CN113014256B - Method for preparing spin compression state by cavity coupling atomic system - Google Patents
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Abstract
The application discloses a method for preparing a spin compression state by a cavity coupling atomic system, which comprises the following steps: providing a cavity-coupled atomic system having an energy level structure whose atomic spin states depend on atomic interactions; applying a bias magnetic field or laser to the cavity-coupled atomic system to shift atomic energy to produce a non-hermitian spin interaction; recording spin fluctuation signals from the cavity-coupled atomic system, and determining the change condition of spin compression from the spin fluctuation signals; and measuring the spin compression property when the spin compression parameter is less than 1 according to the change condition of the spin compression so as to generate a spin compression state. The application has the advantages that: the experimental operability is strong, the interaction of the cavity and atoms is utilized, the atomic system state is easy to control, the realized non-hermetia effect does not destroy the spin compression state, but maintains the anti-intuitionistic physical mechanism of stable existence of the spin compression effect, and the application range of the method is wide.
Description
Technical Field
The application belongs to the technical field of quantum precision measurement, and particularly relates to a method for preparing a spin compression state by a cavity coupling atomic system.
Background
Along with the development of a laser technology and an ion or atom trapping technology, precise control on microscopic particles is realized. The atomic frequency standard technology is based on accurate control of atomic transition, and ultra-high-precision time frequency standard is obtained by taking transition frequency as a frequency discrimination signal. Atomic frequency standard based on microwave frequency band, measurement uncertainty reaches 10 -16 The magnitude of the method is widely applied to the fields of satellite navigation, space detection, network communication and the like, and plays an important role in the fields of national defense, military, finance and the like.
The resonant cavity can generate a series of high-frequency electromagnetic fields, can continuously oscillate in the cavity, and has a high quality factor. The high-frequency electromagnetic field generated by the resonant cavity interacts with atoms, so that the energy level conversion of the atoms can be excited, and the state of an atomic system is controlled. The resonant cavity and the laser are combined to act on an atomic system at the same time, so that the precise control of the atomic state can be realized.
Among the seven basic physical quantities of the new international unit system, six international units other than the mole are all on a "second" basis, and are centered among the plurality of basic parameters. So far, with the further development of the technology, the atomic frequency standard based on the optical frequency band is developed, and the measurement uncertainty reaches 10 -19 Magnitude, approaches the standard quantum limit. In order to further break through the limit and achieve a higher precision of the precision measurement, new quantum effects and principles need to be adopted, and the compression effect is an important method. The optical frequency scale is based on the interaction of laser light with atoms, and the multiple energy levels of an atomic system can be equivalently represented as a multi-spin system. In the optical frequency scale, in order to further improve the measurement accuracy, the standard quantum limit is broken through, and a spin compression method can be adopted. The state of the atoms is prepared in a spin compression state, so that the quantum entanglement effect is achieved, and the measurement accuracy of physical parameters is improved. The cavity-coupled atomic system generates non-hermeticity, and the non-hermeticity is usually decoherence, dissipation and the like, and usually damages quantum association and quantum entanglement characteristics to cause system state change, so that a scheme for preparing a spin compression state by the cavity-coupled atomic system is needed to more comprehensively measure state evolution of a physical system.
Disclosure of Invention
The application aims to provide a method for preparing a spin compression state by a cavity coupling atomic system, which solves the problems of maintaining the stable spin compression effect and entanglement effect.
In view of this, the present application provides a method for preparing a spin-compressed state by a cavity-coupled atomic system, comprising:
providing a cavity-coupled atomic system having an energy level structure whose atomic spin states depend on atomic interactions;
applying a bias magnetic field or laser to the cavity-coupled atomic system to shift atomic energy to produce a non-hermitian spin interaction;
recording spin fluctuation signals from the cavity-coupled atomic system, and determining the change condition of spin compression from the spin fluctuation signals;
and measuring the spin compression property when the spin compression parameter is less than 1 according to the change condition of the spin compression so as to generate a spin compression state.
Further, the spin compression parameter is a ratio of a minimum spin ripple to a spin average value when perpendicular to an average spin direction.
Further, the atomic spin states include quantum coherent states.
Further, measuring the spin compression property when the spin compression parameter is stable, includes: determining experimental parameters for preparing the spin compression state.
Further, the experimental parameters for determining the preparation spin compression state are calculated by a Matlab program.
Further, the method further comprises the following steps: the best experimental parameters for preparing the spin compression state are obtained by calculating the eigenstates.
Further, the energy level structure adopts ultra-fine energy levels.
Further, the atomic spin states include spin-up states at an upper energy level of the hyperfine energy level.
Further, the atomic spin states include spin down states at a lower energy level of the hyperfine energy level.
Further, determining a change in spin compression from the spin ripple signal, further includes: and calculating the average value of the rotation components in the x, y and z directions.
The application realizes the following remarkable beneficial effects:
the realization is simple, including: providing a cavity-coupled atomic system having an energy level structure whose atomic spin states depend on atomic interactions; applying a bias magnetic field or laser to the cavity-coupled atomic system to shift atomic energy to produce a non-hermitian spin interaction; recording spin fluctuation signals from the cavity-coupled atomic system, and determining the change condition of spin compression from the spin fluctuation signals; and measuring the spin compression property when the spin compression parameter is less than 1 according to the change condition of the spin compression so as to generate a spin compression state. The experimental operability is strong, the interaction of the cavity and atoms is utilized, the atomic system state is easy to control, the realized non-hermetia effect does not destroy the spin compression state, but maintains the anti-intuitionistic physical mechanism of stable existence of the spin compression effect, and the application range of the method is wide.
Drawings
FIG. 1 is a flow chart of a method of preparing a spin-compressed state for a cavity-coupled atomic system in accordance with the present application.
Detailed Description
The advantages and features of the present application will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings and detailed description. It should be noted that the drawings are in a very simplified form and are adapted to non-precise proportions, merely for the purpose of facilitating and clearly aiding in the description of embodiments of the application.
It should be noted that, in order to clearly illustrate the present application, various embodiments of the present application are specifically illustrated by the present embodiments to further illustrate different implementations of the present application, where the various embodiments are listed and not exhaustive. Furthermore, for simplicity of explanation, what has been mentioned in the previous embodiment is often omitted in the latter embodiment, and therefore, what has not been mentioned in the latter embodiment can be referred to the previous embodiment accordingly.
While the application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood that the application is not to be limited to the particular embodiments disclosed, but on the contrary, the application is to cover all modifications, equivalents, and alternatives falling within the spirit or scope of the application as defined by the appended claims. The same element numbers may be used throughout the drawings to refer to the same or like parts.
Referring to fig. 1, a method for preparing a spin-compression state by a cavity-coupled atomic system according to the present application includes:
step S101, providing a cavity coupling atomic system, wherein the cavity coupling atomic system has an energy level structure with atomic spin states dependent on atomic interactions;
step S102, applying a bias magnetic field or laser to the cavity-coupled atomic system to enable atomic energy to move, and generating non-Hermite spin interaction;
step S103, recording spin fluctuation signals from the cavity coupling atomic system, and determining the change condition of spin compression from the spin fluctuation signals;
step S104, measuring the spin compression property when the spin compression parameter is less than 1 according to the change condition of the spin compression so as to generate a spin compression state.
Further, the spin compression parameter is a ratio of a minimum spin ripple to a spin average value when perpendicular to an average spin direction.
In one embodiment of the application, in particular, the atomic spin states comprise quantum coherence states.
In one embodiment of the application, in particular, measuring the spin-compression properties when the spin-compression parameters are stable, comprises: determining experimental parameters for preparing the spin compression state.
In one embodiment of the application, in particular, the experimental parameters defining the preparation spin compression state are calculated by the Matlab program.
In one embodiment of the present application, specifically, the method further includes: the best experimental parameters for preparing the spin compression state are obtained by calculating the eigenstates.
In one embodiment of the application, in particular, the energy level structure employs ultra-fine energy levels.
In one embodiment of the application, in particular, the atomic spin states comprise spin-up states, at an upper energy level of the hyperfine energy level.
In one embodiment of the application, in particular, the atomic spin states comprise spin down states, at a lower energy level of the hyperfine energy level.
In one embodiment of the present application, specifically, determining the change condition of spin compression from the spin ripple signal further includes: and calculating the average value of the rotation components in the x, y and z directions.
According to an aspect of an embodiment of the present application, the specific steps of generating spin compression are: first, atoms are prepared in coherent state +.>Preparation of a multiparticulate System in the coherent initial State ψ 0 ＝|↓↓...↓>. Spin down state +.>And spin up state +|and +|indicate that the particle is in two hyperfine energy level structures, and the lower energy level uses +|and +|>The upper energy level of the hyperfine energy level structure is represented by +.>Representing, state from +.>To +.>Indicating a transition of the particles from the ultra-fine lower energy level to the upper energy level.
Spin down state +.>Represented asSpin-up state +.i.>Thus the straight product state of a plurality of atoms is
Taking two atoms as an example, the direct product state is
The cavity coupled atomic system then prepares multiple atoms at two energy levels, with the two hyperfine energy levels being equivalent to a two component spin system. The laser interacts with atoms while the cavity field interacts with atoms to create raman transitions between the atomic ground and excited states, all of which are trapped within the trap.
According to an aspect of the embodiment of the application, the bias magnetic field or the laser causes the atomic energy to move along with the originalThe sub-radicals evolve, producing non-hermetic spin interactions, denoted asAt this time, a is taken as an imaginary number.
Taking two particles as an example of this,
thus, the total spin is expressed as
According to an aspect of an embodiment of the present application, the evolution ψ over time t ＝e -iHt ψ 0 The system is characterized by evolving from one state to another under the action of the non-Hermite spin interaction system, and the final state of evolution of A=iA' is expressed asAnd C is the normalized coefficient. The hamiltonian of the spin interaction can be written as +.>A four-dimensional matrix. By calculating->Can obtain the final state psi t Time-dependent, the above-mentioned ψ t We used Matlab programming calculations.
As a specific embodiment, finally, over time, in the eigenstate ψ t The experimental parameters for preparing the spin compression state are determined by theoretical research of the spin compression parameters.
Spin compression is defined as
Wherein the method comprises the steps ofFor spin mean>Represents the minimum spin ripple perpendicular to the average spin direction,/->For the spin direction in which the average value lies, +.>Perpendicular to the average spin direction. When ζ=1, the system is in a coherent state. When xi<1, the system generates a spin compression state, and the spin compression state preparation is realized. Wherein->Is spin average value, by the above-mentioned psi t The average value of the respective rotation component can be calculated,
<S x,y,z >＝<ψ t |S x,y,z |ψ t >，
as a specific example, for the two-particle case, S x,y,z Is a four-dimensional matrix |ψ t >Is a column vector andis |psi t >And (5) conjugate transpose vector. The spin average value is calculated as a matrix product.
The above calculation procedure is substituted into the definition of the spin compression parameter.
Represents the minimum spin ripple perpendicular to the average spin direction,/->The spin direction in which the average value lies is then the average spin direction +.>
Then
The other two directions of the coordinate system are expressed as
And->
And is also provided withAnd->Calculation method and->Similarly to this, the process is carried out,
wherein θ and φ represent angles and
when (when)
For a given wave function ψ, the spin mean value can be determined by the equation<S x,y,z >＝<ψ|S x,y,z The I phi is calculated and obtained by calculating,
when < S y ＞≤0，Perpendicular to the average spin direction, and +.>And->And (5) correlation.
Representing minimum spin ripple perpendicular to the average spin direction and
therefore, spin compression is expressed as
The spin interaction systemThe non-herm system and herm system calculate the spin-compression properties using a=i as an example, respectively, when t=0, the system is in a coherent state, when ζ=1. Over time, for the non-hermy spin interaction system a=i, state +.>
Finally, a stable spin compression state is achieved along with time evolution, an anti-intuitive physical effect is generated, the spin compression effect is not destroyed, and the spin compression state is stable at the optimal spin compression state along with time evolution, so that the spin compression state is easier to obtain and more stable.
From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:
the realization is simple, including: providing a cavity-coupled atomic system having an energy level structure whose atomic spin states depend on atomic interactions; applying a bias magnetic field or laser to the cavity-coupled atomic system to shift atomic energy to produce a non-hermitian spin interaction; recording spin fluctuation signals from the cavity-coupled atomic system, and determining the change condition of spin compression from the spin fluctuation signals; and measuring the spin compression property when the spin compression parameter is less than 1 according to the change condition of the spin compression so as to generate a spin compression state. The experimental operability is strong, the interaction of the cavity and atoms is utilized, the atomic system state is easy to control, the realized non-hermetia effect does not destroy the spin compression state, but maintains the anti-intuitionistic physical mechanism of stable existence of the spin compression effect, and the application range of the method is wide.
Any other suitable modification may also be made according to the technical solution and the idea of the application. All such alternatives, modifications and improvements will readily occur to those skilled in the art and are intended to be within the scope of the application as defined in the appended claims.
Claims (10)
1. A method for preparing a spin-compressed state by a cavity-coupled atomic system, comprising:
providing a cavity-coupled atomic system having an energy level structure whose atomic spin states depend on atomic interactions;
applying a bias magnetic field or laser to the cavity-coupled atomic system to shift atomic energy to produce a non-hermitian spin interaction;
recording spin fluctuation signals from the cavity-coupled atomic system, and determining the change condition of spin compression from the spin fluctuation signals;
and measuring the spin compression property when the spin compression parameter is less than 1 according to the change condition of the spin compression so as to generate a spin compression state.
2. The method of preparing a spin-compressed state for a cavity-coupled atomic system according to claim 1, wherein the spin-compression parameter is a ratio of a minimum spin ripple to a spin average value when perpendicular to an average spin direction.
3. The method of preparing a spin-compressed state for a cavity-coupled atomic system according to claim 1, wherein the atomic spin states comprise quantum coherence states.
4. The method for preparing a spin-compression state of a cavity-coupled atomic system according to claim 1, wherein measuring the spin-compression property when the spin-compression parameter is stable comprises: determining experimental parameters for preparing the spin compression state.
5. The method for preparing a spin-compressed state of a cavity-coupled atomic system according to claim 4, wherein the experimental parameters for determining the preparation of the spin-compressed state are calculated by Matlab program.
6. The method of preparing a spin-compressed state for a cavity-coupled atomic system according to claim 5, further comprising: the best experimental parameters for preparing the spin compression state are obtained by calculating the eigenstates.
7. The method of preparing a spin-compressed state of a cavity-coupled atomic system according to claim 1, wherein the energy level structure employs ultra-fine energy levels.
8. The method of preparing a spin-compressed state for a cavity-coupled atomic system according to claim 7, wherein the atomic spin states comprise spin-up states at an upper energy level of a hyperfine energy level.
9. The method of preparing a spin-compressed state for a cavity-coupled atomic system according to claim 8, wherein the atomic spin states comprise spin-down states at a lower energy level of a hyperfine energy level.
10. The method of preparing a spin-compression state of a cavity-coupled atomic system of claim 1, wherein determining a change in spin-compression from the spin-ripple signal further comprises: and calculating the average value of the rotation components in the x, y and z directions.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1253294A (en) * | 1998-11-05 | 2000-05-17 | 施卢默格控股有限公司 | Equipment and method for calculating spin-spin relaxation time distribution |
| CN105719719A (en) * | 2016-04-18 | 2016-06-29 | 山西大学 | Device for non-classical state teleportation between continuous variable quantum storage nodes |
| CN105807535A (en) * | 2016-05-16 | 2016-07-27 | 山西大学 | Generation device of quantum entanglement among three atomic ensembles |
| CN111060747A (en) * | 2018-10-17 | 2020-04-24 | 北京自动化控制设备研究所 | High-sensitivity nuclear spin precession detection method based on electron spin |
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| US10466317B2 (en) * | 2013-06-03 | 2019-11-05 | The Trustees Of Princeton University | Atomic magnetometry using pump-probe operation and multipass cells |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1253294A (en) * | 1998-11-05 | 2000-05-17 | 施卢默格控股有限公司 | Equipment and method for calculating spin-spin relaxation time distribution |
| CN105719719A (en) * | 2016-04-18 | 2016-06-29 | 山西大学 | Device for non-classical state teleportation between continuous variable quantum storage nodes |
| CN105807535A (en) * | 2016-05-16 | 2016-07-27 | 山西大学 | Generation device of quantum entanglement among three atomic ensembles |
| CN111060747A (en) * | 2018-10-17 | 2020-04-24 | 北京自动化控制设备研究所 | High-sensitivity nuclear spin precession detection method based on electron spin |
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