless nuclear spin polarization flipping; apply a constant bias magnetic field along the Z-axis. A radio frequency magnetic field with amplitude and frequency that varies smoothly with time is applied along the X-axis. The frequency of the radio frequency magnetic field is much lower than 21 Larmor precession frequency of Ne nucleus spin Start with a linear scan to much higher This causes the nuclear spin to adiabatically flip from the initial polarization direction to the opposite direction, following the direction of the effective magnetic field.

[0011] S5: After the flip is complete, set the compensation point to restore the normal working state under the SERF self-compensation mechanism.

[0012] Preferably, in S2, the laser source polarizes the electron spin of the alkali metal through D1 line resonance, and the hyperpolarized inert gas is achieved through spin exchange between electron spin and nuclear spin. 21 Ne's nuclear spin.

[0013] Preferably, the Z-axis magnetic field in S3 is set at the self-compensation point. Self-compensation point The internal magnetic field, generated by the combined electron and nuclear spins, determines the following relationship:

[0014] ;

[0015] in The average magnetic field generated by the electron spin polarization of alkali metals. for 21 The average magnetic field generated by the spin polarization of the Ne nucleus; in the current state, the macroscopic polarization direction of the nuclear spin is along the +Z axis.

[0016] Preferably, the Larmor precession frequency in S4 By constant bias magnetic field Size determines:

[0017] ;

[0018] in for 21 The nuclear gyromagnetic ratio of Ne and the width of the resonant region are jointly determined by the radio frequency field amplitude and the magnetic field homogeneity, and the width is... Magnitude;

[0019] Radio frequency magnetic field The waveform is generated by a signal generator that drives the X-axis coil; the waveform is a linear sweeping continuous wave, and both the amplitude and frequency change smoothly over time.

[0020] Preferably, radio frequency magnetic field Amplitude envelope is determined by rise time Stable time and descent time It consists of three segments, in the rising time Within, it increases linearly from 0 to the maximum value. During the stable period During this period, maintain the maximum value. Through the resonance region, during the descent time Linear smoothing reduced to 0; total scan time The total scan time is less than the transverse relaxation time of the nuclear spin.

[0021] Preferably, radio frequency magnetic field The frequency from the initial value Begin linear scan across Larmor frequencies of nuclear spin To the end value The entire frequency sweep range Covering the resonance zone;

[0022] Radio frequency magnetic field rate of change Satisfying the adiabatic following condition, .

[0023] Preferably, a compensation point is set in S5. Simultaneously change the direction of the circularly polarized pump light. .

[0024] Therefore, the present invention employs the aforementioned method for non-destructive nuclear spin reversal using a SERF inertial measurement device, with the following technical effects: Non-destructive reversal of the nuclear spin polarization direction is achieved by applying a specific radio frequency magnetic field to the SERF inertial measurement device. The frequency and amplitude of the applied radio frequency magnetic field change over time, causing the effective magnetic field experienced by the nuclear spin in the rotating coordinate system to slowly change from initially parallel to the polarization direction to an antiparallel polarization direction, thereby achieving non-destructive reversal of the nuclear spin polarization direction. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for non-destructive nuclear spin flipping in a SERF inertial measurement device according to the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] Example

[0029] This invention provides a method for non-destructive nuclear spin flipping in a SERF inertial measurement device, such as... Figure 1 As shown, it includes the following steps:

[0030] S1, Heating the atomic gas chamber to establish a high-temperature, weak magnetic environment: [This involves] introducing K-Rb-... 21 The atomic gas cell of Ne's SERF inertial measurement unit is placed in a demagnetized magnetic shielded barrel, and the gas cell is heated to the operating temperature by an oven with a heating coil; ensuring that it is in a high-temperature and extremely weak magnetic environment.

[0031] S2: Circularly polarized pump light is applied along the Z-axis to polarize the electron spins of the alkali metal and the nuclear spins of the inert gas; in S2, the laser source polarizes the electron spins of the alkali metal through the D1 line resonance, and the inert gas is hyperpolarized through spin exchange between electron and nuclear spins. 21 Ne's nuclear spin.

[0032] S3: After the optical pumping process in S2 reaches a steady state, triaxial magnetic compensation is performed, and the SERF enters the self-compensation working state; the Z-axis magnetic field in S3 is set at the self-compensation point. Self-compensation point The internal magnetic field, generated by the combined electron and nuclear spins, determines the following relationship:

[0033] ;

[0034] in The average magnetic field generated by the electron spin polarization of alkali metals. for 21 The average magnetic field generated by the spin polarization of the Ne nucleus; in the current state, the macroscopic polarization direction of the nuclear spin is along the +Z axis.

[0035] S4: Perform lossless nuclear spin polarization flipping; apply a constant bias magnetic field along the Z-axis. A radio frequency magnetic field with amplitude and frequency that varies smoothly with time is applied along the X-axis. The frequency of the radio frequency magnetic field is much lower than 21 Larmor precession frequency of Ne nucleus spin Start with a linear scan to much higher This causes the nuclear spin to adiabatically follow the direction of the effective magnetic field, flipping from the initial polarization direction (+Z axis) to the opposite direction (-Z axis).

[0036] S4 Lamor precession frequency By constant bias magnetic field Size determines:

[0037] ;

[0038] in for 21 The nuclear gyromagnetic ratio of Ne and the width of the resonant region are jointly determined by the radio frequency field amplitude and the magnetic field homogeneity, and the width is... Magnitude;

[0039] Radio frequency magnetic field The waveform generated by the signal generator drives the X-axis coil to generate a linear sweeping continuous wave. The amplitude and frequency change smoothly with time, so that the effective magnetic field felt by the nuclear spin in the rotating coordinate system changes slowly from the initial parallel to the polarization direction to the antiparallel polarization direction, thereby achieving lossless reversal of the nuclear spin polarization direction.

[0040] Radio frequency magnetic field Amplitude envelope is determined by rise time Stable time and descent time It consists of three segments, in the rising time Within, it increases linearly from 0 to the maximum value. During the stable period During this period, maintain the maximum value. Through the resonance region, during the descent time Linear smoothing reduced to 0; total scan time The total scan time is less than the transverse relaxation time of the nuclear spin.

[0041] Radio frequency magnetic field The frequency from the initial value Begin linear scan across Larmor frequencies of nuclear spin To the end value The entire frequency sweep range Covering the resonance zone;

[0042] Radio frequency magnetic field rate of change Satisfying the adiabatic following condition, Nuclear spin flips mainly occur in this frequency range.

[0043] S5: After the flip is complete, set the compensation point to restore the normal working state under the SERF self-compensation mechanism.

[0044] Set compensation points in S5 Simultaneously change the direction of the circularly polarized pump light. At this time, the macroscopic polarization direction of the nuclear spin is along the -Z axis, and it is also maintained under the SERF self-compensation mechanism.

[0045] Example 1

[0046] This method is applied to the SERF ultra-high sensitivity inertial measurement unit, and the specific implementation process is as follows: Figure 1 As shown, it includes the following steps:

[0047] S1, Heating the atomic gas chamber to establish a high-temperature, weak magnetic environment: In the SERF ultra-sensitive inertial measurement unit, K-Rb- 21The atomic gas chamber of Ne's SERF inertial measurement unit is housed in a demagnetized magnetically shielded container and heated to its operating temperature of 195°C by an oven equipped with heating coils; this ensures that the hybrid atomic ensemble is in a high-temperature and extremely weak magnetic environment. To achieve the system's ultimate sensitivity, the SERF ultra-sensitive inertial measurement unit is placed on a composite vibration isolation system to isolate ground vibration noise.

[0048] S2: Circularly polarized pump light is applied along the Z-axis to polarize the electron spins of the alkali metal and the nuclear spins of the inert gas; in S2, the laser source polarizes the electron spins of the alkali metal through the D1 line resonance, and the inert gas is hyperpolarized through spin exchange between electron and nuclear spins. 21 Ne's nuclear spin.

[0049] S3: After the optical pumping process in S2 reaches a steady state, triaxial magnetic compensation is performed, and the SERF enters the self-compensation working state; the Z-axis magnetic field in S3 is set at the self-compensation point. Self-compensation point The internal magnetic field, generated by the combined electron and nuclear spins, determines the following relationship:

[0050] ;

[0051] in The average magnetic field generated by the electron spin polarization of alkali metals. for 21 The average magnetic field generated by the spin polarization of the Ne nucleus; in the current state, the macroscopic polarization direction of the nuclear spin is along the +Z axis.

[0052] S4: Perform lossless nuclear spin polarization flipping; apply a constant bias magnetic field along the Z-axis. A radio frequency magnetic field with amplitude and frequency that varies smoothly with time is applied along the X-axis. The frequency of the radio frequency magnetic field is much lower than 21 Larmor precession frequency of Ne nucleus spin Start with a linear scan to much higher This causes the nuclear spin to adiabatically follow the direction of the effective magnetic field, flipping from the initial polarization direction (+Z axis) to the opposite direction (-Z axis).

[0053] S4 Lamor precession frequency By constant bias magnetic field Size determines:

[0054] ;

[0055] in for 21 The nuclear gyromagnetic ratio of Ne and the width of the resonant region are jointly determined by the radio frequency field amplitude and the magnetic field homogeneity, and the width is... Magnitude;

[0056] Radio frequency magnetic field The waveform generated by the signal generator drives the X-axis coil to generate a linear sweeping continuous wave. The amplitude and frequency change smoothly with time, so that the effective magnetic field felt by the nuclear spin in the rotating coordinate system changes slowly from the initial parallel to the polarization direction to the antiparallel polarization direction, thereby achieving lossless reversal of the nuclear spin polarization direction.

[0057] Radio frequency magnetic field Amplitude envelope is determined by rise time Stable time and descent time It consists of three segments, in the rising time Within, it increases linearly from 0 to the maximum value. During the stable period During this period, maintain the maximum value. Through the resonance region, during the descent time Linear smoothing reduced to 0; total scan time The total scan time is less than the transverse relaxation time of the nuclear spin.

[0058] Radio frequency magnetic field The frequency from the initial value Begin linear scan across Larmor frequencies of nuclear spin To the end value The entire frequency sweep range Covering the resonance zone;

[0059] Radio frequency magnetic field rate of change Satisfying the adiabatic following condition, Nuclear spin flips mainly occur in this frequency range.

[0060] S5: After the flip is complete, set the compensation point to restore the normal working state under the SERF self-compensation mechanism.

[0061] Set compensation points in S5 Simultaneously change the direction of the circularly polarized pump light. At this time, the macroscopic polarization direction of the nuclear spin is along the -Z axis, and it is also maintained under the SERF self-compensation mechanism.

[0062] Therefore, this invention employs the aforementioned method for non-destructive nuclear spin reversal using a SERF inertial measurement device. This method involves applying a specific radio frequency magnetic field to the SERF inertial measurement device to non-destructively reverse the nuclear spin polarization direction. The frequency and amplitude of the applied radio frequency magnetic field vary over time, causing the effective magnetic field experienced by the nuclear spin in the rotating coordinate system to slowly change from initially parallel to the polarization direction to an antiparallel polarization direction, thereby achieving non-destructive reversal of the nuclear spin polarization direction.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for non-destructive nuclear spin flipping in a SERF inertial measurement device, characterized in that, Includes the following steps: S1, Heating the atomic gas chamber to establish a high-temperature, weak magnetic environment: [This involves] introducing K-Rb-... 21 The atomic gas cell of Ne's SERF inertial measurement unit is placed in a demagnetized magnetic shielded barrel, and the gas cell is heated to the working temperature by an oven with heating coils. S2: Apply circularly polarized pump-polarized alkali metal electron spin and inert gas nuclear spin along the Z-axis; S3: After the optical pumping process in S2 reaches a steady state, triaxial magnetic compensation is performed, and the SERF self-compensation working state is entered. S4: Perform lossless nuclear spin polarization flipping; apply a constant bias magnetic field along the Z-axis. A radio frequency magnetic field with amplitude and frequency that varies smoothly with time is applied along the X-axis. The frequency of the radio frequency magnetic field is much lower than 21 Larmor precession frequency of Ne nucleus spin Start with a linear scan to much higher This causes the nuclear spin to adiabatically flip from the initial polarization direction to the opposite direction, following the direction of the effective magnetic field. S4 Lamor precession frequency By constant bias magnetic field Size determines: ； in for 21 The nuclear gyromagnetic ratio of Ne and the width of the resonant region are jointly determined by the radio frequency field amplitude and the magnetic field homogeneity, and the width is... Magnitude; Radio frequency magnetic field The waveform is generated by a signal generator that drives the X-axis coil; the waveform is a linear sweeping continuous wave with both amplitude and frequency changing smoothly over time. Radio frequency magnetic field Amplitude envelope is determined by rise time Stable time and descent time It consists of three segments, in the rising time Within, it increases linearly from 0 to the maximum value. During the stable period During this period, maintain the maximum value. Through the resonance region, during the descent time Linear smoothing reduced to 0; total scan time The total scan time is less than the transverse relaxation time of the nuclear spin; S5: After the flip is complete, set the compensation point to restore the normal working state under the SERF self-compensation mechanism.

2. The method for non-destructive nuclear spin flipping in a SERF inertial measurement device according to claim 1, characterized in that, In S2, the laser source, through D1 line resonance, polarizes the electron spin of the alkali metal, and through spin exchange between electron and nuclear spins, hyperpolarizes the inert gas. 21 Ne's nuclear spin.

3. The method for non-destructive nuclear spin flipping in a SERF inertial measurement device according to claim 1, characterized in that, The Z-axis magnetic field in S3 is set at the self-compensation point. Self-compensation point The internal magnetic field, generated by the combined electron and nuclear spins, determines the following relationship: ； in The average magnetic field generated by the electron spin polarization of alkali metals. for 21 The average magnetic field generated by the spin polarization of the Ne nucleus; in the current state, the macroscopic polarization direction of the nuclear spin is along the +Z axis.

4. The method for non-destructive nuclear spin flipping in a SERF inertial measurement device according to claim 1, characterized in that, Radio frequency magnetic field The frequency from the initial value Begin linear scan across Larmor frequencies of nuclear spin To the end value The entire frequency sweep range Covering the resonance zone; Radio frequency magnetic field rate of change Satisfying the adiabatic following condition, .

5. The method for non-destructive nuclear spin flipping in a SERF inertial measurement device according to claim 1, characterized in that, Set compensation points in S5 Simultaneously change the direction of the circularly polarized pump light. ; In the formula, This is the self-compensation point.

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