An acceleration sensor based on trapped ions

Abstract

The application discloses an acceleration sensor based on trapped ions and relates to the technical field of quantum sensing, comprising an ion trap module, wherein the ion trap module is connected with an optical frequency comb module through a cable, and the ion trap module is connected with an ultra-stable laser module through a spatial light path. The application is provided with a Paul ion trap in the ion trap module, and ions are trapped in the Paul ion trap for detection. The ultra-stable laser module is provided with a laser locked in a Fabry-Perot cavity, which can generate laser for detecting a clock transition line. An acousto-optic modulator is used to move the laser frequency for feedback. The optical frequency comb module can collect and store the measured data, and the required acceleration can be obtained.

Description

Technical Field

[0001] This invention relates to the field of quantum sensing technology, and in particular to an accelerometer based on trapped ions. Background Technology

[0002] Trapped ion devices are used in fields such as testing physical laws, satellite navigation, and time reference due to their extremely high quality factor, very small second-order Zeeman shift, and very small blackbody radiation shift. A complete trapped ion device consists of three parts: an ultrastable laser, a femtosecond optical comb, and an ion trap, with the ion trap being the core component.

[0003] Currently, ion traps are mainly divided into two types: Paul-type ion traps and Penning-type ion traps. Because the structure of a Penning-type ion trap requires a four-level uniform strong magnetic field, a very large magnetic field is needed, which can significantly affect precision measurements. In contrast, a Paul-type ion trap uses only an electrostatic magnetic field, allowing the fine structure to exist for a longer period and providing a longer trapping time. A linear Paul trap uses a radio frequency electric field to provide confinement force in one two-dimensional plane and an electrostatic field to provide confinement in the remaining one-dimensional plane, thus trapping ions. Trapped ion devices require laser-based state preparation and detection. For clock lasers, the linewidth is typically very narrow at the Hz level, while the linewidth of a laser is very wide at the kHz level, making direct detection impossible. Therefore, ultra-stable lasers are needed. Ultra-stable laser technology further narrows the linewidth of a freely operating laser to obtain extremely high frequency stability. Qualitative laser output is achieved by locking the laser to the resonant peak of the Fabry-Perot cavity using a Pound-Drever-Hall locking scheme. Before the laser enters the cavity, an electro-optic modulator generates two first-order sidebands with opposite phases. When the laser frequency does not resonate with the Fabry-Perot cavity, most of the incident laser is reflected. Only when the carrier or sideband frequency is near a certain resonant peak of the Fabry-Perot cavity will the laser at the resonant frequency be injected into the Fabry-Perot cavity. At this time, the reflected light contains the phase information carried by the injection into the Fabry-Perot cavity, which is coupled into a fast photodetector. After demodulation, an error signal is obtained and fed back to the laser, thereby locking the laser frequency to the resonant peak of the Fabry-Perot cavity and finally outputting a stable laser.

[0004] Combining a femtosecond optical comb, an ultra-stable laser, and an ion trap creates an ion device. Using ions trapped in the ion trap as probes, acceleration can be measured. The most common existing acceleration measurement device is the Earth's gravitational accelerometer, which is an instrument that measures the acceleration due to gravity on the Earth's surface or in near-Earth space. Earth's gravitational accelerometers are divided into absolute gravimeters and relative gravimeters. An absolute gravimeter measures the acceleration due to gravity by measuring the time and distance of motion of a living body or a thrown object in a vacuum, allowing the object to move freely naked or vertically upwards. A relative gravimeter connects an inertial body to a spring or piezoelectric crystal in a vacuum. The inertial body moves under the action of a force, causing the connected spring or piezoelectric crystal to deform. The magnitude of the deformation has a linear or non-linear relationship with the magnitude of the force. Measuring the magnitude of the deformation can determine the change in gravitational acceleration.

[0005] However, measuring devices, mainly absolute gravimeters and relative gravimeters, are relatively complex in structure, large in size and weight, and are only suitable for measurements at fixed locations. They are also greatly affected by the environment during measurement, making it difficult to perform measurements with higher precision. Summary of the Invention

[0006] This invention provides an accelerometer based on trapped ions, which can solve the problem in the prior art that it is not easy to perform higher precision measurements.

[0007] This invention provides an accelerometer based on trapped ions, comprising an ion trap module and an ultrastable laser module;

[0008] The ion trap module includes an ion trapping device, which is connected to an acousto-optic modulator, a mechanical pump, a molecular pump, and an ion pump.

[0009] The ion trapping device is an octahedral metal cavity structure, inside which a linear Paul trap is installed.

[0010] The mechanical pump and molecular pump evacuate the ion trapping device to a specified vacuum level. The ion pump then activates to maintain the specified vacuum level. As the external environment continues to change, the ions trapped in the linear Paul trap undergo continuous motion. According to the Doppler effect, the frequency of the ions changes. The ultra-stable laser module generates a laser to detect the clock transition. After passing through an acousto-optic modulator, the laser enters the ion trapping device to detect the frequency change of the ions, obtaining the clock transition frequency and the frequency shift caused by the Doppler effect. Based on the acceleration measurement formula, the measured acceleration is obtained.

[0011] Preferably, the ultra-stable laser module includes a laser, which is connected to an electro-optic modulator via a spatial optical path. The electro-optic modulator is connected to a signal source via a cable. The signal source is connected to a phase shifter via a cable. The phase shifter is connected to a mixer via a cable. The mixer is connected to a photodiode detector via a cable. The mixer is also connected to a low-pass filter via a cable. The low-pass filter is connected to a servo amplifier via a cable. The servo amplifier is connected to the laser via a cable. The electro-optic modulator and the photodiode detector are connected via a spatial optical path. The photodiode detector is also connected to an FP cavity via a spatial optical path. The photodiode detector is also connected to an acousto-optic modulator via a spatial optical path.

[0012] Preferably, the ion trapping device has an electron multiplier (EMCCD) window and a photomultiplier tube (PMT) window on its side, multiple first vacuum observation windows, a microwave antenna interface, and a DC signal interface on its top, and multiple second vacuum observation windows and a radio frequency signal interface on its bottom.

[0013] Preferably, the ion trapping device is connected to the acousto-optic modulator via a spatial optical path, and the ion trapping device is connected to the mechanical pump, molecular pump, and ion pump via a vacuum pipeline.

[0014] Preferably, the device further includes an optical frequency comb module, which is connected to the ion trapping device via a cable.

[0015] Preferably, the linear Paul trap includes a support on which a pair of end cap electrodes and two pairs of blade electrodes are disposed.

[0016] Preferably, the FP cavity comprises two different endoscopes.

[0017] Preferably, the cable is an SMA cable or a BNC cable.

[0018] Preferably, the laser is a gas laser, a solid-state laser, a semiconductor laser, or a dye laser.

[0019] Preferably, the acceleration measurement formula is:

[0020] a=v / δυ*d(Δf) / dt=c / υ0*d(Δf) / dt

[0021] Where: v is the velocity of the ion, v0 is the clock transition frequency of the ion, δυ is the frequency shift caused by the Doppler effect, c is the speed of light, and d(Δf) / dt is the rate of change of frequency.

[0022] This invention provides an accelerometer based on trapped ions, which has the following advantages compared with the prior art:

[0023] The ion trapping device in the ion trap module provides an ultra-high vacuum environment for trapping ions. A linear Paul trap is placed inside the ion trapping device, and the ions are trapped using a radio frequency electric field. The radio frequency electric field provides the binding force only in one two-dimensional plane, while an electrostatic field provides the binding force in the remaining direction. When ions are trapped in the linear Paul trap, they can be used as probes to measure physical quantities. After a laser generates a laser to detect clock transitions, the laser passes through an acousto-optic modulator and enters the ion trapping device to detect the ions, thereby obtaining the ion clock transition frequency. An optical frequency comb is then used to measure and record the laser frequency. Different clock transition detection sequences are designed to obtain the results of a single clock self-comparison. The data collected by the optical frequency comb is then processed to obtain the ion-detected acceleration. This measurement, using ions trapped in the linear Paul trap as probes to measure physical quantities, and then using an ultra-stable laser to measure and process the frequency changes of the ions to obtain the detected physical quantity, is more accurate than existing acceleration measurement methods and is more convenient for applications in precision measurement. Attached Figure Description

[0024] Figure 1 A schematic diagram of the overall structure of an accelerometer based on trapped ions provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of an ion trapping device based on an accelerometer of trapped ions provided in an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a linear Paul trap for an accelerometer based on trapped ions, provided as an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the FP cavity structure of an accelerometer based on trapped ions, provided for an embodiment of the present invention.

[0028] Among them: 100, ion trap module; 101, ion trapping device; 102, acousto-optic modulator; 103, mechanical pump and molecular pump; 104, ion pump; 200, optical frequency comb module; 300, ultra-stable laser module; 301, laser; 302, electro-optic modulator; 303, signal source; 304, phase shifter; 305, mixer; 306, low-pass filter; 307, servo amplifier; 308, photodiode detector; 309, FP cavity. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0034] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0035] See Figures 1-4 This invention provides an accelerometer based on trapped ions. The ions are relatively stationary relative to the trapped ion device. When there is relative motion between the external environment and the ions, the ions can act as a probe to detect changes in the frequency of the entire system. At this time, the external frequency and the frequency received by the sensor are not the same; this effect is called the Doppler effect. Assuming the ion's velocity is v, the clock transition frequency of the trapped ion optical clock system is v0, and the frequency shift caused by the Doppler effect is δυ, then according to the Doppler effect, the relationship between these physical quantities is δυ / υ. O = v / c, where c is the speed of light. At the 17th General Conference on Weights and Measures in 1983, the speed of light was defined as a constant with a value of 299,792,458 m / s. Therefore, by measuring the frequency change of ions caused by the Doppler effect, the velocity of the ions can be obtained, and thus the acceleration can be obtained. Let the acceleration be a, the formula for measuring acceleration is a = v / δυ*d(Δf) / dt = c / υ0*d(Δf) / dt. For a trapped ion optical clock system, its clock transition frequency v0 can be obtained by measuring the absolute frequency. The frequency change rate d(Δf) / dt can be obtained by self-comparison of a trapped ion device. The acceleration measured by this method is more accurate than the existing acceleration measurement methods and is more conducive to the development of precision measurement physics.

[0036] like Figure 1 The diagram shown is a schematic representation of the overall structure of an accelerometer based on trapped ions provided in an embodiment of the present invention. It mainly consists of an ion trap module 100, an optical frequency comb module 200, and an ultra-stable laser module 300.

[0037] The laser used to detect clock transitions is generated by laser 301 and phase-modulated by electro-optic modulator 302. The modulated laser is input into FP cavity 309, and the laser reflected in front of the cavity enters photodiode detector 308 to obtain an output voltage signal. This signal is mixed with the signal after phase shifter 304 at the operating frequency of electro-optic modulator 302. After passing through closed-loop feedback ultra-stable laser, the laser passes through acousto-optic modulator 102 and enters ion trapping device 101 to detect ions. After obtaining the clock transition frequency, the frequency is corrected by acousto-optic modulator 102. The laser frequency is measured and recorded by optical frequency comb module 200. By designing different clock transition detection sequences, the results of single-set clock self-comparison are obtained. The data collected by optical frequency comb module 200 is processed to obtain the acceleration detected by ions.

[0038] The ion trap module 100 is used to provide an ultra-high vacuum environment for trapping ions and includes an ion trapping device 101, a mechanical pump and a molecular pump 103, an ion pump 104, and an acousto-optic modulator 102.

[0039] like Figure 2 The diagram shown is a structural schematic of an ion trapping device based on an accelerometer of trapped ions provided in an embodiment of the present invention.

[0040] The ion trapping device 101 has an octahedral metal cavity structure with at least eight vacuum observation windows on its sides. Two of these windows are used as EMCCD (electron multiplier CCD) windows and PMT (photomultiplier tube) windows. At least one vacuum observation window is located on each of the top and bottom sides, along with a total of three vacuum flange electrode interfaces. These interfaces serve as microwave antenna interfaces, radio frequency signal interfaces, and DC signal interfaces, respectively. A linear Paul trap is placed inside, such as... Figure 3 It has two pairs of blade electrodes and one pair of end cap electrodes, which are fixed by a bracket. It uses a radio frequency electric field to achieve confinement. The radio frequency electric field is used to provide the binding force in only one two-dimensional plane, while the electrostatic field is used to provide the binding force in the other direction. When ions are confined in a linear Paul trap, the ions can be used as probes to measure physical quantities.

[0041] The acousto-optic modulator 102 is placed on the peripheral optical path of the ion trapping device 101. It acts on the laser entering the ion trapping device 101 to adjust and feed back the laser frequency. The reason for using this device is that even if the laser passes through the optical path of the device twice and the radio frequency signal frequency of the driving device is changed when using a dual-path optical path, the angle of the final emitted laser remains unchanged, which improves the stability and durability of the optical path.

[0042] Mechanical pump and molecular pump 103, ion pump 104 are connected to ion trapping device 101 through vacuum pipeline. Mechanical pump and molecular pump 103 are used to pre-pump the vacuum system to a specified vacuum level. Ion pump 104 works to maintain the system vacuum level after the vacuum system reaches the specified vacuum level. The reason for using these two devices is that the present invention uses ions, which react very easily with the background gas. Using an ultra-high vacuum environment can optimize this.

[0043] The optical frequency comb module 200 is used to collect and store data. The ultra-stable laser module 300 generates an ultra-stable laser, which acts on the ion trap module 100 through a spatial optical path. The ions trapped in it undergo transitions after sensing the laser effect. The generated frequency data can be collected and stored by the optical frequency comb module 200. The two are connected by using SMA or BNC cables. The main component of this device is an ultrashort pulse laser, which can output a spectrum composed of a series of uniformly spaced frequency components with coherent and stable phase relationships. The reason for using this device is that the frequency data obtained by this invention is in the optical frequency band, and it is necessary to convert the frequency data to the microwave frequency band so that this device can stably achieve the conversion.

[0044] Laser 301 is used in various types including, but not limited to, semiconductor lasers, to provide a stable laser source. It requires the ability to adjust the pump current of the laser tube and an external grating to achieve frequency adjustment. The reason for using this device is that laser action is required for ion detection.

[0045] The electro-optic modulator 302 is connected to the laser 301 via a spatial optical path and is used to generate a modulated laser electric field and a locking signal. The reason for using this device is that it is small in size, has a fast response speed, and a high modulation frequency.

[0046] The signal source 303 is used to provide a frequency signal to the electro-optic modulator 302 and drive the electro-optic modulator 302. It is connected using an SMA cable or a BNC cable. The reason for using this device is that it can output a stable radio frequency signal, which is convenient for high-precision measurement.

[0047] Phase shifter 304 is used to generate phase signals and is connected to signal source 303 via SMA or BNC cable. The signal is output to mixer 305 via SMA or BNC cable to form a feedback loop.

[0048] Mixer 305 is used to mix the beat frequency signal generated by photodiode detector 308 with the signal generated by phase shifter 304 and output it to low-pass filter 306, which is connected using SMA cable or BNC cable.

[0049] The low-pass filter 306 is used to remove other resonant or unrelated signals from the mixing signal generated by the mixer 305, so that only the required feedback signal is obtained. It is connected using an SMA cable or a BNC cable. The reason for using this device is that the feedback signal generated by the mixer 305 is in the low-frequency band, while the spurious signals are located in the mid-to-high frequency band, so this device can be used to remove them.

[0050] The servo amplifier 307 is used to amplify the feedback signal to meet the input requirements of the laser 301, and is connected using an SMA cable or a BNC cable.

[0051] The photodiode detector 308 obtains two laser signals: one modulated by the electro-optic modulator 302 and the other by the FP cavity 309. The two laser signals are beat to obtain a beat frequency signal, which is then output to the mixer 305 via an SMA cable or a BNC cable.

[0052] FP cavity Figure 4 It is used to lock and stabilize the frequency generated by laser 301 to obtain laser with higher frequency stability, thereby improving the laser accuracy used for ion detection. The two are connected by a spatial optical path. Its main internal structure consists of two cavity mirrors. The reason for using this device is that it can achieve a large optical path in a short distance, thereby obtaining a stable laser.

[0053] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An accelerometer based on trapped ions, characterized in that, include: Ion trap module (100) and ultra-stable laser module (300); The ion trap module (100) includes an ion trapping device (101), which is connected to an acousto-optic modulator (102), a mechanical pump and a molecular pump (103) and an ion pump (104). The ion trapping device (101) is an octahedral metal cavity structure, and a linear Paul trap is provided inside it; Among them, the mechanical pump and the molecular pump (103) pump the ion trapping device (101) to a specified vacuum level, and the ion pump (104) is turned on to maintain the specified vacuum level in the ion trapping device (101). After the continuous change of the external environment, the ions trapped in the linear Paul trap undergo continuous motion. According to the Doppler effect, the frequency of the ions will change. The ultra-stable laser module (300) generates laser for detecting clock transitions. After the laser passes through the acousto-optic modulator (102), it enters the ion trapping device (101) to detect the frequency change of the ions, and obtains the clock transition frequency of the ions and the frequency shift caused by the Doppler effect. According to the acceleration measurement formula, the measured acceleration is obtained. The ultra-stable laser module (300) includes a laser (301), which is connected to an electro-optic modulator (302) via a spatial optical path. The electro-optic modulator (302) is connected to a signal source (303) via a cable. The signal source (303) is connected to a phase shifter (304) via a cable. The phase shifter (304) is connected to a mixer (305) via a cable. The mixer (305) is connected to a photodiode detector (308) via a cable. The mixer (305) is also connected to... A low-pass filter (306) is connected to a servo amplifier (307) via a cable. The servo amplifier (307) is connected to the laser (301) via a cable. The electro-optic modulator (302) is connected to the photodiode detector (308) via a spatial optical path. The photodiode detector (308) is also connected to an FP cavity (309) via a spatial optical path. The photodiode detector (308) is also connected to an acousto-optic modulator (102) via a spatial optical path. The ion trapping device (101) has an electron multiplier (EMCCD) window and a photomultiplier tube (PMT) window on its side, multiple first vacuum observation windows, a microwave antenna interface and a DC signal interface on its top, and multiple second vacuum observation windows and a radio frequency signal interface on its bottom. The ion trapping device (101) is connected to the acousto-optic modulator (102) via a spatial optical path, and the ion trapping device (101) is connected to the mechanical pump, the molecular pump (103), and the ion pump (104) via a vacuum pipe. It also includes an optical frequency comb module (200), which is connected to the ion trapping device (101) via a cable; The linear Paul trap includes a support, on which a pair of end cap electrodes and two pairs of blade electrodes are disposed; The FP cavity (309) includes two different endoscopes; The laser used to detect clock transitions is generated by a laser (301) and phase-modulated by an electro-optic modulator (302). The modulated laser is input into an FP cavity (309). The laser reflected in front of the cavity enters a photodiode detector (308) to obtain an output voltage signal. This signal is mixed with the signal after the operating frequency of the electro-optic modulator (302) is passed through a phase shifter (304). After passing through a closed-loop feedback ultra-stable laser, the laser passes through an acousto-optic modulator (102) and enters an ion trapping device (101) to detect ions. After obtaining the clock transition frequency, the frequency is corrected by the acousto-optic modulator (102). The laser frequency is measured and recorded by an optical frequency comb module (200). By designing different clock transition detection sequences, the results of a single clock self-comparison are obtained. The data collected by the optical frequency comb module (200) is processed to obtain the acceleration detected by the ions.

2. The accelerometer based on trapped ions according to claim 1, characterized in that, The cable used is either an SMA cable or a BNC cable.

3. An accelerometer based on trapped ions according to claim 1, characterized in that, The laser (301) is a gas laser, a solid-state laser, a semiconductor laser, or a dye laser.

4. An accelerometer based on trapped ions according to claim 1, characterized in that, The acceleration measurement formula is as follows: Where: v is the velocity of the ion. denoted as , where is the clock transition frequency of the ion. The frequency shift is caused by the Doppler effect. c At the speed of light, This represents the rate of change of frequency.

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