Miniaturized absolute gravity measuring device based on ion trap suspended nano-diamond

Abstract

The invention relates to the technical field of precision measurement, and discloses a miniaturized absolute gravity measurement device based on ion trap suspended nano-diamond, which comprises a vacuum module, a position detection and feedback control module and a laser and microwave module, the vacuum module comprises a vacuum cavity, a vacuum pump, an ion trap, nano-diamond, a convex lens, an objective lens and a copper wire; the vacuum cavity is matched with the vacuum pump to provide a vacuum environment; the nano-diamond is trapped in the ion trap through triboelectrification, stable trapping and free falling of the nano-diamond are completed by controlling instantaneous on-off of voltage of a cap pole of the ion trap, and a Tesla-level magnetic field gradient is generated by using a copper wire. The device is used for coupling the electron spin state of the NV color center and the motion state of the nano-diamond to generate spin-related wave packet splitting, beam splitting, reflection and beam combining operation of matter waves are achieved, a Mach-Zehnder interference sequence is constructed in combination with the free falling body process to accumulate gravitational acceleration related phase shift, and the device has the advantages of being high in sensitivity, small in size and capable of conducting measurement repeatedly.

Description

Technical Field

[0001] The invention relates to the technical field of precision measurement, in particular to a miniaturized absolute gravity measurement device based on ion trap suspended nano-diamonds. Background Art

[0002] As one of the most successful applications of quantum mechanics, quantum sensing has been widely used in various fields such as time and frequency measurement, electric and magnetic field sensing, gravity and rotation sensing, etc. Among them, the precise measurement of gravity has immeasurable value in many applications such as basic scientific research, resource exploration, inertial navigation, etc.

[0003] The two key points for the practical application of gravimeters are high sensor sensitivity and miniaturization of the device. From free-falling block corner cube prisms to free-falling a group of atoms, gravity interferometry has transformed from laser interferometry to matter wave interferometry, and its sensitivity has reached It has a sensitivity that exceeds that of traditional gravimeters. However, the typical size of existing atomic gravimeters is meter-level, and the miniaturization of the equipment comes at the expense of sensitivity. In order to obtain a smaller device size without affecting the interference sensitivity, a feasible method is to use particles with larger mass as the interference system; in order to further improve the sensitivity, a feasible strategy is to increase the number of interfering particles, increase momentum splitting, and use quantum resources such as entanglement.

[0004] As early as 1970, Askin et al. had used the radiation pressure of light to trap dielectric nanoparticles, but it was not until the last decade that ground state cooling of suspended nanoparticles marked a higher controllability. Suspended nanoparticles have a larger mass and density than atomic systems, and therefore have a shorter de Broglie wavelength. When used for gravity sensing, it is expected to further reduce the size of the device while maintaining the sensitivity of interferometry. Nanodiamonds containing NV color centers have optically controllable electron spin states, providing a promising method for coupling with external motion states through magnetic field gradients. However, there is still a lack of a miniaturized gravity interferometry solution for using it as a gravity sensor. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes an absolute gravity measurement device based on ion trap suspended nanodiamonds, which integrates the interference area and the detection area in a single ion trap, aiming to further improve the sensing sensitivity on the basis of reducing the size of the gravimeter.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: a miniaturized absolute gravity measurement device based on ion trap suspended nanodiamonds, comprising: a vacuum module, a position detection and feedback control module, a laser and microwave module;

[0007] The vacuum module includes a vacuum chamber, a vacuum pump, an ion trap, a nanodiamond, a convex lens, an objective lens and a copper wire;

[0008] The vacuum pump is connected to the vacuum chamber, the ion trap is fixed in the vacuum chamber, the nanodiamond is loaded in the ion trap, and the copper wire is fixed in the vacuum chamber above the nanodiamond, so as to generate a Tesla-level magnetic field gradient to achieve the coupling of the electronic spin state of the NV color center in the nanodiamond and the motion state of the nanodiamond particles, and react the gravitational acceleration introduced in the motion state during the free fall process to the phase of the spin state;

[0009] Glass windows for letting light in are arranged on both sides of the vacuum chamber, and a convex lens and an objective lens are respectively fixed in the vacuum chamber on both sides of the nanodiamond, and both the convex lens and the objective lens are directly facing the glass windows;

[0010] The position detection and feedback control module comprises a four-quadrant detector, a programmable logic gate array and a high-voltage amplifier, wherein the four-quadrant detector (9) is connected to the programmable logic gate array (10) via an ADC module, the four-quadrant detector is used to collect scattered light of the nanodiamond through an objective lens, and obtain a position signal of the nanodiamond for analysis, the programmable logic gate array is connected to the high-voltage amplifier via a DAC module, the output end of the high-voltage amplifier is connected to a cap pole in the ion trap, a feedback voltage is generated via the programmable logic gate array, the feedback voltage is amplified by the high-voltage amplifier, and feedback control is performed on the cap pole of the ion trap to cool the axial movement of the nanodiamond;

[0011] The laser and microwave module comprises a first laser, a second laser, a first acousto-optic modulator, a second acousto-optic modulator, a first reflector, a second reflector, a first dichroic mirror, a second dichroic mirror, a radio frequency signal source, a pulse signal generator and a single photon detector installed on one side of the first dichroic mirror, wherein the light beam emitted by the first laser passes through the first acousto-optic modulator and reaches the first reflector, then passes through the first dichroic mirror in the direction facing the glass window and enters the vacuum cavity, and reaches the nano-diamond confinement region through the convex lens, so as to illuminate the confinement region and assist feedback cooling, and the first acousto-optic modulator is used to generate a light beam. The optical modulator, the radio frequency signal source and the second acousto-optic modulator are all connected to the data transmission end of the pulse signal generator, and the output end of the single-photon detector is connected to the pulse signal generator. The light beam emitted by the second laser passes through the second acousto-optic modulator to reach the second reflector, and then passes through the second dichroic mirror along the direction opposite to the glass window to reach the objective lens, so as to excite the spin state of the NV color center electrons in the nanodiamond. The spontaneously radiated fluorescence is collected by the single-photon detector, and the electrical signal is transmitted to the pulse signal generator for photon counting, so as to realize the spin polarization and fluorescence detection process.

[0012] Preferably, a plurality of through holes are left on the side of the vacuum chamber, with one through hole at the top and one at the bottom. The through holes on the side of the vacuum chamber are divided into four groups, one group is an interface for connecting a vacuum feedthrough, used to power the ion trap electrode and the copper wire, one group is an interface for connecting a resistance gauge and an ionization gauge, used to detect the vacuum degree in the vacuum chamber, one group is connected to a glass window for passing light to realize position detection and feedback cooling of the nanodiamond, and the remaining group is connected to a glass window for monitoring the trapping status of the nanodiamond. The through holes at the top and bottom of the vacuum chamber are connected to glass windows for passing light to manipulate the electron spins of the NV color center contained in the nanodiamond.

[0013] Preferably, the vacuum pump is a composite pump of a mechanical pump and a molecular pump, which is used to pump the vacuum in the chamber from atmospheric pressure to 10 -5 Pa vacuum environment.

[0014] Preferably, the ion trap is a standard quadrupole trap, a U-shaped ceramic bracket is fixed in the vacuum chamber, the ion trap is fixed on the U-shaped ceramic bracket, the cap pole of the ion trap is embedded in the ceramic bracket, the cap pole direction driving frequency is lower than the radial frequency, and the stable trapping and free fall of the trapped particles in the trap are controlled by controlling the on and off of the cap pole voltage, and the axial vibration frequency of the particles is defined as ω, and the vibration period is τ=2π / ω.

[0015] Preferably, the copper wire is fixed on a U-shaped ceramic bracket on one side of the ion trap through a copper wire bracket.

[0016] Preferably, the nanodiamond has a radius of 10-100 nm and contains a single or multiple NV color centers, which are loaded into the ion trap by laser induced acoustic desorption technology.

[0017] Preferably, the microwaves in the laser and microwave module cover a frequency of 2.87 GHz, and microwave signals are emitted by a radio frequency signal source and radiated by the copper wire to achieve population regulation between NV spin ground state triplet states.

[0018] Preferably, the first laser is a 1064nm laser, the second laser is a 532nm laser, the first dichroic mirror reflects the 600-800nm ​​light beam through the 1064nm light beam, and the second dichroic mirror reflects the 1064nm light beam through the 532nm light beam.

[0019] The present invention provides a miniaturized absolute gravity measurement device based on ion trap suspended nanodiamonds. It has the following beneficial effects:

[0020] 1. The present invention controls the instantaneous on and off of the ion trap cap voltage to achieve stable trapping and free fall of nanodiamonds, and uses copper wire to generate Tesla-level magnetic field gradients to couple the spin state of the NV color center with the motion state of the nanodiamond to produce spin-related wave packet splitting, thereby realizing the splitting, reflection, and combining operations of matter waves. It is combined with the free fall process to construct a Mach-Zehnder interferometer sequence to accumulate phase shifts related to gravitational acceleration, which has the advantages of high sensitivity, miniaturization, and repeatable measurement.

[0021] 2. When the total free fall time is 2 ms, the present invention can achieve a sensitivity level of 300 ms for the free fall time of a single atom. The effective interference size can be reduced by five orders of magnitude compared with the atomic system. The interference area and the detection area are integrated in the ion trap, which greatly enhances the compactness of the device.

[0022] 3. Compared with the scheme of suspending nanoparticles by optical tweezers, the present invention suppresses the heating effect caused by scattered photons, increases the coherence time of the system and thus improves the sensing sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a module of an absolute gravimeter based on ion-trap suspended nanodiamonds proposed by the present invention;

[0024] Figure 2 It is a schematic diagram of the control sequence of the ion trap electrode, laser, microwave and magnetic field gradient of the present invention;

[0025] Figure 3 It is a schematic diagram of the interior of the vacuum chamber of the present invention;

[0026] Figure 4 It is a schematic diagram of the installation of the ion trap and copper wire of the present invention.

[0027] Among them, 1. vacuum chamber; 2. vacuum pump; 3. ion trap; 4. nano diamond; 5. convex lens;

[0028] 6. Objective lens; 7. Copper wire; 8. First laser; 9. Four-quadrant detector; 10. Programmable logic gate array; 11. High-voltage amplifier; 12. Second laser; 13. First acousto-optic modulator; 14. First reflector; 15. First dichroic mirror; 16. Radio frequency signal source; 17. Pulse signal generator; 18. Second acousto-optic modulator; 19. Second reflector; 20. Second dichroic mirror; 21. Single-photon detector; 22. U-shaped ceramic bracket; 23. Copper wire bracket. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Please see attached Figure 1 -Attached Figure 4 , an embodiment of the present invention provides a miniaturized absolute gravity measurement device based on ion trap suspended nanodiamonds, the device comprising three modules, namely, a vacuum module, a position detection and feedback control module, and a laser and microwave module;

[0031] Please see attached Figure 1 As shown, the vacuum module in the present invention comprises: a vacuum chamber 1, a vacuum pump 2, an ion trap 3, a nanodiamond 4, an objective lens 5, a convex lens 6 and a copper wire 7, wherein the vacuum chamber 1 is made of titanium alloy;

[0032] Specifically, eight through holes are left on the side of the vacuum chamber 1 in the device, one through hole at the top and one at the bottom, and glass windows for letting light in are arranged on both sides thereof, one through hole at the top and one at the bottom, and the side through holes are divided into four groups: one group is connected to a feedthrough for supplying power to the electrodes of the ion trap 3 and the copper wire 7, one group is connected to a resistance gauge and an ionization gauge for detecting the vacuum degree in the chamber 1, one group is connected to a glass window for letting light in to detect the position of the nanodiamond 4 and provide feedback cooling, and the remaining group is connected to a glass window for monitoring the trapped state of the nanodiamond 4, and the top and bottom through holes are connected to glass windows for letting light in to manipulate the electron spins of the NV color centers contained in the nanodiamond 4;

[0033] Furthermore, the vacuum pump 2 is a composite pump of a mechanical pump and a molecular pump, which can pump the vacuum in the chamber from atmospheric pressure to 10 -5 Pa vacuum environment;

[0034] Please see attached Figure 3 As shown, the ion trap 3 in the present invention is a standard quadrupole trap, the ion trap 3 is fixed on a U-shaped ceramic bracket 22, the cap pole is embedded in the U-shaped ceramic bracket 22, and the driving frequency in the cap pole direction is much lower than the radial frequency, so that only the evolution of the nanodiamond 4 in the cap pole direction is concerned, and the stable trapping and free fall of the trapped particles in the trap are controlled by controlling the on and off of the cap pole voltage, and the axial vibration frequency of the particles is defined as ω, and the vibration period is τ=2π / ω. After the nanodiamond 4 is feedback cooled to the motion ground state, the motion coherent state is generated by non-adiabatic change of the cap pole trapping voltage.

[0035] Specifically, the radius of the nanodiamond 4 in the present invention is in the range of 10-100 nm. In this embodiment, the case of a radius of 100 nm is used for illustration, wherein a single NV color center is contained and loaded into the ion trap 3 by laser induced acoustic desorption technology;

[0036] Please see attached Figure 3 As shown, the copper wire 7 is used to generate a Tesla-level magnetic field gradient. The copper wire (7) is located above the nanodiamond 4 and close to the nanodiamond. The copper wire 7 is fixed by a copper wire bracket 23 installed on a U-shaped ceramic bracket 22, and is used to achieve the coupling of the NV color center spin state and the nanodiamond 4 motion state, so that the gravitational acceleration introduced in the free fall process in the motion state is reflected to the phase of the spin state. In addition, when the copper wire 7 is connected to the radio frequency signal source 16, it can be used to generate microwaves to regulate the electron spin of the NV color center.

[0037] Please see attached Figure 1 As shown, in this embodiment, the position detection and feedback control module includes a four-quadrant detector 9, a programmable logic gate array 10, and a high-voltage amplifier 11. The first laser 8 emits light on and off through a first acousto-optic modulator 13, and reaches a dichroic mirror 15 through a reflector 14. Specifically, the dichroic mirror 15 reflects a 600-800nm ​​light beam through a 1064nm light beam, and then enters the vacuum chamber, and reaches the nano-diamond 4 confinement area through a convex lens 5. The scattered light of the nano-diamond 4 is collected by the objective lens 6 and reaches the four-quadrant detector 9, which is converted into an electrical signal and transmitted to the programmable logic gate array 10. The feedback signal is amplified by the high-voltage amplifier 11 to modulate the cap voltage of the ion trap 3, thereby achieving the effect of cooling the axial movement of the nano-diamond 4.

[0038] Please see attached Figure 1 As shown, the laser and microwave module includes: a first laser 8 and a second laser 12. The first laser 8 is a 1064nm laser, which is used to illuminate the confinement area. On the one hand, it can be used to monitor the confinement of ions. On the other hand, the 1064nm laser is scattered by the nanodiamond 4, and the scattered light can be collected by the objective lens to the four-quadrant detector 9 for feedback cooling;

[0039] The second laser 12 is a 532nm laser, which is used to realize the spin polarization and fluorescence detection process;

[0040] This module is divided into two parts. The laser is provided by the above structure, and the microwave is generated by the radio frequency signal source 16. In this embodiment, the radio frequency signal source 16 and the first acousto-optic modulator 13 and the second acousto-optic modulator 18 are all controlled by the pulse signal generator 17, and cover the frequency of 2.87 GHz. Specifically, in the actual operation process, the light beam emitted by the second laser 12 reaches the reflector 19 through the second acousto-optic modulator 18, and reaches the objective lens 6 through the dichroic mirror 20 to excite the NV color center electron spin state in the nanodiamond 4. The dichroic mirror 20 reflects the 1064 nm light beam through the 532 nm light beam. After that, the spontaneously radiated fluorescence is collected by the single photon detector 21, and the electrical signal is transmitted to the pulse signal generator 17 for photon counting. The microwave module covers 2.87 GHz frequency microwaves, and the microwave signal is emitted by the radio frequency signal source 16 and radiated by the copper wire 7 to realize the population regulation between the NV spin ground state triplet states.

[0041] In the actual application process of the present invention, the specific implementation steps are:

[0042] S1, loading the nano-diamond 4 into the ion trap 3, using the laser induced acoustic desorption technology, so that the first laser 8 placed outside the vacuum chamber 1 bombards the aluminum sheet with the nano-diamond 4 placed in the vacuum chamber 1 through the glass window, and the small balls that bounce off the aluminum sheet are charged by friction with the remaining gas in the chamber, and then trapped in the ion trap 3, and the trapped state of the particles is observed by using a charge coupled device placed outside the chamber, and the particles are repeatedly loaded until the trap stably traps a single particle, and then the vacuum chamber 1 is evacuated to a high vacuum. This dry loading scheme does not introduce moisture and pollutants, and is convenient for multiple loading of nano-particles;

[0043] S2, position detection and feedback cooling of the nano-diamond 4 in the trap, using the first laser 8 to illuminate the confinement area through the convex lens 5, using the objective lens 6 to collect scattered light to the four-quadrant detector 9 to analyze the position information of the nano-diamond 4, and using the programmable logic gate array 10 to generate a feedback signal, which is amplified by the high-voltage amplifier 11 to feedback control the cap voltage of the ion trap 3 to feedback cool the nano-diamond 4;

[0044] S3. Reference Figure 2 As shown in the content, regarding the initial state preparation, for the spin state, the 532nm laser emitted by the second laser 12 is applied to spin polarize the NV color center electron state contained in the nanodiamond 4 to the state of zero magnetic quantum number |m=0>, and then microwave pulses are radiated through the copper wire 7 to distribute |m=0> to |m=±1> with equal probability, generating

[0045] For the moving state, the bang-bang control theory is used to non-adiabatically change the axial voltage to produce an instantaneous movement of the trapped center position of the ion trap 3 to produce a coherent state |α 0>, get the initial state Then the magnetic field gradient is combined with the free fall process to produce the Mach-Zehner interferometer sequence for gravity measurement;

[0046] (Beam splitting operation) S4, reference Figure 2 The content shown here constructs the beam splitter operation sequence, which is completed by the copper wire 7 being powered on for τ / 2 time and then continuing to evolve freely in the trap 3 for τ / 4 time. When the copper wire 7 is not powered on, the trapped center is determined by the balance between the electric field force provided by the ion trap 3 and the gravity exerted on the nano-diamond 4. After power is turned on, the magnetic field gradient causes the two spin states to be subjected to forces in opposite directions, and the corresponding trapped centers of different spins are offset in opposite directions. Therefore, the wave packet is periodically split during the movement, and the position splitting reaches the maximum after half a period of vibration. After the copper wire 7 is powered off, the free evolution of the nano-diamond 4 in the potential well for τ / 4 can transform the position splitting into momentum splitting, thereby generating spin-related momentum splitting, and thus completing the beam splitting operation;

[0047] (Free fall) S5, please refer to the attached Figure 2 The content shown is free fall, the cap voltage of the ion trap 3 is instantly disconnected to make the nano diamond 4 free fall for T=1ms, thereby introducing gravity acceleration into its motion state;

[0048] (Reflection operation) S6, please refer to the attached Figure 2 The contents shown are used to construct a reflector operation sequence. After the nanodiamond 4 is in free fall for T=1ms, a trapping potential is applied. After the trapping potential is applied for 3τ / 4, the copper wire 7 is energized with twice the original amount for τ / 2. The current is then turned off to allow the nanodiamond 4 to continue to evolve freely in the well 3 for 3τ / 4 to complete the operation.

[0049] (Free fall again) S7, please refer to the attached Figure 2 As shown, the cap pole trapped potential of the ion trap 3 is disconnected again to allow the nanodiamond 4 to fall freely for T=1 ms, so that the motion wave packets corresponding to different spin states are merged in space. At this time, the momentum of the two wave packets is different.

[0050] (Bundle operation) S8, please refer to the attached Figure 2 As shown in the figure, a beam combining operation sequence is constructed to combine the momentums corresponding to different spins. This process is the reverse process of the beam splitting operation. The nanodiamond 4 is allowed to evolve freely in the trap for 1 / 4τ time by turning on the cap voltage of the ion trap 3. Then, the copper wire 7 is energized for τ / 2 time to complete the operation. At this time, the two moving wave packets are closed and the gravity-related phase is accumulated on the spin state, thus avoiding the reduction of interference contrast due to the interference of the moving state during interferometric measurement.

[0051] S9. Please refer to the attached Figure 2As shown in the figure, the copper wire 7 is connected to the RF signal source 16 to radiate microwave pulses to control the spin state population, and the gravity-related phase accumulated on the spin state is converted into the population probability on the spin state. Then, the second laser 12 is turned on to obtain the population probability by fluorescence counting. The relationship between the population probability and the gravitational acceleration is:

[0052]

[0053] Where g is the acceleration due to gravity, η = γ e B′z 0 / ω represents the magnetic Lambdic parameter induced by the magnetic field gradient, γ e =28GHz / T is the gyromagnetic ratio of the nanodiamond 4, B′ is the magnetic field gradient intensity generated by the copper wire 7, z 0 is the zero-point fluctuation of nanodiamond 4; η g =Mgz 0 / ω, M is the mass of nanodiamond 4, and obviously η g It is positively correlated with the gravity of nanodiamond 4. Since the mass of nanodiamond 4 is much larger than the mass of atomic ion system, this effect is not ignored. When the free fall time T is 1ms and the magnetic field gradient is 10 4 T / m, when the vibration frequency ω is 2π×10kHz, the sensing sensitivity of the scheme is obtained: At this time, the effective interference size is 20μm, while in the single-atom case, the interference area size needs to be increased by five orders of magnitude to achieve the same sensitivity.

[0054] In the present invention, the instantaneous on and off of the ion trap cap voltage is controlled to complete the stable trapping and free fall of the nanodiamond 4, and the copper wire 7 is used to generate a Tesla-level magnetic field gradient to couple the spin state of the NV color center with the motion state of the nanodiamond 4 to generate spin-related wave packet splitting, thereby realizing the beam splitting, reflection, and beam combining operations of the matter wave. It is combined with the free fall process, that is, the on and off of the ion trap cap voltage, to construct a Mach-Zehnder interference sequence to accumulate phase shifts related to gravitational acceleration. It has the advantages of high sensitivity, miniaturization, and repeatable measurement, and has a compact and miniaturized structure and good application value.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds, characterized in that: include: Vacuum module, position detection and feedback control module, laser and microwave module; The vacuum module comprises a vacuum chamber (1), a vacuum pump (2), an ion trap (3), a nanodiamond (4), a convex lens (5), an objective lens (6) and a copper wire (7); The vacuum pump (2) is connected to the vacuum chamber (1) at its exhaust end, the ion trap (3) is fixed in the vacuum chamber (1), the nanodiamond (4) is loaded in the ion trap (3), and the copper wire (7) is fixed in the vacuum chamber (1) above the nanodiamond (4) to generate a Tesla-level magnetic field gradient, thereby coupling the electron spin state of the NV color center in the nanodiamond (4) with the motion state of the nanodiamond (4), and reacting the gravitational acceleration introduced in the motion state during the free fall process to the phase of the spin state; Glass windows for letting light in are provided on both sides of the vacuum chamber (1); a convex lens (5) and an objective lens (6) are respectively fixed in the vacuum chamber (1) on both sides of the nanodiamond (4), and both the convex lens (5) and the objective lens (6) are directly opposite to the glass windows; The position detection and feedback control module comprises a four-quadrant detector (9), a programmable logic gate array (10) and a high-voltage amplifier (11), wherein the four-quadrant detector (9) is connected to the programmable logic gate array (10) via an ADC module, the four-quadrant detector (9) is used to collect scattered light of the nanodiamond (4) through an objective lens (6), and obtain a position signal of the nanodiamond (4) for analysis, the programmable logic gate array (10) is connected to the high-voltage amplifier (11) via a DAC module, the output end of the high-voltage amplifier (11) is connected to the cap electrode in the ion trap (3), a feedback voltage is generated by the programmable logic gate array (10), the feedback voltage is amplified by the high-voltage amplifier (11), and the cap electrode voltage of the ion trap (3) is feedback-controlled to cool the axial movement of the nanodiamond (4); The laser and microwave module comprises a first laser (8), a second laser (12), a first acousto-optic modulator (13), a second acousto-optic modulator (18), a first reflector (14), a second reflector (19), a first dichroic mirror (15), a second dichroic mirror (20), a radio frequency signal source (16), a pulse signal generator (17), and a single-photon detector (21) installed on one side of the first dichroic mirror (15), wherein the light beam emitted by the first laser (8) passes through the first acousto-optic modulator (13) and reaches the first reflector (14), passes through the first dichroic mirror (15) in a direction facing the glass window, enters the vacuum chamber (1), and reaches the nanodiamond (4) confinement area through the convex lens (5), and is used to illuminate the confinement area and assist Feedback cooling is assisted, the first acousto-optic modulator (13), the radio frequency signal source (16) and the second acousto-optic modulator (18) are all connected to the data transmission end of the pulse signal generator (17), the output end of the single-photon detector (21) is connected to the pulse signal generator (17), the light beam emitted by the second laser (12) passes through the second acousto-optic modulator (18) and reaches the second reflector (19), then passes through the second dichroic mirror (20) along the direction opposite to the glass window and reaches the objective lens (6), thereby exciting the spin state of the NV color center electron in the nanodiamond (4), and the spontaneously emitted fluorescence is collected by the single-photon detector (21), and the electrical signal is transmitted to the pulse signal generator (17) for photon counting, so as to realize the spin polarization and fluorescence detection process.

2. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: A plurality of through holes are left on the side of the vacuum chamber (1), with one through hole at the top and one at the bottom. The through holes on the side of the vacuum chamber (1) are divided into four groups, one group is an interface for connecting a vacuum feedthrough, used for supplying power to an ion trap (3) electrode and a copper wire (7), one group is an interface for connecting a resistance gauge and an ionization gauge, used for detecting the vacuum degree in the vacuum chamber (1), one group is connected to a glass window for passing light, realizing position detection and feedback cooling of the nanodiamond (4), and the remaining group is connected to a glass window for monitoring the trapped state of the nanodiamond (4). The through holes at the top and bottom of the vacuum chamber (1) are connected to the glass window for passing light to manipulate the electron spin of the NV color center contained in the nanodiamond (4).

3. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: The vacuum pump (2) is a composite pump of a mechanical pump and a molecular pump, which is used to pump the vacuum in the cavity from atmospheric pressure to 10 -5 Pa vacuum environment.

4. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: The ion trap (3) is a standard quadrupole trap. A U-shaped ceramic bracket (22) is fixed in the vacuum chamber (1). The ion trap (3) is fixed on the U-shaped ceramic bracket (22). The cap of the ion trap (3) is embedded in the ceramic bracket. The driving frequency of the cap direction is lower than the radial frequency. The stable trapping and free fall of the trapped particles in the trap are controlled by controlling the on and off of the cap voltage. The axial vibration frequency of the particles is defined as ω, and the vibration period is defined as τ=2π / ω.

5. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: The copper wire (7) is fixed on a U-shaped ceramic bracket (22) on one side of the ion trap (3) via a copper wire bracket (23).

6. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: The nanodiamond (4) has a radius of 10-100 nm and contains a single or multiple NV color centers, which are loaded into an ion trap through laser-induced acoustic desorption technology.

7. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: The microwaves in the laser and microwave module cover a frequency of 2.87 GHz, and microwave signals are emitted by a radio frequency signal source (16) and radiated by a copper wire (7), thereby achieving population control between the NV color center spin ground state triplet states.

8. The miniaturized absolute gravity measurement device based on ion-trap suspended nanodiamonds according to claim 1, characterized in that: The first laser (8) is a 1064nm laser, the second laser (12) is a 532nm laser, the first dichroic mirror (15) reflects a 600-800nm ​​beam through a 1064nm beam, and the second dichroic mirror (20) reflects a 1064nm beam through a 532nm beam.

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