CN111948462B - Coaxial structure broadband quantum microwave measuring device and method - Google Patents
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Abstract
The invention relates to a broadband quantum microwave measuring device and a broadband quantum microwave measuring method. The measuring device has a quantum-microwave interaction physical structure similar to a coaxial line, and specifically comprises an inner conductor, an outer conductor, a filling medium and a quantum sample; the device is simple in a TEM working mode, and the broadband quantum microwave measurement can be realized under the condition that a physical system is not replaced; the method has the advantages that the extremely small amount of the sub-sample space is arranged in the filling medium, so that the material of the quantum sample carrier is the background material of the microwave field area, and the design strategy of 'used by the inventor' can obviously reduce the interference of the quantum sample carrier to the microwave signal to be measured in the current quantum microwave measurement, and is favorable for improving the measurement precision; the coaxial structure measuring device can be directly connected with the existing microwave transmission system through impedance transformation, so that the function of the coaxial structure measuring device is similar to that of a conventional microwave sensor, and the coaxial structure measuring device is conveniently used for microwave monitoring of the microwave transmission system. In addition, the invention also has the advantages of traceability, miniaturization, easy expansion and the like.
Description
Technical Field
The invention relates to the field of quantum precision measurement and microwave engineering, in particular to a coaxial structure broadband quantum microwave measurement device and method.
Background
Accurate evaluation of microwave field and microwave power is always a core subject in the fields of microwave engineering, high-precision measuring instruments, electromagnetic measurement and the like, and the rise of quantum technology provides a brand-new solution strategy for the subject. Particularly, atoms are used as a microwave field sensing substance, and the direct conversion from electromagnetic quantity to atomic frequency can be realized by utilizing the proportional relation (proportionality coefficients are basic physical constants) between the atomic transition Rabi frequency and the electric/magnetic field intensity in the atom-microwave interaction process. The novel microwave measurement strategy has the advantages of self calibration and traceability to International systems of Units (International System of Units) naturally, the theoretical measurement capability can break through the traditional limitation, and the novel microwave measurement strategy is expected to be used for constructing quantum precise microwave measurement instruments and novel national electromagnetic standards and has huge potential.
Recently, the academia has conducted a series of highly productive research works for atomic measurements of electric/magnetic fields, as demonstrated by the wo p.treulein team, 2010, on coplanar waveguide-based atomsA microwave magnetic field detection device (P.
Et al "Imaging of microwave fields using ultrasound atoms", applied Physics Letters,97 (5), 051101, 2010); the free space Rydberg atomic Microwave electric field detection device was demonstrated by professor J.P.Shaffer, 2012 (J.Sedlacek, et al, "Microwave electrometric with Rydberg atoms in a vacuum cell using bright atomic detectors", nature Physics,8,819-824, 2012); the group of professor g.miltei switzerland and the group of the university of electronic technology in 2015 and 2017 reported cavity-based atomic microwave magnetic field detection devices based on different quantum theories, respectively (c.affolderbach et al, "Imaging microwave and DC magnetic fields in a vacuum-cell Rb atomic clock", IEEE Transactions on Instrumentation and Measurement,64 (12), 3629-3637,2015 f.sun et al, "Measuring microwave access using atomic radar responses", applied Physics Letters,111 (5), 051103, 2017); the NIST team in 2018 reported atomic microwave power standards based on rectangular waveguides (C. Holloway et al, "A quality-based power standards: using Rydberg atoms for a SI-convertible radio-frequency power measurement technologies in rectangular waveguides", applied Physics Letters,113 (9), 094101, 2018).
Although quantum microwave measurement has become an international leading-edge hotspot, its common deficiencies include (but are not limited to) the following in view of current research results:
1. the measuring device is too complex, the working bandwidth of the quantum-microwave interaction structure is very limited, and the microwave excitation structure is required to be replaced frequently when signals with different frequencies are measured, so that the measuring device is not suitable for engineering application;
2. the material property of a quantum sample bearing body (such as an alkali metal atom glass air chamber) is different from the measurement background (such as air), so that the field to be measured is disturbed, and the measurement result is inaccurate;
3. only application scenes such as free space, resonant cavity, waveguide and the like are considered, so that the developed quantum microwave measuring device cannot be similar to the conventional universal microwave power sensor, and practical application of the quantum microwave measuring device is limited.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a broadband quantum microwave measuring device with a coaxial structure and a method thereof, wherein the broadband quantum microwave measuring device comprises the following steps:
a coaxial structure broadband quantum microwave measuring device comprises: an inner conductor, an outer conductor, a filling medium and a quantum sample;
the outer conductor is sleeved on the inner conductor according to a set distance; the set distance is b-a; wherein, a is the radius of the inner conductor and the inner radius of the filling medium, and b is the inner radius of the outer conductor and the outer radius of the filling medium;
the filling medium is uniformly and densely filled between the outer conductor and the inner conductor;
a sample space is arranged in the filling medium; the outer conductor is provided with a light through hole for laser to pass through, and the light through hole and the sample space are arranged in a collinear way;
the quantum sample is arranged in the sample space and used for sensing the microwave to be detected;
the inner conductor, the outer conductor and the filling medium form a coaxial structure; the coaxial structure works in a TEM mode, and quantum-based measurement and evaluation are allowed to be carried out on the microwave signal to be measured with the working wavelength larger than pi (a + b);
the radius of the inner conductor and the inner radius of the outer conductor are determined according to the frequency of the microwave to be measured, the relative dielectric constant of the filling medium and the impedance matching requirement; the impedance matching requirement is according to the formula
Determining that the obtained characteristic impedance reaches a target impedance value; wherein, Z c Is characteristic impedance,. Epsilon r Is the relative dielectric constant of the fill dielectric.
Preferably, the size of the sample space is equal to the size of the light-passing hole.
Preferably, the inner conductor is cylindrical in shape; the inner conductor is made of copper.
Preferably, the outer conductor is a round tubular structure; the outer conductor is made of copper or stainless steel.
Preferably, the filling medium is glass or polytetrafluoroethylene.
Preferably, the number of the light through holes is one or two;
when the filling medium is polytetrafluoroethylene, the number of the light through holes is one; an optical fiber channel is formed in the filling medium, and the light through hole, the optical fiber channel and the sample space are arranged in a collinear manner;
when the filling medium is glass, the number of the light through holes is two; and the two light through holes are arranged in a collinear way with the sample space.
A coaxial structure broadband quantum microwave measuring method is applied to the coaxial structure broadband quantum microwave measuring device; the coaxial structure broadband quantum microwave measurement method comprises the following steps:
acquiring the frequency of the microwave to be detected according to the quantum sample, and determining the filling medium and the relative dielectric constant thereof;
determining the radius of a conductor in the measuring device according to the frequency of the microwave to be measured, the relative dielectric constant of the filling medium and the impedance matching requirement; the conductor radius includes a radius of the inner conductor and an inner radius of the outer conductor; the impedance matching requirement is according to the formula
Determining that the obtained characteristic impedance reaches a target impedance value; wherein Z is c For the characteristic impedance, a is the radius of the inner conductor and the inner radius of the filling medium, b is the inner radius of the outer conductor and the outer radius of the filling medium, ε r Is the relative dielectric constant of the fill medium;
extracting quantum transition Rabi frequency through microwave-light-quantum interaction;
determining the microwave field intensity to be detected according to the Rabi frequency; the microwave field intensity to be detected is a microwave magnetic field intensity amplitude or a microwave electric field intensity amplitude;
and determining the microwave power transmitted in the measuring device according to the conductor radius, the relative dielectric constant and the field intensity.
Preferably, the determining the radius of the conductor in the measuring device according to the frequency of the microwave to be measured, the relative dielectric constant of the filling medium and the impedance matching requirement specifically includes:
and defining the radius of the conductor according to the frequency of the microwave to be measured, namely ensuring that the microwave measurement is carried out in a TEM mode, wherein the defined relation is as follows: f < c/[ π (a + b) ]; wherein f = c/λ is the frequency of the microwave to be detected, λ is the wavelength of the microwave to be detected, and c is the speed of light in vacuum;
adjusting the radius of the inner conductor and the inner radius of the outer conductor under the aforementioned defined relationship until the impedance matching requirement is met;
the target impedance value is generally the impedance value of the existing common coaxial line; the common coaxial line has an impedance value of 50 ohms or 75 ohms.
Preferably, the determining the microwave field strength to be measured according to the Rabi frequency specifically includes:
using a formula
Determining the microwave field intensity to be detected according to the Rabi frequency; wherein Ω is the Rabi frequency, μ is the transition matrix cell,. Mu.>
Is the Planck constant, S is the field strength.
Preferably, the calculating the microwave power transmitted in the measuring device according to the radius of the conductor, the relative dielectric constant and the field strength specifically includes:
using a formula
Or>
Determining the microwave power transmitted in the measuring device according to the conductor radius, the relative dielectric constant and the field intensity; wherein P is the microwave power transmitted in the measuring device,h is the microwave magnetic field intensity amplitude, and E is the microwave electric field intensity amplitude.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention mainly comprises an inner conductor, an outer conductor, a filling medium and a quantum sample to form a quantum-microwave interaction physical structure similar to a coaxial cable, simplifies a microwave measuring device, greatly improves the microwave measuring bandwidth, can realize direct connection with the existing common 50 ohm or 75 ohm impedance microwave transmission system, and enlarges the application range; the invention not only allows the measurement of the microwave magnetic field and the microwave power through the magnetic dipole quantum transition, but also allows the measurement of the microwave electric field and the microwave power through the electric dipole quantum transition. According to the invention, a very small amount of the sub-sample space is arranged in the filling medium, so that the material of the quantum sample carrier is the background material of the microwave field, and the design strategy of 'used by the inventor' can obviously reduce or even eliminate the interference of the quantum sample carrier to the microwave signal to be measured in the current quantum microwave measurement, and is favorable for improving the measurement precision.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings for implementing the idea of the present invention without any inventive work.
FIG. 1 is a schematic structural diagram of a broadband quantum microwave measuring device with a coaxial structure provided by the invention;
FIG. 2 is a longitudinal cross-sectional view of a broadband quantum microwave measuring device with a coaxial structure provided by the invention;
FIG. 3 is a transverse cross-sectional view of a coaxial broadband quantum microwave measuring device according to the present invention, wherein the filling medium is glass;
FIG. 4 is a transverse cross-sectional view of a polytetrafluoroethylene filled medium in the coaxial broadband quantum microwave measuring device according to the present invention;
FIG. 5 is a flow chart of a coaxial broadband quantum microwave measurement method provided by the present invention;
FIG. 6 is an energy level diagram of cesium atoms in an embodiment of the present invention;
fig. 7 is a compatible structure diagram of the coaxial structure broadband quantum microwave measuring device and the existing common 50 ohm or 75 ohm impedance microwave transmission system in the embodiment of the invention.
Description of the symbols:
1-inner conductor, 2-outer conductor, 3-filling medium, 4-sample space, 5-first light through hole, 6-second light through hole, 7-laser, 40-quantum sample, 32-air filling medium, 51-light through hole, and 111-inner conductor of current common 50 ohm or 75 ohm impedance coaxial transmission line.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a coaxial structure broadband quantum microwave measuring device and method, which have the advantages of simple structure, wide frequency band, good compatibility, accurate measurement, wide application range and the like.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic structural diagram of a coaxial broadband quantum microwave measuring device provided by the present invention, and fig. 2 is a longitudinal cross-sectional view of the coaxial broadband quantum microwave measuring device provided by the present invention. As shown in fig. 1 and fig. 2, a coaxial structure broadband quantum microwave measuring device includes: an inner conductor 1, an outer conductor 2, a filling medium 3 and a quantum sample 40.
The outer conductor 2 is sleeved on the inner conductor 1 according to a set distance. The set interval is b-a. Wherein, a is the radius of the inner conductor and the inner radius of the filling medium, and b is the inner radius of the outer conductor and the outer radius of the filling medium.
The inner conductor 1 is preferably cylindrical in shape and made of copper. The shape of the outer conductor 2 is preferably tubular (hollow cylindrical), and the material is preferably copper or stainless steel, but not limited thereto.
The filling medium 3 is uniformly and closely filled between the outer conductor 2 and the inner conductor 1. Wherein, the filling medium is glass or polytetrafluoroethylene, but is not limited thereto.
The inner conductor 1, the outer conductor 2 and the filling medium 3 form a coaxial structure. The coaxial structure operates in a TEM mode, allowing quantum-based measurement evaluation of microwave signals to be measured having operating wavelengths greater than pi (a + b). A sample space 4 is arranged in the filling medium 3, which sample space 4 is preferably a very small sample space. The outer conductor 2 is provided with a light through hole for laser to pass through, and the light through hole and the sample space 4 are arranged in a collinear manner. In order to further improve the accuracy of the measurement, the size of the sample space 4 corresponds to the size of the light-passing hole.
In order to facilitate the transition excitation of different quantum samples, the number of the light passing holes is one or two. In practical application, however, the user can expand the specific number of the light-transmitting holes and the sample spaces according to practical requirements.
When the filling medium 3 is polytetrafluoroethylene, the number of the light through holes is one. And an optical fiber channel 42 is opened in the filling medium 3, and the light through hole 51, the optical fiber channel 42 and the sample space 4 are arranged collinearly.
When the filling medium 3 is glass, the number of the light-passing holes is two. And both of the light-passing holes 5 and 6 are arranged in line with the sample space 4.
The quantum sample 40 is placed in the sample space 4.
The radius of the inner conductor 1 and the inner radius of the outer conductor 2 are determined according to the frequency of the microwave to be measured, the relative dielectric constant of the filling medium 3 and the impedance matching requirement.
The invention relates to a broadband quantum microwave measuring method based on a coaxial interaction structure, which is mainly realized by the following steps:
And 3, injecting laser 7 through the light through hole 5 or 51 to prepare a quantum state, wherein the quantum sample 40 prepared in the state generates quantum transition under the excitation of a microwave field, and the state inversion is realized. The quantum transition Rabi frequency omega is in direct proportion to the microwave field intensity S:
wherein, μ is a transition matrix cell ^ H>
Planck constants, both basic physical constants.
And 4, detecting quantum transition through laser to realize accurate extraction of the Rabi frequency omega, and further calculating the field intensity S of the microwave signal to be detected.
And step 6, because the measuring device works in a TEM mode of a coaxial structure and allows broadband microwaves to be fed in, the microwave precision measurement of the broadband based on the quantum effect can be realized by adjusting the energy of a specific energy level or selecting energy level transitions of different frequencies through the three-dimensional strong static magnetic field.
The following provides a specific embodiment to further illustrate the scheme of the present invention, and the specific embodiment of the present invention is illustrated by taking the filling medium as glass or teflon as an example, and in a specific application, the scheme of the present invention is also applicable to a technical scheme of performing measurement by using other filling media.
Example one
When the filling medium is glass, as shown in fig. 3, a first light-passing hole 5 and a second light-passing hole 6 for passing laser are formed in the outer conductor 2, and the first light-passing hole 5 and the second light-passing hole 6 are arranged in a collinear manner with the sample space 4.
The sample space 4 is loaded with an atomic sample 40, and the laser 7 is single-frequency light or dual-frequency light.
When the laser 7 is a single-frequency light, the laser has dual functions of pumping and detecting, and at the moment, rabi frequency omega corresponding to a microwave magnetic field can be extracted by methods such as Rabi resonance or Rabi oscillation, and the like, so that the microwave magnetic field and the transmission microwave power in the measuring device can be calculated. When the laser 7 is dual-frequency light, the laser specifically includes coupling light and probe light which are transmitted in an antiparallel manner, and AT this time, the Rabi frequency Ω corresponding to the microwave electric field can be extracted by methods such as EIT and AT splitting of Rydberg atoms, so that the microwave electric field and the transmitted microwave power in the measuring device can be calculated.
Specifically, the invention provides a method for carrying out broadband quantum microwave measurement by relying on the coaxial structure broadband quantum microwave measurement device. As shown in fig. 5, the broadband quantum microwave measurement method includes:
step 100: the frequency of the microwave to be measured and the relative dielectric constant of the filling medium (also a quantum sample carrier) are obtained according to the quantum sample.
Step 101: and determining the radius of the conductor in the measuring device according to the frequency of the microwave to be measured, the relative dielectric constant of the filled medium and the impedance matching requirement. The conductor radius includes the radius of the inner conductor and the inner radius of the outer conductor. The method specifically comprises the following steps:
determining the characteristic impedance of the measuring device according to the frequency of the microwave to be measured and the relative dielectric constant of the quantum sample carrier:
wherein a is the radius of the inner conductor and the inner radius of the filling medium, b is the inner radius of the outer conductor and the outer radius of the filling medium, epsilon r Is the relative dielectric constant of the quantum sample carrier.
Adjusting the radius of the inner conductor and the inner radius of the outer conductor to make the characteristic impedance Z meet the condition that lambda is larger than pi (a + b) c The value is 50 ohm or 75 ohm, the radius of the inner conductor and the radius of the outer conductor obtained at this time are the radius of the conductor, wherein, lambda is the frequency of the microwave to be measured.
Step 102: and extracting the Rabi frequency in the quantum transition process. The method specifically comprises the following steps: and detecting the quantum transition to be detected by laser to realize accurate extraction of the Rabi frequency omega.
Step 103: the field strength is determined from the Rabi frequency. The field intensity is microwave magnetic field intensity amplitude or microwave electric field intensity amplitude.
This step 103 preferably uses a formula
Determining the field strength on the basis of the Rabi frequency, where Ω is the Rabi frequency and μ is the transition matrix element->
Is PlanckConstant, S is field strength.
Step 104: and calculating the power of the microwave transmitted by the measuring device according to the radius of the conductor, the relative dielectric constant and the field intensity.
Step 104 specifically includes:
using a formula
Or->
And determining the microwave power transmitted in the measuring device according to the radius of the conductor, the relative dielectric constant and the field intensity, wherein P is the microwave power transmitted in the measuring device, H is the amplitude of the microwave magnetic field intensity, and E is the amplitude of the microwave electric field intensity.
Based on the device and the method, the quantum measurement of the microwave signal of the X wave band is realized by taking cesium atoms as the quantum sample 40 of the sensing microwave and taking glass as the filling medium. The transition frequency of the undisturbed cesium atom hyperfine ground state F =3 → F =4 is 9.192631770GHz and is just in the X wave band, and the energy level of the transition frequency is shown in FIG. 6.
In the present embodiment, the inner conductor 1 of the coaxial structure is made of an oxygen-free copper material, and has a cylindrical shape, and the outer diameter 2a =1.24mm. The outer conductor 2 of the coaxial structure is hollow cylindrical and made of stainless steel, and the inner diameter 2b =7mm. The filling medium 3 of the coaxial structure is made of a material with a relative dielectric constant epsilon r Glass of =4.3, cylindrical, with an inner diameter and an outer diameter of 1.24mm and 7mm, respectively. In this way, the inner conductor 1, the outer conductor 2, and the filling medium 3 are in close contact with each other to constitute the coaxial structure, and the impedance thereof is high
Europe.
A very small sample space 4 with the side length of 0.5mm is arranged in the filling medium 3 at a position 1mm away from the inner conductor 1, and a cesium atom sample is loaded in the sample space 4. The outer conductor 2 is provided with a first light through hole 5 and a second light through hole 6 which are used for allowing 852nm laser 7 to penetrate through and have the diameter of 0.5mm, and the sample space 4, the first light through hole 5 and the second light through hole 6 are collinear and are not positioned on the same horizontal plane with the inner conductor. The laser 7 is locked on a cesium atom D2 line and is used as pumping light and probe light of hyperfine transition prepared by a cesium atom energy state. The coaxial structure and the quantum sample 40, in cooperation with the laser 7, together form the core of the coaxial structure broadband quantum microwave measuring device of the invention.
In operation, a 852nm laser 7 of the D2 line produces 6 ground state cesium atoms 40 in the sample space 4 2 S 1/2 F =3 energy level, and the ground state cesium atoms on the F =3 energy level are transited to 6 under the excitation of the magnetic field component of the microwave signal to be measured 2 S 1/2 F =4 energy level, and once the cesium atom is at 6 2 S 1/2 The layout at the F =4 level is recorded by the laser light 7, which laser light 7 then acts as a probe light. The recorded information can be used for fitting the Rabi frequency omega corresponding to the microwave magnetic field to be measured, and then the microwave magnetic field and the transmission microwave power in the coaxial structure broadband quantum microwave measuring device can be calculated by adopting the coaxial structure broadband quantum microwave measuring method provided by the invention.
In order to make the coaxial structure broadband quantum microwave measuring device provided by the invention compatible with the existing microwave transmission system, the glass-filled coaxial structure can be gradually transited to the conventional coaxial interface of the air-filled medium 32 through impedance transformation. Air relative dielectric constant epsilon of conventional coaxial interface r =1, inner diameter 2b of outer conductor 2 =7mm, outer diameter of inner conductor 111 is 3.04mm, characteristic impedance
Europe, (shown in FIG. 7). After the impedance matching is completed, the electromagnetic wave can be fed into the quantum sample segment coaxial interaction structure through the existing commercial coaxial cable with low loss. Therefore, the coaxial-structure broadband quantum microwave measuring device provided by the invention is very convenient to be applied to the traceable high-precision sensing of the microwave field and power of the existing microwave transmission link.
Part (a) of fig. 7 is a specific structure diagram of the coaxial-structure broadband quantum microwave measuring device compatible with the existing microwave transmission system, and part (b) of fig. 7 is a transverse cross-sectional diagram of the coaxial-structure broadband quantum microwave measuring device compatible with the existing microwave transmission system.
Example two
When the filling medium is polytetrafluoroethylene commonly used in the existing microwave transmission line, as shown in fig. 4, the outer conductor 2 is provided with a light through hole 51 for passing laser, and the filling medium 3 is provided with an optical fiber channel 42. The vacuum sample space 4 is located at the top end of the fiber channel 42, and the light-passing hole 51 is communicated with the fiber channel 42. Wherein the optical fiber channel 42 is a micrometer-scale optical fiber channel.
When the quantum sample 40 loaded in the sample space 4 is a vacuum loaded atom or an NV color center sample loaded in air, the optical fiber inputs and leads laser into and out of the coaxial structure comprising the inner conductor 1, the outer conductor 2 and the filling medium 3 through the optical fiber channel 42 and the light through hole 51. At this time, the microwave magnetic field, the microwave electric field and the microwave power in the measuring device can be accurately measured through the same microwave-quantum-laser interaction process as that of the previous embodiment.
Based on the above arrangement, compared with the prior art, the technical scheme provided by the invention has the following advantages:
1. compared with the prior complex and narrow-band quantum microwave measuring device, the coaxial quantum-microwave interaction physical structure working in the TEM mode has the advantages of miniaturization, wide frequency band and compatibility with the prior 50 ohm or 75 ohm impedance microwave transmission system, and is more beneficial to practical engineering application;
2. in the existing quantum microwave measuring device, the material of a quantum sample carrier is different from the background material of a microwave field area to be measured, so that the measured field to be measured deviates from a real field to different degrees. The coaxial quantum-microwave interaction structure constructed by the invention limits the microwave field to be detected in the filling medium, and meanwhile, the filling medium also serves as a carrier of the quantum sample. If the quantum sample is an alkali metal atom in the glass sample space, the invention selects the glass with the same or extremely similar material properties as the filling medium of the coaxial interaction structure, and the 'used' design strategy can obviously reduce or even eliminate the interference of the quantum sample carrier body per se on the microwave signal to be measured in the current quantum microwave measurement, and the measurement precision is high;
3. the coaxial-structure broadband quantum microwave measuring device can use atoms as quantum samples of a sensing microwave field and can also use NV color centers as quantum samples of the sensing microwave field. The compact physical structure allows the measuring device to be arranged in a three-dimensional strong static magnetic field structure with uniform and adjustable field intensity, and the microwave precision measurement of broadband and even ultra-wideband based on quantum effect can be realized by adjusting the specific energy level energy or selecting energy level transitions with different frequencies through the static magnetic field;
4. when the quantum sample is an atom, the filling medium is glass, and the sample space is vacuum loaded with atoms, so that the microwave field and microwave power can be measured traceably; when the quantum sample is NV color center, the filling medium is polytetrafluoroethylene, and the invention can adopt micron-sized hollow optical fiber (with NV color center sample on the head) to be embedded into the filling medium, so that the microwave signal to be detected is almost completely free of interference.
In conclusion, the invention has the advantages of traceability, miniaturization, wide frequency band, high precision, good compatibility and the like.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. A coaxial structure broadband quantum microwave measuring device is characterized by comprising: an inner conductor, an outer conductor, a filling medium and a quantum sample;
the outer conductor is sleeved on the inner conductor according to a set distance; the set distance is b-a; wherein, a is the radius of the inner conductor and the inner radius of the filling medium, and b is the inner radius of the outer conductor and the outer radius of the filling medium;
the filling medium is uniformly and densely filled between the outer conductor and the inner conductor;
a sample space is arranged in the filling medium; the outer conductor is provided with a light through hole for laser to pass through, and the light through hole and the sample space are arranged in a collinear way;
the quantum sample is arranged in the sample space and used for sensing the microwave to be detected;
the inner conductor, the outer conductor and the filling medium form a coaxial structure; the coaxial structure works in a TEM mode, and quantum-based measurement and evaluation are allowed to be carried out on the microwave signal to be measured with the working wavelength larger than pi (a + b);
the radius of the inner conductor and the inner radius of the outer conductor are determined according to the frequency of the microwave to be measured, the relative dielectric constant of the filling medium and the impedance matching requirement; the impedance matching requirement is according to the formula
Determining that the obtained characteristic impedance reaches a target impedance value; wherein Z is c Is characteristic impedance,. Epsilon r Is the relative dielectric constant of the fill medium.
2. The broadband quantum microwave measurement device with the coaxial structure according to claim 1, wherein the size of the sample space is equal to the size of the light through hole.
3. The broadband quantum microwave measurement device of claim 1, wherein the inner conductor is cylindrical in shape; the inner conductor is made of copper.
4. The broadband quantum microwave measurement device with the coaxial structure as claimed in claim 1, wherein the outer conductor is a circular tubular structure; the outer conductor is made of copper or stainless steel.
5. The broadband quantum microwave measurement device with the coaxial structure as claimed in claim 1, wherein the filling medium is glass or polytetrafluoroethylene.
6. The broadband quantum microwave measurement device with the coaxial structure according to claim 1, wherein the number of the light passing holes is one or two;
when the filling medium is polytetrafluoroethylene, the number of the light through holes is one; an optical fiber channel is formed in the filling medium, and the light through hole, the optical fiber channel and the sample space are arranged in a collinear manner;
when the filling medium is glass, the number of the light through holes is two; the two light-transmitting holes and the sample space are arranged in a collinear manner.
7. A coaxial structure broadband quantum microwave measuring method is characterized by being applied to the coaxial structure broadband quantum microwave measuring device as claimed in any one of claims 1 to 6; the coaxial structure broadband quantum microwave measurement method comprises the following steps:
acquiring the frequency of the microwave to be detected according to the quantum sample, and determining the filling medium and the relative dielectric constant thereof;
determining the radius of a conductor in the measuring device according to the frequency of the microwave to be measured, the relative dielectric constant of the filling medium and the impedance matching requirement; the conductor radius includes a radius of the inner conductor and an inner radius of the outer conductor; the impedance matching requirement is according to the formula
Determining that the obtained characteristic impedance reaches a target impedance value; wherein Z is c For the characteristic impedance, a is the radius of the inner conductor and the inner radius of the filling medium, b is the inner radius of the outer conductor and the outer radius of the filling medium, ε r Is the relative dielectric constant of the fill medium;
extracting quantum transition Rabi frequency through microwave-light-quantum interaction;
determining the microwave field intensity to be detected according to the Rabi frequency; the microwave field intensity to be detected is a microwave magnetic field intensity amplitude or a microwave electric field intensity amplitude;
and determining the microwave power transmitted in the measuring device according to the conductor radius, the relative dielectric constant and the field intensity.
8. The method for measuring broadband quantum microwaves of coaxial structures according to claim 7, wherein the determining the radius of the conductor in the measuring device according to the frequency of the microwaves to be measured, the relative dielectric constant of the filling medium and the impedance matching requirement specifically comprises:
and defining the radius of the conductor according to the frequency of the microwave to be measured, namely ensuring that the microwave measurement is carried out in a TEM mode, wherein the defined relation is as follows: f < c/[ π (a + b) ]; wherein f = c/λ is the frequency of the microwave to be detected, λ is the wavelength of the microwave to be detected, and c is the speed of light in vacuum;
adjusting the radius of the inner conductor and the inner radius of the outer conductor under the aforementioned defined relationship until the impedance matching requirement is met;
the target impedance value is 50 ohms or 75 ohms.
9. The method for measuring broadband quantum microwaves of coaxial structures according to claim 7, wherein the determining the microwave field strength to be measured according to the Rabi frequency specifically comprises:
using a formula
Determining the microwave field intensity to be detected according to the Rabi frequency; wherein omega is the Rabi frequency, mu is the transition matrix element,
is the Planck constant, S is the field strength.
10. The method for microwave measurement of broadband quantum in coaxial structure according to claim 7, wherein the calculating the microwave power transmitted in the measuring apparatus according to the radius of the conductor, the relative dielectric constant and the field strength specifically comprises:
using a formula
Or
Determining the microwave power transmitted in the measuring device according to the conductor radius, the relative dielectric constant and the field intensity; wherein, P is the microwave power transmitted in the measuring device, H is the microwave magnetic field intensity amplitude, and E is the microwave electric field intensity amplitude.
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