CN112068043B - Alkali metal atom spin exchange collision relaxation inhibition method controlled by magnetic field pulse - Google Patents
Alkali metal atom spin exchange collision relaxation inhibition method controlled by magnetic field pulse Download PDFInfo
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- CN112068043B CN112068043B CN202010910641.6A CN202010910641A CN112068043B CN 112068043 B CN112068043 B CN 112068043B CN 202010910641 A CN202010910641 A CN 202010910641A CN 112068043 B CN112068043 B CN 112068043B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/0023—Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration
- G01R33/0029—Treating the measured signals, e.g. removing offset or noise
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
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Abstract
The invention discloses a method for restraining spin exchange collision relaxation of alkali metal atoms controlled by magnetic field pulses, which comprises the steps of firstly determining the duration T of the magnetic field pulses, wherein T is more than T alk Wherein, T alk Is the spin exchange collision time of the alkali metal atoms; then according to the ratio of external magnetic field and alkali metal gyromagnetic field, adopting the following formula to calculate the range T of pulse period T, T is less than 1/gamma alk B, again according to gamma alk B 0 t =2 pi calculates the magnetic field pulse amplitude B required when the spin vector rotation radian is 2 pi 0 And finally, determining a plane XOY of the pumping light and the detection light of the atomic magnetometer, and applying a magnetic field pulse to a Z axis vertical to the plane to perform relaxation suppression. The method prevents alkali metal atoms from precessing during the pulse, thereby maintaining the atomic magnetometer in a non-spin exchange relaxation state, and improving the stability of the atomic magnetometer.
Description
Technical Field
The invention relates to the field of quantum instruments and measurement, in particular to a magnetic field pulse controlled alkali metal atom spin exchange collision relaxation inhibition method.
Background
The weak magnetic field measuring device with high sensitivity is widely applied to various fields such as industry, agriculture, geological exploration, national defense and the like. With the rapid development of quantum manipulation technology, many ultra-high sensitive magnetic field devices applying new principles and new effects have emerged. Among them, the Spin-Exchange Relaxation Free (SERF) atomic magnetometer, in particular, based on the Spin-Exchange Relaxation theory, has been rapidly developed. In a natural state, the spins of atoms are disordered, a beam of circularly polarized laser is adopted to pump the atoms to a specific Zeeman sub energy level, so that the atoms have a macroscopic direction, the energy levels of the atoms can be redistributed by spin exchange collision, the coherent life of the atoms is limited, namely, the continuity of spin-polarized alkali metal atoms under the action of an external magnetic field is destroyed, the signal to noise ratio is reduced, and the line width of a system is widened. Therefore, suppression of spin-exchange collision relaxation has become an important research direction for an ultrahigh-sensitivity magnetic field device for atomic spins.
At present, mainly adopted methods comprise magnetic shielding and magnetic compensation to reduce the remanence environment of atoms and improve the performance of pumping light, but quantum basic noise including spin projection noise and photon shot noise cannot be eliminated by the methods, so that the method needs to be designed to enable the spin vectors of the atoms to be in an ordered state without being influenced by mutual collision from the perspective of atomic spin evolution.
When alkali metal atoms are under the action of an external magnetic field, the spin vector rotates, called Larmor precession, the frequency is in direct proportion to the amplitude of the external magnetic field, and if magnetic field pulses with specific frequency and amplitude are applied, the spin vector of the atoms can generate precession with a specific radian. Radio frequency magnetic field pulses are the fundamental means of nuclear magnetic resonance detection, which function to transfer energy to atoms. Therefore, the magnetic field pulse has better technical advantages in the aspect of atom control, is combined in an atom magnetic field meter, and can effectively inhibit spin-exchange collision relaxation in principle by selecting a proper pulse duty ratio according to the gyromagnetic ratios of different alkali metals.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a magnetic field pulse-controlled alkali metal atom spin-exchange collision relaxation suppression method, which can reduce disordered states of spin vectors of atoms due to spin collision.
The purpose of the invention is realized by the following technical scheme:
a method for suppressing spin-exchange collision relaxation of alkali metal atoms by magnetic field pulse manipulation, the method comprising the steps of:
(1) Determining the duration T of the magnetic field pulse, T satisfying T < T alk Wherein, T alk Is the spin exchange collision time of the alkali metal atoms;
(2) Calculating the range of the pulse period T according to the ratio of the external magnetic field to the alkali metal gyromagnetic field by adopting the following formula
t＜T＜1/（γ alk B）
Wherein, gamma is alk Represents the gyromagnetic ratio of alkali metal atoms, and B is the intensity of an external magnetic field;
(3) Calculating the magnetic field pulse amplitude B required when the rotation radian of the spin vector is 2 pi according to the following formula 0
γ alk B 0 t=2π
(4) Determining the plane XOY of the pumping light and the detection light of the atomic magnetometer, and applying a magnetic field pulse to the Z axis vertical to the plane to perform relaxation suppression.
Further, the magnetic field pulse application mode is as follows: either positive continuously along the Z axis, negative continuously along the Z axis, or alternating positive and negative Z axis.
Further, the pulse period T satisfies
t＜T＜1/（10 2 γ alk B）。
The invention has the following beneficial effects:
the method of the invention utilizes the physical property that atoms can generate Larmor precession under the action of an external magnetic field, considers the condition that intrinsic parameters of different atom spin exchange collision time are different, and ensures that alkali metal atoms do not generate precession during a pulse by designing a pulse period range, thereby maintaining an atomic magnetometer in a non-spin exchange relaxation state and improving the stability of the atomic magnetometer. The method can be applied to weak magnetic field tests in a plurality of fields such as medical treatment, military affairs and the like, and has positive significance for improving the sensitivity of the atomic magnetometer and promoting the miniaturization and industrialization development of the magnetometer.
Drawings
FIG. 1 is a flow chart of the operation of the method;
FIG. 2 is a schematic diagram of an atomic spin vector rotated by π radians under pulsed magnetic field.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will be more apparent, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
As shown in fig. 1, the method for suppressing spin-exchange collision relaxation of alkali metal atoms by magnetic field pulse manipulation of the present invention comprises the following steps:
(1) Determining the duration T of the magnetic field pulse, T satisfying T < T alk Wherein, T alk Is the spin exchange collision time of the alkali metal atoms;
(2) Calculating the range of the pulse period T according to the ratio of the external magnetic field to the alkali metal gyromagnetic field by adopting the following formula
t＜T＜1/（γ alk B）
Wherein, gamma is alk Represents the gyromagnetic ratio of alkali metal atoms, and B is the intensity of an external magnetic field;
(3) Calculating the magnetic field pulse amplitude B required when the rotation radian of the spin vector is 2 pi according to the following formula 0
γ alk B 0 t=2π
(4) Determining the plane XOY of the pumping light and the detection light of the atomic magnetometer, and applying a magnetic field pulse to the Z axis vertical to the plane to perform relaxation suppression.
In order to reduce the spin-exchange collision relaxation by continuous pumping, the magnetic field pulse application mode is as follows: either positive continuously along the Z-axis or negative continuously along the Z-axis or alternating positive and negative Z-axis applications.
The pulse period T is such that the pumping time is less than the spin-exchange collision time
t＜T＜1/（10 2 γ alk B）。
As shown in fig. 2, it is a schematic diagram of the method of the present invention, which makes the atomic spin vector rotate pi radians under the action of the pulse magnetic field. The X direction is a pumping light direction, the Y direction is a detection light direction, and a pulsed magnetic field is applied along a Z axis perpendicular to the XY plane. The spin vector rotates about the axis of the pulsed magnetic field, and in step (3), the amplitude of the pulsed magnetic field is such that the spin vector rotates by pi radians.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.
Claims (3)
1. A method for inhibiting the spin-exchange collisional relaxation of alkali metal atoms by magnetic field pulse manipulation, the method comprising the steps of:
(1) Determining the duration T of the magnetic field pulse, T satisfying T < T alk Wherein, T alk Is the spin exchange collision time of the alkali metal atoms.
(2) Calculating the range of the pulse period T according to the ratio of the external magnetic field to the alkali metal gyromagnetic field by adopting the following formula
t＜T＜1/（γ alk B）
Wherein, γ alk Represents the gyromagnetic ratio of alkali metal atoms, and B is the intensity of an external magnetic field;
(3) Calculating the magnetic field pulse amplitude B required when the rotation radian of the spin vector is 2 pi according to the following formula 0
γ alk B 0 t=2π
(4) Determining the plane XOY of the pumping light and the detection light of the atomic magnetometer, and applying a magnetic field pulse to the Z axis vertical to the plane to perform relaxation suppression.
2. The method according to claim 1, wherein the magnetic field pulse is applied in a manner that: either positive continuously along the Z-axis or negative continuously along the Z-axis or alternating positive and negative Z-axis applications.
3. Method for suppressing spin-exchange collision relaxation of alkali metal atoms according to magnetic field pulse manipulation, characterized in that said pulse period T is such that
t＜T＜1/（10 2 γ alk B）。
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106017451A (en) * | 2016-07-20 | 2016-10-12 | 北京航空航天大学 | High-precision measurement method for magnetic field compensation inertial angular rate based on of SERF (spin-exchange relaxation free) atomic device |
| AU2018203814A1 (en) * | 2017-05-31 | 2018-12-20 | Northrop Grumman Systems Corporation | Pulsed-beam atomic magnetometer system |
| CN111060088A (en) * | 2019-12-12 | 2020-04-24 | 北京航天控制仪器研究所 | High-pressure atomic gas chamber manufacturing system and method |
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| US20120112749A1 (en) * | 2010-11-01 | 2012-05-10 | The Regents Of The University Of California | Apparatus and method for increasing spin relaxation times for alkali atoms in alkali vapor cells |
| US9329152B2 (en) * | 2011-08-05 | 2016-05-03 | Wisconsin Alumni Research Foundation | Gas magnetometer |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106017451A (en) * | 2016-07-20 | 2016-10-12 | 北京航空航天大学 | High-precision measurement method for magnetic field compensation inertial angular rate based on of SERF (spin-exchange relaxation free) atomic device |
| AU2018203814A1 (en) * | 2017-05-31 | 2018-12-20 | Northrop Grumman Systems Corporation | Pulsed-beam atomic magnetometer system |
| CN111060088A (en) * | 2019-12-12 | 2020-04-24 | 北京航天控制仪器研究所 | High-pressure atomic gas chamber manufacturing system and method |
Non-Patent Citations (2)
| Title |
|---|
| Nuclear magnetic resonance at millitesla fields using a zero-field spectrometer;Michael C.D.Tayler;《Journal of Magnetic Resonance》;20160512;全文 * |
| 基于光偏振旋转效应的碱金属...化率测量方法及影响因素分析;尚慧宁;《光谱学与光谱分析》;20160215;全文 * |
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